بسم الله الرحمن الرحيم
Nature’s Destiny
How the Laws of Biology Reveal Purpose in the Universe
By: Michael J. Denton
شارك في العمل: الأستاذ مُصطفى نصر قديح
للتحميل: (PDF) (DOC)
نبذة مُختصرة عن الكتاب:
كتاب «قَدَر الطَّبيعة» مِن أشهر كُتُب العالم البريطاني ذو الأصول الأسترالية المشهور جداً «مايكل دينتون».
الكتاب مُكوَّن من قسمين، القسم الأوَّل بعُنوان الحياة، والقسم الثاني بعُنوان التَّطوُّر.
في الحقيقة، شعرت بالصَّدمة عندما أدركت طبيعة موقف «مايكل دينتون» تجاه نظرية التَّطوُّر، وهي نفس موقف «مايكل بيهي» تجاه النَّظرية، ولا أظنّ أنَّ اسم «مايكل» المُشترك بينهما هو السَّبب في ذلك!
في الحقيقة، موقف «دينتون» الرُّبُوبي، واضح جداً، من مُجرَّد بعض التَّأمُّل في عُنوان الكتاب «قَدَر الطَّبيعة»، والذي يُعبِّر عن أنَّ كل ما نراه في الطَّبيعة الآن مِن حولنا، هو أمر مُقدَّر حتمي، بداية من الضَّبط الدَّقيق للثوابت الفيزيائية للكون، مُرُوراً بنشأة الحياة، ووُصولاً في النِّهاية لظُهُور الإنسان على الأرض!
«دينتون» يستخدم بوُضُوح عبارة «التَّطوُّر المُوجَّه» (Directed Evolution)، والذي يقصد منه نفس ما قصده «بيهي» في كتابيه «صندوق داروين الأسود» و «حدّ التَّطوُّر»، وهو أنَّ النَّتيجة النهائية التي وصلت إليها التَّطوُّر، وهو الإنسان، جاء نتاج توجيه، وليس أمراً عشوائياً، وفي الوقت نفسه، ليس نِتاج تدخُّل إلهي، فهو لم يستخدم عبارة «التَّطوُّر الإلهي» (Theistic Evolution)، وعلى هذا فإنَّ «بيهي» و «دينتون» يؤمنان بأنَّ كلّ أشكال الحياة المُختلفة على الأرض الآن جاءت من سلف أوَّل مُشترك، وأنَّ هذا الكائن الحيّ الأوَّل يحمل في داخله ما يجعله قادراً على أن يتطوَّر إلى كل أشكال الحياة الأخرى!
«بيهي» و «دينتون» ينتقدان نظرية التَّطوُّر الدَّاروينية في أنَّها تنقض التَّصميم الواضح في كلّ أشكال الحياة المُختلفة على الأرض، وكذلك ينتقدان أنَّ العشوائية قادرة على الوصول للتَّصميم الواضح في الكائنات الحيَّة، وهكذا يعرض «دينتون» في كتابه هذا أدلَّة التَّصميم الموجودة في الكون، بداية من الضَّبط الدَّقيق للثَّوابت الفيزيائية، مُرُوراً باستعراض أهمّ الظُّرُوف الأرضية المضبوطة خصِّيصاً لنشأة الحياة الإنسانية ومنفعتها، وُصُولاً في النِّهاية لاستعراض التَّصميم الموجود في الكائنات الحية، والتي تُنافي أنَّ التَّطوُّر كان نتيجة عشوائية.
وهكذا في النِّهاية نستطيع أن نقول إنَّ موقف «دينتون» من نظرية التَّطوُّر الدَّاروينية موقف مُحدَّد جداً، فهو يرفض مسائل بعينها، ولكنَّه يقبل بعض أركانها الأساسية، ومع أنَّ الكتاب مُمتاز جداً في جُزئه الأوَّل، إلَّا أنَّنا لا نستطيع أن نُعوِّل على الجزء الثاني وحده فيما يخُص نقد نظرية التَّطوُّر الدَّاروينية، وعلينا أن ننتبه إلى أنَّ قضية أصل الإنسان من القضايا الرَّئيسية التي تجعل النَّظرية مُخالفة للنُّصُوص الدِّينية (خلق آدم عليه السلام)، ومن الواضح جداً أنَّ «دينتون» يقول بأنَّ الإنسان جاء نِتاج تطوُّر كائنات أدنى منه، أشبه بالقرود، وفي الوقت نفسه يقول إنَّ إمكانيات الإنسان الفسيولوجية والعقلية الذهنية أكبر بكثير من أن ننسب الفضل في وجوده للتَّطوُّر العشوائي الأعمى!
الكتاب يستحقّ – في رأيي – تقدير جيِّد جداً، وللكتاب ترجمة عربية من إصدارات «مركز براهين»، تستطيع الحصول عليه عن طريق «دار الكاتب»، ومع أنَّني لم أقرأ مُقدِّمة المركز للكتاب، إلَّا أنَّ غالب ظنَّي أنَّها كمُقدِّمة كتاب «صندوق داروين الأسود»، والذي يعني أنَّه لم يتمّ تنبيه الكاتب إلى خُطُورة بعض أفكار «دينتون» التي تتعارض مع الإسلام، وهذه إشكالية كبيرة نُواجهها في مُعظم الكُتُب المُترجمة إلى اللغة العربية، ولا حول ولا قوة إلَّا بالله العلي العظيم. ولكن على كلّ حال، هذه نتيجة لمشاكل كثيرة جداً نُعاني منها، كأمَّة ضعيفة علمياً.
Part 1: Life
Note to the Reader
· Readers familiar with the views of physicists such as Freeman Dyson, Fred Hoyle, and Paul Davies will be aware that over the past few decades many physicists have pointed out that the existence of life in the cosmos is critically dependent on the laws and constants of physics having the precise values they do [P. C. W. Davies (1982) The Accidental Universe (Cambridge: Cambridge University Press). See also J. D. Barrow and F. J. lipler (1986) The Anthropic Cosmo/.ogical Principle (Oxford: Oxford University Press).]. The values are so critical that several well-known authors have argued that the cosmos gives every appearance of having been very finely adjusted or “prefabricated” for our existence. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p xii]
· As Paul Davies points out in his Accidental Universe: “If nature had opted for a slightly different set of numbers, the world would be a very different place. Probably we would not be here to see it.” In his words: “The impression of design is overwhelming.” [Davies (1982); see Preface.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p xii]
· Davies is careful to distance himself &om any claim that humanity is central in the cosmic scheme: “Where do human beings fit into this great cosmic scheme? Can we gaze out into the cosmos, as did our remote ancestors, and declare God made it all for us? I think not.” [P. C. W. Davies (1995) “Physics and the Mind of God,” the Templeton ‘Prize Address, First Things, August-September, pp. 31-35.] And in his latest book he states explicitly that “I am not saying that we Homo sapiens are written into the laws of physics in a basic way.” [P. C. W. Davies (1995) Art we A/.one? (London: Penguin Books), pp. 70, 85.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p xii]
· And continues: “We should not expect extraterrestrial life to resemble our own in its basic chemistry …. There is no need, for example, to demand liquid water or even carbon. We could anticipate exotic life forms, such as creatures that float in the dense atmosphere of Jupiter or swim in the liquid nitrogen seas ofTitan.” [P. C. W. Davies (1995) Art we A/.one? (London: Penguin Books), p.25] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p xii – xiii]
· Contrary to Davies and others, I believe the evidence strongly suggests that the cosmos is uniquely fit for only one type of biology-that which exists on earth and-that the phenomenon of life cannot be instantiated in any other exotic chemistry or class of material forms. Even more radically, I believe that there is a considerable amount of evidence for believing that the cosmos is uniquely fit for only one type of advanced intelligent life-beings of design and biology very similar to our own species, Homo sapiens. I do not agree with Davies when he claims,” The physical species Homo sapiens may count for nothing.” [P. C. W. Davies (1992) The Mind of God (London: Penguin), p. 232.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p xiii]
· To defend the postulate that the cosmos is specifically fit for biological life as it exists on earth nec. essarily involves consideration of a vast number of natural laws, phenomena, and processes which are quite outside of the areas of physics and cosmology and penain uniquely to the biological realm, phenomena such as the thermal properties of water, the characteristics of the carbon atom, the solubility of carbon dioxide, the self-assembling propenies of proteins, the nature of the cell, and so forth. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p xiii]
· What is particularly striking is that, in almost every case, each constituent appears to be the only available or unique candidate for its particular biological role and, further, gives every appearance of being ideally fit not in one or two but in all its physical and chemical characteristics. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p xiii- xiv]
· Also reviewed is evidence drawn from other areas of science that attests to the fitness of the earth’s hydrosphere, the fitness of the electromagnetic radiation of the sun, and the fitness of the periodic table for the carbon-based type of life as it exists on earth. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p xiv]
· if the laws of nature are so finely tuned to facilitate life’s being in the form of a unique set of carbon-based organisms, both simple and complex, on the surface of a terraqueous planet like the earth, then it seems conceivable that their becoming through the process of evolution might have been determined also by natural law. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p xiv]
· And we need to understand clearly, as William Paley emphasized in his famous discourse on the watch, “that if the parts had been differently shaped from what they are,” the watch could never function. [W. Paley (1807) Natural Theology (London: Faulder & Son).] The same is true in arguing that the constituents of the cosmos are uniquely fit for life. The argument only works if we have some knowledge of “the machinery of the cell” and some understanding of the many reciprocal adaptations in the nature of its constituents that make life possible. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p xv]
· One recent book that invites some comparison is Stuart Kauffman’s At Home in the Universe, in which he argues that much of the course of evolution has been determined and driven by self-organizing and emergent properties of complex systems. [S. Kauffman (1995) At Home in the Universe (New York: Oxford University Press).]There is certainly more than a whiff of teleology about Kauffman’s arguments, and his overall conclusion is consistent with my own when he claims, for example: “We will have to see that we are all natural expressions of a deeper order. Ultimately, we will discover in our creation myth that we are expected after all.” [S. Kauffman (1995) At Home in the Universe (New York: Oxford University Press).p.112] And further: “We may be at home in the universe in ways we have hardly begun to comprehend. “18 Another book that also invites comparison is Vital Dust by the biologist and Nobel laureate Christian de Duve. De Duve has also “opted in favour of a meaningful universe” [C. de Duve (1995) Vital Du.st (New York: Basic Books).] and argues that the cosmos is fit for the origin and evolution of life and that the progress of evolution from simple to complex life forms was largely inevitable. However, de Duve’s position falls a long way short of defending the traditional anthropocentric view of the cosmos. The unique fitness of the laws of nature for the biology of higher, air-breathing life forms such as ourselves is not discussed in any depth and nowhere does de Duve argue that the pattern of evolution was directed specifically toward the human race. egarding man’s place in the cosmos, de Duve concludes in his final chapter, “The human mind may be only a side link in an evolutionary saga far from completed.” [C. de Duve (1995) Vital Du.st (New York: Basic Books). p.301] (My emphasis.) [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p xvii]
Chapter 1: The Harmony of the Spheres
· The fitness of the universe for life depends on a number of factors, including: the relative strength of the four fundamental forces (gravity, electromagnetism, and the strong and weak nuclear forces), the speed of expansion of the universe, the spacing and frequency of supernovae, the nuclear energy levels of certain atoms, etc. If these were not precisely what they are, then carbon-based life would certainly not exist. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p7]
· This now tells us how precise the Creator’s aim must have been, namely to an accuracy of one part in 10^(10123). This is an extraordinary figure. One could not possibly even write the number down in full in the ordinary denary notation: it would be [C. Sagan (1985) Cosmos (New York: Ballantine Books), p. 192.] followed by 10123 successive O’s. Even if we were to wrice a 0 on each separate proton and on each separate neutron in the entire universe–and we could throw in all the other particles for good measure-we should fall far short of writing down the figure needed. [Roger Penrose, The Emperor’s New Mind, 1989] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p9]
· As a result of advances in astronomy and physics over the past half century, we now know that the dying of stars in these immense self-destructive explosions is intimately related to our own existence as living organisms on earth. All the elements necessary for life-carbon (C), nitrogen (N), oxygen (0) and iron (Fe), etc.-are manufactured in the nuclear furnaces in the interiors of the stars. If these elements are to accumulate in rocky planets such as earth, they must be released from the stellar interiors and dispersed widely throughout the cosmos. The crucial release and dispersal of these key building blocks of life is one of the results of a supernova explosion. It is in the dying of stars that life has its birth. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p10]
Biocentric Fine-Tuning
· Over the past three decades, facts such as these drawn from astrophysics and cosmology have led many physicists to argue that the cosmos appears to be finely tuned for life. The evidence and argument has been presented many times; [J. D. Barrow and F. J. Tipler (1986) The Anthropic Cosmological Principle (Oxford: Oxford University Press), see chap. 1.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p10]
supernova
· Supernovae play another role which is critical to the existence of life. The shock waves they generate are probably important in i.nitiating the condensation of interstellar gas and dust into planetary systems such as our own solar system. Those ancient stargazers in China and America would surely have been amazed to know that without such strange new stars, like that which so dramatically lit up the sky on chat far-off July night, there would be no astronomers, no stargazers, no earth, perhaps no life of any sore. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p11]
· If that supernova had been closer to the earth, then it might have bathed the earth in a lethal radiation, obliterating life. If it had been very dose, the earth might have been engulfed in a fireball and vaporized. The frequency and distribution of exploding stars are therefore also critical parameters. Supernovae are essential for life-without them none of the chemical building blocks of life will ever accumulate on the surface of a planet like earth-but they are also immensely destructive phenomena, eliminating all life on any nearby solar systems. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p11]
· The distances between supernovae and indeed between all stars is critical for other reasons. The distance between stars in our galaxy is about 30 million miles. If this distance was much less, planetary orbits would be destabilized. If it was much more, then the debris thrown out by a supernova would be so diffusely distributed that planetary systems like our own would in all probability never form. [H. Ross (1989) The Finger of God (Orange, Calif: Promise Publishing Co.), p.127.] If the cosmos is to be a home for life, then the flickering of the supernovae must occur at a very precise rate and the average distance between them, and indeed between all stars, must be very dose to the actual observed figure. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p11]
· In addition, it turns out that the production of the key elements for carbonbased life not only requires the enormous energy levels within the interiors of stars but is also critically dependent on what appears to be another set of very precise conditions in the nuclear structure of certain atoms, more specifically, the nuclear energy levels of the atoms 8beryllium, 12carbon, and 16oxygen. These energy levels affect the manufacture and abundance of carbon, oxygen, and other heavier elements essential for life. If they had been slightly different, no life-giving carbon or oxygen would have been manufactured. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p11]
· That the manufacture of the key elements of life should depend on a set of such highly specific conditions is commented on by Paul Davies in his book The Accidental Universe. [P. C. W. Davies (1982) The Accidental Universe (Cambridge: Cambridge University Press), p. 118.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p11]
· Fred Hoyle considers the carbon-oxygen synthesis coincidence so remarkable that it seems like a “put-up job.” Regarding the delicate positioning of the nuclear resonances, he comments: If you wanted to produce carbon and oxygen in roughly equal quantities by stellar nucleosynthesis, these are the two levels you would have to fix, and your fixing would have to be just about where these levels are actually found to be …. A commonsense interpretation of the facts suggests that a super intellect has monkeyed with physics, as well as chemistry and biology, and that there are no blind forces worth speaking about in nature. [P. C. W. Davies (1982) The Accidental Universe (Cambridge: Cambridge University Press), p. 118.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p11-12]
· The picture that has emerged from modern physics and astronomy suggests that the formation of the chemical elements for life, and planetary systems capable of sustaining life and evolution over millions of years, are only possible if the overall structure of the universe and all the laws of nature are almost precisely as they are. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p12]
· Physicists recognize four fundamental forces. These largely determine the way in which one bit of matter or radiation can interact with another. In effect, these four forces determine the main characteristics of the universe. 6 They are the gravitational force, the electromagnetic force, the strong or nuclear force, and the weak force. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p12]
· An extraordinary feature of these four fundamental forces is that their strength varies enormously over many orders of magnitude. In the table below they are given in international standard units: [Davies (1982), p. 39.] Gravitational force = 5.90. 10 – 39 *Nuclear or Strong force = 15 *Electromagnetic force = 3.05 . 10 – 12 *Weak force = 7.03. 10-3 [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p12]
· The fact that the gravitational force is fantastically weaker than the strong nuclear force by an unimaginable thirty-eight orders of magnitude is critical to the whole cosmic scheme and particularly to the existence of stable stars and planetary systems. [J. Boslough (1985) Stephen Hawking’s Universe (New York: Quill), p. 101.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p12]
· If, for example, the gravitational force was a trillion times stronger, then the universe would be far smaller and its life history far shorter. An average star would have a mass a trillion times less than the sun and a life span of about one year-far too short a time for complex life to develop and flourish. On the other hand, if gravity had been less powerful, no stars or galaxies would ever have formed. As Hawking points out, the growth of the universe-so close to the border of collapse and external expansion that man has not been able to measure it-has been at just the proper rate to allow galaxies and stars to form. [J. Boslough (1985) Stephen Hawking’s Universe (New York: Quill), p. 101.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p12-13]
· The other relationships and values are no less critical. If the strong force had been just slightly weaker, the only element that would be stable would be hydrogen. No other atoms could exist. If it had been slightly stronger in relation to electromagnetism, then an atomic nucleus consisting of only two protons would be a stable feature of the universe-which would mean there would be no hydrogen, and if any stars or galaxies evolved, they would be very different from the way they are. [For a discussion of the sorts of universe that would result if the constants were different, see J. R. Gribbin and M. J. Rees (1989) Cosmic Coincidences (New York: Bantam Books), chap. 10, pp. 241-269. See also Trimble, op. cit.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p13]
· Clearly, if these various forces and constants did not have precisely the values they do, there would be no stars, no supernovae, no planets, no atoms, no life. As Paul Davies summarizes: The numerical values that nature has assigned to the fundamental constants, such as the charge on the electron, the mass of the proton, and the Newtonian gravitational constant, may be mysterious, but they are crucially relevant to the structure of the universe that we perceive. As more and more physical systems, from nuclei to galaxies, have become better understood, scientists have begun to realise that many characteristics of these systems are remarkably sensitive to the precise values of the fundamental constants. Had nature opted for a slightly different set of numbers, the world would be a very different place. Probably we would not be here to see it. More intriguing still, certain crucial structures, such as solar-type stars, depend for their characteristic features on wildly improbable numerical accidents that combine together fundamental constants from distinct branches of physics. And when one goes on to study cosmology-the overall structure and evolution of the universe-incredulity mounts. Recent discoveries about the primeval cosmos oblige us to accept that the expanding universe has been set up in its motion with a cooperation of astonishing precision. [Davies (1982), Preface.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p13]
· In short, the laws of physics are supremely fit for life and the cosmos gives every appearance of having been specifically and optimally tailored to that end: to ensure the generation of stable stars and planetary systems, to ensure that.; these will be far enough apart to avoid gravitational interactions which would destabilize planetary orbits; to ensure that a nuclear furnace is generated in the interior of stars in which hydrogen will be convened into the heavier elements essential for life; to ensure that a proportion of stars will undergo supernovae explosions to release the key elements into interstellar space; to ensure that galaxies last several times longer than the lifetime of an average star, for only then will there be time for the atoms scattered by an earlier generation of supernovae within any one galaxy to be gathered into second-generation solar systems; to ensure that the distribution and frequency of supernovae will not be so frequent that planetary surfaces would be repeatedly bathed in lethal radiation but not so infrequent that there would be no heavier atoms manufactured and gathered onto the surface of newly formed planets; to ensure in the cosmos’s vastness and in the trillions of its suns and their accompanying planetary systems a stage immense enough and a time long enough to make certain that the great evolutionary drama of life’s becoming will inevitably be manifest sometime, somewhere on an earchlike planet.[Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p13-14]
· And so we are led toward life and our own existence via a vast and everlengthening chain of apparently biocentric adaptations in the design of the cosmos in which each adaptation seems adjusted with almost infinite precision toward the goal of life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p14]
· If the existence of life had been compatible with a greater range of values for the fundamental constants, or, in other words, if the design of the celestial machine could have been different at least to some degree and yet still have sustained life, then the teleological conclusion would be far weaker. It is the necessity that it be exactly as it is-adjusted to what is in effect near infinite precision in a long train and series of things that makes the teleological conclusion so compelling. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p15]
· As Davies comments in the last paragraph of The Cosmic Blueprint, “The impression of Design is overwhelming.” [P. C. W. Davies (1987) The Cosmic Blueprint (London: Penguin), p. 203.] And Paul Davies is not alone. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p15]
· Several well-known physicists and astronomers, among them Brandon Caner, Freeman Dyson, John Wheeler, John Barrow, Frank Tipler, and Sir Fred Hoyle, to cite only a few, have all made the point in recent publications that our type of carbon-based life could only exist in a very special sort of universe and that if the laws of physics had been very slightly different we could not have existed. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p16]
Chapter 2: The Vital Fluid
· In which it is argued that water gives every appearance of being uniquely fit for the type of carbon-based life that exists on earth. Every one of its chemical and physical properties seems maximally fit not only for microscopic life but also for large warm-blooded organisms such as mammals, as well as for the generation and maintenance of a stable chemical and physical environment on the surface of the earth. Some of the properties of water reviewed include its thermal properties, its surface tension, its capacity to dissolve a vast number of different substances, and its low viscosity, which allows small molecules to enter and leave cells by diffusion and which also makes possible a circulatory system. If the properties of water were not almost precisely what they are, carbon-based life wou/.d in all probability be impossible. Even the viscosity of ice is fit. !fit were any greater, then all the water on earth might be trapped in vast immobile ice sheets at the poles. If the thermal properties of water were even slightly different, the maintenance of stable body temperatures in warm-blooded organisms would be problematical No other fluid comes close to water as the ideal medium for carbonbased life. Indeed, the properties of water in themselves provide perhaps as much evidence as physics and cosmology in support of the proposition that the laws of nature are specifically arranged for carbon-based life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p19]
· But as we shall see, they are not nearly as extraordinary or amazing as the various ways in which water is so ideally and uniquely adapted to serve its biological role as the medium or matrix for life on earth. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p22]
· Water has long been seen to have some special significance. That it is essential to life has been evident since the earliest of times, and many cultures have invested it with magical life-giving qualities. It is fitting that Thales, the first of the Greek philosophers, should have based his science on the assenion that water is the origin of all things, and that Bentley should describe it as “the vital blood of the Earth.” [I. B. Cohen (1958) Isaac Newton’s Papers and Letters on Natural Philosophy (Cambridge: Cambridge University Press), pp. 381-382.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p22]
· Water forms the fluid matrix in which occur all the vital chemical and physical activities upon which life on earth depends. Without water, life that exists on earth would be impossible. If the vital activities of the cell are the movements of pieces on a chess board, then water would be the board. Chess is impossible without the board; life is impossible without water. Water also forms most of the bulk of most living things. Most organisms are made up of more than SO percent water; in the case of man, water makes up more than 70 percent of the weight of the body. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p22-23]
The Necessity of Liquid
· If the laws of physics sanctioned matter to exist in our universe only in the solid or gaseous state and outlawed liquids, then life, defined above as a complex chemical system capable of assembling and replicating itself, of manipulating its components and drawing its vital nutrients and constituents from its environment, would almost certainly not exist. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p23]
· Interestingly, John von Neumann, one of the fathers of the computer, in his Theory of Self-Reproducing Automata, envisaged his mechanical replicators floating on an infinite lake, the surface of which was covered with all the basic constituents they required to construct themselves. In other words, the medium in which the replicators “lived” was a fluid. [J. Von Neumann (1966) Theory of Self reproducing Automata, ed. W. A. Burks (Urbana: University of Illinois Press); seep. 82.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p23]
Water’s Unique Thermal Properties
· Water expands by heat and contracts by cold [but if this contraction were continued all the way to the freezing point] … the lower parts of water would have been first frozen and being once frozen hardly any heat applied at the surface could have melted them …. This is so far the case that in a vessel containing ice at the bottom and water at the top, Rumford made the upper fluid boil without thawing the congealed cake below. Now a law of water with respect to heat operating in this manner would have been very inconvenient if it had prevailed in our lakes and seas …. They would all have had a bed of ice, increasing with every occasion, till the whole was frozen. We would have no bodies of water, except such pools on the surfaces of these icy reservoirs as the summer sun could thaw to be again frozen to the bottom with the first frosty night. How is this inconvenience obviated? [This situation] is obviated by a modification of the law which takes place when the temperature approaches this limit. Water contracts by the increase of cold till we come near the freezing temperature; but then … expands till the point at which it becomes ice. Hence the water [at 4°C] will lie at the bottom with cooler water … above it …. In approaching the freezing point the coldest water will rise to the surface where congealment will take place. [But this is only part of the story.] … Another peculiarity in the laws which regulate the action of cold on water is, that in the very act of freezing sudden and considerable expansion takes place …. [Consequently, ice floats.] [W. Whewell (1871) Astronomy and General Physics Considered with Reference to Natural Theology, 8th ed. (London: Bohn). pp. 70-72.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p25]
· Thus, because of these two anomalous properties, water is not bound up in vast beds of submarine ice. We now know that these two properties of water are practically unique, a fact not known in 1832, as Whewell admits: “We do not know how far these laws of expansion are connected with or depend on, more remote and general properties of this fluid or of all fluids.”7 Note that what we have here are two different characteristics of water, both of which are mutually adapted toward the end of preserving bodies of liquid water on a planetary surface. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p25]
· The Fitness of the Environment deals with the peculiar fitness not only of water but with other important chemical components of living things, including carbon dioxide, carbonic acid, and carbon compounds in general. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p27]
· To show, in other words, that in fundamental characteristics the environment [that is, the various chemicals and physico-chemical processes which constitute living things and the chemical and physical character of the hydrosphere] is the finest possible abode for life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p27]
· He continues by admitting that: This is not a novel hypothesis. In rudimentary form it has already a long history behind it, and it was a familiar doctrine in the early nineteenth century. It presents itself anew as a result of the science of physical chemistry. [Henderson, op. cit.; see Preface.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p27]
· In presenting his argument for the unique fitness of water, Henderson alludes to the following thermal properties: 1. The anomalous facts (already referred to above) that water contracts as it cools until just before freezing, after which it expands until it becomes ice, and that it expands on freezing. These properties are practically unique. 2. When ice melts or water evaporates, heat is absorbed from the environment. Heat is released when the reverse happens. This is the phenomenon known as latent heat. The latent heat of freezing of water is again one of the highest of all known fluids. In the ambient temperature range only ammonia has a higher latent heat of freezing. Water’s latent heat of evaporation is the highest of any known fluid in the ambient temperature range. [Henderson, op. cit.; see Preface.pp.99-100] 3. That the thermal capacity or specific heat of water, which is the amount of heat required to raise the temperature of water one-degree centigrade, is higher than most other liquids. 4. That the thermal conductivity of water, which is its capacity to conduct heat, is four times greater than any other common liquid. [Henderson, op. cit.; see Preface.p.106. See also F. Franks (1972) “Water, the Unique Chemical,” in .water: A Comprehensive Treatise, vol. 1 (New York: Plenum Press), p. 488.] 5. That the thermal conductivities of ice and snow are low. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p28]
· If it were not for the properties given in point 1, most of the water on earth would be permanently frozen into vast beds of ice at the bottom of the oceans. Lakes would freeze completely from the bottom up each winter in the higher latitudes. Without those properties in point 2, the climate would be subject to far more rapid temperature changes. Small lakes and rivers would vanish and reappear constantly. Without 3, the difference between winter and summer would be more extreme and weather patterns would be less stable, [Henderson, op. cit., pp. 86-89.] and the great ocean currents such as the Gulf Stream, which currently transfer vast quantities of heat from the tropics to the poles, would be far less capable of moderating the temperature differences between high and low latitudes. Without 2, again, warm-blooded animals would have a far harder time ridding their bodies of heat. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p28].
· Henderson was particularly struck by the adaptive significance of the cooling effect of the latent heat of evaporation in the case of warm-blooded animals. Because, as Henderson points out, “in an animal like man … heat is a most prominent excretory product, which has to be constantly eliminated in great amounts, and to this end only three important means are available–conduction, radiation, and evaporation.” [Henderson, op. cit., pp. 86-89.]. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p28-29]
· which the existence of large complex life forms depend. Moreover, complex macroscopic life forms astonishingly utilize these same thermal properties to buffer themselves against thermal change, which is the inevitable outcome of their metabolic processes. And so via a series of deeply interconnected and wondrously teleological thermal adaptive properties, water bestows its vital magic on earth and its living inhabitants. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p30]
· The parsimony and elegance in this design is self-evident. As far as its thermal properties are concerned, water would appear to be uniquely, and in many different ways ideally, adapted for life on earth. In thermal terms, water is the unique and ideal candidate for its biological role. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p30]
Surface Tension
· Of course, the thermal properties of water are by no means the only physical characteristics which make this remarkable fluid so supremely fit for its biological role. Yet another is its very high surface tension. This has many biological implications. [Henderson, op. cit., pp. 126-127.] It is the high surface tension of water which draws water up through the soil within reach of the roots of plants and assists its rise from the roots to branches in tall trees. Large terrestrial plants would probably be a physiological impossibility if the surface tension of water was similar to that of most liquids. Recently, A. E. Needham commented on the utility of the high surface tension of water: Water has a uniquely high surface tension exceeded by few substances other than liquid selenium and this at a very much higher temperature. Water, therefore, is ideal for the formation of discrete living bodies, with stable limiting membranes. Air-water interfaces are less important, perhaps, than those between water and lipids, which likewise have high values. Other biologically useful consequences of the high tension are that materials which can lower the tension, surface active materials, tend to accumulate at the surface, and also to orientate there. Most of the biologically important carbon compounds have this property, which promotes their aggregation and concentration, as well as the formation of organised membranes. [A. E. Needham, op. cit., p. 11.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p30]
· Remarkably, the very high surface tension, because it tends to draw water into the narrow cracks and fissures in the rocks, assists in the process of weathering and washing chemicals from the rocks. Also, when it freezes, the rocks are fragmented, which in turn also assists the weathering process and the formation of soils. [Franks, op. cit., p. 20.] Here is another instance where a physical property of water is adapted for a role in fashioning the planetary environment for life while at the same time being adapted for a number of specific biological functions. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p30-31]
The Alkahest
· Water could have no biological role if it was not a good solvent. The capacity to dissolve a great number of different chemical substances is presumably a criterion that must be satisfied by any fluid if it is to function as a matrix for any kind of chemical “life” remotely similar to our own. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p31]
· It turns out that, as a solvent, water is indeed ideally fit, so much so that water approaches far nearer than any other liquid to the alcahest, the universal mythical solvent of the alchemists.23 This is a.property of critical importance to water’s biological role. Felix Franks recently commented on the solvent action of water: Other remarkable properties include the almost universal solvent action of liquid water, making its rigorous purification extremely difficult. Nearly all known chemicals dissolve in water co a slight, but detectable extent. [Franks, op. cit., p. 20.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p31]
· Water’s power as a universal solvent is also geologically significant, as the distribution of vital minerals through the hydrosphere would be far less equitable if its salvation powers were less marked. [Henderson, op. cit., pp. 112-115.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p31]
· The salvation power of water and the distribution of diverse chemical species in large amounts throughout the hydrosphere is illustrated by the vast amount of dissolved materials carried to the sea by all the rivers of the earth in one year. This quantity has been estimated to be some 5 billion tons. Henderson lists thirty-three different elements which can be found in the sea, and probably many more are present in trace amounts. To illustrate the utility of its salvation power in biological systems, he cites over fifty different compounds which are found dissolved in human urine. [Henderson, op. cit., pp. 113-115.] Today one could cite many hundreds. As one might expect from such a universal solvent, water is also a surprisingly reactive chemical. It catalyzes almost all known reactions. [A. E. Needham, op. cit., p. 23.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p31]
Viscosity and Diffusion
· The fitness of water would in all probability be less if its viscosity were much lower. The structures of living systems would be subject to far more violent movements under shearing forces if the viscosity were as low as liquid hydrogen. Shearing forces are set up in a structure when a force applied to it tends to distort its shape. A structure composed of pitch, which has a high viscosity, will tend to resist such shearing forces far more effectively than a structure composed of treacle. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p32-33]
· If the viscosity of water was much lower, delicate structures would be easily disrupted by shearing forces and water would be incapable of supporting any permanent intricate microscopic structures. The delicate molecular architecture of the cell would probably not survive. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p33]
· On the other hand, if the viscosity was much higher than it is, no fish or anything we would call a fish would be possible. One can well imagine the difficulty of attempting to sail or swim through treacle! Nor would any microorganism or cell be able to move. If the viscosity of water was higher, the controlled movement of large macromolecules and particularly structures such as mitochondria and small organelles would be impossible, as would processes like cell division. All the vital activities of the cell would be effectively frozen, and cellular life of any sort remotely resembling that with which we are familiar would be impossible. The development of higher organisms, which is critically dependent on the ability of cells to move and crawl around during embryogenesis, would certainly be impossible if the viscosity of water was even slightly greater than it is. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p33]
· Viscosity also has a very important influence on the vital process of diffusion, and this has enormous bearing on the existence of our type of cellular life. It is difficult to see how else but by diffusion the necessary flow of matter into and out of any conceivable chemical self-replicating system based in a fluid medium could be maintained. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p33]
· Diffusion rates in water are very rapid over short distances. Oxygen, for example, will diffuse across the average body cell in approximately onehundredth of a second. [K Schmidt-Nielsen (1975)Anima/Physiology (Cambridge: Cambridge University Press), p. 671.] The very great rapidity of diffusion of small molecules in water over short distances explains why small microorganisms, bacteria and protozoa, and even very small multicellular organisms are able to obtain their nutrients and get rid of their waste products simply by diffusion, without the need for a circulatory system. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p33]
· The rate of diffusion of a molecule in a fluid varies inversely with its viscosity. If the viscosity goes up, the rate of diffusion goes down. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p33]
· If diffusion rates were a hundred times less, cells would have co be a million times smaller to maintain their metabolic activities-a volume equivalent to a sphere containing a few protein molecules. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p34]
· The low viscosity of water is fie in another way because in a liquid of low viscosity the rate of diffusion of different molecules does not vary greatly from molecule co molecule. [H. Davson and J. F. Danielli (1952) The Permeability of Natural Membranes (Cambridge: Cambridge University Press), pp. 51-52.] Measurement of the actual diffusion rates of a variety of compounds in water shows that the diffusion rate varies inversely as the cube root of the molecular weight. This is a fascinating and important law, which is probably of critical significance. As Herbert Stern and D. L. Nanney explain in their Biology of Cells, “it means that the rate of diffusion is much the same for most molecules.” [H. Stern and D. L. Nanney (1965) The Biology of Cells (New York: Wiley), p. 77.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p34]
· To serve its biological role, diffusion must not be only very rapid over short distances, but its rate must be approximately the same for most of the key metabolites used by the cell. Both these criteria are satisfied by the diffusion of small metabolites in water. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p34]
· The diffusion of molecules in any fluid, whatever its viscosity, including water, has an important characteristic in that it is very rapid over short distances but very slow if there is far to go. In fact, the diffusion time increases with the square of the diffusion distance. Thus, if the diffusion distance is increased ten times, the time taken will be increased a hundred times. The physiologist Knut Schmidt-Nielsen calculated that in the case of oxygen diffusing into the tissues, it will attain an average diffusion distance of 1 micron (one-thousandth of a millimeter) in one ten-thousandth of a second, 10 microns in one-hundredth of a second, 100 microns in one second, 1 millimeter in one hundred seconds, 10 millimeters in three hours, and 1 meter in three years. [Schmidt-Nielsen, op. cit., p. 671.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p34]
Viscosity and the Circulatory System
· Because of the increasing inefficiency of diffusion as a transport mechanism over distances greater than a fraction of a millimeter, no highly active organism more than a few millimeters thick can acquire and dispose of its metabolites by diffusion. Hence, to be viable all large organisms must have some additional means of acquiring and disposing of metabolites. In practice, this means some sort of circulatory or perfusion system. [As M. W. Clark (1948) Topics of Physical Chemistry (Baltimore: Williams & Wilkins), p. 128, explains, “The slowness of diffusion over long distances and its great rapidity over short distances is, as the physiologist A. V. Hill who carried out pioneering work on diffusion in the thirties pointed out: ‘the basis of the capillary circulation and therewith the whole design of the larger animals.'”] In mammals billions of tiny capillaries permeate all the tissues of the body, transporting the necessary nutrients, including oxygen and glucose, to within diffusional reach of all cells where metabolic activities are occurring. Because diffusion is so ineffective over large distances, no active cell can survive in a mammal unless it is within about 50 microns from a capillary. In the active muscles of a guinea pig, there may be 3,000 open capillaries per square millimeter of muscle. This is a great number, occupying approximately 15 percent of the volume of the muscle, equivalent to 10,000 tiny parallel tubes running down a pencil lead. [As M. W. Clark (1948) Topics of Physical Chemistry (Baltimore: Williams & Wilkins), p. 146, explains, “The slowness of diffusion over long distances and its great rapidity over short distances is, as the physiologist A. V. Hill who carried out pioneering work on diffusion in the thirties pointed out: ‘the basis of the capillary circulation and therewith the whole design of the larger animals.'”][Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p35]
· It seems, then, the viscosity of water must be very close to what it is if water is to be a fit medium for life. It is sufficiently high to provide some protective buffering against shearing forces for the delicate structures of the cell and sufficiently low to ensure diffusion rates fast enough to allow for material exchange between the cell and its environment. In the case of higher organisms it must be low enough to permit perfusion of the tissues via a system of capillaries down to 3 to 5 microns in diameter, which are sufficiently small to bring within diffusional distance all the tissue cells of the body without their occupying a large proportion of the volume of the tissues. If it was much higher, diffusion would be prohibitively slow, and while very simple cell systems might be possible, large, complex, metabolically active organisms would not. No conceivable set of compensatory changes increasing the number or diameter of the capillaries, increasing the flow rate or decreasing average cell size, etc.—could be engineered to make mammalian life possible. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p36-37]
Non-Newtonian Fluids
· Ordinary homogeneous fluids have a constant viscosity. Their fl.ow is directly related to the pressure applied. However, as Marcus Reiner points out in his Scientific American article “The Flow of Matter,” when a nonhomogeneous fluid, containing a suspension of particles like blood, is forced to fl.ow through a tube, it exhibits a curious behavior: when the pressure is doubled, the rate of fl.ow may triple. Remarkably, its viscosity becomes less as the pressure is increased. Liquids that behave in this way are called non-Newtonian. [M. Reiner (1959) “The Flow of Matter,” Scientific American 201(6):122-137.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p37]
· Now this apparently esoteric aspect of the phenomenon of viscosity is no triviality but rather a crucial adaptive property of blood. It means that when the blood supply to a tissue must be increased several fold, because blood behaves as a nonhomogeneous fluid consisting of red cells suspended in a watery fluid, then as the perfusion pressure increases, the viscosity conveniently declines. This effect greatly facilitates the increased delivery of blood to an organ when its metabolic activity is increased. The twenty-fold increase in the perfusion of mammalian muscles as strenuous activity commences is only possible because of this characteristic of a non-Newtonian fluid. What is particularly remarkable about this adaptive property is that the packaging of the hemoglobin (the oxygen carrying molecules in the red blood cell) in small particles, i.e., the red cells, rather than having them free in solution in the plasma, is itself adaptive, but for reasons completely unrelated to fluid flow or viscosity. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p37]
· These include the linking of the association and dissociation of oxygen and hemoglobin to a variety of sophisticated metabolic controls, which among other things assist in the buffering of the body against changes in its acidity and assist in the transport of carbon dioxide to the lungs. If the oxygen carrying molecules were free in solution, many of these adaptations associated with the reversible oxygenation of hemoglobin would have been in all likelihood impossible, and at the same time the advantage of the anomalous drop in viscosity when a suspension of particles is subjected to increased perfusion pressure would not accrue. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p37-38]
The Viscosity of Ice
· Remarkably, the viscosity of ice, the solid form of water, is also adaptive for life on earth. Just as the viscosity of liquids varies greatly, the viscosity of solids also varies over many orders of magnitude. Pitch, one of the least viscous of solids, has a viscosity about 1012 (1 trillion) times greater than that of water, while ice, which is a crystalline solid, has a viscosity 1016 times that of water. The rocks which make up the crust of the earth have viscosities ranging between 1025 and 1028 times that of water. So the range of viscosities of solids is 1016 [G. Ranalli (1987) Rheology of the Earth (Boston: Allen & Unwin), p. 71. A. Holmes (1965) Principles of Physical Geology (London: Nelson), pp. 61-62.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p38]
· If the viscosity of ice had been several times lower than it is, then glacial activity would have been much less effective in grinding down the mountains and releasing vital minerals into the hydrosphere. If ice had the viscosity of pitch, then glaciers would only have been a few feet thick and would have run gently down mountainsides, making little impression on the much harder rocks that make up the earth’s crust. On the ocher hand, it is fortunate that the viscosity of ice is not much higher than it is. If it were anything approaching that of granite, then all the water on earth would be immobilized at the poles and on the high mountain ranges. The earth’s higher latitudes would have been covered in vast sheets of granite-solid ice caps and the earth would have been sterile. There would be no liquid water on earth and no life. Today about 10 percent of the earth’s water is locked up as ice in the Antarctic and Greenland ice caps. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p38]
· It is possible that even if the viscosity of ice had been only 100 times greater, there would have been far less liquid water on earth and the climate would have been subject to rapid fluctuations from extreme heat to extreme cold, and it is very doubtful whether life as rich as it now exists on earth would have evolved. The actual value of the viscosity of ice would appear to be yet another adaptation of “water” that ensures that large bodies ofliquid water can exist on a planetary surface such as the earth’s. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p38]
The Density of Water
· It is clear that as living organisms are made up largely of water, then the density of water largely determines their weight. In the case of large terrestrial organisms on a planet the size of the earth, if water were several times as dense, then the maximum size chat could be attained would be only a fraction of chat actually attained by existing organisms. An upright bipedal humanoid species of design similar co Homo sapiens would not be feasible, for the weight of the body might well prevent its being lifted off the ground and maintained in an upright position. Nor could the limbs be moved unless the proportion of muscle was greatly increased. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p39]
· One set of adaptations that would theoretically be facilitated if water were less dense and organisms consequently less heavy per unit volume are chose associated with flight. However, as far as aquatic life is concerned, the consequences of water having a density much less than 1 gram per cubic centimeter would be severe. In such a hypothetical world, all other things being equal, carbon-based life forms (composed of 30 percent nonaqueous materials, mainly organic carbon compounds) would tend to sink like lead balloons to the ocean floor. On the other hand, if water was just a fraction heavier than it is, all carbon-based aquatic life would be restricted to floating on the surface. It is doubtful that many life forms, particularly microorgan40 isms, could survive the intense ultraviolet radiation that they would be subjected to if they were restricted permanently to the upper few millimeters of the sea. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p39-40]
Recent Discoveries
· Over the last few decades additional properties of water have come to light which further confirm its remarkable fitness. Morowitz points out: The past few years have witnessed the developing study of a newly understood property of water [i.e., proton conductance] that appears to be almost unique to that substance, is a key element in biological-energy transfer, and was almost cenainly of importance to the origin of life. The more we learn the more impressed some of us become with nature’s fitness in a very precise sense …. Proton conductance has become a subject of central interest in biochemistry because of its role in photosynthesis and oxidative phosphorylation. [Morowitz, op. cir., pp. 152-153.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p40]
· As Morowitz explains, both these key processes use proton conductance and hydrated ions which are major features of water: Once again the fitness enters in, in the detailed way in which the molecular properties of water are matched to the molecular mechanisms of bioenergetics. A property never imagined in Henderson’s time turns out to be a significant part of the fitness of the environment. [Morowitz, op. cir., p. 154.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p40]
· [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p41]
· [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p42]
Keeping Cool
· As a final example, consider the way that the large heat capacity, high latent heat of evaporation, heat conductivity, and low viscosity conspire together to serve the end of temperature regulation in a large organism like a man. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p42]
· Altogether, the work expended when a 100-kilogram man runs 10 miles in one hour will generate approximately 1,000 kilocalories of heat. If none of this heat were lost from the body during the run, it would raise the temperature of the body by I0°C. Such a temperature rise would almost certainly be fatal. If the body was constructed mainly out of, say, iron, salt, lead, or alcohol, rather than water, the temperature would be raised by I00°C, 50°C, 300°C, and 2o·c respectively. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p43]
· Liquids are poor conductors C8mpared with metals, but of all liquids, again water is at a unique maximum, having a thermal conductivity several times as great as the vast majority of liquids at ambient temperatures. [A. E. Needham, op. cir., p. 22.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p43-44]
· If the conductivity of water had been several times less, like that of absorbent cotton or wood, then even with the circulatory system conductivity would almost certainly have been too low to transfer heat to the surface of the body, and its elimination from the body, especially in situations of strenuous exercise, would pose insurmountable problems. The body would seize up like an overheated car engine. On the other hand, if the thermal conductivity of water was many times more, like that of copper, then the temperature of living things would equilibrate very rapidly with their environment, so that temperature regulation would be far more difficult to achieve. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p44]
· Changes in the environmental temperature would be rapidly conducted (as is the case with a piece of metal) throughout the body of the organism, which consequently would suffer continual swings of temperature. Small warm-blooded animals would probably be impossible, and even a large organism would experience difficulties in drinking a large quantity of cold water. To be fit for macroscopic life the thermal conductivity of water must be close to what it is. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p44]
· We see, then, that the very modest rise in body temperature after strenuous exercise is no ordinary phenomenon. It turns out to be dependent on the unique fitness of water as a buffer against changes in temperature. This fitness is dependent on four quite different physical properties of water that all exhibit a coincidental mutual fitness and which together perfectly fit water for this biological role. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p44]
· No other liquid is known which can even remotely approach the fitness of water for temperature regulation of a large terrestrial carbon-based form of life at the ambient temperature range of o·c to so·c. And, moreover, although some liquids such as ammonia and liquid sodium exhibit some of the thermal properties of water, none possess quite the same set of mutually adaptive properties. At certain temperatures liquid sodium, for example, exhibits a higher latent heat of evaporation than water but its thermal conductivity is very many times more than water, too high to permit any theoretical organism based in that medium to maintain a steady temperature in the face of environmental challenges. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p45]
· [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p45]
Conclusion
· As Henderson concluded, If doubts remain, let a search be made for any other substance which, however slightly, can claim to rival water as the milieu of simple organisms, as the milieu Interieur of all living things or in any of the countless physiological functions which it performs. [Henderson, op. cit., pp. 130-131.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p45]
· There is indeed no other candidate fluid which is remotely competitive with water as the medium for carbon-based life. If water did not exist, it would have to be invented. Without the long chain of vital coincidences in the physical and chemical properties of water, carbon-based life could not exist in any form remotely comparable with that which exists on earth. And we, as intelligent carbon-based life forms, would almost certainly not be here to wonder at the life-giving properties of this vital fluid. And if there is life like our own anywhere in the cosmos on some other earth, there will also be water and in all probability there will be seas and rivers and clouds and rain. There will be storms and waterfalls and icebergs, and surf will break on the beaches of that distant world. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p46]
· In the many mutually adaptive properties of this most remarkable of all fluids, we are brought dramatically face-to-face with an extraordinary body of evidence of precisely the sort we would expect on the hypothesis that the laws of nature are uniquely fit for our own type of carbon-based life as it exists on earth. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p46]
Chapter 3: The Fitness of the Light
· The sun provides heat and light, both of which are essential to life.It is the heat provided by solar radiation in the infrared region of the spectrum which warms the earth, keeping the mean temperature of the earth above the freezing point of water and within the temperature range where the chemical reactions upon which life depends cart occur. It is the sun’s heat which energizes the great water cycle, drawing water by evaporation from the oceans into the atmosphere which then, via the precipitation of rain and snow, forms rivers and glaciers which carry the evaporated water back again to the ocean. And it is the energy provided by solar radiation within the visual region of the spectrum which drives the process of photosynthesis through which light energy is utilized to synthesize the fuels of life, the sugars and fats, which power the activities of virtually all complex forms of life on earth. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p50]
· The sun’s radiation is essential in two ways: it provides the heat energy which keeps the earth’s temperature within the appropriate range for life and it provides the light energy necessary for photosynthesis. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p50]
Solar Radiation
· When electromagnetic radiation interacts with matter, energy is imparted. If the radiation is highly energetic in the X-ray or gamma-ray regions, this can tear acorns and molecules apart. On the other hand, radiation in the radio region imparts so little energy that it passes through matter with hardly any detectable effect. Only radiation in this tiny band-in the visual and infrared region-interacts gently enough with matter co be of utility co life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p51]
· Infrared radiation is also essential to life but for a different reason. When radiation in the infrared region of the spectrum interacts with matter, energy is imparted, which causes the random movement and vibration of atoms and molecules to increase. This we register as heat. As already mentioned, it is the heat imparted to the earth by radiation in the infrared region of the spectrum that keeps the earth’s hydrosphere warm, keeps water a liquid, and drives the climatic systems and the water cycle. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p52]
· Moreover, heat energy is important in another way. At least some heat is necessary for chemical reactions, because to interact chemically with one another, atoms and molecules must come into contact and this can only occur if they are in motion and may collide. Note, however, that heat energy is only of utility to the orderly chemical processes of life in a narrow temperature range-approximately that in which water is a liquid, [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p52]
· Our amazement grows further when we note that not only is the radiant energy in this tiny region the only radiation of utility to life but that radiant energy in most other regions of the spectrum is either lethal or profoundly damaging. Electromagnetic radiation from gamma rays through X rays to ultraviolet rays is all harmful to life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p53]
· Similarly, radiation in the far infrared and microwave regions is also damaging to life. Just about the only region of the electromagnetic spectrum which is harmless to life apart from the visible and the near infrared is the region of very long wavelength radiation-the radio waves. So the sun not only puts out all its radiant energy in the tiny band of utility to life but virtually none, in those region of the spectrum which are harmful to life. This coincidence is expressed in graphic form in the two diagrams below. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p53-54]
The Absorption of the Atmosphere
· Now this is a remarkable enough coincidence in itself But there are further coincidences to consider. To be of any utility to life, the radiation of the sun has to reach the surface of the earth. To do so it must pass through the atmosphere. Necessarily, any atmosphere surrounding a terraqueous planet containing carbon-based life is bound to contain some carbon dioxide gas, water vapor, at least some nitrogen, and for advanced highly active life forms considerable concentrations of oxygen. It is difficult to see how the actual concentrations of these gases could be very different from what they are in any atmosphere supporting a carbon-based biosphere (see discussion in chapter 6). [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p55]
· At the temperature range that exists at the earth’s surface, there is bound to be water vapor in considerable amounts in the atmosphere. The fact that the atmospheric gases oxygen, nitrogen, carbon dioxide, and water vapor transmit 80 percent of the sun’s radiation in the visible and near infrared and allow it to reach the earth’s surface is another coincidence of enormous significance. The great majority of all atoms and molecular substances are completely opaque to visible light and radiation in the near-infrared region of the spectrum. Window glass, an example of a transparent solid which transmits light in the visible region, is exceptional. If the atmosphere had contained gasses or other substances which absorbed strongly visible light, then no life-giving light would have reached the surface of the earth. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p55]
· In the case of nearly all solid substances, layers only a fraction of a millimeter thick are sufficient to prevent the penetration of light. Even the atmospheric gases themselves absorb electromagnetic radiation very strongly in those regions of the spectrum immediately on either side of the visible and near infrared. The diagram below indicates the spectral regions absorbed by the atmosphere. [Encyclopaedia Britannica (1994), 15th ed., vol. 18, p. 200, fig. 5.] Note that the only region of the spectrum allowed to pass through the atmosphere over the entire range of electromagnetic radiation from radio to gamma rays is the exceedingly narrow band including the visible and near infrared. Virtually no gamma, X, ultraviolet, far-infrared, and microwave radiation reaches the surface of the earth. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p55]
· Despite these three remarkable coincidences, life would still not be possible without a fourth coincidence-the fact that liquid water is highly transparent to visible light. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p55]
The Absorption of Water
· The significance of the transparency of water to light cannot be exaggerated. All biological chemistry occurs in liquid water. If the energy of sunlight is to sustain life in the ocean then it must be capable of penetrating some distance below the surface of the sea. Even on land if light energy is co reach the chemical machinery of the cell it must invariably penetrate a thin layer of water. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p56]
· Nearly all electromagnetic wavelengths are strongly absorbed by water, except radio waves and light within the visible spectrum. 8 Even far ultraviolet and infrared radiation, the two bands immediately adjacent to the visible band, are absorbed readily by water and only penetrate a fraction of a millimeter below the surface. The absorption of visible light by water varies markedly across the visible spectrum. No red light can be observed below 18 meters. Yellow light only penetrates to 100 meters. By 240 meters most of the green and blue light has been absorbed. The absorbency spectrum of liquid water is shown in the diagram below.[Encyclopaedia Britannica (1994), 15th ed., vol. 18, p. 198, fig. 5.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p56]
· The very remarkable fact that the only region of the spectrum allowed through the atmosphere and allowed to penetrate liquid water is the tiny range of the spectrum useful for life is commented on in the latest edition (15th) of the Encyclopedia Britannica: “Considering the importance of visible sunlight for all aspects of terrestrial life, one cannot help being awed by the dramatically narrow window in the atmospheric absorption … and in the absorption spectrum of water. “[Encyclopaedia Britannica (1994), 15th ed., vol. 18, p. 203, fig. 5.] (My emphasis.) [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p56-57]
· The fact that water absorbs light in the far ultraviolet is of obvious biological significance, as it aces as another device co shield life from the damaging influence of ultraviolet radiation. Note that there are three independent mechanisms attenuating the UV flux reaching biological systems: 1. The radiant output of the sun falls dramatically from 0.40 microns to 0.30 microns so that very little ultraviolet radiation leaves the sun in the first place. 2. Ozone in the upper atmosphere absorbs UV light strongly below 0.30 microns. 3. Water (liquid and vapor) absorbs strongly below 0.20 microns. These factors together create a discontinuity at about 0.30 microns (see diagram below). [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p57-58]
· The very small amount of ultraviolet radiation that does reach the earth’s surface has clearly not hindered the evolution and development of life on earth. The spectacular success and persistence of life over the past 4 billion years indicates that life can thrive when subjected to at least some ultraviolet radiation and that the ultraviolet reaching the earth’s surface must have had little, if any, deleterious effect on life in general. In fact, very small amounts of ultraviolet may have played a significant role in evolution by raising slightly the average mutation rate. Without mutations, there can be no evolutionary change, and it is possible that the raised levels of mutation caused by the ultraviolet flux could have played a critical role in the evolutionary history of life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p58-59]
· Another fascinating aspect of the fitness of the electromagnetic spectrum for life is the fact that both types of useful radiation, the visible and the infrared, are adjacent in the spectrum. What we have in effect are two adjacent playing cards back-to-back in a deck which extends across the cosmos. Just as the transparency of water to visible light and the fitness of the solar radiation for photochemistry are of necessity, so the close proximity of these two vital types of radiant energy gives every appearance of also being of necessity. If these two vital types of radiation were far apart in the spectrum, the possibility of prearranging nature so that they could both reach the surface of a watery planet in appropriate quantities from one unique source, such as the sun, would in all probability have been impossible. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p60]
· We should indeed be awed and staggered by this series of coincidences: that the electromagnetic radiation of the sun should be restricted to a tiny region of the total electromagnetic spectrum, equivalent to one specific playing card in a deck of 1025 cards stretching across the universe; that the very same infinitely minute region should be precisely that required for life; chat the atmospheric gases should be opaque to all regions of the spectrum except this same tiny region; that water should likewise be opaque to all regions of the spectrum save this same infinitesimally tiny region, etc. It is as if a cardplayer had drawn precisely the same card on four occasions from a deck of 1025[Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p60]
· Even with all these coincidences, unless the sun’s radiation reaching the earth’s surface had remained virtually constant throughout the past 4 billion years, life could never have survived and evolved as it has. The sun is fit as an energy source for carbon-based life forms not only in providing radiant energy with precisely the levels necessary for life, but also because it has provided that vital and necessary energy at an almost perfectly constant intensity for unimaginable eons of time. Even the slightest change in the output of radiant energy from the sun at any stage during the history of life would have had disastrous consequences. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p60-61]
Fitness for Vision
· The light of the sun is uniquely fit in yet another way for life on earth-the energy levels and wavelength of electromagnetic radiation in the visual spectrum are both uniquely fit for high-resolution vision. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p61]
· One reason that visual light is fit for biological vision is that if an eyes to “see” it must be able to detect the type of radiation forming the image. Light radiation is the only type of electromagnetic radiation that has the appropriate energy level for detection by biological systems. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p61-62]
· Not only are the energy levels and absorbance characteristics of light waves fit for detection by biological systems, but the actual length of the waves in the visual region of the spectrum is perfectly fit for the high-resolution camera-type eye of the precise design and dimension as that found in all higher vertebrate species, including man. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p62]
· Thus, various factors, including the wavelength of light, diffraction, the size of aperture, and chromatic and spherical aberration, together impose what we might term, after Horace Barlow, an instrumental limit on the resolution of the camera-type eye. However, this instrumental limit is not the only limit to the resolving power of the eye. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p65]
Micro-optical Constraints
· Clearly, no eye can resolve images smaller than the diameter of its individual photoreceptor units, and because of the inevitable constraints on cell design it is difficult to envisage photoreceptors much smaller than a few microns in diameter. (Most cells in higher organisms are between 10 and 50 microns in diameter.) This suggests that the cellular limit cannot be far removed from the instrumental limit of 2 microns imposed by the various factors alluded to above. Interestingly, the smallest photoreceptors in the vertebrate retina are in fact about 2 microns across. 20[Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p65-66]
· The energy levels and the wavelength of light are of course only two aspects of the natural order that must possess precisely the properties and values they do for high-resolution vision to be possible. There are other features as well: there is the transparency of water to light; there is the low refractive index of water; there is the diffusion rates of small organic compounds in water to nourish the lens, which is a living tissue; there is the necessity for a large nervous system to analyze the visual data; and so on. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p67]
Seeing Outside the Visual Spectrum
· Compared with the visual spectrum, the other regions of the electromagnetic spectrum are not only totally unfit for biological vision, they would also appear to be far less fit for nonbiological vision. Even today, despite the development of radio and X-ray telescopes, much of our knowledge of astronomy has come from observations made through light telescopes. The following diagram summarizes some of the conclusions discussed above. And so it would appear that for several different reasons the visual region of the electromagnetic spectrum is the one region supremely fit for biological vision and particularly for the high-resolution vertebrate camera eye of a design and dimension very close to that of the human eye. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p69]
Conclusion
· While high-quality vision may not be essential to all life on earth, human existence would be inconceivable without it. While other species may be as reliant on seeing as humans are for survival, our uniquely human desire for knowledge could only have been satisfied, as Aristotle rightly points out in the opening paragraph of his Metaphysics, by the gift of sight. Virtually all our knowledge of the world, and particularly scientific knowledge, acquired over the past four centuries has been largely dependent on our possession of eyes of very high resolving power, or visual acuity, and capable therefore of bringing us a very detailed and information-rich image of our surroundings. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p70]
· We saw in the previous chapter that water, in many fascinating and highly intriguing ways, is uniquely and ideally fit for the type of carbonbased life that exists on earth, not just for simple unicellular microbial life but also for large terrestrial organisms. The evidence presented in this chapter shows that the light of the stars is also, no less than water, supremely fit for life, again in a multitude of different ways. Moreover, again, as in the case of water, this fitness is not merely for simple microbial life, but for large complex organisms such as ourselves. It is fit to provide the warmth upon which all life on the earth’s surface depends. It is fit for photosynthesis, which generates the reduced carbon fuels, whose oxidation provides energy for all complex life on earth, and it is fit for vision, the key adaptation through which our own species gained knowledge of the world. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p70]
Chapter 4: The Fitness of the Elements and the Earth
· In which the biological significance of various elements of the periodic table is examined. The fitness of the cosmos for carbonbased life is highlighted by the fact that the cosmic abundance of the elements corresponds to their abundance in living organisms and that the space between the stars is filled with immense quantities of organic compounds. Further representatives of every class of atoms in the periodic table are necessary for life. Even uranium atom 92 is essential for life, providing the heat and energy required for tectonic activity and the turnover of the earth’s crustal rocks, which in conjunction with the water cycle ensures the chemical constancy of the earth’s surficial layers. The properties of some of the mineral.r which play such a vital role in the maintenance of this chemical constancy are examined. The fact that recent astronomical studies suggest that solar systems not too dissimilar to our own, containing rocky planets somewhat like the earth, may be relatively common can be taken as farther evidence of nature’s fitness for carbon-based life. It is concluded that habitats like the earth which are so fit for a rich complex carbon-based biosphere are not freakish events but rather the inevitable end of natural law. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p71]
· This, as most other of the Atheists’ Arguments, proceeds from a deep Ignorance of Natural Philosophy; for if there were but half the sea that now is, there would be also but half the Quantity of Vapours, and consequently we could have but half as many Rivers as now there are to supply all the dry land we have at present, and half as much more; for the quantity of Vapours which are raised, bears a proportion to the Surface whence they are raised, as well as to the heat which raised them. The Wise Creator therefore did so prudently order it, that the seas should be large enough to supply Vapours sufficient for all the land.[-John Ray, The WisMm of God Manifested in the WOrdr of Creation, 170] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p73]
· The earth, “with its atmosphere and oceans, its complex biosphere, its crust of relatively oxidised, silica rich, sedimentary, igneous, and metamorphic rocks overlying [a magnesium silicate mantle and core] of metallic iron, with its ice caps, deserts, forests, tundra, jungles, grasslands, fresh-water lakes, coal beds, oil deposits, volcanoes, fumaroles, factories, automobiles, plants, animals, magnetic field, ionosphere, mid-ocean ridges, convicting mantle … is a system of stunning complexity.” [-J. S. Lewis, in F. Press and R Siever, Earth, 1986] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p73]
· many different atoms are used in living things, and in many cases life is critically dependent on these atoms having precisely the properties they possess. Of the 92 naturally occurring atoms, 25 are presently considered essential for life. Of these 25, 11 are present in all living things and in approximately the same proportions. These are hydrogen (H), carbon (C), oxygen (0), nitrogen (N), sodium (Na), magnesium (Mg), phosphorus (P), sulfur (S), chlorine (Cl), potassium (K), and calcium (Ca). Together these atoms make up 99.9 percent of the human body. Another 14 atoms are present in very small amounts in most living organisms, but often in varying amounts, and are known as trace elements. These are vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), molybdenum (Mo), boron (B), silicon (Si), selenium (Se), fluorine (F), and iodine (I). Another 3 atoms, arsenic (As), tin (Sn), and tungsten (W), are known to be essential in many organisms, but in many cases their biological role is obscure. [J. J. R. Frausto da Silva and R. J.P. Williams (1991) The Biological Chemistry of the elements (Oxford: Oxford University Press), pp. 3-4. P. A. Cox (1995) The Elements on Earth (Oxford: Oxford University Press).] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p75-76]
· Thus, life processes utilize atoms from nearly all the groups in the table. As J. J. R. Frausto da Silva and R. J. P. Williams comment: The biological elements seem to have been selected from practically all groups and subgroups of the periodic table (the only exceptions are groups III A and IV B, besides that of the inert gases) and this means that practically all kinds of chemical properties are associated with life processes within the limits imposed by environmental constraints. [Frawto and Williams, op. cit., p. 5.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p76]
· Cosmic and Biological Abundance of the Elements Most of the atoms actually utilized in living organisms occur in the first half of the periodic cable from hydrogen (H), atom 1, to molybdenum (Mo), atom 42. After molybdenum only selenium (Se), iodine (I), and tungsten (W) play any role in living things, and even these atoms are not essential in most organisms. The fact that the atoms in the first half of the table are also the most abundant fits well with the notion that the atom-building system is designed specifically to generate the elements of life. Note that the atoms from carbon (C) to iron (Fe), which are the most important atoms utilized by living things, are all relatively abundant. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p76]
· The fact that the majority of the uranium and thorium rose to the surface layers during differentiation is fortunate and may be of great significance. Rock is not a good conductor, and it is possible that unless a major fraction of these radioactive elements had floated to the surface, the heat generated by radioactivity may not have been so easily lost by conduction from the crustal layers. Being trapped in the earth’s interior may have caused a very large increase in temperature over time, and with no conductive escape this might have led to a far more violent level of volcanism and turbulence in the earth’s center. This may well have repeatedly destabilized the crustal layers and the hydrosphere in violent and explosive episodes of volcanism, rendering the earth’s surface far less fit as a habitat for life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p82-83]
· The actual cosmic abundance of the radioactive elements has also been critical to their geophysical role in heating the earth. If too abundant, the earth-sized planets would be molten for eons of time; if too rare, no heating would ever have occurred. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p83]
Plate Tectonics
· But briefly, when two tectonic plates collide, one plate, “the overriding plate,” is crumpled and uplifted into great mountain chains, while the other, “the underlying plate,” is forced down into the Earth’s interior. This remarkable process results in the continual recycling of the Earth’s crustal material, including the many elements essential for life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p83]
· In itself the tectonic cycle would be insufficient to maintain an environment fit for life. It is only through the integration of the tectonic cycle with another great geophysical cycle, the hydrologic cycle, that the physical and chemical constancy of the environment is ensured. The water cycle is so familiar that it needs little further comment here except to say chat it is almost entirely due co the weathering by water that the elements in the uplifted crustal rocks are returned again to the sea. The extraordinary mutual fitness of these two cycles for the maintenance of the constancy of the environment is self-evident (see below). Like two gigantic cogwheels engineered to fit perfectly together, these two great cycles have turned together in perfect unison for billions of years, ensuring the continual turnover and essential cycling of the vital elements of life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p83-84]
The Magnetic Shield
· The earth has a magnetic field which shields it from ionizing radiation from the sun and cosmic radiation originating from the depths of space. The way in which the field is generated has not yet been fully worked out, yet it seems likely that the movement of molten iron in the center of the planet, driven by convection currents, plays a critical role.[Press and Siever, op. cit., p. 479.] About 1 billion amperes of current is needed to produce the earth’s magnetic field. This is nearly as much electric current as the total amount generated by man throughout history. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p85-86]
· We now know that the magnetic field deflects away from the earth, the solar wind, cosmic radiation, and the intense ionizing radiation which periodically bursts from the surface of the sun, preventing all but about 0.1 percent from reaching the earth. The biological significance of this protective shield is controversial. Even without the shield, the atmosphere would absorb most of this radiation before it reached the earth’s surface. Moreover, during periods when the earth’s magnetic field reversed, the earth was temporarily left without any protection, perhaps for a duration of several years, and such reversals have occurred repeatedly. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p86]
· Another possible “biological role” of the magnetic field may be to protect the ozone layer, which prevents most of the damaging ultraviolet radiation from reaching the earth’s surface. Ionizing radiation, which reaches the upper atmosphere, is known to be a major cause of nitrous oxide (NO) production, which in turn causes the destruction of ozone. Without the magnetic field, it is doubtful if more than a fraction of the current ozone levels could be maintained. [W. D. Parkinson (1983) Introduction to Geomagnetism (Edinburgh: Scottish Academic Press), pp. 356-357. M W. McElhinney (1973) Paleomagnetism and Plate Tectonics (Cambridge: Cambridge University Press), pp. 146-147.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p86]
Silicates and Clay
· Another feature of the earth which is ultimately the result of the heat generated by radioactivity is the fact that the surface rocks of the earth are largely silicates. This apparently esoteric fact is of great biological significance because the end product of silicate weathering by water and carbon dioxide is clay, which forms a major component of soil and plays a vital biological role by absorbing and retaining water and the key elements for plant life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p86]
· This water- and ion-absorbing characteristic of clay resides in its unique layered structure-like the pages of a book-in which each page consists basically of a layer of silicon and oxygen atoms. These atoms carry charges which attract other charged atoms (ions) and water so that the whole structure acts as a great reservoir holding ions in the soil and preventing their being leached out by water as it percolates through the soil. The total internal surface area of clays vastly exceeds the area of their external surfaces. [N. C. Brady and R. R. Weill (I 996) The Nature and Properties of Soils (En’f)ewood Cliffs: Prentice Hall), pp. 242, 270.] As two leading soil scientists point out: “Next to photosynthesis and respiration, probably no process in nature is as vital to plant life as the exchange of ions between soil particles and growing plant roots. These cation and anion exchanges take place mostly on the surfaces of the finer or colloidal fractions of both the inorganic matter–clays and humus. ” [N. C. Brady and R. R. Weill (I 996) The Nature and Properties of Soils (En’f)ewood Cliffs: Prentice Hall), p. 241] “Cation exchange joins photosynthesis as a fondamental life-supporting process. Without this property of soils terrestrial ecosystems would not be able to retain sufficient nutrients to support natural or introduced vegetation.” [N. C. Brady and R. R. Weill (I 996) The Nature and Properties of Soils (En’f)ewood Cliffs: Prentice Hall), p.270.] (My emphasis.) [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p86-87]
· There seems little doubt that were it not for the almost universal occurrence of clay minerals in soil, there would be no large terrestrial plants on earth and consequently no large terrestrial mammals. [C. F. Ugolini and H. Spaltenstein (1992) “Pedosphere,” in Global Biogeochemical Cycles, ed. S.S. Butcher et al. (London: Academic Press), pp. 123-153; seep. 128.] In a very real sense our existence depends on the fact that the most common crustal rocks weather to what would appear to be an ideal material for the growth of plant life, absorbing both water and the essential nutrients needed for growth. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p87]
· It is surely a “coincidence” of great significance that the very rocks which by virtue of their viscosity and density will inevitably form the crustal rocks on a planet like the earth are weathered by the two substances water and carbon dioxide, the key ingredients of any carbon-based biosphere, into a substance that forms an ideal substratum for the growth of plants. It is clear from this brief excursion into the fields of geophysics and geochemistry chat uranium is in a very real sense, no less than carbon, essential for life. Moreover, co gee co uranium from hydrogen, obeying the acombuilding rules which nature has decreed means that inevitably a considerable number of “intermediate atoms” such as the “rare earths” will necessarily be created, albeit in very small amounts. So we can at least tentatively conclude that the whole periodic table is in essence biocentric, from alpha to omega, from hydrogen to uranium, the lase naturally occurring element. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p87]
· Moreover, although many of the elements in the second half of the table seem, at present, of no direct relevance to life, we should recall that the origin of life is still mysterious, and it is certainly conceivable that the properties of many of the elements considered nonessential today may eve11.tually prove to have some exotic but perhaps critical biological role in the process. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p87]
The Properties of Minerals
· It is obvious that a great many of the physical and chemical properties of the minerals that make up the earth’s crust and mantle must be very close to the observed values or the whole crustal recycling system would be untenable; indeed, the earth would be, in all probability, unrecognizable and quite incapable of supporting carbon-based life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p87-88]
· If the crustal rocks were less viscous, say, like pitch, the mountains would have melted into vast flat plains and nothing we would call a mountain chain would exist on the surface of the earth. If the viscosity of the rocks of the mantle had been substantially less, the convective turbulence would have been immense and the surface of the earth subject to daily movements and volcanism. If the viscosity of the mantle had been much greater than it is, on the other hand, the convection currents would have ceased and the tectonic system would have ground to a halt. And it is not only the viscosity of the minerals which must be very close to the observed values. If the elements essential for life are to be effectively recycled through the crustal rocks and hydrosphere, the solubility of the various compounds in which the key elements occur in the crustal rocks must also be close to the observed values. For example, the solubility of silicate minerals (which contain the element silica) is thousands of times lower than the solubility of the carbonate minerals (which contain carbon) such as calcite and dolomite, which make up limestone. If the carbonates had been less soluble, then all the carbon on earth would have been locked up in the limestone sediments and there would have been insufficient carbon in the hydrosphere to support life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p88]
· On the other hand, if the silicates had been as soluble as the carbonates, then the hydrosphere would have been overwhelmed with vast quantities of potassium, aluminum, silica dioxide, calcium, chloride, and other elements converting the sea into a supersaturated viscous sludge. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p88]
· Every one of the cycles essential to life on earth-the carbon cycle, the oxygen cycle, the nitrogen cycle, the phosphorus cycle, the sulfur cycle, the calcium cycle, the sodium cycle, and so on-involves a host of different chemical compounds and processes which carry the essential elements from the rocks to the sea, where they are deposited in the oceanic sediments, incorporated into the crustal rocks, and then via tectonic uplift and volcanism carried again to the surface, where the weathering cycle can recommence. [J. E. Fergusson (1982) Inorganic Chemistry and the Earth (Oxford: Pergamon Press); see chap. 7.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p88-89]
· The maintenance of the approximately constant levels of each of the twenty-five or so elements essential to life in the hydrosphere over the past 4 billion years via a set of interlocking cycles-the water, carbon, iron, magnesium, tectonic cycle, and so on–conjures up the image of a vast terrestrial dock with the size and configuration of all its component cogs superbly tailored to fit perfectly together to ensure that the whole turns harmoniously and fine tuned to ensure that the individual cycles turn at the appropriate rate to maintain the required level of each of the elements, essential to life, in the hydrosphere. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p89]
Gaia
· The constancy of the chemical and physical characteristics of the hydrosphere, maintained as it is by a complex and exquisitely integrated set of interlocking geochemical cycles, has led a number of authors to regard the earth as a homeostatic system analogous to a living organism. As Siever comments in a Scientific American anicle entitled “The Dynamic Earth”: “In spite of all the changes that are observed at many different scales of space and time, the Earth as a whole stays remarkably constant …. it has become apparent … that the core, the mantle, the crust, the oceans and the atmosphere can be … viewed as a complex, interacting system in which there is a cyclic flow of materials from one reservoir to another …. The Earth as a vast recycling system has its counterpart in the physiological model of dynamic equilibrium known as homeostasis. “[R. Siever (1983) “The Dynamic Eanh,” Scientific American 249(3), pp. 30-39.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p90]
· The way in which these various factors-tectonic uplift, the crustal silicates, etc.-work together to ensure temperature stability and constant carbon dioxide levels over millions of years is very striking. The fact that (1) the silicates are the major crustal rocks, that (2) their weathering by the two major components of a carbon-based biosphere, water and carbon dioxide, produces a substance–clay-which is an ideal substratum for the growth of plants, and that (3) at the same time, the very same weathering process controls, via a negative feedback loop, both global temperature and carbon dioxide levels (which must be stringently controlled if plant life or any form of life is to thrive on earth) is further striking evidence of the fitness of the cosmos for carbon-based life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p90-91]
· If the Gaia hypothesis is correct, then Gaia would be, as Lovelock points out, “the largest living creature on Earth”[J. E. Lovelock (1987) Gaia: A New Look at Life on earth (Oxford: Oxford University Press); see Preface.p.34] and we and all other living things would be parts and partners of a vast being who in her entirety has the power to maintain our planet as a fit and comfortable habitat for life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p93]
· Although the position taken here differs from Lovelock’s Gaia hypothesis, there are some obvious parallels and the two viewpoints are not, of course, mutually exclusive. From the teleological position advocated here, when biology interacts with chemistry to maintain the constancy of the environment, this is the result of a preexisting mutual fitness of carbon-based life and the earth’s hydrosphere. Thus, the constancy of the environment does not arise because the earth is itself a “living, self-regulating entity” but rather because the laws of nature are fit to that end. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p91]
· When the trees on the edge of a forest suffer some injury, which might be from insects or microorganisms, they send messages across the forest warning the other trees of the impending attack. Forewarned of the danger, the trees preempt the attack by secreting chemicals that are harmful to the invading insects or microorganisms. In the case of the African Acacia, the pheromone is ethylene gas.[D. Attenborough (1995) The Private Life of Plants (London: BBC Books), p. 70.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p91-92]
· le is possible to think of all the individual members of a particular bacterial species as being members of a superorganism spread out all over the earth. [E. Pennisi (1995) “The Secret Language of Bacteria,” New Scientist, September 16, pp. 30-33.] This is not so far-fetched as it seems, because all the members of a bacterial species are in continuous genetic communication by the exchange of genetic material via the plasmid system. If one individual bacteria acquires resistance to an antibiotic, it is this genetic communication system which spreads resistance very rapidly throughout the world to all the other bacterial members of the same species. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p92]
The Earth’s Fitness
· This excursion into the earth’s sciences has shown that the criteria that must be satisfied by a planet if it is to possess a stable hydrosphere fit for carbonbased life are quite stringent. Press and Siever comment:35 “Life as we know it is possible over a very narrow temperature interval … this interval is perhaps 1 or 2% of the range between the temperature of absolute zero and the surface temperature of the sun.” And they note that chis range of temperatures is only found on a planet at approximately the distance that the earth is from the sun. Continuing, they comment on the size of the Earch:36 Earth’s size is just about right-not too small that its gravity was too weak to hold the atmosphere and not so large that its atmosphere would hold too much atmosphere including harmful gases …. the Earth’s interior is a delicately balanced heat engine fuelled by radioactivity …. were it running too slowly … the continents might not have evolved to their present form …. Iron may never have melted and sunk to the liquid core, and the magnetic field would never have developed …. If there had been more radioactive fuel, and therefore a faster running engine, volcanic dust would have blotted out the Sun, the atmosphere would have been oppressively dense, and the surface would have been racked by daily earthquakes and volcanic explosions. [Press and Siever, op. cit., p. 4.] -[Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p93]
· The impression gained from these considerations is that there is nothing unusual about Earth and that, given the cosmic abundance of the elements, the laws of nature will generate a planet with chemical and physical characteristics very similar to those of Earth, with a hydrosphere supremely fit for life. The fact that the other rocky planets, Mars, Mercury, and Venus, and the Moon appear to have undergone analogous changes serves to support the conclusion. Recent studies of the voluminous data brought back by the various space missions to Mars since the 1970s, reviewed by Jeffrey Karge! and Robert Strom in Scientific American, suggest that in the past Mars may have been a world remarkably similar to Earth: “with flowing rivers, thawing seas, melting glaciers and perhaps abundant life.”[J. S. Kargel and R. G. Strom (1996) “Global Climatic Change on Mars,” Scientific Amnican 275 (5):80-85; see p. 80.] -[Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p94]
· The evidence suggests that Mars has experienced a complex climatic history punctuated with many relatively warm episodes. The evidence for glaciation on Mars consists of geological features which closely resemble those on Eanh: “bouldery ridges of sediment left by melting glaciers at their margins and meandering lines of sand and gravel deposited beneath glaciers by streams running under the ice … and apron-shaped lobes of rocky debris seen on the flank of some Martian mountains [which are probably] ‘rock glaciers’ like the ones that form within the Alaska Range.”[J. S. Kargel and R. G. Strom (1996) “Global Climatic Change on Mars,” Scientific Amnican 275 (5):80-85; see p. 82] And even the recent pictures beamed back to earth by NASA, from the Mars Rover, are reminiscent of a typical desert scene on Earth today. -[Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p94]
· Why, for instance, did Mars cool down and lose its seas? Why is Venus so hot? But reasonably plausible explanations can be provided. In answer to the question “How did the three planets-especially Earth-get to their present-day states?” [A. Henderson-Sellers ( 1986) “The Evolution of the Earth’s Atmosphere,” in The Breathing Planet, ed. J. Gribbin (Oxford: Basil Blackwell), pp. 19-26; seep. 21.] Ann Henderson-Sellers suggests: “The most important parameter, by a long way, is the mean global surface temperature at the time when an atmosphere began to form. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p94-95]
· Given gravity, the cosmic abundance and properties of the atoms, the properties of the minerals formed by the combining of atoms, the phenomenon of radioactivity, the viscosity of silicate rocks, etc., then an earthlike planet with a stable hydrosphere, with oceans and rivers and rain, with mountains and volcanoes, with clay soils, with calcite rock, with a silicate crust, with plate tectonics, may be an almost inevitable end of geophysical evolution. The fact that two adjacent planets in our own solar system, Mars and Earth, are so strikingly similar, provides strong evidence in support of the notion that life-supporting planets are the inevitable end of natural law. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p95]
Other Solar Systems
· If the cosmos is indeed uniquely fit for life as it exists on earth, then the existence of planetary systems capable of harboring life should be relatively common. Over the past few years techniques capable of detecting large planets the size of Jupiter and Saturn have for the first time provided convincing evidence that other planetary systems do in fact exist and may also be quite cornmon.42[Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p95-96]
· Indeed, as the authors of a recent Nature article comment: “Our inference … suggests that planetary systems are abundant in the Galaxy. We speculate that if life arises readily on terrestrial planets, then life, too, may be abundant. The recent announcement that rocks from Mars may contain evidence of life would, if confirmed, support this speculation. Our nearest neighbours may be very near indeed.” [See “Worlds Around Other Scars Shake Planet Birth Theory,” in the “Research News” section, Science 276: 1336-1339. p.144]There may even be life in the oceans of Europa, perhaps drawing energy from geothermal sources like the hydrothermal fauna on the ocean floor of our own planet. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p96]
· And there is another final and intriguing twist to the story. The fact that a significant proportion of all planetary systems may contain large Jupiter sized gaseous planets in the same approximate position they occupy in our solar system has further teleological significance: first, because recent theoretical modeling of the dynamics of solar systems suggest that a large gaseous planet occupying the same position as Jupiter does in our own solar system confers dynamical stability to the whole planetary system, ensuring that the orbits of the other smaller planets are stable over billions of years and, second, because as planetary scientist George Wetherill points out, “without a large planet positioned precisely where Jupiter is, the earth would have been struck a thousand times more frequently in the past by comets and meteors and other interplanetary debris. [G. W. Wetherill (1995) “How Special is Jupiter?” Nature 373:470. See also G. W. Wetherill (1993) “Our Friend Jove,” Discover, July, p. 15. See also M.A. Corey (1995) The Natural History of Creation (Boston: University Press of America); seep. 69.] Wetherill continues that if it were not for Jupiter “we wouldn’t be around to study the origin of the solar system. “[Wetherill (1993).] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p96]
· The emerging picture is entirely in keeping with the teleological presumption that nature is ordered to generate terraqueous planets closely resembling Earth-uniquely fit for the origin, and evolution, of carbon-based life. As we did with water and carbon, we can represent again the unique fitness of the earth for our kind of carbon-based life in the form of a graph plotting all known planetary environments against their utility or fitness for carbon-based life. What we get is a unique optimum indicated by the uniqueness and sharpness of the peak. This is perfectly consistent with the hypothesis: that there is one environment determined by the laws of nature (the hydrosphere of a planet of the same size and distance from its sun as Earth) that is uniquely and ideally fit for carbon-based life. If there had been. several other types of environment having some fitness for carbon-based life, so that the plot resembled the pattern seen in the graph below, the design hypothesis would have been effectively disproved . [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p97-98]
Conclusion
· all possible planetary environments We have learned several lessons &om this excursion into the earth sciences: first, that atom building must continue to uranium if there is to be life; second, that the existence of a stable hydrosphere uniquely fit for life on the surface of a planet like the earth is not a matter of chance but the determined end of natural law; and third, that the existence of carbon-based life in this unique and marvelously stable hydrosphere depends on a vast panoply of geophysical and geochemical conditions and processes as well as the physical and chemical properties of a very great number of chemical compounds, minerals, and gases. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p 98]
· And we also learn that what appears to be the ideal and unique physical and chemical environment for life, the earth’s hydrosphere, depends on a series of genuine and profound coincidences in the nature of things. There is the coincidence that main sequence stars like the sun provide a uniquely constant and ideal source of radiant energy to energize the water cycle on which life itself depends while at the same time emitting visible light of just the required energy levels for photobiology. Then there is, first, the coincidence chat planets the size of the earth have just the proper mass to heat up sufficiently co cause, by outgassing, the formation of a hydrosphere shortly after their formation; second, that this mass provides sufficient gravitational force to retain the atmosphere and hydrosphere after the initial formation; and, third, a planet of a mass equal to the earth’s has the required geophysical properties co-drive the crustal tectonic cycle, which itself is so perfectly fit to function in unison with the water cycle. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p 98-99]
· It is hard co escape the feeling chat planets fit for our type of life will not only have seas and booming surfs and gentle rain, they will also have volcanoes and great mountain chains on which glaciers will form and from which rivers will emerge and carry the vital nutrients of weathering into the seas and throughout the hydrosphere. There will be continental drift and plate tectonics. It is a familiar picture, and not in the least contingent, but rather the inevitable and determined outcome of natural law. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p99]
Chapter 5: The Fitness of Carbon
· Nature has been kinder to us than we had any right to expect. As we look out into the universe and identify the many accidents of physics and astronomy that have worked together for our benefit, it almost seems as if the universe in some sense must have known that we were coming. [-Freeman Dyson, Scientific American magazine, 1971] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p103]
Organic Compounds
· The possibility that living things might be some sort of carbon-based chemical machine had already been raised in the late eighteenth century when Antoine Lavoisier and Pierre Laplace established that water and carbon dioxide are the products of animal and human respiration and that the oxidation of carbon and hydrogen was the source of animal heat and an essential process of life.[R. E. D. Clark (1961) The Universe: Plan or Accident? (London: Paternoster Press), p. 119.] However, the critical role of carbon and its compounds in the design of life was only fully appreciated in the second half of the nineteenth century. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p105]
· Shortly after Wohler and the collapse of the vitalistic doctrine, the English chemist William Prout suggested for the first time in his 1834 Bridgewater Treatise entitled Chemistry, Meteorology, and the Function of Digestion that the carbon atom may be uniquely fit for life because of its potential to form vast numbers of diverse compounds.[W. Prout (1855) Chemistry. Meteorology, and the Function of the Digestion, 2nd ed. (London: Bohn), p. 6. Prout was well-known in his day as the first to propose the notion chat the atomic weights of all the elements were multiples of the atomic weight of hydrogen, the first to divide foods into sugars, fats, and proteins, and as the discoverer of hydrochloric acid in the stomach.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p105]
The Carbon Atom
· The reason for the unique diversity and number of carbon compounds lies in certain unique characteristics of the carbon atom, atom 8 in the periodic table.6 & the British. chemist Nevil Sidgwick explains in his classic textbook Chemical Elements and Their Compounds: Carbon is unique among the elements in the number and variety of the compounds which it can form. Over a quarter of a million have already been isolated and described, but this gives a very imperfect idea of its powers, since it is the basis of all forms of living matter. Moreover it is the only element which could occupy such a position. We know enough now to be sure that the idea of a world in which silicon should take the place of carbon as the basis of life is impossible …. [N. V. Sidgwick (1950) The Chemical Elements and their Compounds, vol. 1 (Oxford: Oxford University Press), p. 490. As Sidgwick explains, the reason for the stability of carbon compounds is chat “in the first place the typical four-covalent state of the carbon atom is one in which all the formal elements of stability are combined. It has an octet, a fully shared octet, an inen gas number, and in addition, unlike all the other elements of the group, on octet which cannot increase beyond 8, since 4 is the maximum covalency possible for carbon. Hence the saturated carbon atom cannot co-ordinate either as donor or as acceptor, and since by far the commonest method of reaction is through co-ordination, carbon is necessarily very slow to react and even in a thermodynamically unstable molecule may actually persist for a long time unchanged. More than 50 years ago Victor Meyer drew attention to the characteristic unevenness (Tragheit) of carbon in its compounds, and there is no doubt that this is its main cause.”] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p106]
· A striking aspect of this great molecular plenitude is that the atoms which comprise it–carbon, hydrogen, oxygen, and nitrogen-are among the first few atoms manufactured in the stars and also among the most abundant overall in the cosmos. And remarkably, two of these atoms, hydrogen and oxygen, form water, the matrix of carbon-based life. It is as if from the very moment of creation the biochemistry of life was already preordained in the atom building process, as if Nature were biased to this end from the beginning . [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p109]
· The vast and unique plenitude of organic compounds can only be exploited by living systems within a temperature range of approximately -20°C to 120°C. It is only within this range that the majority of carbon compounds have their characteristic metastability, which permits the intricate and sophisticated manipulation of their constituent atoms by the chemical machinery of life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p111]
· The diagram below indicates the temperature range in which carbon compounds exhibit the necessary metastability to make them of utility to life. It is surely a highly suggestive coincidence that the chemical reactivity of the one great class of compounds, uniquely fit in so many other ways to serve as the building blocks of life, is of optimal utility far the complex atomic and molecular manipulations associated with life in precisely that temperature range-0°C to J00°C-in which water, the one fluid supremely fit to serve as the matrix for carbon-based life forms, exists as a liquid at sea level on the earth. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p112]
· It is interesting to note in passing that liquid water would not exist on earth if the atmospheric pressure was less than half what it is. Which implies (since the density and pressure of a planet’s atmosphere is largely determined by its size) that it is unlikely that planets much smaller than the earth would contain large quantities of liquid water for any long period of time. At pressures much higher than atmospheric, liquid water can exist at temperatures of up to several hundred degrees. Much of the water in the earth’s crust is in fact much hotter than 100°C. However, water at such temperatures is of little utility for carbon-based life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p112]
The Weak Bonds
· The covalent chemical bonds which link the atoms together in organic compounds are not the only type of chemical bond utilized in living systems. There is another class of bonds, known as weak, or noncovalent, bonds. There are several different types of weak bonds. [The bonds are: ionic bonds, van de Waals forces, hydrogen bonds, and the hydrophobic force. A detailed description of these bonds can be found in any major textbook of biochemistry.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p113]
· Nature has provided no other glue to hold together the molecular superstructure of the cell. While we cannot have carbon-based life in the cosmos without covalent bonds, as there would be no molecules, just as certainly, we cannot have carbon-based life without these weak noncovalent bonds-because the molecules would not have stable, complex 3-D shapes. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p114]
· In fact, weak bonds are even more temperature-sensitive than covalent bonds.· Most weak bonds in existing biomolecules such as proteins are disrupted by increases in temperature which leave covalent bonds intact. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p114]
· The disruption of weak bonds occurs in two very familiar processes in the kitchen-in the heating and beating of egg white, both of which cause the egg white to whiten and coagulate. In a fascinating discussion in Scientific American in 1981, Jearl Walker described the role of the weak bonds in the making of a lemon meringue pie: When a cook forces a whisk through egg whites, shearing the fluid, some of the weaker bonds are ruptured and parts of the 30 structure of the proteins [present in the egg white] are destroyed. The cook does not totally disrupt the proteins because the forces [the covalent bonds] holding them in their primary structures are comparatively strong …. Any such altering of the structure of a protein is called denaturing. Once the proteins are partially unravelled [denatured] they begin to attach themselves co one another to form a three-dimensional mesh or gel. This interaction between the proteins is unlikely before denaturation because the proteins are relatively globular and relatively few of their sites for possible [weak] bonds are exposed. When the mixture is heated … the heat further denatures the proteins, unravelling them further and thus enabling the mesh to stretch … coagulating the whites into a firm structure. 25 [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p114-115]
Conclusion
· In short, then, the covalent compounds of carbon, and especially those containing oxygen, hydrogen, and nitrogen, the substances of life, possess just those characteristics of complexity, diversity, and metastability essential if any sort of complex chemical system is to manipulate its atomic and molecular components in complex and intricate ways. Moreover, this plenitude is of maximum utility in the same temperature range that water, the ideal matrix for life based on carbon chemistry, is a liquid, and where the weak bonds can be utilized to maintain the delicate three-dimensional molecular conformations upon which the functions of the cell’s molecular machinery depend. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p116]
· Carbon is so uniquely fit for its biological role, its various compounds so vital to the existence of life, that we may repeat the aphorism, “If carbon did not exist, it would have to be invented.” The unique fitness of the carbon atom can be represented graphically as shown below. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p116]
Chapter 6: The Vital Gases
Oxidation
· All higher organisms obtain their energy supply from one of the most important chemical reactions on earth-the complete oxidation of reduced hydrocarbons to carbon dioxide and water: reduced carbon compounds + oxygen = water + carbon dioxide. As the oxidant in this reaction is oxygen itself, the process can only occur in an aerobic environment. This key reaction provides many times more energy than any of the multitude of alternative energy-generating reactions. Without it, higher active forms of life would not be possible. [Fenchel and Findlay, op. cit.; see chap. 2, pp. 62-63, and chap. 5.] The energy generated is used to manufacture the energy-rich molecules of ATP (adenosine triphosphate) in the mitochondria-a process called oxidative phosphorylation. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p120]
· Oxidation has many advantages. First, oxygen far surpasses any other chemical element except fluorine in the amount of energy liberated in the process of combining with other elements. Fluorine is, however, dangerously reactive at ambient temperatures. Also, while the chemical combination of hydrogen and oxygen results in the formation of water, when fluorine reacts with hydrogen, the product hydrofluoric acid is one of the most dangerously reactive of all acids. Moreover, fluorine has a great affinity for carbon and consequently the bonds between fluorine and carbon are very strong and can only be broken with considerable difficulty. [N. V. Sidgwick (1950) The Chemical Elements and Their Compounds, vol. l (Oxford: Oxford University Press), pp. 1124-1129.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p120-121]
· Second, the compounds of carbon and hydrogen, which are the two most common atoms in organic compounds, are especially well qualified to be reservoirs of chemical energy liberated by oxidation, because hydrogen far exceeds any other element in the amount of energy that it yields upon oxidation and carbon is surpassed only by hydrogen and one other element, boron. Although there is less energy in compounds of hydrogen and carbon that also contain oxygen, such as sugars, proteins, and fats, a sufficient amount remains to make them highly efficient energy stores, holding far more energy than most other elements and far greater reservoirs of energy than the compounds of any other elements. Henderson was struck by the coincidence that oxygen is very nearly the most reactive atom, releasing great amounts of energy when reacting with other atoms, and that of all oxidations, those of reduced carbon compounds yield the most energy: “The very chemical changes, which for so many other reasons seem to be best fitted to become the processes of physiology, turn out to be the very ones which can divert the greatest flood of energy into the stream of life. “[L. J. Henderson (1958) The Fitness of the Environment (Boston: Beacon Press), pp. 247-248.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p121]
· To summarize, oxygen is fit (1) because of the great amount of energy released when it combines with hydrogen and carbon, and (2) because its chemical reactivity is attenuated at ambient temperatures (below about 50°C), allowing living systems to utilize this awesome energy source in a controlled and efficient manner. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p123]
The Solubility of Oxygen
· The chemical fitness of oxygen to living systems can only be exploited if additional conditions are satisfied. The solubility and rate at which oxygen diffuses in water is obviously critical. Since water is the matrix oflife, if oxygen was either insoluble in water or chemically unstable in an aqueous solution, it would be incapable of playing any biological role. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p123]
· If it was any lower, organisms would not be able to extract oxygen from an aqueous solution at a sufficient rate to satisfy their metabolic needs. Even as it is, all actively metabolizing organisms depend on complex physiological adaptations to extract and transport sufficient quantities of oxygen to satisfy their energy needs. . [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p123]
· Clearly, if the solubility of oxygen or its rate of diffusion in water had been significantly less, then no conceivable type of circulatory or respiratory system would have been capable of delivering sufficient oxygen to suppon the metabolic activities of highly active, warm-blooded, air-breathing organisms in an atmosphere with a partial pressure of oxygen of 150 mm Hg. . [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p124]
· if the solubility constant of oxygen had been significantly lower, then oxygen would be of little utility to life on earth, especially to organisms with high metabolic rates, such as mammals. It is doubtful indeed if any complex active organisms would have been possible, as no other chemical means of energy generation remotely as efficient as oxidation is available to carbon-based life forms. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p125]
· The very oxygen which supports their lives is toxic to them and they survive precariously, only by virtue of elaborate defence mechanisms.” [I. Fridovich (1976) “Oxygen Radicals, Hydrogen Peroxide, and Oxygen Toxicity” in Free Radicalr in Biology. ed. W. A. Pryor, vol. 1 (New York: Academic Press), pp. 239-240.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p125]
· Many body cells die if directly exposed to the oxygen in the atmosphere, 18 and in fact the partial pressure of oxygen in most of the tissues is only about 50 mm Hg, which is about one third of that in the atmosphere. [V. B. Mountcastle (1968) Medical Physiology. vol. 1 (St. Louis: C. V. Mosby), p. 631.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p125]
· It is evident, then, that oxygen’s solubility (and diffusion rate) in an aqueous fluid must be very close to what it is. This is all the more remarkable considering the fact that the solubility of substances in water varies over many orders of magnitude. The solubility of many common gases varies over a range of nearly 1 million. The solubility of carbon dioxide, another gas of vital importance to life, is about twenty times greater than that of oxygen. [Pollack, op. cit., p. 1324.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p126]
· In summary, oxidation is fine because (1) of the enormous energies released when oxygen combines with other atoms, (2) the activity of oxygen is attenuated at ambient temperatures, and (3) oxygen has the appropriate solubility in water. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p126]
· Curiously, the very many simple microbial species that utilize reactions which do not require the presence of free oxygen in the atmosphere are probably essential to aerobic life in a number of ways. For example, many may be involved in the cycling of the elements through the hydrosphere, and it may be that the origin of life occurred in an anoxic environment; and save for the capacity of some primitive unicellular organisms to thrive without oxygen, it may never have occurred. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p127]
· The total pressure of the earth’s atmosphere is critical to life, particularly to highly active aerobic organisms like mammals, which depend on a complex respiratory system to deliver the oxygen in the air to the blood in the lungs. Recall first that respiration in vertebrates involves drawing air into the lungs (inspiration) via a system of branching tubes into tiny air sacs, or alveoli, where the oxygen in the air is absorbed by the blood, and then its expulsion (expiration) via the same set of tubes. Again, it is hard to imagine how the respiratory system in higher vertebrates could be much improved. In the adult human, gaseous exchange occurs across a special respiratory membrane lining the lungs which consists of 300 million alveoli. . [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p127]
· The very low viscosity and density are particularly critical because a significant proportion of the work of breathing is involved in overcoming what is termed “airway resistance,” and this is determined directly by the density and viscosity of the air. [Ibid. V. B. Mountcastle (1968) Medical Physiology. vol. 1 (St. Louis; C V. Mosby), pp. 622-626. Encyclopaedia Britannica (1994), 15th ed., vol. 26, p. 745.] . [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p128]
· When the pressure is increased to several times atmospheric pressure, this resistance becomes prohibitive. [Bennett and Elliott, op. cit.; see chap. 4, pp. 76-109; p. 81.] It is clear that if either the viscosity or the density of air were much greater, the airway resistance would be prohibitive and no conceivable redesign of the respiratory system would be capable of delivering sufficient oxygen to a metabolically active air-breathing organism. If the atmospheric pressure were ten times greater, the work of respiration would be prohibitive. If it were about ten times less, the body fluids would vaporize at 38°C.28. . [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p128]
· if the atmosphere was several times more dense, this might reduce the amount of water vapor in the atmosphere and the continents might be converted to arid wastelands. . [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p129]
· Oxygen makes another contribution to life in providing the ozone layer in the upper atmosphere which performs the vital function of protecting life from what would otherwise be lethal levels of ultraviolet radiation. The ozone shield effectively absorbs all the damaging UV radiation below 0.30 microns. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p130]
· Curiously, ultraviolet radiation is a particularly potent activator of oxygen in the near ultraviolet and it is via the activation of oxygen that ultraviolet radiation exerts many of its mutagenic effects. [J. W. Drake (1970) The Molecular Basis of Mutation (San Francisco: Holden-Day), p. 171.] In effect, oxygen, by providing ozone in the upper atmosphere, protects life not only from ultraviolet radiation but also from its own reactivity, which is dangerously enhanced by ultraviolet light. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p130]
· Our ability to breathe and to utilize the vital properties of the oxygen atom depends on a long and deep chain of coincidences in the nature of things. There is in the end nothing contingent about the choice of oxidation as the major source of energy for life on earth. Without the energy inherent in the chemistry of oxidation, life would have remained frozen forever at the primitive unicellular stage it reached on earth long before the Cambrian explosion and the development of complex multicellular life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p130]
· It is not that life adapted to oxygen or to the atmospheric conditions on the earth, but rather that long ago, long before the first or ganisms, long before the formation of the earth, the design of oxidative metabolism and the general character of the atmosphere of our planet was already built into the order of the cosmos. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p130-131]
Carbon Dioxide
· Despite all the energy that oxidation supplies to life, unless the end products of oxidative metabolism were innocuous and harmless and easy to dispose of, oxidative energy would not be available co life. In fact, the final two products of the oxidative breakdown of organic compounds are water and carbon dioxide. ( reduced carbon + oxygen = water + carbon dioxide ) Water is not only harmless to life, it is the very matrix of life. And we have already seen just how wonderfully and in so many ways water is adapted to life. Organisms have at their disposal a great number of means by which to rid themselves of excess water produced in the course of metabolism: via kidneys, via evaporation, via contractile vacuoles, and so forth . . [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p131]
· The other end product of oxidative breakdown of organic compounds, carbon dioxide (C02), possesses a number of physical and chemical properties which are critical to life on earth. If carbon dioxide had been a toxic substance, if it had been a liquid insoluble in water, if it had been a solid, if it had dissolved in water forming a strong acid, the complete oxidation of carbon to carbon dioxide would have been impossible and complex carbonbased life would in all probability never have evolved. However, carbon dioxide is none of these things. . [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p131]
Excretion
· In fact, carbon dioxide is a relatively unreactive compound and a gas at ambient temperatures. That it is a gas should, as Needham points out, “be emphasised since it is one of the very few gaseous oxides at ordinary temperatures (water vaporises more than most others).”[A. E. Needham (1905) The Uniqueness of Biological Materialr (Oxford: Pergamon Press), p. 35.] Moreover, that carbon dioxide is an innocuous soluble gas which car1 be readily excreted from the body of terrestrial organisms via respiration is of enormous utility. As Henderson says: In the course of a day a man of average size produces as a result of his active metabolism, nearly two pounds of carbon dioxide. All this must be rapidly removed from the body. It is difficult to imagine by what elaborate chemical and physical devices the body could rid itself of such enormous quantities of material were it not for the fact that … in the lungs … [carbon dioxide] can escape into air which is charged with little of the gas. Were carbon dioxide not gaseous, its excretion would be the greatest of physiological tasks; were it not freely soluble, a host of the most universal physiological processes would be impossible. [Henderson, op. cit., pp. 139-140.] . [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p131-132]
The Regulation of Acidity
· Like Henderson, the protein chemist John Edsall was also struck by the remarkable nature of the system: “The combination of the acidity and buffering power of H2 C03 with the volatility of C02 provides a mechanism of unrivalled efficiency for maintaining constancy of pH in systems which are constantly being supplied as living organisms are with acidic products of metabolism.”[Henderson, op. cit., p153]. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p133]
· It turns out, then, that both the maintenance of acid-base balance in the body and the excretion of the end product of oxidative metabolism, co2, depend crucially on the chemical and physical properties of co2 itself and its hydration product, bicarbonate. Thus both the problem of excretion of the end product of carbon metabolism and the problem of acid-base balance are both elegantly solved in the properties of the same remarkable compound–carbon dioxide. It is a solution of breathtaking elegance and parsimony based on another set of mutual adaptation in life’s constituents. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p133]
· The mutual fitness of the chemical actors for their respective roles in this the central metabolic drama of life is simply astounding. If these compounds did not possess precisely the chemical and physical properties they do, the drama would be impossible, and it is exceedingly difficult to envisage an alternative. . [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p134]
· For Bentley’s point is well taken. Things could have been otherwise as far as we can tell. For example, if 0 2 and C02 were not gases, the design of large terrestrial carbon-based organisms obtaining energy by oxidative metabolism would in all probability be impossible. Carbon-based life forms such as mammals are critically dependent not only on the fact that 0 2 and co2 are gases but also on the low viscosity of water which makes possible (as we saw in the previous chapter) a circulatory system which is itself essential if the gaseous properties of 0 2 and C02 are to be exploited. Water is not only a key chemical player in the metabolic scheme of oxidative metabolism, but also through its low viscosity it provides the physical means, i.e., the circulatory system, by which the various chemical and physical properties of the other players, particularly the gases O2 and co2‘ may be utilized in the case of large terrestrial life forms. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p135]
· If hydration was instantaneous, this would mean that whenever the metabolism of carbon was increased, the increased quantities of Co2 generated would immediately hydrate, producing carbonic acid which would then dissociate, releasing H ions and subjecting the cell to sudden violent fluctuations in acidity that might well be lethal in higher organisms. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p135]
· Thus, as Henderson remarks, “the waters can never wash [C02] out of the air, nor keep it from the waters. It is the one substance which thus, in considerable quantities relative to its total amount, everywhere accompanies water.”[Henderson, op. cit., p.138] Not only does the gaseous nature of carbon dioxide greatly facilitate the excretion of the carbon from the body of large organisms; this same gaseous nature and its solubility and absorption properties provide what would seem to be the perfect means of distributing the carbon atom to every pan of the hydrosphere in the atmosphere and in the rivers, lakes, and seas. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p137]
Photosynthesis
· Photosynthesis is another absolutely vital biological process. Nearly all complex plant and animal life on earth depends upon it. It generates all the fuel-the reduced carbon compounds such as the sugars and fats, etc. which energize complex life on earth. Like respiration, it is so familiar that its remarkable nature fails to strike us. And like respiration, it is very hard to imagine any other process which could replace it to sustain complex life. Simple forms of life can obtain energy from sources other than sunlight, but for a rich, complex world on the surface of a planet there is no alternative to photosynthesis. And just like respiration, photosynthesis is possible only because each of the key players in the process-water, carbon dioxide, and oxygen-have precisely those properties they have. The fact that both C02 and 0 2 are gases which can be readily taken up or excreted by the plant cells is crucial; also important are the facts that carbon dioxide is distributed universally throughout the hydrosphere, that water is ubiquitous, and that the solubilities of carbon dioxide and oxygen are as they are. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p137]
· Moreover, we have already seen that in addition to all this, the sun’s light is perfectly fit for photochemistry, and the transparency of the atmosphere and liquid water are perfectly fit for sunlight’s penetration to the surface of the earth. Photosynthesis also depends on the unique light-absorbing characteristics of the magnesium atom in chlorophyll. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p137-138]
· Henderson’s conclusion in The Fitness of the Environment has certainly stood the test of time: Accordingly, we may finally conclude chat the fitness of water, carbonic acid, and the three elements make up a unique ensemble of fitness for the organic mechanism …. There is nothing about these substances which is … inferior to the same thing in any ocher substance … not a single disability of the primary constituents … has come to light. [Henderson, op. cit.,pp. 266-267.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p138]
· The fitness … [of these compounds constitutes] a series of maximaunique or nearly unique properties of water, carbon dioxide, the compounds of carbon, hydrogen and oxygen and the ocean-so numerous, so varied, so complete among all things which are concerned in the problem chat together they form certainly the greatest possible fitness. [Henderson, op. cit., p. 272.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p139]
· The organizer of the symposium, Christopher Langton, explained: Anificial Life is the study of man-made systems chat exhibit life-like behaviour characteristic of natural living systems …. By extending the empirical foundations upon which biology is based beyond the carbon-chain life chat has evolved on earth, Artificial Life can contribute to theoretical biology by locating life as we know it within the larger picture of life as it could be.[C. G. Langton (1989) “Artificial Life,” in Artificial Lift, ed. C. G. Langton, Proceedings of an Interdisciplinary Symposium held in September 1987 in Los Alamos, New Mexico (Redwood City, Calif: Addison-Wesley), pp. 1-48; seep. l.] [My emphasis.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p145]
· According to an article in a recent issue of the Scientific American: Such products, depending on design and purpose, might roam through the human body, invading cancerous cells and rearranging their DNA. Other machines might swarm as a barely visible metallic sheen over an outdoor construction site. In a few days an elegant building would take shape …. Every hour entire factories no larger than a grain of sand might generate billions of machines that would look like a mass of dust streaming steadily from the factory doors-or like a cloudy solution suspended in water. [A. K. Dewdney (1988) “Computer Recreations,” Scientific American 258(1):88-91.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p146-147]
· The sheer genius of modern technology and its achievements encourages the belief that, however complex life’s design, it must eventually be equaled in a machine. Possessing a technology so sophisticated that we can contemplate the design and construction of a submarine as small as a red blood cell, a computer smaller than a bacterium, objects which are every bit as complex in terms of number of components per unit volume as living systems, encourages the belief that machines will one day be built which are capable of self-replication, and that artificial life based on a completely different design to that on earth will finally be achieved. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p147]
· The contrast between the apparent ease with which life forms assemble and replicate themselves and the absolute failure to simulate this effortless activity in any son of nonliving artificial system is very striking. While engineers have been dreaming about the possibilities of artificial self-replicating automata over the past fifty years, advances in biology since the early fifties have gradually revealed how the miracle of self-replication is actually realized in living things. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p148]
· It is evident, then, that DNA has not one, but many properties which are wonderfully fit for its role as the genetic molecule: (1) the essential double helical structure, which is fit for self-replication and for the transmission of genetic information, (2) great chemical stability in water, (3) a metastable character consequent on the relatively low binding affinity of the two strands, which assists the machinery of the cell in pulling apart the helix for example during replication-and which confers flexibility on the molecule permitting it to adopt a variety of alternative shapes which are critical to gene expression, (4) the tiny distortions along the length of the helix-another consequence of its metastability-which greatly facilitates information retrieval by proteins, (5) the ability to be superfolded and -compressed into highly compact structures, which allows the storage of massive amounts of information in very tiny volumes (an essential requirement if it is to perform the genetic role in complex multicellular forms of life). [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p156]
· One fascinating aspect of this work is the possibility that some of the various alternative helical replicators, such as the PNAs, may have been used by very primitive life before the current DNA-RNA system evolved. They may even have played a crucial role in the origin of life. If indeed some alternative DNA-like replicators were utilized by early life on earth, then on purely selectionist grounds it is hard to see how they could have been superior and yet selected against and thus have lost out in the evolutionary race. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p159]
· The fact that proline has 4 codons may relate to its helix-breaking properties (a probable reason for its original choice as one of the 20 amino acids in the first place-see the discussion in the next chapter). Before concluding that the code is not maximally fit, we should remember also that the origin of the coding system and its early evolution are still mysterious. It may be that there is a reason for these apparent anomalies rooted in as yet undiscovered necessities associated with the evolution of the code. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p165-166]
Conclusion
· If life is the result of design, then every component must be perfectly fit for the end it serves. There can be no exceptions. If the genetic code is indeed less than optimum, then the entire teleological worldview collapses. Fortunately, in the case of the code we still have insufficient knowledge of protein structure and function to judge the code as clearly “nonoptimal.” Our knowledge of evolution is also incomplete. In the case of DNA and RNA, we are on safer ground; nearly everything we have learned since 1953 is at least consistent with the possibility that DNA and RNA are both ideally and uniquely fit. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p166]
· And DNA may be fit for its biological role in other ways of which at present we have only the haziest notion. For example, DNA can form many other conformations in addition to the double helix. It can also form what are called cruciform structures and the so-called triple helices. Triplex DNA is particularly intriguing, as there are a number of possible biological processes in which it could function, such as in recombination and in regulating gene expression. [D. Maxime, M. D. Frank-Kamenecskii, and S. M. Mirkin (1995) “Triplex DNA Structures,” Annual Review of Biochemistry 64:65-95.] Then there is the equally intriguing possibility raised recently by a paper in Science that DNA may provide the basis for a subcellular computing system.[D. K. Gifford (1994) “On the Path to Computation with DNA,” Science266:993-994.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p166-167]
· The biological solution to the “constructor device problem,” the way through the wall, is of course to be found in the characteristics and properties of a remarkable class of self-assembling biopolymers-the proteins. As I shall try to explain in the following chapter, as the universal nanoconstructors in a self-replicating automaton, they have no peer. They represent a solution of surpassing brilliance to von Neumann’s problem of the universal constructor. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p167]
Chapter 8: The Nano-manipulators
· The very great structural and functional diversity of proteins is one of the key characteristics of these remarkable molecules which contributes to their unique fitness as the molecular constructor devices of the cell. To appreciate more fully some of the other characteristics of proteins that tailor them so superbly for their biological role as the working components of life, it is necessary to digress here and review some basic aspects of their chemical design for those readers unfamiliar with this area of biochemistry. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p174]
· Finally, in this context it is interesting to note that the amino acids in proteins are often modified chemically in a variety of ways after the amino acid chain has folded into its native form. In effect, because of these chemi cal modifications, nature has available far more amino acids than the twenty actually used as the basic building blocks of proteins. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p178-179]
· In effect, those amino acids that are only sparingly soluble in water are forced by water into a tight water-avoiding ball. This ball provides the environment in which synthetic reactions, particularly condensation reactions that involve the removal of a molecule of water and which are almost impossible to carry out in an aqueous medium, can be easily performed. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p181-182]
· The strength of the weak bonds is obviously critical to the ability of the proteins to interact selectively with other ligands in the cell. If the weakbonds were weaker, then no protein would be able to bind specifically to any other molecule in the cell. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p182-183]
· If on the other hand these bonds were stronger, then proteins and their ligands would be bound so strongly that, once in place, they could never be removed. Consequently, the rapid association and dissociation of the protein and ligand on which so many protein functions, such as enzymic functions, depend would be impossible. In effect, proteins and all the constituents of the cell would be frozen into rigid immobile structures. The low diffusion rates would be incompatible with cellular existence. As Watson points out in Molecular Biology of the Gene, the low energy levels of these bonds are precisely what is required for enzymic function: Enzyme-substrate complexes can be both made and broken apart rapidly as a result of random thermal movement. This fact explains why enzymes can function so quickly, sometimes as often as 106 times per second. If enzymes were bound to their substrates by more powerful bonds they would act more slowly. [J. Wacson (1976) The Molecular Biology of the Gene, 3rd ed. (Menlo Park, Calif: W. A. Benjamin), p. 100. Chap. 4 contains a discussion of the role and biochemical significance of weak bonds.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p183]
· If we imagine a world in which the ratio between the strength of covalent and weak bonds was, say, 2 to 1 rather than 20 to l, then the weak interactions would tend to rip the strong bonds apart. Pulling off and reattaching our tape would break the very string holding our plastic balls together. On the other hand, if the ratio between the strength of covalent and weak bonds was increased to 200 to l, combinations of weak bonds would be incapable of achieving the necessary energy levels to strain, break, and form specific covalent bonds within the substrate. The atomic manipulation of matter by proteins would be impossible. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p183]
· Precisely because of their metastability and the weakness of the interactions that hold them on the edge of chaos, the conformation of a protein can easily be altered if it binds to another molecule. Any such interaction will cause molecular distortions which will be transmitted throughout the molecule. These discrete conformational changes effect the functioning of the protein. In the case of an enzyme, they often result in significant changes in its activity. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p184]
· Recent advances in protein chemistry have revealed that the millions of different functional proteins appear to fall into about a thousand major families which share basic structural characteristics. But it is still uncertain whether these families represent a major fraction of all possible structural forms or just a small subset. Again, our knowledge is too limited. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p186]
RNA
· During the 1980s the unexpected finding was made by Thomas Cech that RNA molecules could act like enzymes and catalyze chemical reactions. Since then a considerable number of RNA-catalyzed reactions have been documented.7 However, despite their many catalytic capabilities, it seems very unlikely that RNA molecules could carry out the vast diversity of biological functions carried out by proteins. For example, many synthetic reactions catalyzed by proteins are carried out in hydrophobic niches where water is excluded and RNA molecules are unable to form large nonpolar niches. The chemical properties of RNA molecules are also less diverse, being constructed out of only four bases, while proteins are made up of twenty different amino acids. Also, as the authors of a recent review point out, RNA is far less fit for allosteric regulation than proteins. 8 RNA strands are also far less amenable to being folded into complex, compact molecular structures. Although we cannot completely exclude the possibility, it seems extremely unlikely RNA could substitute for proteins in the great majority of diverse devices and materials used in living systems. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p186]
· Although RNA molecules cannot compete with modern proteins, RNA, because it can both carry information and function as an enzyme, may have served the function of both DNA and proteins in the most primitive cells shortly after the origin of life. It is an intriguing fact that RNA molecules are particularly suited for carrying out manipulations of RNA molecules self-manipulations-and in a world where the cell was largely a collection of RNA molecules, this may have been an ability of critical significance. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p186]
· In the entire realm of science no class of molecule is currently known which can remotely compete with proteins. It seems increasingly unlikely that the abilities of proteins couU be realized to the same degree in any other material form. Proteins are not only unique, but give every impression of being ideally adapted for their role as the universal constructor devices of the cell. Again, we have an example in which the only feasible candidate for a particular biological role gives every impression of being supremely fit for that role. And there is yet another, final aspect to the remarkable fitness of proteins. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p188]
· The mutual fitness of the large groove and the a helix for DNA-protein recognition must be considered a coincidence of very great significance, as recent work in this area has revealed that a great many DNA-recognizing proteins insert a protruding a helix into the major groove of the DNA helix when binding to the DNA. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p190]
· The protein-DNA recognition system contains a particularly intriguing play on the number four. In the largest genomes unique combinations of 4 bases are about 15 bases long. As we have seen above, given the existing energy levels of the weak chemical bonds involved in protein-DNA binding, protein recognition complexes can bind reversibly to DNA sequences up to this length but not to lengths much greater. We have also seen that because of the natural twist in the DNA double helix, protein recognition motifs such as the a helix can only feel along about 4 bases in the DNA double helix. It has often been said that God is a mathematician; on the evidence of molecular biology we might add that He is keen on the number four. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p192]
Conclusion
· Everything that has been learned about the chemical and physical properties of DNA and protein since the early 1950s increasingly confirms the wonderful fitness of these two remarkable molecules for their respective biological roles in the replicative cycle. The number and complexity of their mutual adaptations is growing continually as biological knowledge advances. But already the picture is impressive enough: the mutual fit of the a helix into the large groove of the DNA; the fact that both DNA and proteins are linear polymers so that the information in a DNA sequence can be translated via a coding system into the amino acid sequence of a protein; the fact that the four bases confer geometric perfection and great chemical stability on the DNA helix; the fact that four bases seems to be the ideal number for two different coding systems-the well-known genetic code specifying for the 20 amino acids in proteins and the DNA-protein recognition system whereby proteins are able to recognize unique DNA sequences long enough to function as unique target sequences in the genome; the fantastic diversity of proteins and their ability to regulate their own activities; the fact that the energy levels of the weak interactions are at precisely the level needed to confer on proteins their metastable character and to bind reversibly to unique DNA sequences and thereby to retrieve the information in the genes. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p192-193]
· We have seen that, in the case of water, the carbon atom, the process of oxidation, the light of main sequence stars, the earth’s hydrosphere, etc., the evidence suggests strongly that each is uniquely and optimally fit for its particular biological role. If the teleological position is correct, the DNA protein system should also be uniquely and maximally fit for the advanced type of cellular life that exists on earth today. Note that the teleological position does not imply that all self-replicating chemical systems will necessarily utilize or depend on this particular partnership, that self-replication can only be achieved using DNA and protein. The early evolution of life, for example, may have proceeded via a series of simpler replicating systems which contained neither DNA nor proteins-including some based entirely on RNA or RNA analogues. Teleology only implies that the partnership should be uniquely fit for the self-replication of a biochemical system as sophisticated and complex as the current cell system. And the evidence is certainly consistent with such a conclusion. Considering the bewildering suite of mutual adaptations–discussed above and in the previous chapter-it seems hardly conceivable that there could be any other two molecules as mutually fit, or more perfectly adapted to play the fundamental roles of “information bearer” and “constructor device” in a self-replicating automaton as complex and intricate as the cell. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p193]
Chapter 9: The Fitness of the Metals.
· Of all the metals there is none more essential to life than iron. It is the accumulation of iron in the center of a star which triggers a supernova explosion and the subsequent scattering of the vital atoms of life throughout the cosmos. It was the drawing by gravity of iron atoms to the center of the primeval earth that generated the heat which caused the initial chemical differentiation of the earth, the outgassing of the early atmosphere, and ultimately the formation of the hydrosphere. It is molten iron in the center of the earth which, acting like a gigantic dynamo, generates the earth’s magnetic field, which in turn creates the Van Allen radiation belts that shield the earth’s surface from destructive high-energy-penetrating cosmic radiation and preserve the crucial ozone layer from cosmic ray destruction. And it is iron which by its delicate association with oxygen in the hemoglobin in human blood is able to convey in subdued form this most ferociously reactive of atoms, the precious giver of energy, to the respiratory machinery of the cell, where oxygen’s energies are utilized to fuel the activities of life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p198]
· Without the iron atom, there would be no carbon-based life in the cosmos; no supernovae, no heating of the primitive earth, no atmosphere or hydrosphere. There would be no protective magnetic field, no Van Allen radiation belts, no ozone layer, no metal to make hemoglobin, no metal to tame the reactivity of oxygen, and no oxidative metabolism. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p198]
· Professor Robert J. P. Williams of Oxford University, in a fascinating review entitled “The Symbiosis of Metals and Protein Function,” which summarized current knowledge in this area, concludes: In this essay I have not wanted just to repeat the message that metal ions are incorporated and used in biology in a particular way. Rather I wish to assert that biology without metal ions does not exist any more than biology exists without DNA or proteins. Metal ions are … an essential part of energy and dynamics …. No matter what we know about DNA and RNA and even of sugars the nature of the machinery of life rests with these two components, metal ions and proteins …. The all pervading influence of metal ions in biological systems is such that I now declare that in my mind there is no biology without metal ions.3 [My emphasis.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p198-199]
· Iron, for example, is nearly as common as carbon. Given their abundance, in any biocentric view, one would expect that the metals would be of considerable utility for life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p199]
· And it has turned out that many of the metals do indeed play a vital role in some of the most fundamental biological processes and the evidence increasingly suggests that many of these processes are dependent on the precise chemical and physical properties of particular metal atoms. Close to one-third of all enzymes involve a metal ion as an essential participant. [E. Frieden (1974) “Evolution of Metals as Essential Elements,” in Protein-Metal Interactions,ed. M. Friedman (New York: Plenum Press), pp. 1-31; seep. 11.] An excellent review of this topic is given by Frausto da Silva and Williams in their Biological Chemistry of the Elements. [J. J. R. Fralisto da Silva and R. J.P. Williams (1991) The Biological Chemistry of the Ekments (Oxford: Oxford University Press).] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p199]
Electron Conductors
· One key role plays by metals in the cell is the formation of electronic circuits, and one area where these play a vital role is in energy metabolism. Moreover, it is only the transitional metal atoms, particularly iron and copper, which possess precisely the properties required to form an electronic circuit. No other atoms will do. Only the transitional metals, having far more complex electron shells with many more energy states than the simpler atoms such as sodium (Na), calcium (Ca), carbon (C), nitrogen (N), etc., possess the appropriate electrochemical characteristics to trap and channel electronic energy. The unique electric conducting properties of the transitional metals are also utilized in human technology to make wire conductors. As Frausto da Silva and Williams comment, “man makes his wires from metals such as copper; biology makes hop conductors from metal ions embedded in protein.” [J. J. R. Fralisto da Silva and R. J.P. Williams (1991) The Biological Chemistry of the Ekments (Oxford: Oxford University Press).p.107] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p199]
· If no atoms in the periodic table were specifically fit for this highly specialized role, then the controlled and efficient utilization of the energy of oxidation could not be achieved. Advanced life forms would in all probability be impossible. If we are to have electronic circuits in living organisms, these will be made of transitional metal wires. But the transitional metal atoms not only provide the electronic circuits of the cell upon which the efficient exploitation of oxidative energy is critically dependent, they also possess precisely the required complement of chemical and physical properties which permit organisms to manipulate the oxygen atom, without which oxidative metabolism would be impossible. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p200]
· As Ernest Baldwin points out in his Introduction to Comparative Biochemistry. “It must take up oxygen where the partial pressure is high and give it up again equally readily to the tissues in which the pressure is low …. in other words, the compound of the … respiratory pigment with oxygen must be such that it readily dissociates.” [E. Baldwin (1964) An Introduction to Comparative Biochemistry. 2nd ed. (Cambridge: Cambridge University Press), p. 81.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p201]
· The question arises as to whether a respiratory pigment designed on radically different principles to hemoglobin might be possible. The question was raised by Earl Frieden when he asked, “Why has no other essential metal … or other type of respiratory protein developed to satisfy this important function?” Because, he continues, such a pigment “needs to be able to form a stable dissociable complex with the highly reactive molecule, 0 2 , and, as he points out: “Transition metals excel in this capacity; few other chemical groups can do this. In fact all efforts to devise other physiologically compatible, model oxygen carriers have failed to date …. The compounds that come closest to emulating the oxygen-binding properties of hemoglobin … contain transitional metal iom.” [Frieden, op. cit., pp. 20-21.] (My emphasis.) [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p201-202]
· Water would also almost certainly have to be excluded from the binding site, and this would lead inevitably to something like the hydrophobic heme cleft in hemoglobin.The evidence is consistent with the possibility that hemoglobin is the ideal and unique respiratory pigment for metabolically active air-breathing organisms such as ourselves, and that its unique abilities depend in turn not only on the unique properties of the transitional metal atoms but on the specific properties of one of these atoms-iron. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p202]
· The fitness of the iron atom for reversible binding to oxygen is of course only one of many mutual adaptations in the nature of things which make possible the delivery of oxygen to the metabolically active tissues in a large organism like a mammal. There is also the fact that oxygen is soluble in water; that the viscosity of water is sufficiently low to make the design of a circulatory system possible; that the viscosity of a non-Newtonian fluid. i.e., one containing a suspension of particles–decreases as the pressure increases, a phenomenon which greatly facilitates the propulsion of the blood through the tissues in times of high metabolic activity; that carbon dioxide is a gas, and so on. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p202]
· On its significance, Frieden comments: “If a biochemist is asked to identify the one enzyme which is most vital to all forms of life, he would probably name cytochrome c oxidase. This is the enzyme, found in all aerobic cells, which introduces oxygen into the oxidative machinery that produces the energy we need for physical activity and biochemical synthesis …. This enzyme may be regarded as the ultimate in the integration of the function of iron with copper in biological systems. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p203-204]
· Remarkably, cytochrome c oxidase also contains two other metal atomszinc (Zn) and magnesium (Mg)-alchough their function is mainly structural. All in all, the activity of this remarkable nanomachine depends on the unique properties of four metal atoms-iron (Fe), copper (Cu), zinc (Zn) and magnesium (Mg) and as well as these metal atoms, like any other protein, its basic structure is built up of hydrogen (H), carbon (C), nitrogen (N), oxygen (0), and sulfur (S). In other words, here is one atomic machine which is composed of and exploits the unique chemical and physical properties of nine of the ninety-two naturally occurring elements. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p204]
Molybdenum
· we have what appears to be another case in which life on earth is critically dependent on the specific chemical properties of a unique constituent. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p205]
· In biological systems, it is calcium which is preeminently used where chemical information must be transmitted at great speed, as in the triggering of muscle contraction, transmission of nerve impulses across the synapse, triggering hormone release, the changes following fertilization, etc. As Williams points out in his review, “Amongst the metal ions available to biology only calcium can be high in concentration, can diffuse rapidly, can bind and dissociate strongly.” [Williams, op. cit., p. 238.] (My emphasis.) [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p206]
· As one author, commenting on the suitability of the helical structures in proteins to respond rapidly to the stimulus of calcium, remarks: “The proteins which are in the muscle or the internal filamentous units of cells must have activity matching that of calcium ….These proteins are largely based on helices. In a general sense a helical rod is useful in that its movement economically connects activities at either end through rotational-transitional movements like that of a screw or worm gear. It is fast since helix-helix movements need not break hydrogen bonds. We see in the helix the potential for matching the dynamics of the calcium ion.” [Williams, op. cit., p. 238.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p206]
Magnesium
· Magnesium is calcium’s sister atom in the periodic table and is similar in many of its properties to calcium, but it binds to proteins less quickly and less tightly than calcium. It is certainly less fit for the role of chemical messenger than calcium, but its gender affinity for proteins is utilized by the cell in the more subtle molecular rearrangements which accompany enzymic activities. In present day life forms its involvement is vital to many crucial enzymic processes. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p207]
· George Wald, who elucidated the biochemistry of vision, raised chis question in 1959 in a Scientific American article entitled “Life and Light”: “What properties do the chlorophylls have that are so profoundly advantageous for photosynthesis as to override their disadvantageous absorption spectra.”[G. Wald (1959) “Life and Light,” Scientific American 201 (4):92-108. Seep. 97.] Chlorophyll would appear on the face of it to be less than maximally fit for its biological role; maximal fitness would appear to demand chat it absorb light in the blue-green range of the spectrum. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p207]
· There are several other metal atoms-vanadium (V), chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn)which are also essential to life and where the unique property of the individual atom appears to be exploited in some vital biological process. An excellent summary of the biological role of these metals is given in Biological Chemistry of the Elements, cited earlier. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p208]
Conclusion
· The emerging picture of the role of metals in biology is increasingly one in which it appears that all the metals in each of the main subgroups of the periodic table possess unique properties that are fit for particular vital and essential biological roles. Without them life remotely as rich and complex as it exists on earth would be impossible. The transitional metals, for example, give every impression of having been tailored to form the electronic circuits of the cell and to manipulate in various ways the oxygen atom. Moreover, it increasingly appears that even individual metal atoms such as calcium, iron, copper, magnesium, and molybdenum may be uniquely fit for some of the biological roles they serve. Iron may be uniquely tailored for the sort of reversible binding to oxygen which occurs in hemoglobin, and magnesium for the absorption of light in chlorophyll. Trying to envisage life without metals is every bit as difficult as imagining human technology without them, for, as Robert Williams concludes: “There is no biology without metals.[Williams, op. cit., p. 247.] .. metal elements in some organization are of the essence of life as much as this is true of amino acids and nucleotides.”[Williams, op. cit., p. 246.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p208]
Chapter 10: The Fitness of the Cell
· In which it is argued that the cell is uniquely and ideally fit to fonction as the basic unit of carbon-based life. Cells are capable of carrying out any instruction, adopting any shape, creating the vast diversity of multicellular organisms and ultimately the whole world of life. Evidence is examined which suggests that the cell membrane is uniquely and ideally fit for its role of bounding the cell’s contents and conferring on the cells of higher organisms the ability to move and adhere selectively to one another. These critical properties are also dependent on the size of the average cell being approximately what it is and on the viscosity of cytoplasm being close to what it is. The membrane is also fit, in that its selective impermeability to charged particles confers additional electrical properties, which form the basis of nerve conduction. A variety of coincidences underlying the ability of cells to selectively adhere and move are discussed. The known properties of cells are remarkable enough, but there is still much to learn. The possibility that cells may possess powerful computing abilities and may even be able to behave intelligently is considered. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p209]
· It is cells that assemble the human brain, putting down a million connections a minute for nine months during gestation. It is cells that build blue whales, butterflies, birds, and grass. It is cells that built the dinosaurs and all past life on earth. Through the activities of some of the simplest of their kind, over the past 4 billion years they gradually terraformed the earth, generating oxygen via photosynthesis and thereby releasing its energizing powers for all the higher life forms. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p212]
· Cells can survive desiccation for hundreds of years, and so on and on. In short, they can do anything, adopt almost any shape, obey any order, and seem in every sense perfectly adapted to their assigned task of creating a biosphere replete with multicellular organisms like ourselves. The astounding nature of the Nano technological miracle the cell represents is self-evident. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p212]
· The fitness of the cell for its biological role in the assembly and functioning of multicellular life gives every indication, as with so many of life’s constituents, of being unique. In the case of many of their key properties and abilities, it is very difficult to imagine how these properties and abilities could be actualized except in a material form with the precise characteristics of the living cell. In other words, if we were to design from first principles a tiny nanoerector about 30 microns in diameter with the capabilities of the cell-with the ability to measure the chemical concentration of substances in its surrounding medium; with the ability to measure time, to move, to feel its way around in a complex molecular environment, to change its form; with the ability to communicate with fellow nanoerectors using electrical and chemical messages and to act together in vast companies to create macroscopic structures-we would end up redesigning the cell. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p213]
Lipids
· All types of lipids contain long hydrophobic chains of carbon and hydrogen atoms which are insoluble or only sparingly soluble in water. The structure of the fatty acid stearic acid is shown below. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p213]
· The fact that many types of lipids are insoluble in water is of great biological significance. Without insoluble components, the compartmentalization of the cell and the persistence of cellular structures would not be possible. Lipids are also the major component of the bounding bilayer membrane which surrounds every living cell. (See page 216.) If there were no carbon compounds insoluble in water, such as the lipids, organic chemistry would not be fit for life. Correspondingly, if water was truly a universal solvent, the alkahest of the alchemists, it would not be a fit medium for life because no compartments or stable structures would be possible and all the cells constituents would merely dissolve away. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p214]
· In addition to providing the cell with stable structures, boundaries, and companmencs, the nonpolar hydrophobic nature of lipids is also of great utility because lipid aggregates provide the cell with tiny nonaqueous microenvironments. Such hydrophobic microenvironments are vital to the life of the cell, because many of the synthetic and enzymic processes upon which the life of the cell depends can only occur in a microenvironment where water has been excluded. So their insolubility plays two roles in the cell, creating the stable insoluble boundaries between compartments and the vital hydrophobic microenvironments in which so much of the cell’s synthetic chemistry takes place. Without the hydrophobic properties of the lipids, carbon-based life would not be possible. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p214]
The Cell Membrane
· One of the most important structures in the cell, which is largely composed of lipids, is the cell membrane. It is difficult to see how a cell could survive without some sort of bounding membrane which was relatively impermeable to the cell’s constituents, especially to small metabolites such as sugars and amino acids, to prevent its contents from diffusing away into the surrounding fluid. Such a membrane would also have to be relatively plastic and able to maintain a continuous barrier between the cell and its environment in the face of the ever-changing shape of the cell. As one leading biologist points out, it is essential that the cell membrane should behave like a “two-dimensional liquid” and be able to flow in all directions over the surface of the cytoplasm to maintain a continuous barrier between the cell and its surroundings in the face of “of the ever changing protrusive activities of the cell surface. “[J.P. Trinkaus (1984) Cells into Organs (Englewood Cliffs, N.J.: Prentice-Hall), p. 53.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p215]
· As cell biologist John Trinkaus comments: Because water is itself a strongly polar molecule, the polar phosphate of the membrane lipids will inevitably be attracted to the surfaces of the membrane, both external and cytoplasmic. And just as inevitably their nonpolar fatty acid pans will tend to be squeezed into a nonpolar phase in the interior of the membrane …. The beauty of it is that everything arranges itself. … Simply because of their intrinsic chemical nature phospholipids naturally and spontaneously self-assemble to form a bilayer in a watery solution …. It is, as it were, “the nature of the beast” for them to do so.[J.P. Trinkaus (1984) Cells into Organs (Englewood Cliffs, N.J.: Prentice-Hall), pp. 51-52] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p216]
· The electrical properties of cells depend on many other factors in addition to the insulating properties of lipid membranes. The propagation, for example, of the nervous impulse depends on the rapid transmission of a wave of depolarization along the nerve fiber. The speed of depolarization is itself due to the speed of diffusion of sodium and potassium cations through special gates in the membrane of the nerve cell. This process is again greatly enhanced by the low viscosity of water and by the unique properties of the actions themselves. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p217]
Cell Adhesion
· The ability of cells to selectively adhere to one another is one of their most important characteristics. According to one authority, “the adhesions that cells make with one another lie at the very basis of multicellularity. The form and functioning of all creatures that consist of more than one cell depend on their cells adhering firmly to one another and to the extracellular materials that intervene.”[Trinkaus, op. cit., p. 69.] . [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p218]
Crawling
· Yet another vital characteristic of cells is their ability to crawl, which is no less important and critical than their adhesive properties. Selective adhesion would be of little utility if cells could not move toward particular targets. Indeed, higher forms of life would not exist if cells could not crawl, and we would certainly not be here to ponder the phenomenon. [T. P. Stossel (1993) “On the Crawling of Animal Cells,” Science 260:1086-1094.] In crawling, a cell puts out fan-shaped extensions called lamellae, the leading edge of which make transient attachments with the underlying surface, and as they glide forward, they pull along the cell body passively behind them. The process is somewhat similar to the crawling of a snail, in which the snail’s foot is analogous to the lamellae and the shell analogous to the cell body. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, pp.220-221]
· Such tiny cells would hardly be able to put out complex arrays of protrusions to feel their way through a developing embryo. Indeed, the surface of such tiny cells might have to be entirely devoted to devices involved in transporting materials across the bounding cell membrane and leave little room for adhesion molecules. Lacking the ability of selective cell adhesion, even if such small cells could crawl, it is doubtful if this ability could be utilized to generate the complex patterns of cell movement and association which underlies much of the morphogenesis of higher organisms. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p.222]
· It is hard to escape the conclusion that the ability of cells to selectively adhere and to crawl, twin abilities upon which the assembly of multicellular organisms during development is critically dependent, could only find instantiation in an entity of the size and with the global biophysical and biochemical properties of the average animal cell. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p.223]
Osmosis
· Another physical phenomenon which has a critical bearing on the design of the cell, and particularly on the design of the cell membrane and hence the ability of cells to crawl and adhere, is the phenomenon of osmosis and its consequence, osmotic pressure. Osmosis is an inevitable consequence of the process of diffusion. It occurs wherever two solutions, one dilute and one concentrated, are separated by a membrane that is permeable to water but not to the solutes. In such a situation water moves from the dilute to the concentrated solution-in other words, the solution containing the most dissolved particles. The influx of water can only be prevented by applying hydrostatic pressure to the concentrated solution. This reverses the influx and forces the water back across the semipermeable membrane into the dilute solution. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p.223]
· If osmotic forces had been, say, ten times greater, the minor but relatively sudden dilution of the body fluids which occurs on drinking water might create osmotic imbalances of catastrophic consequence. Only if the cell walls of animal cells were far more rigid (like plant cells) would they have been capable of existence in a world where the pressures generated by osmosis had been ten times greater. But then the cell membrane would not possess those many critical characteristics upon which the world-building abilities of cells depend. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p.225]
Energy Balance
· Cells require energy not only to defend themselves against osmotic pressures by continuously pumping ions out across the cell membrane. They are also faced with the uphill task of continuously replacing all their molecular constituents, and this also requires energy. The half-life of many proteins in the cell varies from a few minutes to several days. Even those proteins which have relatively long half-lives, such as the hemoglobins, the proteins forming the contractile apparatus in the muscles and collagen, the major component of tendons, all turn over eventually and have to be replaced. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p225]
· In an adult human about 15 percent of the energy expended is devoted to protein synthesis alone. 2° Clearly, if the stability of proteins in the face of oxidative and other types of chemical degradation was even slightly less, then the energy burden imposed on cells would be insurmountable and the cell system would not be possible in any recognizable form. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p226]
· In short, there is much that remains to be discovered. Cells may possess many additional abilities, vastly more complex and sophisticated than any we know of at present. But as it is, from the scientific knowledge we have already acquired, there is no doubt the cell represents an exceptional and unique material form. And one which, as in so many other instances, seems ideally and uniquely fit for its biological role in creating the world of multicellular life. Is it conceivable that there could exist some other tiny material form which could compact, into so small a volume, so many extraordinary abilities as a living cell? [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p230]
Conclusion
· We would find an ideal source of energy in the radiant light of main sequence stars, and ideal habitats for our carbon-based life on the trillions of earthlike rocky planets which abound throughout the cosmos. At every step in the game we would find the same ready-made solution for each particular biological end we sought. And this would be repeated in case after case, leading down through a long, seemingly endless chain of coincidences from the carbon atom to the cell and eventually to a world of life very similar to that which exists on earth. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p231]
· In short, the cell system as revealed by molecular biology has turned out to be a unique and peerless whole in which every component is uniquely fashioned by the laws of nature for its designated role, a three-dimensional jigsaw in which all the pieces fit together as perfectly and harmoniously as the cogs in a watch. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p231]
· A final and very remarkable aspect of the fitness of the constituents of life is that most of the key organic building blocks-sugars, amino acids, nucleotides, etc.-can be manufactured in a relatively small number of chemical steps from a small number of readily available simple molecules. It is a remarkable fact that the great majority of the atoms used in their synthesis are derived from only three very simple molecules that are available freely and in great abundance on the surface of the earth: water, carbon dioxide, and nitrogen. Not only are the key components of life wonderfully fit for their biological roles, they are all only a very small chemical distance away from such universally available starting materials. Indeed, there are not many steps from hydrogen itself-the starting point of atom creation in the stars-to the ingredients of life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p232]
· In the current molecular biological picture of life, we have found a “watch” more complicated and more harmonious than any conceived by William Paley, exhibiting in its design precisely what Richard Bentley was looking for, a “usefalness conspicuous not in one or a few only, but in a long train and series of things.” (My emphasis.) [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p.233]
Chapter 11: Homo Sapiens Fire Maker
· Of all the many varied life forms on earth, only our own species, Homo sapiens, is capable of any genuine understanding of the world. By any standards our success in comprehending and manipulating nature has been astounding. In the space of only four centuries since the scientific revolution, we have measured the diameter of galaxies, we have probed into the heart of the atom, we have peered back to the very beginning of time, and in the past few decades we have even contemplated traveling to the stars. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p238.]
· From the evidence presented in the previous chapters, such a phantasm of alien beings-designed along entirely different principles and instantiated in an exotic chemistry-looks increasingly implausible. For as we have seen, it would appear that there are few if any alternative ways of putting together the atoms of the world into a complex self-replicating system as sophisticated as the living cell. If we start from the carbon atom, our route is highly constrained. Having chosen carbon, we must next choose water, then proteins, DNA, oxygen, and so on until we arrive eventually at the design of the living cell as manifest in all living things on earth. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p238.]
· Six adaptations have been widely cited as being crucial to the unique success of our species: (1) high intelligence, (2) linguistic communication, (3) highly developed visual ability, (4) possession of a superb manipulative tool-the hand, (5) our upright stance, and (6) our being a highly social species. In addition to these six adaptations, our technological success has depended on a crucial ability-the ability to handle and control fire, which led in turn to the development of metallurgy and ultimately, through the use of metals, to scientific and technological knowledge. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p238, 239.]
· As far as our cognitive capacities are concerned, it is true that other species-dolphins, parrots, seals, and apes-possess intelligence, but none, as far as we can tell, comes close to the intelligence of man. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p239.]
· Whatever it is about the architecture of the human brain that confers such a high level of intelligence, and whatever evolutionary processes led to such a prodigious development, as far as life on earth is concerned, our intelligence far surpasses that of any other known form of life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p239.]
Language
· Language is another unique distinguishing characteristic of man. No other species possesses a communication system remotely as competent for the transmission of new information or abstract concepts as human language.1 [G. G. Simpson (1967) The Meaning of Evolution (New Haven: Yale University Press), p. 288.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p239.]
· Human speech depends not only on our special cognitive abilities but also on our possessing the appropriate organs to generate complex sound patterns. In fact, modern man’s speech-producing apparatus is quite different from the comparable systems ofliving nonhuman primates. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p239, 240.]
· Nonhuman primates have supralaryngeal vocal tracts in which the larynx exits directly into the oral cavity. In the adult human the larynx exits directly into the pharynx. This confers on man the capacity to generate a far richer phonetic repertoire than that available to a chimpanzee.2 [P. Lieberman (1975) “On the Evolution of Language: A Unifed View in Primate Functional Morphology and Evolution, ed. R. Tuttle (The Hague: Mouton Publishers), pp. 501-540; see pp. 504-510.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p240.]
· A chimp with a human brain could formulate sophisticated thoughts but would lack the ability to communicate verbally as efficiently as a human.3 [P. Lieberman (1975) “On the Evolution of Language: A Unifed View in Primate Functional Morphology and Evolution, ed. R. Tuttle (The Hague: Mouton Publishers), pp. 508, 536.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p240.]
Vision
· Aristotle, in this famous section from the beginning of his Metaphysics, acknowledges the importance of vision to our ability to comprehend the world: All men by reason desire to know. An indication of this is the delight we take in the senses … and above all in the sense of sight …. The reason is that this, most of all the senses, makes us know and brings many differences to light.4 [Aristotle, Metaphysics l.l,980a21-7.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p240.]
The Hand
· In addition to our brain, our linguistic ability, and our highly developed visual ability, we possess another wonderful adaptation, the ideal manipulative tool-the human hand. No other animal possesses an organ so superbly adapted for intelligent exploration and manipulation of its physical surroundings and environment. Only the great apes, our cousins, come close. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p241.]
· Even a chimp with the intelligence of a human would have considerable difficulty carrying out many of the manipulative tasks that we take for granted, like peeling an apple, tying a knot, or using a typewriter. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p241.]
· One of the earliest and still one of the most fascinating discussions of the adaptive marvel that is the human hand was given by the first-century physician Galen: “To man the only animal that partakes in the Divine intelligence, the Creator has given in lieu of every other natural weapon or organ of defence, that instrument the hand: applicable to every art and occasion.”7 And he continues: “Let us then scrutinise this member of our body; and enquire not simply whether it be in itself useful for all the purposes oflife, and adapted to an animal endowed with the highest intelligence; but whether its entire structure be not such, that it could not be improved by any conceivable alteration.”8 The adaptive perfection of the hand was a popular topic among nineteenth-century natural theologians. [7. J. Kidd (1952) The Bridgewater Treatise on the Physical Condition of Man, 6th ed. (London: Bohn); see chap. 3 on the hand, p. 26.] [8. Ibid., pp. 29-31.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p241.]
· In the context of explaining man’s biological preeminence on earth, the crucial question is not whether the human hand represents the absolute pinnacle of manipulative capability, but whether any other species possesses an organ approaching its capabilities. The answer simply must be that no other species possesses a manipulative organ remotely approaching the universal utility of the human hand. Even in the field of robotics, nothing has been built which even remotely equals the all-around manipulative capacity of the hand. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p241.]
Fire and the Dimensions of the Human Body
· Our ability to handle fire is no trivial ability because it was only through the use of fire that technological advance was possible. Through fire came metallurgy and metal tools and eventually chemical knowledge. Because metals are the only natural conductors of electricity, the discovery of electromagnetism and electricity, even the development of computers, are all in the last analysis the result of our ancient conquest of fire. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p242.]
Fire and the Size of the Earth
· There are some intriguing coincidences related to our biological design and our ability to utilize fire. A carbon-based organism of our size and design possessing an upright bipedal posture is only feasible on a planet of approximately the size and mass of the earth. It is the size of the earth (or more specifically, its total mass) which determines the strength of its gravitational field. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p244.]
· If the earth had only twice the diameter, its gravitational field would be eight times stronger and a large upright bipedal creature like ourselves would not be feasible. In a very important sense, then, the earth’s size is fit for the design of a bipedal animal of the dimensions of a man and therefore fit for our ability to handle fire. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p244.]
Muscles and Movement
· The manipulation of fire necessitates movement. In the case of a large organism the size of a human, chis in turn necessitates special structures muscles capable of exerting mechanical forces. Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p245.]
The Speed of Nerve Conduction
· Muscles, no matter how powerful, would be of little biological value unless their movements could be carefully controlled. In the human body the control of muscular movement is carried out by the nervous system. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p249.]
Alternative to Homo Sapiens
· In a thoughtful analysis of man’s evolutionary history and the acquisition of our unique biological adaptations, Sir Julian Huxley concluded: Writers have indulged their speculative fancy by imagining other organisms endowed with speech and conceptual thought-talking rats, rational ants, philosophic dogs and the like. But closer analysis shows that these fantasies are impossible. A brain capable of conceptual thought could only have been developed in a human body.21 [Huxley, op. cit., p. 8.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p255.]
· Moreover, as Huxley points out, the evolutionary generation of Homo sapiens has come about via a unique path: The essential character of man is . . . conceptual thought. And conceptual thought could only have arisen in a multicellular animal, an animal with bilateral symmetry, head and blood system, a vertebrate against a mollusc or an arthropod, a land vertebrate among vertebrates, a mammal among land vertebrates. Finally it could have arisen only in a mammalian line which was gregarious, which produced one young at birth instead of several, and which had recently become terrestrial after a long period of arboreal life. There is only one group of animals which fulfils these conditions-a terrestrial offshoot of the higher Primates. Thus not merely has conceptual thought been evolved only in man: it could not have been evolved except in man. There is only one path of unlimited progress through the evolutionary maze. The course of human evolution is as unique as its result. It is unique not in the trivial sense of being a different course from that of any other organism, but in the profounder sense of being the only path that could have achieved the essential characters of man. Conceptual thought on this planet is inevitably associated with a particular type of Primate body and Primate brain.22 [Huxley, op. cit., pp. 15-16.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p255.]
The Human Brain
· If the anthropocentric thesis is correct, then the human brain should be the most powerful possible thinking machine-biological or artificial-that can be built out of the atoms of our world. It should be peerless. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p256.]
· However, brain size alone seems to bear little direct relationship to intelligence. In man, for example, there is no obvious correlation between brain size and intellectual ability. 26 And although the brain of a dolphin may be larger than that of man or any other primate species, its neurons are far simpler and the cortical layer in the dolphin is also only about half the thickness than it is in man. 27 (Moreover, the overall design of the cetacean brain appears to have retained many primitive features.) [26. W. E. Le Gros Clark (1969) The Antecttknts of Man, 3rd ed. (Chicago: Quadrangle Books). p. 260.] [27. C. Wills (1993) The Runaway Brain (New York: HarperCollins); sec p. 7.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p256.]
· If intelligence is related to the total number of nerve cells, the total number of connections between them as well as the density of the connections, then as a recent New Scientist article puts it, “on this basis the human brain is the most complex in the animal kingdom.” Moreover, as the article continues, “no radical improvement in synaptic density may be possible because of the need to maintain the fine balance between the size and number of neurons and the blood vessels which nourish them. To produce a significant rise in processing power, the axons would have to be wider than they are now to speed up the rate at which they pass signals. This in turn would demand equivalent increases in the amount of insulation along the axons and a better blood supply, which would take up extra space in the brain cavity, leaving less room for axons.” As the article puts it, “Humans are about as smart as they are going to get.”32 [M. Ward (1997) “End of the Road for Brain Evolution,” New Scientist 153, no. 2066:14.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p]
Artificial Intelligence
· In the words of a recent Nature reviewer, “The latest work on information processing and storage at the single-cell level reveals previously unimagined complexity and dynamism.” We are left with “a feeling of awe for the amazing complexity found in nature. Loops within loops across many temporal and spatial scales.”33 [Nature, op. cit., p. 210.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p258.]
· Although the mechanistic faith in the possibility of AI still runs strong among many researchers in the field, there are also many detractors, including John Searle34 and Roger Penrose. 35 And there is no doubt that to date, as Penrose argues, no one has manufactured anything which exhibits intelligence remotely resembling that of man. [34. J. Searle (1987) “Minds and Brains Without Programs,” in Mindwavts: Thoughts on lntelligmce, Identity and Conciousness, ed. C. Blakemore and S. Greenfield (Oxford: Basil Blackwell). pp. 209-233.] [35. R. Penrose (1990) The Emperor’s New Mind (London: Vintage).] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p258.]
Homo Mathematicus
· However, there is another intriguing aspect to our success-the mutual fitness of the human mind and particularly its propensity for and love of mathematics and abstract thought and the deep structure of reality, which can be so beautifully represented in mathematical forms. In other words, the logic of our mind and the logic of the cosmos would appear to correspond in a profound way. And it is only because of this unique correspondence that it is possible for us to comprehend the world. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p259.]
· The physicist Eugene Wigner, who was much struck by the correspondence between mathematics and the physical world, spoke for many mathematicians and scientists when he remarked: It is hard to avoid the impression that a miracle is at work here …. The miracle of the appropriateness of the language of mathematics for the formulation of the laws of physics is a wonderful gift which we neither understand nor deserve.36 [E. P. Wigner (1960) “The Unreasonable Effectiveness of Mathematics in the Natural Sciences,” Communications on Pure and Applied Mathematics 13: 1-14.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p259.]
· And there are other aspects of the structure of reality which give the impression of having been tailored to facilitate our understanding of nature and ultimately the scientific enterprise itself. On this point Paul Davies comments: It is easy to imagine a world in which phenomena occurring at one location in the universe or on one scale of size or energy, were intimately entangled with all the rest in a way that would forbid resolution into simple sets oflaws. Or, to use the crossword analogy, instead of dealing with a connected mesh of separately identifiable words; we would have a single extremely complicated word answer. Our knowledge of the universe would then be an “all or nothing” affair.37 [P. C. W. Davies (1992) Tht Mina of God (London: Penguin); see p. 157.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p259, 260.]
· That the structure of the world appears to be curiously fit for human comprehension also struck Aristotle. Jonathan Lear comments that for Aristotle “the inquiry into nature revealed the world as meant to be known; the inquiry into man’s soul revealed him as a being who is meant to be a knower. Man and the world are, as it were, made for each other.38 The stupendous success of science since 1600 is testimony enough to the remarkable fitness of our mind to comprehend the world. [J. Lear (1988) Aristotle: Tht Desire to Understand (Cambridge: Cambridge University Press), p. 230.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p260.]
Part 2: Evolution
Chapter 12: The Tree of Life
The Vestiges and Directed Evolution
· An interesting early attempt to provide a comprehensive account of the evolution of life as a process directed by natural law was presented by Robert Chambers in his famous 14-stiges of the Natural History of Creation, published in 1840 and one of the best-selling books of its day. Chambers proposed that the whole pattern of evolution had been written into the cosmic script from the beginning and that all the laws of nature had been specially arranged or programmed at the original creation to generate the tree of life. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p269.]
· Moreover, Chambers’s aim to account for evolution by natural law and his view of the tree oflife as a natural form correspond closely to the view being presented here. Reviewing critically the creationist position which was the orthodox view in the early nineteenth century, he comments: In what way was the creation of animated beings effected? The.ordinary notion may, I chink, be not unjustly described as chis-chat the Almighty author produced the progenitors of all existing species by some sort of personal or immediate exertion …. How can we suppose an immediate exenion of chis creative power at one time to produce zoophytes, another to add a few marine molluscs, another to bring in one or two conchifers again to produce cruscaceous fishes …. This would surely be to take a very mean view of the creative power-to, in shore, anchropomorphise it, or reduce it to some such character as chat borne by the ordinary proceedings of mankind …. Some ocher idea must then be come to with regard to the mode in which the Divine Author proceeded in the organic creation …. We have seen powerful evidence, chat the construction of chis globe and its associates, and inferentially of all the ocher globes of space, was the result not of any immediate or personal exertion on the part of the Deity, but of natural laws which are expressions of his will …. More than chis, the fact of the cosmical arrangements being an effect of natural law, is a powerful argument for the organic arrangements being so likewise, for how can we suppose chat the august Being who brought all these countless worlds into form by the simple establishment of a natural principle flowing from his mind, was to interfere personally and specially on every occasion when a new shell-fish or reptile was to be ushered into existence on one of these worlds? Surely the idea is too ridiculous to be for a moment entertained.2 [R. Chambers ( 1969) Vestiges of the Natural History of Creation (New York: Leicester University Press), pp. 152-154.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p269, 270.]
· In Chambers’s view the “Divine attributes must appear not diminished or reduced in any way by supposing a creation by law, but infinitely exalted.” Chambers continues: If the properties adopted by the elements at the moment of their creation adapted themselves beforehand to the infinity of complicated useful purposes which they have already answered, and may still further to answer, under many such dispensations of the material world, such an aboriginal constitution, so far from superseding an intelligent agent, would only exalt our conceptions of the consummate skill and power that could comprehend such an infinity of future systems, in the original groundwork of his creation.3 [R. Chambers ( 1969) Vestiges of the Natural History of Creation (New York: Leicester University Press), p. 158.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p270.]
· Chambers saw the origin of life as being analogous to crystallization: Crystallisation is confessedly a phenomenon of inorganic matter; yet the simplest rustic observer is struck by the resemblance which the examples of it left upon a window by the frost bear to vegetable forms. In some crystallisations the mimicry is beautiful and complete; for example, in the well known one called the Arbor Dianae. An amalgam of four parts of silver and two of mercury being dissolved in nitric acid, and water equal to thirty weights of the metals being added, a small piece of soft amalgam of silver suspended in the solution quickly gathers to itself the particles of the silver of the amalgam which form upon it a crystallisation precisely resembling a shrub …. Vegetable figures are also presented in some of the most ordinary appearances of the electric fluid …. The correspondence here is curious. A plant thus appears as a thing formed on the basis of a natural electrical operation-the bush realized.4 [R. Chambers (1969) Vestiges of the Natural History of Creation (New York: Leicester University Press), pp. 165-167.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p270.]
· Chambers was led from his deterministic evolutionary model of the universe to the view that all reality, biological and physical, was in the end one immense interconnected Divine artifact.5 [R. Chambers (1969) Vestiges of the Natural History of Creation (New York: Leicester University Press), pp. 25~251.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p270.]
· The idea that behind the apparently random ramifications of the evolutionary tree there is direction imposed by the order of nature has been reiterated over and over again since 1844. One of the most recent examples is in Arthur Koestler’s Ghost in the Machine: Several eminent biologists have in recent years toyed with the idea, but without spelling out its profound implications. Thus von Bertalanffy wrote: ‘While fully appreciating modern selection theory we nevertheless arrive at an essentially different view of evolution. It appears to be not a series of accidents, the course of which is determined only by the change of environments during earth history and the resulting struggle for existence, which leads to selection within a chaotic material of mutations … but is governed by definite laws, and we believe that the discovery of these laws constitutes one of the most important tasks of the future.’ Waddington and Hardy have both re-discovered Goethe’s notion of archetypical forms; Helen Spurway concluded from the evidence of homology that the organism has only ‘a restricted mutational spectrum’ which ‘determines its possibilities of evolution.’ …10 [Such restrictions may mean chat] given the conditions on our particular planet, the chemistry and temperature of its atmosphere, and the available energies and building materials, life from its inception in the first blob of living slime could only progress in a limited number of ways …. If this conclusion is correct, it sheds some additional light on man’s status in chis universe. It puts an end to the fantasies of science fiction regarding future forms oflife on earth. . . . [It means ] … that the evolution of life is a game played according to fixed rules which limit its possibilities but leave sufficient scope for limitless variations. The rules are inherent in the structure of living matter.11 [10. A Koestler (1970) The Ghost in the Machine (London: Pan Books), p. 174.] [11. Ibid., pp. 174-175.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p272.]
The Problem of Direction
· The prevailing view of the cosmos as fundamentally nonbiocentric, governed by lifeless mechanical laws, is strikingly conveyed in this section from Hugh Miller’s Footprints of the Creator published in 1849: Nature lay dead in a waste theatre of rock, vapour, and sea, in which the insensate laws, chemical, mechanical, and electric, carried on their blind, unintelligent processes: the creative fiat went forth; and, amid waters that straightaway teemed with life in its lower forms, vegetable and animal, the dynasty of the fish was introduced.18 [H. Miller (1869) Footsteps oftht Crrator. I Ith ed. (Edinburgh: Nimmo), pp. 293–294.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p273, 274.]
· Like Roger Cotes in his introduction to Newton’s Principia, they were again affirming a faith for which neither nature nor science provided any justification. Their belief in directed evolution was, as Neal Gillespie points out in his Charles Darwin and the Problem of Creation, in effect an article of “faith held despite what nature indicated.”19 Even St. George Mivart, one of the most ferocious critics of Darwinism, conceded in his Genesis of Species (1871) “that one could not find in nature such evidence of design that no man could sanely deny.”20 [19. N. C. Gillespie (1979) Charls Darwin and tht Problem of Creation (Chicago: University of Chicago Press), p. 85.] [20. Ibid., p. 104.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p274.]
The Fitness of DNA for Directed Evolution
· This unidirectional flow of information from DNA to organism is clearly “fit” for directed evolution. In a world where the central dogma did not hold, where the genetic system was designed on different principles, where, for example, organisms had the ability to intelligently manipulate their DNA sequences at will, or where environmental factors could direct changes in DNA sequences, where information flowed from organism to DNA, it is very difficult to imagine how a long-term evolutionary program based on a programmed succession of changes in the DNA could have been feasible. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p276.]
· The Closeness of All Life in DNA Sequence Space One of the most surprising discoveries which has arisen from DNA sequencing has been the remarkable finding that the genomes of all organisms are clustered very close together in a tiny region of DNA sequence space forming a tree of related sequences that can all be interconvened via a series of tiny incremental natural steps. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p276, 277.]
· Organisms which seem very different at a morphological level can be very close together at the DNA level. One of the most dramatic cases of this is that of the cichlid fish species in Africa’s Lake Victoria. As Jared Diamond points out in The Rise and Fall of the Third Chimpanzee: Cichlids are popular aquarium species, of which about two hundred are confined to that one lake, where they evolved from a single ancestor within the last 200,000 years. Those two hundred species differ among themselves in their food habits as much as do tigers and cows. Some graze on algae, others catch ocher fish, and still others variously crush snails, feed on plankton, catch insects, nibble the scales off other fish, or specialise in grabbing fish embryos from brooding mother fish. Yet all those Lake Victoria cichlids differ from each other on the average by about 0.4% of their DNA studied.24 [J. Diamond (1992) The Rise and Fall of the Third Chimpanzee (London: Vintage); see p. 23.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p277.]
· In fact, the differences between the DNA of man and chimp can be accounted for by simple well-known mutational processes which are occurring all the time in nature at present. In the case of primate DNA, for example, all the sequences in the hemoglobin gene cluster in man, chimp, gorilla, gibbon, etc., can be interconverted via single base change steps to form a perfect evolutionary tree relating the higher primates together in a system that looks as natural as could be imagined. There is not the slightest indication of any discontinuity. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p277.]
· As Simon Conway Morris comments, “The story emerging from molecular biology is that what may look very different in anatomical terms can be founded on a basically identical genetic architecture.”25 In the case of organs as dissimilar as the heart in insects and vertebrates, for example, their development may involve common pathways.26 In short, evolution is far easier to conceive of in DNA sequence space than in morphological or phenotypic space. By analogy, it is far simpler to move from mountain to mountain on a two-dimensional map than it is to move from mountain to mountain in actual three-dimensional space. [25. S. Conway Morris (1995) “Book Reviews,” Nature 376:736.] [26. R. P. Harvey (1996) “NK-2 Homeobox Genes and Hean Development,” Deve/.opmmtal BiobJgy 178:203–216.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p278.]
· From the DNA perspective the whole evolutionary tree of life is in essence nothing more or less than a vast set of closely related DNA sequences clustered close together in the immensity of DNA sequence space, where each individual sequence is capable of specifying a viable life form, and where all sequences are interrelated and ultimately derivable via a series of steps from an original primeval sequence, which was the genome of the first life form on earth. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p278.]
Escape from Selective Surveillance
· Overall, the new DNA sequence space is fit for directed evolution in a number of ways: (1) because of the closeness of all life forms at the DNA level and because all known sequences can be interconverted in small natural steps via well-known mutational processes, (2) because information flows only from the genotype to the phenotype, and (3) because functional DNA sequences can be derived via functionless intermediates, a new phenotype or organ system can be generated by saltation. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p279.]
Directed Mutation and Development
· These rearrangements are strictly programmed and occur at precisely predetermined times in the development of the organism. There is no compelling reason why similar types of changes could not have been genetically programmed to occur during the far longer time course of evolution. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p280.]
Constraints in Sequence Space
· Given the fundamental nature of organisms, and given a specially prearranged DNA sequence space, the evolutionary process of tracing out the tree of life becomes a perfectly natural phenomenon; the inevitable unfolding of a preordained pattern, written into the laws of nature from the beginning. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p282.]
The Question of the Spontaneity of Mutation
· One of the major obstacles within the biological community in the way of any widespread acceptance of the idea of directed mutation is the very deeply held belief in the so-called spontaneity of mutation.41 According to the authorities Dobzhansky, Ayala, Stebbins, and Valentine, writing in a standard text on evolution, “Mutations are accidental, undirected, random or chance events in still another sense very important for evolution; namely chat they are unorientated with respect to adaptation.”42 [41. Dawkins, op. cit., p. 313. J. Monod (1972) Chanct and Nectssity (London: Collins), p. 114. E. Mayr (1976) Evolution and the Divmity of Life (Cambridge: Harvard University Press), p. 32.] [42. T. Dobzhansky et al. (1977) Evolution (San Francisco: W. H. Freeman), p. 65.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p285.]
· What is very remarkable about chis whole issue is chat, as is typical of any “unquestioned article of faith,” evidence for the doctrine of the spontaneity of mutation is hardly ever presented. Its truth is nearly always assumed. In nearly all the texts on genetics and evolution published over the past four decades, whenever the author attempts co justify the doctrine of the spontaneity of mutation, he refers back to a series of crucial experiments carried out in the lace forties and early fifties on the bacterium E. coli chat were associated with the names of Salvador Luria, Max Delbruck, and Joshua Lederberg.43 [T. Dobzhansky et al. (1977) Evolution (San Francisco: W. H. Freeman), p. 65.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p285.]
· But the fact that some mutations in bacteria are spontaneous does not necessarily mean that all mutations in all organisms throughout the entire course of 4 billion years of evolution have all been entirely spontaneous. This very point was made by Max Delbruck himself, who carried out with Salvador Luria some of the crucial experiments proving the spontaneity of mutation. As he conceded at a Cold Spring Harbor Symposium over forty years ago, “One should keep in mind the possible occurrence of specifically adaptive mutations.”44 [M. Delbruck (1947) Cold Spring Harbor Symposium on Quantitative Biology 11:154.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p286.]
· Recently, John Cairns, a leading microbiologist in the United States, commented in Nature on the subject of the spontaneity of mutation: “It seems to be a doctrine that has never been put to the test.”45 [J. Cairns, J. Overbaugh, and S. Miller (1988) “The Origin of Mutants,” Nature 335:142-145; seep. 145.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p286.]
The Origin of Life
· At the heart of the problem lay a seeming paradox-proteins can do many things, but they cannot perform the function of storing and transmitting information for their own construction. On the other hand, DNA can store information, but cannot manufacture anything nor duplicate itself. So DNA needs proteins and proteins need DNA. A seemingly unbreakable cycle-the ultimate chickenand- egg problem. As Monod put it in Chance and Necessity: The modern cell’s translating machinery consists of at least fifty macromolecular components which are themselves coded in the DNA: the code cannot be transUtted except by the products of trans/,ation. It is the modern expression of omne vivum ex ova. When and how did this circle become closed? It is exceedingly difficult to imagine.51 [Monod, op. cit., p. 135.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p293.]
· And Crick comments about the problem in Life Itself An honest man, armed with all the knowledge available to us now, could only state that in some sense, the origin of life appears at the moment to be almost a miracle, so many are the conditions which would have to be satisfied to get it going.52 [F. Crick ( 1981) Life Itself (New York: Simon & Schuster), p. 88.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p293.]
· The scenario looks promising, although other studies have revealed serious drawbacks:56 “Tests of the RNA-world hypothesis have shown that RNA is difficult to synthesize in the conditions that probably prevailed when life originated and that the molecule cannot easily generate copies of itself.”57 [J. Horgan (1993) “In the Beginning,” Scientific American 264 (2):101-109; seep. 101.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p294.]
· The fact that life emerged on the early earth as soon as conditions could support it points to the notion that life’s origin was a natural and highly probable event which was inevitable given certain critical conditions. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p295.]
· From a teleological perspective the origin oflife must be viewed as something quite inevitable and built into the laws of nature from the beginning, just as were the properties of water and the mutual fitness of DNA and protein and all the other coincidences in the physical and chemical properties oflife’s constituents. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p296.]
· Stephen Jay Gould, in a recent article entitled “War of the World Views” in the journal Natural History, 65 proposes “that the simplest kind of cellular life arises as a predictable result of organic chemistry and the physics of self-organizing systems but that no predictable directions exist for life’s later development.”66 [65. S. J. Gould (1996) “War of the World Views,” Natural History 105:22-33.] [66. Ibid., p. 30.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p296.]
Conclusion
· This raises the very natural but heretical idea, which has been explored in this chapter, that if the cosmos is fit for the being of higher life forms, then surely it is not inconceivable that an evolutionary mechanism for their actualization could also have been written into the order of things and that perhaps the entire process of biological evolution, from the origin of life to the emergence of man, was somehow directed from the beginning. I believe that our current knowledge of molecular genetics sanctions such possibilities. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p298.]
Chapter 13: The Principle of Plenitude
· Before the rise of Darwinism it was widely believed that all possible living forms had actually been realized in nature. It was argued that an omnipotent Creator who had fashioned all the laws of nature to the end of life and man would surely have so organized these laws to make manifest in material form all possible biological types. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p302.]
Chapter 15: The Eye of the Lobster
· Among the most persistent challenges to the Darwinian model of evolution are those many types of complex and unusual adaptations whose evolution is very difficult to account for in terms of a gradual accumulation of successively advantageous changes. The literature of biology is full of examples. The challenge arises because evolution by natural selection can only occur via functional intermediates. Consequently, to get from A to Z by natural selection each step on the path-A to B, B to C, etc.-must be advantageous, and this imposes very stringent constraints on permissible evolutionary paths. Darwin himself spent two chapters of the Origin attempting to explain how the origin and evolution of what he called “organs of extreme perfection” may be plausibly accounted for by a gradual accumulation of minor undirected changes. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p354.]
The Eye of the Lobster
· One of the most striking features of the lobster eye which is immediately obvious even on superficial inspection is that the facets of the eye are perfect squares (see page 352). It is very unusual to meet with perfectly square structures in biology. As one astronomer commented in Science: “The lobster is the most unrectangular animal I’ve ever seen. But under the microscope a lobster’s eye looks like perfect graph paper.”1 [J. R. P. Angel (1979) “Lobster Eyes as X-ray Telescopes,” AJtrophysical Journal 233:364-373. See also B. K. Hartline (1980) “Lobster-Eye X-ray Telescope Envisioned,” Science 207:47.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p]
· This unique optical system is found in only one group of crustaceans, the so-called long-bodied decapods, which include the shrimps, the prawns, and lobsters. The great majority of crustaceans, and indeed of all invertebrates, have refracting eyes which are based on a completely different design. In these eyes each unit contains a small lens which refracts or bends the light onto the focus on the retina. Moreover, che units are hexagonal or round. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p355.]
· However, just what selection pressures may have been responsible and through what intermediate states the reflecting eye evolved is a mystery. The transformation is puzzling because it is very difficult to imagine how the units in some transitional eye-halfway between a hexagon and a square, halfway between a lens and a reflecting surface-could form a better image than the original refracting eye. Consequently, it is difficult to see how those halfway, intermediate eyes would have been selectively advantageous in an evolutionary sense. This is critical, because evolution by natural selection can only follow an evolutionary route from A to B if each step taken on the route to B is adaptively advantageous and confers some increased survival value on the organism. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p356.]
· Why should an organism drop its perfectly functional refracting eyes and start out on the hazardous journey to reflection? Refracting eyes provide organisms with excellent image-forming capabilities, as witness the flight of the dragonfly. Many crustacean cousins of the lobster-crabs, for example- which occupy the same ecological niche as the lobster and have the same predatory lifestyle-have refracting eyes and obviously survive quite well in the same level of illumination. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p356.]
The Eye of the Scallop
· The visual system is remarkably complex and sophisticated. Amazingly, the scallop has not one but sixty of these tiny image-forming eyes. What is so striking is the apparent gratuity of the whole system. Why has such a simple organism evolved such a complex image-forming eye? [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p357.]
· William J. Dakin, a professor of zoology at Liverpool University before the Second World War and one of the first to describe the eye in detail, had problems accepting the Darwinian explanation. According to Darwin in chapter 6 of the Origin: When we reflect on these facts … with respect to the wide, diversified and graduated range of structure in rhe eyes of rhe lower animals; and when we bear in mind how small the number of living rhings must be in comparison with those which have become extinct, rhe difficulty ceases to be very great in be lieving that natural selection may have converted the simple apparatus of an optic nerve … into an optical instrument as perfect as is possessed by any other member of the Articulate Class. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p357, 358.]
· Commenting on this section, Dakin remarks: This is an optimistic view of the problem rather than evidence; it is a view to which I find it very difficult to subscribe in so far as the eyes of the Pectinidae are concerned. Indeed after a careful comparative study of the visual organs of the invertebrates one finds greater difficulty in accepting the principle of natural selection as the dominant factor in their origin than is the case with any other of their morphological features.5 [W. J. Dakin (1928) “The Eyes of Ptcten, Spondylus, Amussium, and Allied Lamellibranchs, with a Shon Discussion on Their Evolution,” Procttding.r of the Royal Society of London, Snits B 103:355-365; see pp. 359-360.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p358.]
· Dakin continues: Now it is very difficult to conceive of a complex structure, complex as these eyes, being the final result of a sifting by natural selection of a large number of chance variations, stress being laid on external factors. Indeed there is grave doubt as to whether the presence of any variations that might lead to such organs could have any survival value.6 [W. J. Dakin (1928) “The Eyes of Ptcten, Spondylus, Amussium, and Allied Lamellibranchs, with a Shon Discussion on Their Evolution,” Procttding.r of the Royal Society of London, Snits B 103:355-365; see p. 361.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p358.]
· Dakin concludes that the size and complexity of the eyes in Pectinidae cannot be explained by natural selection: Whatever may have been the origin of the eyes of the Pecten group I do not hold that utility explains their evolution … in the case of Pectinidae there is no evidence of the elimination of types with less complex eyes as unfit … in view of the diverse conditions existing in the Larnellibranchs there is no evidence that a reduction in the efficiency of the eyes of Pecten would lead to unfitness …. We cannot escape from the conviction that in one particular series of bivalves, all intimately related genetically, a distinct type of visual organ arose, independent of other visual organs, and that apart from adaptation, and apart from utility or advantageousness, it attained a certain extraordinary complexity.7 [W. J. Dakin (1928) “The Eyes of Ptcten, Spondylus, Amussium, and Allied Lamellibranchs, with a Shon Discussion on Their Evolution,” Procttding.r of the Royal Society of London, Snits B 103:355-365; see p. 364.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p358.]
The Marsupial Frogs
· Again, as in the two cases cited above, it is hard to believe that any sort of unguided evolutionary mechanism would have realized such an unusual adaptive end. Moreover, changing the basic organization of an embryo would appear to be far more radical than any of the other changes cited above. And again, for this co happen under the agency of natural selection, each one of the individual seeps along the evolutionary route must have been selectively advantageous. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p360.]
The Avian Lung
· Just how such a different respiratory system could have evolved gradually from the standard vertebrate design without some sort of direction is, again, very difficult to envisage, especially bearing in mind that the maintenance of respiratory function is absolutely vital to the life of the organism. Moreover, the unique function and form of the avian lung necessitates a number of additional unique adaptations during avian development. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p361.]
· The idea that an adaptation like the avian lung might evolve before its full utility can be exploited is perfectly consistent with a directed model of evolution. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p362.]
The Evolution of the Human Brain
· Perhaps the most celebrated and well-known example is the case of human intelligence. Many have commented on the striking fact that our intellectual capabilities, especially our capacity for abstract mathematical thought, upon which the whole enterprise of science is ultimately based, seems vastly in excess of any conceivable intellectual needs of the small tribe of hunter-gatherers who lived in Africa some 200,000 years ago and were the last common ancestors of all modern humans. What selection pressures on the ancient plains of Africa gifted mankind with musical ability, artistic competence, the capacity for profound abstraction, and ultimately the ability to comprehend the entire cosmos from which we sprang. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p]
· Commenting on the evolu~ionary conundrum posed by our intellectual capabilities in his recent book The Mind of God, Paul Davies reminds us “that the success of the scientific enterprise can often blind us to the astonishing fact that science works,” and he continues: What is remarkable is that human beings are actually able to carry out this code-breaking operation, that the human mind has the necessary intellectual equipment for us to “unlock the secrets of nature.” The mystery in all this is that human intellectual powers are presumably determined by biological evolution, and have absolutely no connection with doing science. Our brains have evolved in response to environmental pressures, such as the ability to hunt, avoid predators, dodge falling objects, etc …. John Barrow is also mystified: “Why should our cognitive processes have tuned themselves to such an extravagant quest as the understanding of the entire universe? … None of the sophisticated ideas involved appear to offer any selective advantage to be exploited during the pre-conscious period of our evolution …. How fortuitous that our minds (or at least the minds of some) should be poised to fathom the depths of nature’s secrets.”14 [P. C. W. Davies, (1992) TheMindofGod(London: Penguin), p. 149.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p362, 363.]
· How very fortunate indeed that evolution should have gifted a mind so fit for the scientific enterprise in a physical form so fit to that same unique end long before that enterprise was undertaken. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p363.]
Can Organisms Direct Their Own Evolution?
· Although it seems implausible that such complex adaptations could have resulted from any sort of undirected process, the question arises as to whether or not the direction was built into nature from the beginning or was the result of other secondary phenomena. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p363.]
· In the context of a teleological view of the cosmos, even if much of the overall order of organic nature was determined from the beginning, it is surely conceivable that the Creator, to paraphrase Darwin in the last paragraph of the Origin of Species, could have gifted organisms not only with the capacity for growth, reproduction, inheritance, and variability,19 but also with a limited degree of genuine autonomous creativity so that the world of life might reflect and mirror in some small measure the creativity of God. [Darwin, op. cit., p. 484.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p365.]
Conclusion: The Long Chain of Coincidence
· The fact remains that to date no artifact has ever been discovered on Earth which might be interpreted as a “Chariot of the Gods.” No structure or piece of machinery has ever been found that might have been constructed by aliens here on earth, or left by ancient star travelers from another world. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p377.]
· We still have at present no direct empirical evidence that the laws of physics might permit the existence of life or of intelligent beings designed along principles fundamentally different from those governing life on Earth. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p378.]
· Despite the optimism of the gurus in the fields of exobiology, artificial life, and nanotechnology, no even remotely detailed blueprint for an alternative feasible self-reproducing system has been worked out. Although the possibility cannot be completely excluded, from the evidence now available it seems increasingly unlikely that life can be realized in any other material system in our cosmos. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p380.]
· What is so particularly impressive and so highly suggestive about these life-giving adaptations is that what at first sight seem to be very trivial aspects of the chemistry and physics of a particular component turns out to be of critical significance for its biological role. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p382.]
· It is important also to recall that the vital mutual adaptations are in the essential nature of things and are not the product of natural selection. This was also stressed by Henderson: “Natural selection does but mould the organism without truly altering the primary qualities of environmental ficness.”13 [Feinberg and Shapiro, op. cit., pp. 274-275.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p382.]
· Commenting on Henderson’s arguments, the great biologist Joseph Needham stressed the same point: “Since the properties of water and the … elements antedate the appearance of life … they can be regarded philosophically as some sort of preparation for life. Purposiveness, then, exists everywhere, it permeates the whole universe …. Restricted teleology melts away in the immensity of that discussed by Lawrence Henderson.”14 [J. Needham (1929) The Skeptical Biologist (London: Chatto & Windus), p. 217; see pp. 210-218 for a review of Henderson’s Fitness.] [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p383]
· The evidence that life’s becoming is also built into nature, presented in the second part of the book, is admittedly not as convincing as the evidence presented in the earlier chapters. But it is consistent with the possibility. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p383.]
· The strength of any teleological argument is basically accumulative. It does not lie with any one individual piece of evidence alone but with a whole series of coincidences, all of which point irresistibly to one conclusion. It is the same here. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p384.]
· Rather, it lies in the summation of all the evidence, in the whole long chain of coincidences which leads so convincingly toward the unique end oflife, in the fact that all the independent lines of evidence fit together into a beautiful selfconsistent teleological whole. The evolutionary evidence is similar; it compounds. In isolation, the various pieces of evidence for direction, the speed of evolutionary change, the fantastic complexity of living things, the apparent gratuity of some of the ends achieved, are perhaps no more than suggestive, but taken together, the overall pattern points strongly to final causes. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p384.]
· Note also that theories or worldviews are most often accepted not because they can explain everything perfectly but because they make sense of more than any competitor does. Evolution was accepted in the nineteenth century not because it explained everything perfectly but because it accounted for the facts better than any other theory. Similarly, the teleological model of nature presented here is far more coherent and makes far more sense of the cosmos than any currently available competitor. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p385.]
· The idea that the cosmos is a unique whole with life and mankind as its end and purpose makes sense and illuminates all our current scientific knowledge. It makes sense of the intricate synthesis of carbon in the stars, of the constants of physics, of the properties of water, of the cosmic abundance of the elements, of the existence throughout the cosmos of organic matter, of the fact that the two adjacent planets Earth and Mars appear so similar, that the atombuilding process continues to uranium. No other worldview comes close. No other explanation makes as much sense of all the facts. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p385.]
· Whether one accepts or rejects the design hypothesis, whether one thinks of the designer as the Greek world soul or the Hebrew God, there is no avoiding the conclusion that the world woks as if it has been uniquely tailored for life: it appears to have been designed. All reality appears to be a vast, coherent, teleological whole with life and mankind as its purpose and goal. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p387.]
· All the evidence available in the biological sciences supports the core proposition of traditional natural theology-that the cosmos is a specially designed whole with life and mankind as its fundamental goal and purpose, a whole in which all facets of reality. from the size of galaxies to the thermal capacity of water, have their meaning and explanation in this central fact. [Michael J. Denton, Nature’s destiny: How the Laws of Biology Reveal Purpose in the Universe, The Free Press, New York 1998, p389.]
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