Why Us?: How Science Rediscovered the Mystery of Ourselves
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The discovery of the fossilised bones of Cromagnon man in 1868, together with those of his beetle-browed Neanderthal predecessors, would roll back man’s evolutionary history 200,000 years or more. It was not however till the 1930s that the first evidence of the more distant stages would begin to emerge, and not till the 1970s, when the first of two near-complete fossilised skeletons was unearthed in the harsh landscape of central Africa, that Darwin’s hypothesised transition from that ape-like common ancestor to Homo sapiens would be vindicated.
Those two near-complete skeletons were, first, the three-and-a-half-million-year-old ‘Lucy’, or Australopithecus afarensis to give her her scientific name, whose discovery had such a powerful and emotional effect on Donald Johanson and Tom Gray (‘…we hugged each other, sweaty and smelly, howling and hugging in the heat-shimmering gravel’), as already described. One set of fossilised remains can look remarkably like another, but the vital clue, and the source of their exhilaration, lies in the sharp upward angle of the head of the femur, or upper thigh bone, that locates the centre of gravity of the human skeleton in the small area enclosed by two feet placed together – confirming that Lucy was the first of our most distant ancestors to stand upright.
Lucy’s novel method of locomotion would be confirmed soon after with the discovery of an amazing series of three sets of footprints left behind in the volcanic ash of the Laetoli region of northern Tanzania three and a half million years ago, that provide a most moving insight into the human relationships of those distant ancestors.
‘The footprint records a normal positioning of the left and right feet with human-like big toes,’ writes British neurologist John Eccles.
The special feature is that one individual followed the other, placing its feet accurately in the preceding footsteps. The third was smaller and walked closely to the left following the slightly wavy walk of the larger. We can interpret this as showing that two of the group [mother and child?] walked together holding hands, while another [sibling?] followed accurately placing its feet into the footsteps of the leader. We are given a privileged view of a family taking a walk on the newly formed volcanic ash 3.6 million years ago, just as we might do on soft sand left by the receding tide!
Ten years later, in 1984, near the ancient Lake Turkana in Kenya, the famous palaeontologist Richard Leakey discovered a further near-complete skeleton, ‘Turkana Boy’, an adolescent of the species Homo erectus from around 1.6 million years ago, with a skull intermediate in size between Lucy and ourselves – reflecting that second unique evolutionary characteristic of the human species, his prodigiously enlarging brain.
Turkana Boy’s ‘people’, Homo erectus, were the first to make tools, reflecting that manual dexterity which is a further unique attribute of humans, made possible by the seemingly trivial evolutionary advantage of lengthening the thumb by an extra inch to make it ‘opposable’, allowing it to ‘speak to’ the other four digits.
‘In man the most precise function that the hand is capable of is to place the tip of the thumb in opposition to the tip of the index finger, so they make maximum contact,’ writes the British anatomist John Napier. ‘In this position small objects can be manipulated with an unlimited potential for fine pressure adjustments or minute directional corrections. This is the hallmark of mankind. No non-human primate can replicate it.
This extra inch of the human thumb transforms the grasping power of the hand of our primate cousins into the vast repertoire of the gripping precision of the human hand that would, eventually, allow man to paint and sculpt and record, through the written word, his experiences, without which his history would have disappeared completely into the dark abyss of time.
We cannot know precisely how or why the enlarging brain of Homo erectus released the hand’s (till then, hidden) potential of both grasping and gripping, but we can see its consequences readily enough in his stone tools. Palaeontologists who have taught themselves the technique of stone napping (as it is known) discovered that the necessary skill lies in finding the right-shaped ‘core’ stone, which is then percussed by a hammer stone at precisely the right angle and with a controlled degree of force so as to produce fragments of the right size and sharp enough to cut open the skin of his prey.
There is something immensely moving about the diminutive Lucy, no more than five feet tall, and the strapping Turkana Boy. Their bones may be silent, but nonetheless they speak to us across those aeons of time. What, one wonders, when they looked upwards at that clear African sky at night, did they make of its thousands of shimmering stars and the drama of the waxing and waning of the moon?
It is impossible to exaggerate the importance of those skeletal remains to our understanding of evolutionary heritage, confirming the linear sequence of our predecessors just as Darwin had postulated. Five million years ago the antecedents of Lucy and her tribe forsook the safety of the forest to walk upright on the savannah of central Africa. Two million years passed, and the ever-expanding brain of Homo erectus allowed for the incremental increase in intelligence necessary to fashion tools from stone, and to undertake those extraordinary migrations of tens of thousands of miles that would take him through what is now the Middle East into Asia, and as far as northern China and Indonesia. Then a further million and a half years elapsed before the emergence of Homo sapiens, who from his base in Africa would undertake a second great wave of global migration, this time as far as Australia, across the Bering Straits to America, and up into Europe and the southern Pyrenees, where Cromagnon man would found the first human civilisation.
Thanks to Donald Johanson, Richard Leakey and many others, we now possess the factual evidence for man’s evolutionary ascent, culminating in those images of deer and bison on the ceiling of that Altamira cave whose technical virtuosity so astonished the Marquis de Sautola. There is no deep mystery about our origins. The massively overwhelming prevailing view taught in virtually every school and university in the Western world insists that Darwin’s evolutionary theory of natural selection explains us and our ancestors. ‘Our own existence [that] once presented the greatest of all mysteries is a mystery no longer. Darwin solved it,’ observes the evolutionary biologist Richard Dawkins. ‘We no longer have to resort to superstition … it is absolutely safe to say that anyone who claims not to believe in evolution is ignorant, stupid or insane.’ And how could it not be so? What other conceivable explanation might there be? There is none. That, one would think, should be the end of the matter.
And yet, the more that time has passed since those definitive discoveries of Lucy and Turkana Boy, the more perplexing that evolutionary trajectory seems to be. The Ascent of Man captured in Thomas Huxley’s famous image is no longer a theoretical idea: it is concretely realised in Lucy’s sharp-angled femur and Turkana Boy’s much larger skull; but the more one reflects on what is involved in standing upright or acquiring a larger brain, the less convincing Darwin’s proposed mechanism of natural selection appears to be. Further, the suddenness of the cultural explosion that signalled the arrival of Cromagnon man argues against a progressive, gradualist evolutionary transformation. It suggests rather some dramatic event – as if a switch were thrown, the curtain rose, and there was man at the centre of the stage of world events. The findings of the New Genetics and the Decade of the Brain make it much more difficult to set such doubts aside. The trivial genetic differences that separate our primate cousins from ourselves seem quite insufficient to account for those physical differences that set us apart. Similarly, the elusive workings of the human brain would seem to defy any simple evolutionary explanation.
THE RIDDLE OF ‘THE ASCENT’
Part 1: Setting Out
There are at least half a dozen speculative evolutionary reasons for why Lucy and her kind might have wished to stand upright, and the advantage in doing so: the better to see potential predators, to carry her dependent offspring, or, as Darwin himself supposed, ‘standing on two legs would permit an ape-like predecessor to brace itself by holding on to a branch with one arm as he grabbed the fruit with another’. But the most schematic anatomical comparison with our primate cousins reveals the prodigious difficulties of this novel form of locomotion. The knuckle-walking chimp has four powerful, pillar-like limbs, providing a large rectangular basis of support, with the centre of gravity solidly located in the middle of the torso. For Lucy, the centre of gravity shifts to a small area enclosed by her two feet, and with the bulk of her weight (her head and torso) in the upper part of the body, exacerbating her tendency to topple over. While the chimpanzee might be compared to a solid, four-legged table, Lucy’s upright frame, like an unsupported pole balancing a heavy ball (her head), must constantly defy the laws of gravity.
So how did she come to stand upright? The main anatomical transformations pivot around the pelvis, where the powerful gluteus maximus of our buttocks, a minor player in our primate cousins, pull the human form upright like a drawbridge. This novel stance must then be held in place by a redesign of several other muscles that fulfil a propulsive function in our primate cousins, but need to act as stabilisers of the human skeleton. For that to happen, the bony pelvis to which they are all attached must itself undergo a major redesign, being first pulled up and back, then shortened and widened.
This redesign of the pelvis and its stabilising muscles entails a further series of knock-on effects: the skull must now be repositioned directly over the erect human frame, while the vertebrae of the spinal column must become progressively wider as they descend, to sustain the weight pressing upon them. The head of the femur (as noted) must be angled inwards, the ligaments of the knee strengthened to ‘lock’ into position, while the foot, particularly the big toe, must undergo a dozen anatomical changes to provide a firm basis of support. The arms, that no longer need to swing through branches, become shortened, while the legs, now proportionally too short relative to the body, must be lengthened – but by how much? There is, it would seem, an ‘ideal’ length that creates a pendulum-type movement of the legs, like the pendulum of a clock, where walking becomes almost automatic, the combination of the force of gravity and inertia carrying the body forward with hardly any intentional muscular effort. ‘The human frame is built for walking,’ observes the biomechanist Tad McGeer. ‘It has both the right kinematics and the right dynamics – so much so in fact that our legs are capable of walking without any motor control.’
And that shortening of the arms and lengthening of the legs for walking gives the symmetry and harmony that reflect the hidden laws of geometric proportion captured by Leonardo da Vinci’s famous ‘Vitruvian’ image of man, his span matching his height, encompassed within the two most elemental of shapes – the circle and the square. ‘It is impossible to exaggerate what this simple-looking proposition meant to Renaissance man,’ the art historian Kenneth Clark observed. ‘It was the foundation of their whole philosophy,’ where man was ‘the measure of all things’.
These, however, are merely the obvious anatomical changes, as Lucy would still be quite unable to stand upright without both a rewiring of her nervous system to cope with the flood of feedback information from the millions of sensors monitoring the relative position of the bones and muscles, and a more sophisticated circulatory system. Thus, those obvious similarities that so impressed Darwin and Huxley conceal a myriad of hidden but necessary modifications, because there can be no change in one structure without influencing many others. The hundreds of different bones, muscles and joints are ‘inseparably associated and moulded with each other’, the distinguished twentieth-century biologist D’Arcy Wentworth Thompson would observe. ‘They are only separate entities in this limited sense that they are part of a whole – that can no longer exist when it loses its composite integrity.’
Lucy was already an experienced ‘bipedal walker’, as shown by those emotive footprints in the volcanic ash – so we must presuppose, if Darwin’s evolutionary theory is correct, numerous preceding species of hominids marking out those anatomical changes from the rock-like stability of the knuckle-walking primates to her own upstanding, pole-like form. We can only speculate how those changes occurred. The strengthening of the gluteus muscle was essential to ‘raise the drawbridge’ – but it would have been quite unable to do so without the simultaneous redesign of the bones of the pelvis and upper thigh, the ligaments to lock the knees, the adaptation of the foot to standing upright, and so on. Thus the biological advantage of ‘freeing the hands’ would be more than offset by the profound instability of any transitional species, that without this full house of anatomical changes would have had a stuttering, shuffling gait – vulnerable prey to any hungry carnivore it encountered when tottering across the savannah. Put another way, the necessity for these many anatomical changes confirms what one would expect: the upright stance is staggeringly difficult to pull off, which is presumably why no other species has attempted it. Standing upright is, on reflection, a rather bizarre thing to do, and would seem to require a sudden and dramatic wholescale ‘redesign’ that is clearly incompatible with Darwin’s proposed mechanism of a gradualist evolutionary transformation. Lucy’s pivotal role in man’s evolutionary ascent as the beginning or anchor of that upward trajectory would seem highly ambiguous.
These difficulties seem less acute when we turn to that second evolutionary innovation, represented by Turkana Boy’s larger brain, which would at least have conferred the obvious advantage of greater intelligence – and progressively so, each incremental increase in brain size and intelligence furthering his chances of survival. Except, there is no direct evidence for the benefits of that greater intelligence, other than those stone tools which, for all their technical ingenuity, remained virtually unchanged for two million years. The human brain started to increase in size, and continued to do so over a period of several million years, with precious little to show for it until right at the end, with that extraordinary intellectual leap of the Cromagnons’ ‘cultural explosion’. Why, one might reasonably ask, should man’s evolutionary progress equip him with powers he would not realise for so long?
This is no mere rhetorical question, for man, during his Ascent, paid a heavy price for that expanding brain, which together with standing upright would massively increase the risk of obstetric catastrophe in childbirth – a fact that could scarcely be more biologically disadvantageous to the survival of his species. A simple diagram of the foetal head passing down through the bony pelvis explains all.
The main effect of the reorientation of Lucy’s pelvis to permit her to stand upright is to transform a straight and shallow ring of bone into a deep, curved tube. First we note the situation for our primate cousins, the chimps, where there is a generous margin around the foetal head. Next we see the much tighter fit of Lucy’s pelvis, which becomes a potentially lethal crush for both mother and infant. And further, the foetal head must now overcome the greater resistance of the mother’s much more powerful pelvic muscles, strengthened to retain her internal organs within the abdomen against the downward force of gravity. A million years on, and the ‘bigger brain’ of Turkana Boy further compounds these difficulties, so now it requires massive protracted (and very painful) contractions of the muscles of the uterus (ten times more powerful than in other mammals) to force the foetus down that ‘deep, curved tube’, causing potential damage to the pelvic muscles, bowel and bladder. The predictable consequence of all this is that while the chimpanzee can give birth on her own, almost without breaking stride, humans right from the beginning would have required the assistance of others to support them in this most traumatic of all human experiences – with a mortality rate of 100 per cent for both mother and child in the not unusual circumstance of obstructed labour.
And that is only the beginning, for the human brain continued to increase in size, which would have created an insurmountable obstacle to reproduction were it not for the extraordinary evolutionary ‘solution’ of slowing the growth rate of the foetal brain within the womb, and accelerating it afterwards. From Turkana Boy onwards, the human newborn, with its now relatively immature brain at birth, is completely helpless, and it will take a further year and a half before it starts to acquire the sort of motor skills that permit the newborn infant chimp to hang on to its mother’s back. And that dependency in turn would require that further unique feature of humanity, the long-term pair bond between mother and father, hinted at in those footsteps in the volcanic ash, to share the responsibility for carrying, caring for and feeding their dependent offspring.
It can be difficult to appreciate the devastating implications of these reflections. The Ascent of Man from knuckle-walking chimp to upright human seems so logical and progressive as to be almost self-evident, yet it conceals events that are without precedent in the whole of biology. The only consolation would be that man must have evolved somehow, but then the hope of understanding how would seem to evaporate with the revelation of the near-equivalence of the human and chimp genomes. There is nothing to suggest the major genetic mutations one would expect to account for the upright stance or that massively enlarged brain – leading the head of the chimp Genome Project to concede, as already cited, somewhat limply: ‘Part of the secret is hidden in there, we don’t know what it is yet.’ Or as a fellow researcher put it, rather more bluntly: ‘You could write everything we know about the genetic differences in a one-sentence article.’ The reports in 2006 of a family in northern Turkey with a bizarre genetic defect that caused them to walk on all fours suggested, according to Professor Uner Tan of Cukurova University, the breakthrough of ‘a live model for human evolution’. Perhaps, but then perhaps not, as the anatomy of the family’s bones and muscles was otherwise entirely human, so with relatively short arms and long legs, their ungainly quadrupedal locomotion only served to emphasise the ‘full house’ of anatomical transformation necessary for the upright stance.
So, while the equivalence of the human and chimp genomes provides the most tantalising evidence for our close relatedness, it offers not the slightest hint of how that evolutionary transformation came about – but rather appears to cut us off from our immediate antecedents entirely. The archaeological discoveries of the last fifty years have, along with Lucy and Turkana Boy, identified an estimated twenty or more antecedent species, and while it is obviously tempting to place them in a linear sequence, where Lucy begat Turkana Boy begat Neanderthal man begat Homo sapiens, that scenario no longer holds. Instead we are left with a bush of many branches – without there being a central trunk linking them all together.
‘Over the past five million years new hominid species have regularly emerged, competed, co-existed, colonised the environment and succeeded or failed,’ writes palaeontologist Ian Tattersall. ‘We have only the dimmest of perceptions of how this dramatic history of innovation and interaction unfolded, but it is evident that our species is simply one more of its many terminal twigs.’
The methods of the New Genetics have confirmed that all the human races – Negroes, Caucasians, Asians and so on – are genetically identical, thus all descendants of an entirely novel species, Homo sapiens, ourselves, who emerged it is presumed in east or south Africa in 120,000 BC before spreading out to colonise the world. But that leaves the ‘terminal twig’ of ourselves suspended in limbo, with no obvious attachment to those earlier branches of that evolutionary bush. The account of ourselves which until recently seemed so clear now seems permeated with a sense of the deeply inexplicable – whose implications we will return to after considering the second aspect of the riddle of that evolutionary trajectory: the Cromagnons with their ‘passion for art’.
THE RIDDLE OF THE ASCENT
Part 2: The Cultural Explosion and the Origins of Language
‘Homo sapiens is not simply an improved version of his ancestors, but a new concept, qualitatively distinct from them … A totally unprecedented entity has appeared on the earth. All the major intellectual attributes of modern man are tied up in some way with language.’
Ian Tattersall, Curator, American Museum of Natural History
The most striking feature of the arrival of modern man is its suddenness and completeness, epitomised most obviously by the beauty and originality of those artefacts he left behind: the ‘pride of lions’ portrayed in perspective on the walls of the Chauvet cave; the beads and jewellery for self-adornment in this and the ‘next’ world; drums fashioned from mammoths’ bones to celebrate, with singing and dancing, the wonders of the natural world; oil lamps, harpoons, spear-throwers. All the features in short – artistic, technical, economic and religious – that can be found in contemporary society.
The precipitating factor in that cultural explosion must, by common consent, be tied up in some way with language. The Cromagnons had a ‘passion for art’, so an obvious starting point in searching for the qualitative difference that language might make, and which would distinguish them from their antecedents, is to ask what a painting or a sculpture of, say, a bison, is. It clearly is not a bison, nor the reflection of a bison, nor the imaginative figment of a bison – as in a dream. It is not a sculpture of a specific object, but rather a generalised image of a class of objects: it stands for, is symbolic of, bison in general. It is the idea of a bison. This ability of Cromagnon man to conceptualise things and feelings as ideas, and to express those ideas as words, introduces an entirely new dimension into the universe.
First, language – and it is a most extraordinary thing – allows us to ‘think’, by assigning words to objects and ideas. Then it becomes possible to express a logical idea by applying grammatical rules to the arrangement of those words, and linking them together sequentially in a sentence. And more, the faculty of language allows us to take those thoughts ‘brought into existence’ by language and insert them with complete precision into the minds of others for them to share, or to disagree with. Language makes the world intelligible, by allowing man to transmit his thoughts and experiences in the form of accumulated knowledge from generation to generation – leading, perhaps inevitably, to the moment at the close of the twentieth century when he would ‘hold in his mind’s eye’ the history of the universe he inhabits. Language makes it possible to distinguish truth, the faithful reflection of reality, from falsehood, and this, as the philosopher Richard Swinburne points out, is the foundation of reason (obviously), but also of morality, for ‘it gives man the capacity to contrast the worth of one action to that of another, to choose what he believes worthwhile … and that gives us a conception of the goodness of things’. Thus humans, like all living things, are biological beings constrained by nature’s laws; nonetheless language liberates our mind from the confines of our material brain, allowing us to transcend time and space to explore the non-material world of thought, reason and emotion. So, ‘All the major intellectual attributes of modern man are tied up in some way with language,’ as Ian Tattersall argues. Where then did language come from?