Chapter 9 The Mystery of the Possibility of Life
Chapter 9
The Mystery of the Possibility of Life
One of the most significant scientific discoveries of the last generation is that the universe was pregnant with the possibility of human existence right from its very start. The laws of nature seem to be “fine-tuned” in order to make life possible. As we noted in an earlier chapter, the early universe produced nearly nothing other than hydrogen and helium. Yet the chemistry upon which life depends is ultimately the chemistry of carbon, and there is only one place in the whole universe where carbon can be created: inside stars. If the fundamental constants of nature were not what they actually are, stars might never have formed. The heavier elements on which life depends—such as carbon, nitrogen, and oxygen—were all created within stellar cores.
So how are we to account for the origins of life? Nobody really knows the answer to this question. What can be said, however, is that biochemically critical elements such as carbon, nitrogen, and oxygen did not form, and could not have formed, in the early history of the universe. Their existence is the consequence of the “clumping” or “accretion” of material into stars, with the subsequent initiation of nuclear fusion reactions. Carbon is essential to life. Yet its origins depend totally on how the universe developed after the big bang. The ratio of the gravitational binding force to rest-mass energy is such that it permitted the gradual “clumping” of material into larger bodies: the stars. Stars form as a result of turbulence in giant clouds of matter within the tenuous interstellar medium. All the heavier elements of the universe, from carbon upward, are believed to be the result of nuclear fusion within stars, and not to be a direct outcome of the primordial fireball. Without the formation of stars, the universe would have been limited to hydrogen and helium, with only a tiny percentage of other elements, such as lithium and beryllium.1
The nucleosynthesis of carbon, nitrogen, and oxygen must therefore be regarded as essential to the emergence of life. The formation of carbon requires the fusion of three helium nuclei (also known as “alpha-particles”), through a twofold process involving the element beryllium as an intermediate. Two helium nuclei initially fuse to form beryllium, which then captures a third helium nucleus to create carbon. We can set this out technically as follows:
4He + 4He → 8Be
8Be + 4He → 12C
This fusion process occurs rapidly only at very high temperatures in stellar interiors having a high helium abundance. The probability of such a double fusion is very low, since 8Be is a very unstable and short-lived nucleus. This could lead to a “beryllium bottleneck,” preventing the production of heavier nuclei, including oxygen, which would result from the fusion of a carbon nucleus with a further helium nucleus, as follows:
12C + 4He → 16O
Yet if all the 12C was converted to 16O, carbon would not be produced in sufficient quantities to allow for the emergence of life.
In what is recognizably an anthropic argument, the astronomer Fred Hoyle argued during the 1950s that there had to be a yet-undiscovered aspect of the nuclear chemistry of carbon that would allow the production of carbon and oxygen in comparable biophilic quantities. There had to be some yet-undiscovered secret about the deep structure of carbon which accounted for this. The secret was subsequently discovered by William Fowler, who investigated the matter at Hoyle’s request. It turned out that the energy levels of oxygen and carbon nuclei were “just right” to allow both to form in the proportions necessary for carbon-based life forms, such as those which we know.
In a later reflection, Hoyle mused about the possible theological implications of this remarkable observation:
From 1953 onward, Willy Fowler and I have always been intrigued by the remarkable relation of the 7.65 MeV [million electron volts] energy level in the nucleus of 12C to the 7.12 MeV level in 16O. 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 where these levels are actually found to be. Another put-up job? Following the above argument, I am inclined to think so. A commonsense interpretation of the facts suggests that a superintellect has monkeyed with physics, as well as with chemistry and biology, and that there are no blind forces worth speaking about in nature.2
The origins of life are thus unquestionably anthropic. They depend upon the fundamental values of constants of nature being such that the universe is able to progress beyond the formation of atomic hydrogen and thus bring about the nucleosynthesis of biologically critical elements. If they had been otherwise, this process might never have begun.
No life forms are known that are based solely upon hydrogen, helium, or lithium—the three lightest elements, all of which were created in the primordial big bang. The big bang, in itself and of itself, was not capable of producing the elements upon which life depends: carbon, nitrogen, and oxygen. Stellar nucleosynthesis is required for their production, which in turn depends upon the clumping of matter after the big bang to form stars. The formation of stars depends upon the value of the gravitational constant, which is regularly cited as an example of fine-tuning. Similarly, the strong nuclear force defines how firmly atomic nuclei bind together and hence the extent to which stars can transmute hydrogen into atoms of the heavier elements. Its value is of critical importance if nucleosynthesis is to take place in stellar interiors.
Yet it is not simply the origins of the universe that seem to show evidence of fine-tuning. A good case can be made for the same patterns emerging at the biological level.3 It is generally agreed that living systems require two fundamental components: (1) a self-maintaining metabolic system and (2) a genetic system capable of transmitting biological information. Both of these turn out to be critically dependent on the properties of certain chemical elements, which could have been very different.
In recent years, a new field of research has opened up, exploring the remarkable role played in the development of life by metal ions. The term “bioinorganic chemistry” is sometimes used to refer to the exploration of the remarkable biological significance of small traces of metal ions in critical processes, such as photosynthesis and oxygen transport. This field was pioneered in the 1950s by R. J. P. Williams at Oxford University: since then it has become a leading area of scientific research.4 If the chemical properties of the elements were slightly different, many of the key chemical reactions on which life depends could not take place. The conversion of light to chemical energy in photosynthesis, and the “fixation” of atmospheric nitrogen by plants to produce essential nutrients—these are examples of critical chemical processes upon which life depends. If the fundamental properties of the elements of the universe were different, these reactions might not be able to take place, and life as we know it could not have emerged.
Furthermore, it is clear that a capacity to encode information is of decisive importance for evolution in general and evolvability in particular. And that is critically dependent upon the organic chemistry of carbon, which permits the formation of long, stable chains. No other element has this property; without it, complex molecules essential to life such as RNA (ribonucleic acid) and DNA (deoxyribonucleic acid) would be impossible, as would the replicative processes they control. The capacity of evolution to fine-tune itself is thus ultimately dependent on fundamental chemical properties which in themselves can thus be argued to represent a case of robust and fruitful fine-tuning.
This point is consistently overlooked in many accounts of evolution, which seem to treat physics and chemistry as essentially irrelevant background information to a discussion of evolution. Yet before life can begin, let alone evolve, this biological process requires the availability of a stable planet, irradiated by an energy source capable of chemical conversion and storage, and the existence of a diverse array of core chemical elements with certain fundamental properties. Biology has become so used to the existence and aggregation of highly organized attributes that they are seen primarily as core assumptions of evolutionary theory, rather than something that requires explanation in its own right. There is an implicit assumption that life would adapt to whatever hand of physical and chemical cards were dealt it. Yet this is untested and intrinsically questionable. The emergence of life cannot be studied in isolation from the environment that creates the conditions and provides the resources that make this possible.
So how are these observations to be explained and their significance to be assessed? For the theist, unsurprisingly, these observations point to the inherent potentiality with which the Creator has endowed creation. The relatively recent and unexpected discovery of anthropic phenomena has led to considerable discomfort on the part of some cosmologists, who are uneasy that a new lease of life has been given to discussion of apparent design in the cosmos. This has led to intense discussion of possible explanations of these observations, sometimes driven as much by the hope of eliminating the new styles of natural theology that have emerged in recent years as by the yearning to understand the cosmos better.
It is quite clear that anthropic phenomena fit easily and naturally into a theistic framework, especially its Trinitarian forms. Theologians do not hold that the Christian doctrine of God allows us to predict the specifics of the universe; the general view has always been that, since God made the cosmos with no constraining influences other than the divine will and nature, it could have been created in a variety of manners. René Descartes (1596–1650) thus argued that we must use empirical evidence to determine the structure of the world. There is no question of predicting the form of the world on theological grounds; rather, the form of the world is a contingency which is to be determined empirically and then shown to be consistent with the known will of God.
There is no question of predicting the form of the world on theological grounds; rather, the form of the world is a contingency which is to be determined empirically and then shown to be consistent with the known will of God.
The observation of anthropic phenomena is thus situated within a long tradition of theological and metaphysical reflection on God as an explanation of the universe. It holds that the general phenomenon of fine-tuning is consonant with Christian belief in a creator God, arguing that the nature of things is such that the most appropriate outcome for a natural theology is to demonstrate that observation of the natural world furnishes conceptual resonance with the Christian vision of God, but not deductive proof of that vision. On this approach, theism offers the best “empirical fit” of the various theories which set out to account for anthropic phenomena. Yet it must be emphasized that Christian theology has never seen itself as charged with the task of inventing an explanation for these observations; rather, they fit within, and resonate with, an existing way of thinking, which proves capable of satisfactorily incorporating such observations.
God, then, unquestionably represents a plausible explanation of anthropic phenomena. But is this the best explanation? We can’t be sure. Alternative perspectives certainly exist. For example, some argue that apparent cosmic fine-tuning is nothing more than an interesting happenstance, a delightful fluke. The fundamental constants in question had to have some value—so why not these values? They need possess no further significance. To give an example: the population of the United States of America is a bit over 300 million. There is only one president. The odds of any one American becoming president are thus about one in three hundred million. But so what? Someone has to be president. It may be highly improbable that any given individual should be president, but it is a certainty that someone will be.
Yet this presidential analogy is clearly invalid. The rules of the game are that somebody has to be president of the United States. But the universe didn’t have to come into being. It’s the fact that it’s here, as much as the fact that it is highly improbable, which calls out for explanation. In any case, the “biofriendliness” we observe in the universe is far in excess of what is needed to give rise to a few observers like us. If it were the result of random processes, we might expect the observed universe to be minimally rather than optimally biofriendly. But the degree of biofriendliness seems to exceed that in many ways.
Another approach has generated considerable interest: the multiverse. On this view, a multiplicity of universes exist, so that the one we inhabit is an inevitability. We happen to live in a universe with these biologically friendly properties; we do not observe other universes, where these conditions do not pertain. Our insights are restricted by observation-selection effects, which means that our location within a biophilic universe inclines us to propose that the entire cosmos possesses such properties, when in fact other universes will exist which are inimical to life. Indeed, such biophobic universes are predicted to be the norm. We happen to exist in an exceptional universe. On this model, our observable and life-friendly universe is just one of many, a miniscule region or “bubble” within this vast spatial structure of multiple universes.
At present, the multiverse hypothesis remains little more than a fascinating yet highly speculative mathematical exercise. It has, perhaps unwisely, been adopted by atheists anxious to undermine the potential theological significance of fine-tuning in the universe. Thus part of the attraction of the multiverse hypothesis to atheistic physicists such as Steven Weinberg and Leonard Susskind seems to be that it appears to avoid any inference of design or divinity. In fact, however, substantially the same arguments can be brought to bear for the existence of God in the case of a multiverse as in that of a universe, with the multiverse hypothesis being consistent with a theistic understanding of God, not the intellectual defeater of that understanding.5
Let’s consider this possibility of the multiverse in more detail. If valid, it means that there is no universal set of laws governing the totality of reality. The laws of physics we observe in our universe are not universal, but are more like local by-laws, valid only in our own locality. This immediately raises some difficult questions about the universality of natural science, which increasingly becomes seen as a local, rather than a cosmic, enterprise. To understand the universe we know, we have to propose something outside our universe to explain it. In this case, the explanation takes the form of an unexplained universe-generating and law-generating mechanism, not to mention a vast array of invisible universes. These cannot be seen or proved. In terms of its structure, this argument is remarkably like the Christian claim that an unexplained transcendent God is the ultimate ground and explanation of all things. Those who appeal to God and those who appeal to the multiverse both seek a final explanation of the universe from outside.
So where does this leave us? As I have stressed, the fine-tuning of the universe proves nothing. But it resonates strongly with the Christian vision of reality, fitting easily and naturally into the map of reality which emerges from the Christian faith. The capacity of Christianity to map these phenomena is not conclusive proof of anything. It is, however, highly suggestive. It is one among many clues, accumulating to give an overall big picture of reality. It is one among many threads which can be woven together to yield a patterned tapestry. Fine-tuning is a clue to the meaning of the universe, insignificant in isolation, but richly suggestive when set alongside other such clues—some of which we shall consider in what follows.