The popular literature on human fossils is hyped up with alleged ambition to discover the 'earliest' human ancestor. This is silly. You can ask a specific question like 'Which was the earliest human ancestor to walk habitually on two legs?' Or 'Which was the first creature to be our ancestor and not the ancestor of a chimpanzee?' Or 'Which was the earliest human ancestor to have a brain volume larger than 600 cc?' Those questions at least mean something in principle, although they are hard to answer in practice and some of them suffer from the vice of erecting artificial gaps in a seamless continuum. But 'Who was the earliest human ancestor?' means nothing at all.

More insidiously, the compet.i.tion to find human ancestors means that new fossil discoveries are touted as on the 'main' human line whenever remotely possible. But as the ground yields up more and more fossils it becomes increasingly clear that, during most of hominid history, Africa housed several species of hominid simultaneously. This has to mean that many fossil species now thought of as ancestral will turn out to be our cousins.

At various times since h.o.m.o h.o.m.o first appeared in Africa, it shared the continent with more robust hominids, perhaps several different species of them. As usual their affinities, and the exact number of species, are hotly disputed. Names that have been attached to various of these creatures (we met them in the graph at the end of the Handyman's Tale) are first appeared in Africa, it shared the continent with more robust hominids, perhaps several different species of them. As usual their affinities, and the exact number of species, are hotly disputed. Names that have been attached to various of these creatures (we met them in the graph at the end of the Handyman's Tale) are Australopithecus Australopithecus (or (or Paranthropus Paranthropus) robustus, Australopithecus robustus, Australopithecus (or (or Paranthropus Paranthropus or or Zinjanthropus Zinjanthropus) boisei boisei, and Australopithecus Australopithecus (or (or Paranthropus Paranthropus) aethiopicus aethiopicus. They seem to have evolved from more 'gracile' apes (gracile being the opposite of robust). The gracile apes are also placed in the genus Australopithecus Australopithecus, and we too almost certainly emerged from among gracile australopithecine ranks. Indeed, it is often difficult to distinguish early h.o.m.o h.o.m.o from gracile australopithecines which prompted my diatribe on the naming conventions that place them in separate genera. from gracile australopithecines which prompted my diatribe on the naming conventions that place them in separate genera.

The immediate ancestors of h.o.m.o h.o.m.o would be cla.s.sified as some kind of gracile australopithecine. Let's look at some of the gracile fossils. Mrs Ples is one for whom I have had special affection ever since the Transvaal Museum in Pretoria presented me with a beautiful cast of her skull, on the fiftieth anniversary of her discovery at Sterkfontein nearby, when I gave the Robert Broom Memorial Lecture in honour of her discoverer. She lived about 2.5 million years ago. Her nickname comes from the genus would be cla.s.sified as some kind of gracile australopithecine. Let's look at some of the gracile fossils. Mrs Ples is one for whom I have had special affection ever since the Transvaal Museum in Pretoria presented me with a beautiful cast of her skull, on the fiftieth anniversary of her discovery at Sterkfontein nearby, when I gave the Robert Broom Memorial Lecture in honour of her discoverer. She lived about 2.5 million years ago. Her nickname comes from the genus Plesianthropus Plesianthropus, to which she was originally a.s.signed before people decided to incorporate her into Australopithecus; Australopithecus; and from the fact that she was thought (perhaps erroneously as is now suspected) to be female. Individual fossil hominids often pick up pet names like this. 'Mr Ples', naturally, is a more recently discovered fossil from Sterkfontein who is in the same species as Mrs Ples, and from the fact that she was thought (perhaps erroneously as is now suspected) to be female. Individual fossil hominids often pick up pet names like this. 'Mr Ples', naturally, is a more recently discovered fossil from Sterkfontein who is in the same species as Mrs Ples, Australopithecus africa.n.u.s Australopithecus africa.n.u.s. Other fossils with nicknames include 'Dear Boy', a robust australopithecine also known as 'Zinj' because he was originally named Zinjanthropus boisei Zinjanthropus boisei, 'Little Foot' (see below) and the famous Lucy, to whom we now turn.

We meet Lucy as our time machine's odometer touches 3.2 million years. Another gracile australopithecine, she is often mentioned because her species, Australopithecus afarensis Australopithecus afarensis, is a hot contender for a human ancestor. Her discoverers, Donald Johanson and his colleagues, also found fossils of 13 similar individuals in the same area, known as the 'First Family'. Other 'Lucys' have since been found between about 3 and 4 million years ago in other parts of East Africa. The 3.6-million-year-old footprints discovered by Mary Leakey at Laetoli (page 76) are attributed to A. afarensis A. afarensis. Whatever the Latin name, evidently somebody was walking bipedally at that time. Lucy is not greatly different from Mrs Ples, and some people think of Lucys as an earlier version of Mrs Ples. They are anyway more like each other than either is like the robust australopithecines. Early East African Lucys are said to have a slightly smaller brain than later South African Mrs Pleses, but there isn't much in it. Their brains were no more different from each other than some modern human brains are from other modern human brains.

As we have come to expect, the more recent afarensis afarensis individuals such as Lucy are slightly different from the earliest 3.9-million-year-old individuals such as Lucy are slightly different from the earliest 3.9-million-year-old afarensis afarensis forms. Differences collect over time and, as we emerge from our time machine 4 million years ago, we find more creatures who might well be ancestral to Lucy and her kin, but who are sufficiently different, in the direction of being more chimpanzee-like, to merit a different species name. Discovered by Meave Leakey and her team, these forms. Differences collect over time and, as we emerge from our time machine 4 million years ago, we find more creatures who might well be ancestral to Lucy and her kin, but who are sufficiently different, in the direction of being more chimpanzee-like, to merit a different species name. Discovered by Meave Leakey and her team, these Australopithecus anamensis Australopithecus anamensis consist of more than 80 fossils from two different sites near Lake Turkana. No intact skull has been found, but there is a splendid lower jaw which plausibly could belong to an ancestor of ours. consist of more than 80 fossils from two different sites near Lake Turkana. No intact skull has been found, but there is a splendid lower jaw which plausibly could belong to an ancestor of ours.

But the most exciting discovery from this time period, and a good reason for calling a temporary halt here, is a fossil yet to be fully described in print. Affectionately known as Little Foot, this skeleton from the Sterkfontein caves of South Africa was originally dated to about three million years ago, but has recently been redated to just over four million. Its discovery is a piece of detective work worthy of a Conan Doyle story. Bits of Little Foot's left foot were dug up from Sterkfontein in 1978, but the bones were stored away, unremarked and unlabelled, until 1994 when the palaeontologist Ronald Clarke, working under the direction of Phillip Tobias, accidentally rediscovered them in a box in the shed used by workers at the Sterkfontein cave. Three years later, Clarke chanced upon another box of bones from Sterkfontein, in a store room at Wit.w.a.tersrand University. This box was labelled 'Cercopithecoids'. Clarke had an interest in this kind of monkey, so he looked in the box and was delighted to notice a hominid foot bone in amongst the monkey bones. Several foot and leg bones in the box seemed to match the bones previously found in the Sterkfontein shed. One was half a right shinbone, broken across. Clarke gave a cast of the shinbone to two African a.s.sistants, Nkwane Molefe and Stephen Motsumi, and asked them to return to Sterkfontein and look for the other half.

The task I had set them was like looking for a needle in a haystack as the grotto is an enormous, deep, dark cavern with breccia exposed on the walls, floor and ceiling. After two days of searching with the aid of hand-held lamps, they found it on 3 July 1997.

Molefe and Motsumi's jigsaw feat was the more astonishing because the bone that fitted their cast was at the opposite end to where we had previously excavated. The fit was perfect, despite the bone having been blasted apart by lime workers 65 or more years previously. To the left of the exposed end of the right tibia could be seen the section of the broken-off shaft of the left tibia, to which the lower end of the left tibia with foot bones could be joined. To the left of that could be seen the broken-off shaft of the left fibula. From their positions with the lower limbs in correct anatomical relationship, it seemed that the whole skeleton had to be there, lying face downwards.

Actually, it wasn't quite there but, after pondering the geological collapses in the area, Clarke deduced where it must be and, sure enough, Motsumi's chisel found it there. Clarke and his team were indeed lucky, but here we have a first-cla.s.s example of that maxim of scientists since Louis Pasteur: 'Fortune favours the prepared mind.'

Little Foot is still to be fully excavated, described and formally named, but preliminary reports suggest a spectacular find, rivalling Lucy in completeness but older. Although more human-like than chimpanzee-like, the big toe is more divergent than our toes. This might suggest that Little Foot grasped tree boughs with its feet in a way that we cannot. Although it almost certainly walked bipedally, it probably climbed too and walked with a different gait from us. Like other australopithecines, it may have spent time in trees, perhaps bivouacking in them at night like modern chimpanzees.

Having paused at the 4-million-year milestone, let's take a quick peek at the journey yet to unfold. There are some fragmentary remains of a possibly bipedal Australopithecus Australopithecus-like creature even further back in time, about 4.4 million years ago. Tim White and his colleagues discovered it in Ethiopia, quite close to Lucy's last resting place. They named it Ardipithecus ramidus Ardipithecus ramidus,1 although some prefer to keep it in the genus although some prefer to keep it in the genus Australopithecus Australopithecus. No skull of Ardipithecus Ardipithecus has so far been found, but its teeth suggest that it was more chimpanzee-like than any later humans. Its tooth enamel was thicker than that of chimpanzees, but not as thick as ours. A few isolated cranial bones have been found, and these indicate that the skull rested on top of the vertebral column, as in us, rather than in front of it, as in chimpanzees. This suggests a vertical stance, and such foot bones as have been found support the idea that has so far been found, but its teeth suggest that it was more chimpanzee-like than any later humans. Its tooth enamel was thicker than that of chimpanzees, but not as thick as ours. A few isolated cranial bones have been found, and these indicate that the skull rested on top of the vertebral column, as in us, rather than in front of it, as in chimpanzees. This suggests a vertical stance, and such foot bones as have been found support the idea that Ardipithecus Ardipithecus was bipedal. was bipedal.

Bipedality separates humans from the rest of the mammals so dramatically that I feel it deserves a tale to itself. And who better fitted to tell it than Little Foot?

LITTLE FOOT'S TALE.

It isn't particularly helpful to dream up reasons why walking on two legs might be generally a good thing. If it were, the chimps would do it too, to say nothing of other mammals. There is no obvious reason for saying that either bipedal or quadrupedal running is faster or more efficient than the other. Galloping mammals can be astonishingly fleet, using the up-and-down flexibility of the backbone to achieve among other benefits a lengthened effective stride. But ostriches show that a man-like bipedal gait can be a match for a quadrupedal horse. Indeed a top human sprinter, though noticeably slower than a horse or dog (or ostrich or kangaroo, for that matter), is not disgracefully slow. Quadrupedal monkeys and apes are generally undistinguished runners, perhaps because their bodily designs have to compromise with the needs of a climber. Even baboons, which normally forage and run on the ground, resort to the trees to sleep and as a defence against predators, but baboons can run fast when they need to.

So, when we ask why our ancestors rose up on their hind legs, and when we imagine the quadrupedal alternative that we forsook, it is unfair to 'think cheetah', or anything like it. When our ancestors first stood up, there was no overwhelmingly strong advantage in efficiency or speed. We should look elsewhere for the natural selection pressure which drove us to this revolutionary change in gait.

Like some other quadrupeds, chimpanzees can be trained to walk bipedally, and they often do it anyway over short distances. So it probably wouldn't be insuperably difficult for them to make the switch if there were strong benefits to doing so. Orang utans are even better at it. Wild gibbons, whose fastest method of locomotion is brachiation swinging under the boughs by their arms also run across clearings on their hind legs. Some monkeys rise upright, to peer over long gra.s.s or to wade through water. A lemur, Verreaux's sifaka, although it lives mainly in trees where it is a spectacular acrobat, 'dances' across the ground between trees on its hind legs, the arms held up with balletic grace.

Doctors sometimes ask us to run on the spot in a mask, so they can measure our oxygen consumption and other metabolic indices when we are exerting ourselves. In 1973 two American biologists, C. R. Taylor and V. J. Rowntree, did this with trained chimpanzees and capuchin monkeys, running on a treadmill. By making the animals run the treadmill either on four legs or on two (they were given something to hold on to), the researchers could compare the oxygen consumption and efficiency of the two gaits. They expected that quadrupedal running would be more efficient. This, after all, is what both species naturally do, and it is what their anatomy fits them for. Maybe bipedalism was helped by the fact that they had something to hold on to. In any case, the result was otherwise. There was no significant difference between the oxygen consumption of the two gaits. Taylor and Rowntree concluded that: The relative energy cost of bipedal versus quadrupedal running should not be used in arguments about the evolution of bipedal locomotion in man.

Even if this is an exaggeration, it should at least encourage us to look elsewhere for possible benefits of our unusual gait. It arouses the suspicion that, whatever non-locomotor benefits of bipedality we might propose as drivers of its evolution, they probably did not have to fight against strong locomotor costs.

What might a non-locomotor benefit look like? A stimulating suggestion is the s.e.xual selection theory of Maxine Sheets-Johnstone, of the University of Oregon. She thinks we rose on our hind legs as a means of showing off our p.e.n.i.ses. Those of us that have p.e.n.i.ses, that is. Females, in her view, were doing it for the opposite reason: concealing their genitals which, in primates, are more prominently displayed on all fours. This is an appealing idea but I don't carry a torch for it. I mention it only as an example of the kind kind of thing I mean by a non-locomotor theory. As with so many of these theories, we are left wondering why it would apply to our lineage and not to other apes or monkeys. of thing I mean by a non-locomotor theory. As with so many of these theories, we are left wondering why it would apply to our lineage and not to other apes or monkeys.

A different set of theories stresses the freeing of the hands as the really important advantage of bipedality. Perhaps we rose on our hind legs, not because that is a good way of getting about, but because of what we were then able to do with our hands carry food, for instance. Many apes and monkeys feed on plant matter that is widely available but not particularly rich or concentrated, so you must eat as you go, more or less continuously like a cow. Other kinds of food such as meat or large underground tubers are harder to acquire but, when you do find them, they are valuable worth carrying home in greater quant.i.ty than you can eat. When a leopard makes a kill, the first thing it normally does is drag it up a tree and hang it over a branch, where it will be relatively safe from marauding scavengers and can be revisited for meals. The leopard uses its powerful jaws to hold the carca.s.s, needing all four legs to climb the tree. Having much smaller and weaker jaws than a leopard, did our ancestors benefit from the skill of walking on two legs because it freed their hands for carrying food perhaps back to a mate or children, or to trade favours with other companions, or to keep in a larder for future needs?

Incidentally the latter two possibilities may be closer to each other than they appear. The idea (I attribute this inspired way of expressing it to Steven Pinker) is that before the invention of the freezer the best larder for meat was a companion's belly. How so? The meat itself is no longer available, of course, but the goodwill it buys is safe in long-term storage in a companion's brain. Your companion will remember the favour and repay it when fortunes are reversed.2 Chimpanzees are known to share meat for favours. In historic times, this kind of Chimpanzees are known to share meat for favours. In historic times, this kind of I.O.U. I.O.U. became tokenised as money. became tokenised as money.

A particular version of the 'carrying food home' theory is that of the American anthropologist Owen Lovejoy. He suggests that females would often have been hampered in their foraging by nursing infants, therefore unable to travel far and wide looking for food. The consequent poor nutrition and poor milk production would have delayed weaning. Suckling females are infertile. Any male who feeds a nursing female accelerates the weaning of her current child and brings her into receptiveness earlier. When this happens, she might make her receptiveness especially available to the male whose provisioning accelerated it. So, a male who can bring lots of food home might gain a direct reproductive advantage over a rival male who just eats where he finds. Hence the evolution of bipedalism to free the hands for carrying.

Other hypotheses of bipedal evolution invoke the benefits of height, perhaps standing upright to look over the long gra.s.s; or to keep the head above water while wading. This last is the imaginative 'aquatic ape' theory of Alister Hardy, ably championed by Elaine Morgan. Another theory, favoured by John Reader in his fascinating biography of Africa, suggests that upright posture minimises exposure to the sun, limiting it to the top of the head which is consequently furnished with protective hair. Moreover, when the body is not hunched close to the ground, it can lose heat more rapidly.

My colleague the distinguished artist and zoologist Jonathan Kingdon has centred a whole book, Lowly Origin Lowly Origin, around the question of the evolution of human bipedality. After a lively review of 13 more-or-less distinct hypotheses, including the ones I have mentioned, Kingdon advances his own sophisticated and multifaceted theory. Rather than seek an immediate benefit of walking upright, Kingdon expounds a complex of quant.i.tative anatomical shifts which arose for some other reason, but which then made it easier to become bipedal (the technical term for this kind of thing is pre-adaptation). The pre-adaptation that Kingdon proposes is what he calls squat feeding. Squat feeding is familiar from baboons in open country, and Kingdon visualises something similar in our ape ancestors in the forest, turning over stones or leaf litter for insects, worms, snails and other nutritious morsels. To do this effectively they would have had to undo some of their adaptations to living up trees. Their feet, previously hand-like for gripping branches, would have become flatter, forming a stable platform for squatting on the haunches. You will already be getting a glimmering of where the argument is going. Flatter, less hand-like feet for squatting are later going to serve as pre-adaptations for upright walking. And you will, as usual, understand that this apparently purposeful way of writing they had to 'undo' their tree-swinging adaptations, etc. is a shorthand which is easily translated into Darwinian terms. Those individuals whose genes happened to make their feet more suitable for squat feeding survived to pa.s.s on those genes because squat feeding was efficient and aided their survival. I shall continue to employ the shorthand because it chimes with the way humans naturally think.

A tree-swinging, 'brachiating' ape could fancifully be said to walk upside down under the branches run and leap in the case of an athletic gibbon using the arms as its 'legs' and the shoulder girdle as its 'pelvis'. Our ancestors probably pa.s.sed through a brachiating phase, and the true pelvis consequently became rather inflexibly bound to the trunk by long blades of bone, which form a substantial part of a rigid trunk that can be swung as a single unit. Much of this, according to Kingdon, would have needed to change, to make an efficient squat feeder out of an ancestral brachiator. Not all, however. The arms could have remained long. Indeed, long brachiating arms would have been a positively beneficial 'pre-adaptation', increasing the reach of the squat feeder and decreasing the frequency with which it had to shuffle to a new squatting position. But the ma.s.sive, inflexible, top-heavy ape trunk would have been a disadvantage in a squat feeder. The pelvis would have needed to free itself and become less rigidly tied to the trunk, and its blades would have shrunk to more human proportions. This, to antic.i.p.ate the later stages of the argument again (you might say that antic.i.p.ation is what a pre-adaptation argument is all about) just happens to make a better pelvis for bipedal walking. The waist became more flexible, and the spine was held more vertically, to allow the squat-feeding animal to search all around with its arms, turning on the platform of the flat feet and the squatting haunches. The shoulders became lighter and the body less top-heavy. And the point is that these subtle quant.i.tative changes, and the balancing and compensating shifts that went with them, incidentally had the effect of 'preparing' the body for bipedal walking.

Not for a moment is Kingdon proposing any kind of antic.i.p.ation of the future. It is just that an ape whose ancestors were tree-swingers, but which has switched to squat feeding on the forest floor, now has a body which feels relatively comfortable comfortable walking on its hind feet. And it would have begun to do this while squat feeding, shuffling to a new squatting position as the old one became depleted. Without realising what was happening, squat feeders were, over the generations, preparing their bodies to feel more comfortable when upright and on two legs; to feel more awkward on four. I use the word comfortable deliberately. It is not a trivial consideration. We are capable of walking on all fours like a typical mammal, but it is uncomfortable: hard work, because of our altered body proportions. Those proportional changes which now make us feel comfortable on two legs originally came about, Kingdon suggests, in the service of a minor shift in food habits to squat feeding. walking on its hind feet. And it would have begun to do this while squat feeding, shuffling to a new squatting position as the old one became depleted. Without realising what was happening, squat feeders were, over the generations, preparing their bodies to feel more comfortable when upright and on two legs; to feel more awkward on four. I use the word comfortable deliberately. It is not a trivial consideration. We are capable of walking on all fours like a typical mammal, but it is uncomfortable: hard work, because of our altered body proportions. Those proportional changes which now make us feel comfortable on two legs originally came about, Kingdon suggests, in the service of a minor shift in food habits to squat feeding.

There is much more in Jonathan Kingdon's subtle and complex theory, but I will now recommend his book, Lowly Origin Lowly Origin, and move on. My own slightly wayout theory of bipedality is very different but not incompatible with his. Indeed, most of the theories of human bipedality are mutually compatible, with the potential to a.s.sist rather than oppose one another. As in the case of the enlargement of the human brain, my tentative suggestion is that bipedality may have evolved through s.e.xual selection, so again I postpone the matter to the Peac.o.c.k's Tale.

Whatever theory we believe about the evolutionary origins of human bipedality, it subsequently turned out to be an extremely important event. In former times it was possible to believe, as respected anthropologists did up to the 1960s, that the decisive evolutionary event that first separated us from the other apes was the enlargement of the brain. Rising up on the hind legs was secondary, driven by the benefits of freeing the hands to do the kind of skilled work which the enlarged brain was now capable of controlling and exploiting. Recent fossil finds point decisively towards the reverse sequence. Bipedality came first. Lucy, who lived long after Rendezvous 1 Rendezvous 1, was bipedal, nearly or completely as bipedal as we are, yet her brain was approximately the same size as a chimpanzee's. The enlargement of the brain could still have been a.s.sociated with the freeing of the hands, but the sequence of events was reversed. If anything it would be the freeing of the hands by bipedal walking that drove the enlargement of the brain. The manual hardware came first, then the controlling brainware evolved to take advantage of it, rather than the other way around.

EPILOGUE TO LITTLE FOOT'S TALE.

Whatever the reason for the evolution of bipedality, recent fossil discoveries seem to indicate that hominids were already bipedal at a date which is pushing disconcertingly close to Rendezvous 1 Rendezvous 1, the fork between ourselves and chimpanzees (disconcerting because it seems to leave little time for bipedality to evolve). In the year 2000, a French team led by Brigitte Senut and Martin Pickford announced a new fossil from the Tugen Hills, east of Lake Victoria in Kenya. Dubbed 'Millennium Man', dated at 6 million years and given yet another new generic name, Orrorin tugenensis Orrorin tugenensis was also, according to its discoverers, bipedal. Indeed, they claim that the top of its femur, near the hip joint, was more human-like than that of was also, according to its discoverers, bipedal. Indeed, they claim that the top of its femur, near the hip joint, was more human-like than that of Australopithecus Australopithecus. This evidence, supplemented by fragments of skull bones, suggested to Senut and Pickford that orrorins are ancestral to later hominids and that Lucys are not. These French workers go further and suggest that Ardipithecus Ardipithecus might be ancestral to modern chimpanzees rather than to us. Clearly we need more fossils to settle these arguments. Other scientists are sceptical of these French claims, and some doubt that there is enough evidence to show whether might be ancestral to modern chimpanzees rather than to us. Clearly we need more fossils to settle these arguments. Other scientists are sceptical of these French claims, and some doubt that there is enough evidence to show whether Orrorin Orrorin was or was not bipedal. If it was, since 6 million years is approximately the time of the split from chimpanzees according to molecular evidence, this raises difficult questions about the speed with which bipedality must have arisen. was or was not bipedal. If it was, since 6 million years is approximately the time of the split from chimpanzees according to molecular evidence, this raises difficult questions about the speed with which bipedality must have arisen.

[image]

Hope of Life. Skull of Skull of Sahelanthropus tchadensis Sahelanthropus tchadensis, or 'Toumai', discovered in the Sahel region of Chad by Michel Brunet and colleagues in 2001.

If a bipedal Orrorin Orrorin pushes back alarmingly close to pushes back alarmingly close to Rendezvous 1 Rendezvous 1, a newly discovered skull from Chad in southern Sahara, found by another French team led by Michel Brunet, is even more disturbing to accepted ideas. This is partly because it is so old, and partly because the site is far to the west of the Rift Valley (as we shall see, many authorities had thought early hominid evolution confined to the east of the Rift). Nicknamed Toumai (Hope of Life in the local Goran language) its official name is Sahelanthropus tchadensis Sahelanthropus tchadensis, after the Sahel region of the Sahara in Chad where it was found. It is an intriguing skull, looking rather human from in front (lacking the protruding face of a chimpanzee or gorilla) but chimpanzee-like from behind, with a chimpanzee-sized braincase. It has an extremely well-developed brow-ridge, even thicker than a gorilla's, which is the main reason for thinking Toumai was male. The teeth are rather human-like, especially the thickness of the enamel which is intermediate between a chimpanzee's and our own. The foramen magnum (the big hole through which the spinal cord pa.s.ses) is placed further forward than in a chimpanzee or gorilla, suggesting to Brunet himself, though not to some others, that Toumai was bipedal. Ideally, this should be confirmed by pelvis and leg bones but, unfortunately, nothing but a skull has so far been found.

There are no volcanic remains in the area to provide radiometric dates, and Brunet's team had to use other fossils in the area as an indirect clock. These are compared with already known faunas from other parts of Africa which can be dated absolutely. The comparison yields a date for Toumai of between 6 and 7 million years. Brunet and his colleagues claim it as older than Orrorin Orrorin, which has predictably elicited indignant ripostes from Orrorin Orrorin's discoverers. One of them, Brigitte Senut, of the Natural History Museum in Paris, has said that Toumai is 'a female gorilla', while her colleague Martin Pickford described Toumai's canine teeth as typical 'of a large female monkey'. These were the two, remember, who (perhaps rightly) wrote off the human credentials of Ardipithecus Ardipithecus, another threat to the priority of their own baby, Orrorin Orrorin. Other authorities have hailed Toumai more generously: 'Astonishing.' 'Amazing.' 'This will have the impact of a small nuclear bomb.'

If their discoverers are right that Orrorin Orrorin and Toumai were bipedal, this poses problems to any tidy view of human origins. The naive expectation is that evolutionary change spreads itself uniformly to fill the time available for it. If 6 million years elapsed between and Toumai were bipedal, this poses problems to any tidy view of human origins. The naive expectation is that evolutionary change spreads itself uniformly to fill the time available for it. If 6 million years elapsed between Rendezvous 1 Rendezvous 1 and modern and modern h.o.m.o sapiens h.o.m.o sapiens, the quant.i.ty of change ought to be spun out, pro rata pro rata one might naively think, through the 6 million years. But one might naively think, through the 6 million years. But Orrorin Orrorin and Toumai both lived very close to the date identified from molecular evidence as that of Concestor 1, the split between our line and that of chimpanzees. These fossils even pre-date Concestor 1 according to some datings. and Toumai both lived very close to the date identified from molecular evidence as that of Concestor 1, the split between our line and that of chimpanzees. These fossils even pre-date Concestor 1 according to some datings.

a.s.suming that the molecular and fossil dates are correct, there seem to be four ways (or some combination from among the four) in which we might respond to Orrorin Orrorin and Toumai. and Toumai.

1. Orrorin Orrorin and/or Toumai walked on all fours. This is not unlikely, but the remaining three possibilities a.s.sume, for the sake of argument, that it is wrong. If we accept option 1, the problem just goes away. and/or Toumai walked on all fours. This is not unlikely, but the remaining three possibilities a.s.sume, for the sake of argument, that it is wrong. If we accept option 1, the problem just goes away.2. An extremely rapid burst of evolution occurred immediately after Concestor 1, which itself walked on all fours like a chimpanzee. The more humanoid Toumai and Orrorin Orrorin evolved their bipedality so swiftly after Concestor 1 that the separation in dates cannot easily be resolved. evolved their bipedality so swiftly after Concestor 1 that the separation in dates cannot easily be resolved.3. Humanoid features such as bipedality have evolved more than once, maybe many times. Orrorin Orrorin and Toumai could represent earlier occasions when African apes experimented with bipedality, and perhaps other human features too. On this hypothesis, they could indeed pre-date Concestor 1 while being bipedal, and our own lineage would const.i.tute a later foray into bipedality. and Toumai could represent earlier occasions when African apes experimented with bipedality, and perhaps other human features too. On this hypothesis, they could indeed pre-date Concestor 1 while being bipedal, and our own lineage would const.i.tute a later foray into bipedality.4. Chimpanzees and gorillas descend from more human-like, even bipedal ancestors, and have reverted to all fours more recently. On this hypothesis, Toumai, say, could actually be Concestor 1.

The last three hypotheses all have difficulties, and many authorities are driven to doubt either the dating, or the supposed bipedality, of Toumai and Orrorin Orrorin. But if we accept these for the moment and look at the three hypotheses that a.s.sume ancient bipedality, there is no strong theoretical reason to favour or disfavour any particular one of them. We shall learn from the Galapagos Finch's Tale and the Lungfish's Tale that evolution can be extremely rapid or can be extremely slow. So Theory 2 is not implausible. The Marsupial Mole's Tale will teach us that evolution can follow the same path, or strikingly parallel paths, on more than one occasion. There's nothing particularly implausible, then, about Theory 3. Theory 4, at first sight, seems the most surprising. We are so used to the idea that we have risen 'up' from the apes that Theory 4 seems to put the cart before the horse, and may even insult human dignity into the bargain (often good for a laugh in my experience). Also there is a so-called law, Dollo's Law, which states that evolution never reverses itself, and it might seem that Theory 4 violates it.

The Blind Cave Fish's Tale, which is about Dollo's Law, will rea.s.sure us that this last is not the case. There is nothing in principle wrong with Theory 4. Chimpanzees really could have pa.s.sed through a more humanoid, bipedal stage before reverting to quadrupedal apehood. As it happens, this very suggestion has been revived by John Gribbin and Jeremy Cherfas, in their two books, The Monkey Puzzle The Monkey Puzzle and and The First Chimpanzee The First Chimpanzee. They go so far as to suggest that chimpanzees are descended from gracile australopithecines (like Lucy), and gorillas from robust australopithecines (like 'Dear Boy'). For such an in-your-face radical suggestion, they make a surprisingly good case. It centres on an interpretation of human evolution which has long been widely accepted, although not without controversy: people are juvenile apes who have become s.e.xually mature. Or, putting it another way, we are like chimpanzees who have never grown up.

The Axolotl's Tale explains the theory, which is known as neoteny. To summarise, the axolotl is an overgrown larva, a tadpole with s.e.x organs. In a cla.s.sic experiment by Vilem Laufberger in Germany, hormone injections persuaded an axolotl to grow into a fully adult salamander of a species that n.o.body had ever seen. More famously in the English-speaking world, Julian Huxley later repeated the experiment, not knowing it had already been done. In the evolution of the axolotl, the adult stage had been chopped off the end of the life cycle. Under the influence of experimentally injected hormone, the axolotl finally grew up, and an adult salamander was recreated, presumably never before seen. The missing last stage of the life cycle was restored.

The lesson was not lost on Julian's younger brother, the novelist Aldous Huxley. His After Many a Summer After Many a Summer3 was one of my favourite novels when I was a teenager. It is about a rich man, Jo Stoyte, who resembles William Randolph Hearst and collects was one of my favourite novels when I was a teenager. It is about a rich man, Jo Stoyte, who resembles William Randolph Hearst and collects objets d'art objets d'art with the same voracious indifference. His strict religious upbringing has left him with a terror of death, and he employs and equips a brilliant but cynical biologist, Dr Sigismund Obispo, to research how to prolong life in general and Jo Stoyte's life in particular. Jeremy Pordage, a (very) British scholar, has been hired to catalogue some eighteenth-century ma.n.u.scripts recently acquired as a job lot for Mr Stoyte's library. In an old diary kept by the Fifth Earl of Gonister, Jeremy makes a sensational discovery which he imparts to Dr Obispo. The old Earl was hot on the trail of everlasting life (you have to eat raw fish guts), and there is no evidence that he ever died. Obispo takes the increasingly fretful Stoyte to England in quest of the Fifth Earl's remains ... and finds him still alive at 200. The catch is that he has finally matured from the juvenile ape which all the rest of us are into a fully adult ape: quadrupedal, hairy, repellent, urinating on the floor while humming a grotesquely distorted vestige of a Mozart aria. The diabolical Dr Obispo, beside himself with gleeful laughter and evidently acquainted with Julian Huxley's work, tells Stoyte he can start on the fish guts tomorrow. with the same voracious indifference. His strict religious upbringing has left him with a terror of death, and he employs and equips a brilliant but cynical biologist, Dr Sigismund Obispo, to research how to prolong life in general and Jo Stoyte's life in particular. Jeremy Pordage, a (very) British scholar, has been hired to catalogue some eighteenth-century ma.n.u.scripts recently acquired as a job lot for Mr Stoyte's library. In an old diary kept by the Fifth Earl of Gonister, Jeremy makes a sensational discovery which he imparts to Dr Obispo. The old Earl was hot on the trail of everlasting life (you have to eat raw fish guts), and there is no evidence that he ever died. Obispo takes the increasingly fretful Stoyte to England in quest of the Fifth Earl's remains ... and finds him still alive at 200. The catch is that he has finally matured from the juvenile ape which all the rest of us are into a fully adult ape: quadrupedal, hairy, repellent, urinating on the floor while humming a grotesquely distorted vestige of a Mozart aria. The diabolical Dr Obispo, beside himself with gleeful laughter and evidently acquainted with Julian Huxley's work, tells Stoyte he can start on the fish guts tomorrow.

Gribbin and Cherfas are in effect suggesting that modern chimpanzees and gorillas are like the Earl of Gonister. They are humans (or australopithecines, orrorins or sahelanthropes) who have grown up and become quadrupedal apes again, like their, and our, more distant ancestors. I never thought the Gribbin/Cherfas theory was obviously silly. The new findings of very ancient hominids like Orrorin Orrorin and Toumai, whose dates push up against our split with chimpanzees, could almost justify them in a and Toumai, whose dates push up against our split with chimpanzees, could almost justify them in a sotto voce sotto voce 'We told you so'. 'We told you so'.

Even if we accept Orrorin Orrorin and Toumai as bipedal, I would not choose with confidence between Theories 2, 3 and 4. And we mustn't forget Theory 1, that they walked on all fours and the problem goes away, which many people think is the most plausible. But of course these different theories make predictions about Concestor 1, our next stopping point. Theories 1, 2, and 3 agree in a.s.suming a chimpanzee-like Concestor 1, walking on all fours, but occasionally rising on the hind legs. Theory 4 by contrast differs in a.s.suming a more humanoid Concestor 1. In narrating and Toumai as bipedal, I would not choose with confidence between Theories 2, 3 and 4. And we mustn't forget Theory 1, that they walked on all fours and the problem goes away, which many people think is the most plausible. But of course these different theories make predictions about Concestor 1, our next stopping point. Theories 1, 2, and 3 agree in a.s.suming a chimpanzee-like Concestor 1, walking on all fours, but occasionally rising on the hind legs. Theory 4 by contrast differs in a.s.suming a more humanoid Concestor 1. In narrating Rendezvous 1 Rendezvous 1, I have been forced to make a decision between the theories. Somewhat reluctantly, I'll go with the majority, and a.s.sume a chimpanzee-like concestor. On to meet it.

1 Some people distinguish a second species, Some people distinguish a second species, Ardipithecus kadabba Ardipithecus kadabba.

2 There is a well-developed theory of reciprocal altruism in Darwinism, beginning with the pioneering work of Robert Trivers and continuing with the modelling of Robert Axelrod and others. Trading favours, with delayed repayment, really works. My own exposition of it is in There is a well-developed theory of reciprocal altruism in Darwinism, beginning with the pioneering work of Robert Trivers and continuing with the modelling of Robert Axelrod and others. Trading favours, with delayed repayment, really works. My own exposition of it is in The Selfish Gene The Selfish Gene, especially the second edition.

3 The American edition rounds off the Tennyson quotation: 'Dies the Swan.' The American edition rounds off the Tennyson quotation: 'Dies the Swan.'

Rendezvous 1.

CHIMPANZEES.

Between 5 and 7 million years ago, somewhere in Africa, we human pilgrims enjoy a momentous encounter. It is Rendezvous 1 Rendezvous 1, our first meeting with pilgrims from another species. Two other species to be precise, for the common chimpanzee pilgrims and the pygmy chimpanzee or bon.o.bo pilgrims have already joined forces with each other some 4 million years 'before' their rendezvous with us. The common ancestor we share with them, Concestor 1, is our 250,000-greats-grandparent an approximate guess this, of course, like the comparable estimates that I shall be making for other concestors.

As we approach Rendezvous 1 Rendezvous 1, then, the chimpanzee pilgrims are approaching the same point from another direction. Unfortunately we don't know anything about that other direction. Although Africa has yielded up some thousands of hominid fossils or fragments of fossils, not a single fossil has ever been found which can definitely be regarded as along the chimpanzee line of descent from Concestor 1. This may be because they are forest animals, and the leaf litter of forest floors is not friendly to fossils. Whatever the reason, it means that the chimpanzee pilgrims are searching blind. Their equivalent contemporaries of the Turkana Boy, of 1470, of Mrs Ples, Lucy, Little Foot, Dear Boy, and the rest of 'our' fossils have never been found.

Nevertheless, in our fantasy the chimpanzee pilgrims meet us in some Pliocene forest clearing, and their dark brown eyes, like our less predictable ones, are fixed upon Concestor 1: their ancestor as well as ours. In trying to imagine the shared ancestor, an obvious question to ask is, is it more like modern chimpanzees or modern humans, is it intermediate, or completely different from either?

Notwithstanding the pleasing speculation that ended the previous section which I would by no means rule out the prudent answer is that Concestor 1 was more like a chimpanzee, if only because chimpanzees are more like the rest of the apes than humans are. Humans are the odd ones out among apes, both living and fossil. Which is only to say that more evolutionary change has occurred along the human line of descent from the common ancestor, than along the lines leading to the chimpanzees. We must not a.s.sume, as many laymen do, that our ancestors were were chimpanzees. Indeed, the very phrase 'missing link' is suggestive of this misunderstanding. You still hear people saying things like, 'Well, if we are descended from chimpanzees, why are there still chimpanzees around?' chimpanzees. Indeed, the very phrase 'missing link' is suggestive of this misunderstanding. You still hear people saying things like, 'Well, if we are descended from chimpanzees, why are there still chimpanzees around?'

[image]

Chimpanzees join. White lines depict the evolutionary tree (or 'phylogeny') of chimps and humans, branching apart at Concestor 1 (marked by a numbered circle). The vertical right branch represents the current set of pilgrims: in this case, only humans. The left branch shows chimps splitting into two species about 2 million years ago. White lines depict the evolutionary tree (or 'phylogeny') of chimps and humans, branching apart at Concestor 1 (marked by a numbered circle). The vertical right branch represents the current set of pilgrims: in this case, only humans. The left branch shows chimps splitting into two species about 2 million years ago.

If we were to zoom in on any of the lines, we would find them not solid, but crisscrossing networks of interbreeding, as depicted in the humankind diagram at Rendezvous 0 Rendezvous 0. From now on we'll continue to use this solid line representation.

Images, left to right: common chimpanzee ( common chimpanzee (Pan troglodytes); bon.o.bo (Pan paniscus).

So, when we and the chimpanzee/bon.o.bo pilgrims meet at the rendezvous point, the likelihood is that the shared ancestor that we greet in that Pliocene clearing was hairy like a chimpanzee, and had a chimpanzee-sized brain. Reluctantly to set aside the speculations of the previous chapter, it probably walked on its hands (knuckles) like a chimp, as well as its feet. It probably spent some time up trees, but also lots of time on the ground, maybe squat feeding as Jonathan Kingdon would say. All available evidence suggests that it lived in Africa, and only in Africa. It probably used and made tools, following local traditions as modern chimpanzees still do. It probably was omnivorous, sometimes hunting, but with a preference for fruit.

Bon.o.bos have been seen to kill duikers, but hunting is more frequently doc.u.mented for common chimpanzees, including highly co-ordinated group pursuits of colobus monkeys. But meat is only a supplement to fruit, which is the main diet of both species. Jane Goodall, who first discovered hunting and intergroup warfare in chimpanzees, was also the first to report their now famous habit of termite fishing, using tools of their own construction. Bon.o.bos have not been seen to do this, but that may be because they have been studied less. Captive bon.o.bos readily use tools. Common chimpanzees in different parts of Africa develop local traditions of tool use. Where Jane Goodall's animals on the east side of the range fish for termites, other groups to the west have developed local traditions of cracking nuts using stone or wood hammers and anvils. Some skill is required. You have to hit hard enough to break the kernel but not so hard as to pulp the nut itself.

Although often spoken of as a new and exciting discovery, by the way, nut cracking was mentioned by Darwin in Chapter 3 of The Descent of Man The Descent of Man (1871): (1871): It has often been said that no animal uses any tool; but the chimpanzee in a state of nature cracks a native fruit, somewhat like a walnut, with a stone.The evidence cited by Darwin (a report by a missionary in Liberia in the 1843 issue of the Boston Journal of Natural History Boston Journal of Natural History) is brief and non-specific. It simply states that 'the Troglodytes niger Troglodytes niger, or Black Orang of Africa' is fond of a species of unidentified nut, which 'they crack with stones precisely in the manner of human beings'.

The especially interesting thing about nut cracking, termite fishing and other such chimpanzee habits is that local groups have local customs, handed down locally. This is true culture. Local cultures extend to social habits and manners. For example, one local group in the Mahale Mountains in Tanzania has a particular style of social grooming known as the grooming hand clasp. The same gesture has been seen in another population in the Kibale forest in Uganda. But it has never been seen in Jane Goodall's intensively studied population at Gombe Stream. Interestingly, this gesture also spontaneously arose and spread among a captive group of chimpanzees.

If both species of modern chimpanzee used tools in the wild as we do, this would encourage us to think that Concestor 1 probably did too. I think it probably did even though bon.o.bos have not been seen using tools in the wild, they are adept tool-users in captivity. The fact that common chimpanzees use different tools in different areas, following local traditions, suggests to me that lack of such a tradition in a particular area should not be taken as negative evidence. After all, Jane Goodall's Gombe Stream chimpanzees haven't been seen to crack nuts. Presumably they would, if the West African nut-cracking tradition were introduced to them. I suspect that the same might be true of bon.o.bos. Maybe they just haven't been studied enough in the wild. In any case, I think the indications are strong enough that Concestor 1 made and used tools. This idea is strengthened by the fact that tool use also occurs in wild orang utans, local populations again differing in ways that suggest local traditions.1 The present-day representatives of the chimpanzee lineage are both forest apes, whereas we are savannah apes, more like baboons except, of course, that baboons are not apes at all but monkeys. Bon.o.bos today are confined to the forests south of the great curve of the River Congo and north of its tributary the Kasai. Common chimpanzees inhabit a wider belt of the continent, north of the Congo, westward to the coast, and extending as far as the Rift Valley in the east.

As we shall see in the Cichlid's Tale, current Darwinian orthodoxy suggests that usually, in order for an ancestral species to split into two daughter species, there is an initial, accidental geographical separation between them. Without the geographical barrier, s.e.xual mixing of the two gene pools keeps them together. It is plausible that the great Congo river provided the barrier to gene flow which a.s.sisted the evolutionary divergence of the two chimpanzee species from each other, two or three million years ago. In the same way, it has been suggested that the Rift Valley, in the throes of its formation at the time, may have provided the barrier to gene flow which, further in the past, allowed our line to separate from that which gave rise to the chimpanzees.

This Rift Valley theory was proposed and supported by the distinguished Dutch primatologist Adriaan Kortlandt. It became better known when it was later espoused by the French palaeontologist Yves Coppens, and it is now widely called by the name Coppens gave it, East Side Story. Incidentally, I don't know what to make of the fact that, in his native France, Yves Coppens is widely cited as the discoverer of Lucy, even as the 'father' of Lucy. In the English-speaking world, this important discovery is universally attributed to Donald Johanson. East Side Story has a hard time dealing with Sahelanthropus Sahelanthropus ('Toumai') from Chad, thousands of miles to the west of the Rift Valley. ('Toumai') from Chad, thousands of miles to the west of the Rift Valley. Australopithecus bahrelghazali Australopithecus bahrelghazali, a poorly known australopithecine also discovered in Chad, adds to the problem, although it is younger.

Whatever I say on this matter will soon be out of date when new fossils are discovered, so I'll hand over at this point to the bon.o.bo and his tale.

THE BOn.o.bO'S TALE.

The bon.o.bo, Pan paniscus Pan paniscus, looks pretty much like a common chimpanzee, Pan troglodytes Pan troglodytes, and before 1929 they were not recognised as separate species. The bon.o.bo, despite its other name of pygmy chimpanzee, which should be abandoned, is not noticeably smaller than the common chimpanzee. Its body proportions are slightly different, and so are its habits, and that is the cue for its brief tale. The primatologist Frans de Waal put it neatly: 'The chimpanzee resolves s.e.xual issues with power; the bon.o.bo resolves power issues with s.e.x ...' Bon.o.bos use s.e.x as a currency of social interaction, somewhat as we use money. They use copulation, or copulatory gestures, to appease, to a.s.sert dominance, to cement bonds with other troop members of any age or s.e.x, including small infants. Paedophilia is not a hang-up with bon.o.bos; all kinds of philia seem fine to them. De Waal describes how, in a group of captive bon.o.bos that he watched, the males would develop erections as soon as a keeper approached at feeding time. He speculates that this is in preparation for s.e.xually mediated food-sharing. Female bon.o.bos pair off to practise so-called GG (genitalgenital) rubbing.

One female facing another clings with arms and legs to a partner that, standing on both hands and feet, lifts her off the ground. The two females then rub their genital swellings laterally together, emitting grins and squeals that probably reflect o.r.g.a.s.mic experiences.The 'Haight-Ashbury' image of free-loving bon.o.bos has led to a piece of wishful thinking among nice people, who perhaps came of age in the 1960s or maybe they are of the 'medieval bestiary' school of thought, in which animals exist only to point moral lessons to us. The wishful thinking is that we are more closely related to bon.o.bos than to common chimpanzees. The Margaret Mead in us feels closer to this gentle role-model than to the patriarchal, monkey-butchering chimpanzee. Unfortunately, however, like it or not, we are exactly equally close to both species. This is simply because P. troglodytes P. troglodytes and and P. paniscus P. paniscus share a common ancestor which lived more recently than the ancestor they share with us. By the same token, molecular evidence suggests that chimpanzees and bon.o.bos are more closely related to humans than they are to gorillas. From this it follows that humans are exactly as close to gorillas as chimpanzees and bon.o.bos are. And we are exactly as close cousins of orang utans as chimpanzees, bon.o.bos and gorillas are. share a common ancestor which lived more recently than the ancestor they share with us. By the same token, molecular evidence suggests that chimpanzees and bon.o.bos are more closely related to humans than they are to gorillas. From this it follows that humans are exactly as close to gorillas as chimpanzees and bon.o.bos are. And we are exactly as close cousins of orang utans as chimpanzees, bon.o.bos and gorillas are.

It does not follow from this that we resemble resemble chimpanzees and bon.o.bos equally. If chimpanzees have changed more than bon.o.bos since the shared ancestor, Concestor 1, we might be more like bon.o.bos than chimpanzees, or vice versa and we shall probably find different things in common with both our chimpanzees and bon.o.bos equally. If chimpanzees have changed more than bon.o.bos since the shared ancestor, Concestor 1, we might be more like bon.o.bos than chimpanzees, or vice versa and we shall probably find different things in common with both our Pan Pan cousins, perhaps in roughly equal measure. They are equally closely related to us because they are linked to us via the same shared ancestor. This is the moral of the Bon.o.bo's Tale, a simple moral and a very general one, which we shall meet again and again at other junctures of our pilgrimage. cousins, perhaps in roughly equal measure. They are equally closely related to us because they are linked to us via the same shared ancestor. This is the moral of the Bon.o.bo's Tale, a simple moral and a very general one, which we shall meet again and again at other junctures of our pilgrimage.

1 Tool use is, in any case, widespread among mammals and birds, as Jane Goodall herself (among others) has doc.u.mented. Tool use is, in any case, widespread among mammals and birds, as Jane Goodall herself (among others) has doc.u.mented.

Rendezvous 2.

GORILLAS.

The molecular clock tells us that Rendezvous 2 Rendezvous 2, where the gorillas join us, again in Africa, is only a million years further into our pilgrimage than Rendezvous 1 Rendezvous 1. Seven million years ago, North and South America were not joined, the Andes had not undergone their major uplift and the Himalayas only just so. Nevertheless the continents would have looked pretty much as now and the African climate, while less seasonal and slightly wetter, would have been similar. Africa was more thoroughly forested then than now even the Sahara would have been wooded savannah at the time.

Unfortunately there are no fossils to bridge the gap between Concestors 2 and 1, nothing to guide us in deciding whether Concestor 2, which is perhaps our 300,000-greats-grandparent, was more like a gorilla or more like a chimpanzee or, indeed, more like a human. My guess would be chimpanzee, but this is only because the huge gorilla seems more extreme, and less like the generality of apes. Don't let's exaggerate the unusualness of gorillas, however. They are not the largest apes that have ever lived. The Asian ape Gigantopithecus Gigantopithecus, a sort of giant orang utan, would have stood head and ma.s.sive shoulders over the largest gorilla. It lived in China, and went extinct only recently, about half a million years ago, overlapping with h.o.m.o erectus h.o.m.o erectus and archaic and archaic h.o.m.o sapiens h.o.m.o sapiens. This is so recent that some enterprising fantasists have gone so far as to suggest that the Yeti or Abominable Snowman of the Himalayas ... but I digress. Gigantopithecus Gigantopithecus presumably walked like a gorilla, probably on the knuckles of its hands and the soles of its feet as gorillas and chimpanzees do, and as orang utans, committed as they are to life up trees, do not. presumably walked like a gorilla, probably on the knuckles of its hands and the soles of its feet as gorillas and chimpanzees do, and as orang utans, committed as they are to life up trees, do not.

It is a reasonable guess that Concestor 2 was also a knuckle-walker but that, like chimpanzees, it spent time in trees as well, especially at night. Natural selection under a tropical sun favours dark pigmentation as protection against ultraviolet rays, so if we had to guess at Concestor 2's colour we would presumably say black or dark brown. All apes except humans are hairy, so it would be surprising if Concestors 1 and 2 were not. Since chimpanzees, bon.o.bos and gorillas are inhabitants of deep forest, it is plausible to locate Rendezvous 2 Rendezvous 2 in a forest, in Africa, but there is no strong reason to guess any particular part of Africa. in a forest, in Africa, but there is no strong reason to guess any particular part of Africa.

[image]

Gorillas join. Phylogeny showing the gorillas diverging from the other African apes around 7 million years ago, as suggested by genetics. The right branch now represents the chimpanzees and humans (Concestor 1 is marked on the branch with a dot at 6 million years ago). The left branch represents the single genus of gorillas, now thought to comprise two species. Phylogeny showing the gorillas diverging from the other African apes around 7 million years ago, as suggested by genetics. The right branch now represents the chimpanzees and humans (Concestor 1 is marked on the branch with a dot at 6 million years ago). The left branch represents the single genus of gorillas, now thought to comprise two species.

Image: western gorilla ( western gorilla (Gorilla gorilla).

Gorillas are not just giant chimpanzees, they are different in other respects which we need to think about in trying to reconstruct Concestor 2. Gorillas are entirely vegetarian. The males have harems of females. Chimpanzees are more promiscuous, and the differences in breeding systems have interesting consequences on the size of their testes as we shall learn from the Seal's Tale. I suspect that breeding systems are evolutionarily labile, meaning easily changed. I don't see any obvious way to guess where Concestor 2 stood in this respect. Indeed, the fact that different human cultures today show a large range of breeding systems, from faithful monogamy to potentially very large harems, reinforces my reluctance to speculate about such matters for Concestor 2, and persuades me to bring my speculations as to its nature to a swift end.

Apes, perhaps especially gorillas, have long been potent generators and victims of human myths. The Gorilla's Tale considers our changing att.i.tudes to our closest cousins.

THE GORILLA'S TALE.

The rise of Darwinism in the nineteenth century polarised att.i.tudes towards the apes. Opponents who might have stomached evolution itself balked with visceral horror at cousinship with what they perceived as low and revolting brutes, and desperately tried to inflate our differences from them. This was nowhere more true than with gorillas. Apes were 'animals'; we were set apart. Worse, where other animals such as cats or deer could be seen as beautiful in their own way, gorillas and other apes, precisely because of their similarity to ourselves, seemed like caricatures, distortions, grotesques.

Darwin never missed an opportunity to put the other side, sometimes in little asides such as his charming observation in The Descent of Man The Descent of Man that monkeys 'smoke tobacco with pleasure'. T. H. Huxley, Darwin's formidable ally, had a robust exchange with Sir Richard Owen, the leading anatomist of the day, who claimed (wrongly as Huxley showed) that the 'hippocampus minor' was uniquely diagnostic of the human brain. Nowadays, scientists not only think we resemble apes. We include ourselves within the apes, specifically the African apes. We emphasise, by contrast, the distinctness of apes, including humans, from monkeys. To call a gorilla or a chimpanzee a monkey is a solecism. that monkeys 'smoke tobacco with pleasure'. T. H. Huxley, Darwin's formidable ally, had a robust exchange with Sir Richard Owen, the leading anatomist of the day, who claimed (wrongly as Huxley showed) that the 'hippocampus minor' was uniquely diagnostic of the human brain. Nowadays, scientists not only think we resemble apes. We include ourselves within the apes, specifically the African apes. We emphasise, by contrast, the distinctness of apes, including humans, from monkeys. To call a gorilla or a chimpanzee a monkey is a solecism.

It has not always been so. In former times, apes were frequently lumped with monkeys, and some of the early descriptions confused apes with baboons, or with Barbary macaques, which indeed are still known as Barbary apes. More surprisingly, long before people thought in terms of evolution at all,