I am a bipedal hominid, of average cranial capacity, write my manuscripts with a fountain pen, and loathe jogging. Thanks to years of work by innumerable biologists I, or anyone else, can tell you to a fair degree of accuracy when the ability to walk upright began, the rate at which our brain increased to its present and seemingly astonishing size, and the origin of the five-fingered forelimb whose present versatility allows me to hold a pen, not to mention the fishy origin of those lungs that make such a noise as the joggers pass me early in the morning on Cambridge's Midsummer Common.
It is obvious that the entire fabric of evolution is imprinted on and through our bodies, from the architecture of our bony skeleton, to the proteins carrying the oxygen surging through our arteries, and our eyes that even unaided can see at least two million years into the past - the amount of time it has taken for the light to travel from the Andromeda Galaxy. In every case - whether for hand or brain - we can trace an ancestry that extends backwards for hundreds of millions, if not billions, of years. Yet, for all that, both the processes and the implications of organic evolution remain controversial. Now at first sight this is rather odd, because it is not immediately clear what is being called into question. Certainly not the fact of evolution, at least as a historical narrative: very crudely, first bacteria, then dinosaurs, now humans. More specifically in terms of process, Darwin's formulation of the mechanisms of evolution is not only straightforward, but seemingly irrefutable. Organisms live in a real world, and evolve to fit their environment by a process of continuous adaptation. This is achieved by a constant winnowing through the operation of natural selection that scrutinizes the available variation to confer reproductive success on those that, by one yardstick or another, are fitter in the struggle for survival.
So is that all there is to say? The recipe for evolution just given is a decidedly bald summary. One intuitively senses that it is an inherently feeble response to an extraordinarily rich history that has brought forth an immense coruscation of form and diversity. Among living forms this ranges across many scales of complexity, from bacteria that build colonies like miniature trees1 to immense societies of ants whose populations run into the millions and, independent of us, have stumbled across the advantages of agriculture (Chapter 8). And it is a history that is by no means confined to the complexity of colonies or the limpidity of a geometric shell. It is as much in the range, scope, and acuity of living organisms. They may be mere machines, but consider those owls whose hearing can pinpoint within a two-degree arc the rustling made by a mouse,2 the navigational abilities of albatrosses across the seemingly trackless Southern Ocean3 (Fig. 1.1), or even Nellie the cat that smelled Madagascar across more than two hundred miles of ocean.4 But despite our admiration, wonder, and - if we are candid - even awe, surely we can still offer the following paraphrase: evolution happens, this bone evolved from that one, this molecule from that one. To be sure, not every transformation and transition will be elucidated, but we are confident this is because of a lack of information rather than a failure of the method.
Yet despite the reality that, as it happens, we humans evolved from apes rather than, say, lizards, let alone tulips, the interpretations surrounding the brute fact of evolution remain contentious, controversial, fractious, and acrimonious. Why should this be so? The heart of the problem, I believe, is to explain how it might be that we, a product of evolution, possess an overwhelming sense of purpose and moral identity yet arose by processes that were seemingly without meaning. If, however, we can begin to demonstrate that organic evolution contains deeper structures and potentialities, if not inevitabilities, then perhaps we can begin to move away from the dreary materialism of much current thinking with its agenda of a world now open to limitless manipulation. Nor need this counter-attack be anti-scientific: far from it. First, evolution may simply be a fact, yet it is in need of continuous interpretation. The study of evolution surely retains its fascination, not because it offers a universal explanation, even though this may appeal to fundamentalists (of all persuasions), but because evolution is both riven with ambiguities and, paradoxically, is also rich in implications. In my opinion the sure sign of the right road is a limitless prospect of deeper knowledge: what was once baffling is now clear, what seemed absurdly important is now simply childish, yet still the journey is unfinished.
figure 1.1 Two trackways, obtained by satellite monitoring, of the Wandering Albatross across the Southern Ocean. Dots indicate data intercepts, and arrows direction of travel. The upper panel is a departure from South Georgia, on its 13-day trip it passed the Falkland Islands and subsequently Tierra del Fuego. Apart from the distance covered, note the near-straight-line intercept for home. Lower panel is an excursion from Crozet Islands; note how close are the outward and return pathways. (Redrawn from fig. 4b of P. A. Prince et al. (1992), Satellite tracking of wandering albatrosses (Diomedea exulans) in the South Atlantic, Antarctic Science, vol. 4, pp. 31-6 (upper panel) and fig. 8A of H. Weimerskirch et al. (1993), Foraging strategy of Wandering Albatrosses through the breeding season: A study using satellite telemetry, The Auk, vol. 110, pp. 325-42 (lower panel), with permission of the authors, Cambridge University Press, and The Auk.)
One such ambiguity is how life itself may have originated. As we shall see (in Chapter 4) there is no reason to doubt that it occurred by natural means, but despite the necessary simplicity of the process, the details remain strangely elusive. Life itself is underpinned by a rather simple array of building blocks. Most notable are the four (or more accurately five) nucleotides (that is molecules, such as adenine, consisting of a ring of carbon atoms with an attached nitrogen, a phosphate, and a sugar) that comprise the DNA (and RNA). The other key building blocks are twenty-odd amino acids that when arranged in chains form the polypeptides and ultimately the proteins. Yet, from this, by various elaborations, has arisen the immense diversity of life. At first sight this would seem to encapsulate the entire process of evolution, yet it soon becomes clear that we hardly understand in any detail the links between the molecular substrate and the nature of the organism. To be sure, there is some crude correlation between the total number of genes and the complexity of the organism, but when we learn that the 'worm' of molecular biologists (the nematode Caenorhabditis elegans), which has a relatively simple body plan with a fixed number of cells, has more genes than the 'fly' (the fruit-fly Drosophila) with its complex form and behaviour, then there should be pause for thought (see Chapter 9).
One response is to reconsider what we mean by 'the gene'. In particular, it is time to move away from a crippling atomistic portrayal and rethink our views. As has been pointed out by numerous workers, the concept of the gene is without meaning unless it is put into the context of what it is coding for, not least an extremely sophisticated biochemistry. Nor are these the only complications. It is well known that significant quantities of DNA, at least in the eukaryotic cell (that is a cell with a defined nucleus and organelles such as mitochondria), are never employed in the process of coding. Pejoratively labelled as 'junk DNA' or 'parasitic DNA', it may be just that, silent and surplus DNA churned out by repeated rounds of duplication of genetic material, like an assembly line commandeered by lunatic robots.5 Such a view fits well with the notion that evolution is a process of blind stupidity, a meaningless trek from primordial pond to glassy oceans dying beneath a swollen Sun.
So, beyond the brute fact that evolution happens, the mechanisms and the consequences remain the subject of the liveliest debate and not infrequently acrimony. But, contrary to the desires and beliefs of creation 'science', the reality of evolution as a historical process is not in dispute. And whatever the divergences of opinion, which as often as not have a tacit ideological agenda concerning the origins of human uniqueness, there is a uniform consensus that vitalism was safely buried many years ago, and the slight shaking of the earth above the grave marking the resting place of teleology is certainly an optical illusion. But is it an illusion? Perhaps as the roots and the branches of the Tree of Life are more fully explored our perspectives will begin to shift. Evolution is manifestly true, but that does not necessarily mean we should take it for granted: the end results, be it the immense complexity of a biochemical system or the fluid grace of a living organism, are genuinely awe-inspiring. Could it be that attempts to reinstall or reinject notions of awe and wonder are not simply delusions of some deracinated super-ape, but rather reopen the portals to our finding a metaphysic for evolution? And this in turn might at last allow a conversation with religious sensibilities rather than the more characteristic response of either howling abuse or lofty condescension.
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