In this way, the females were sure of their males’ support and were able to devote themselves to their maternal duties. The males were sure of their females’ loyalty, were prepared to leave them for hunting, and avoided fighting over them. And the offspring were provided with the maximum of care and attention. This certainly sounds like an ideal solution, but it involved a major change in primate socio-sexual behaviour and, as we shall see later, the process was never really perfected. It is dear from the behaviour of our species today that the trend was only partially completed and that our earlier primate urges keep on re-appearing in minor forms.
This is the manner, then, in which the hunting ape took on the role of a lethal carnivore and changed his primate ways accordingly. I have suggested that they were basic biological changes rather than mere cultural ones, and that the new species changed genetically in this way. You may consider this an unjustified assumption. You may feel—such is the power of cultural indoctrination— that the modifications could easily have been made by training and the development of new traditions. I doubt this. One only has to look at the behaviour of our species at the present day to see that this is not so. Cultural developments have given us more and more impressive technological advances, but wherever these clash with our basic biological properties they meet strong resistance. The fundamental patterns of behaviour laid down in our early days as hunting apes still shine through all our affairs, no matter how lofty they may be. If the organisation of our earthier activities—our feeding, our fear, our aggression, our sex, our parental care—had been developed solely by cultural means, there can be little doubt that we would have got it under better control by now, and twisted it this way and that to suit the increasingly extraordinary demands put upon it by our technological advances. But we have not done so. We have repeatedly bowed our heads before our animal nature and tacitly admitted the existence of the complex beast that stirs within us. If we are honest, we will confess that it will take millions of years, and the same genetic process of natural selection that put it there, to change it. In the meantime, our unbelievably complicated civilisations will be able to prosper only if we design them in such a way that they do not clash with or tend to suppress our basic animal demands. Unfortunately our thinking brain is not always in harmony with our feeling brain. There are many examples showing where things have gone astray, and human societies have crashed or become stultified.
In the chapters that follow we will try to see how this has happened, but first there is one question that must be answered—the question that was asked at the beginning of this chapter. When we first encountered this strange species we noted that it had one feature that stood out immediately from the rest, when it was placed as a specimen in a long row of primates. This feature was its naked skin, which led me as a zoologist to name the creature ‘the naked ape’. We have since seen that it could have been given any number of suitable names: the vertical ape, the tool-making ape, the brainy ape, the territorial ape, and so on. But these were not the first things we noticed. Regarded simply as a zoological specimen in a museum, it is the nakedness that has the immediate impact, and this is the name we will stick to, if only to bring it into line with other zoological studies and remind’ us that this is the special way in which we are approaching it. But what is the significance of this strange feature? Why on earth should the hunting ape have become a naked ape?
Unfortunately fossils cannot help us when it comes to differences in skin and hair, so that we have no idea as to exactly when the great denudation took place. We can be fairly certain that it did not happen before our ancestors left their forest homes. It is such an odd development that it seems much more likely to have been yet another feature of the great transformation scene on the open plains. But exactly how did it occur, and how did it help the emerging ape to survive?
This problem has puzzled experts for a long time and many imaginative theories have been put forward. ‘One of the most promising ideas is that it was part and parcel of the process of neoteny. If you examine an infant chimpanzee at birth you will find that it has a good head of hair, but that its body is almost naked. If this condition was delayed into the animal’s adult life by neoteny, the adult chimpanzee’s hair condition would be very much like ours.
It is interesting that in our own species this neotenous suppression of hair growth has not been entirely perfected. The growing foetus starts off on the road towards typical mammalian hairiness, so that between the sixth and eighth months of its life in the womb it becomes almost completely covered in a fine hairy down. This foetal coat is referred to as the lanugo and is not shed until just before birth. Premature babies sometimes enter the world still wearing their lanugo, much to the horror of their parents, but, except in very rare cases, it soon drops away. There are no more than about thirty recorded instances of families producing offspring that grow up to be fully furred adults.
Even so, all adult members of our species do have a large number of body hairs—more, in fact, than our relatives the chimpanzees. It is not so much that we have lost whole hairs as that we have sprouted only puny ones. (This does not, incidentally, apply to all races—negroes have undergone a real as well as an apparent hair loss.) This fact has led certain anatomists to declare that we cannot consider ourselves as a hairless or naked species, and one famous authority went so far as to say that the statement that we are the least hairy of all the primates is, therefore, very far from being true; and the numerous quaint theories that have been put forward to account for the imagined loss of hairs are, mercifully, not needed. This is clearly nonsensical. It is like saying that because a blind man has a pair of eyes he is not blind. Functionally, we are stark naked and our skin is fully exposed to the outside world. This state of affairs still has to be explained, regardless of how many tiny hairs we can count under a magnifying lens. The neoteny explanation only gives a clue as to how the nakedness could have come about. It does not tell us anything about the value of nudity as a new character that helped the naked ape to survive better in leis hostile environment. It might be argued that it had no value, that it was merely a by-product of other, more vital neotenous changes, such as the brain development. But as we have already seen, the process of neoteny is one of differential retarding of developmental processes. Some things slow down more than others—the rates of growth get out of phase. It is hardly likely, therefore, that an infantile trait as potentially dangerous as nakedness was going to be allowed to persist simply because other. changes were slowing down. Unless it had some special value to the new species, it would be quickly dealt with by natural selection.
What, then, was the survival value of naked skin? One explanation is that when the hunting ape abandoned its nomadic past and settled down at fixed 38 home bases, its dens became heavily infested with skin parasites. The use of the same sleeping places night after night is thought to have provided abnormally rich breeding-grounds for a variety of ticks, mites, fleas and bugs, to a point where the situation provided a severe disease risk. By casting off his hairy coat, the den-dweller was better able to cope with the problem.
There may be an element of truth in this idea, but it can hardly have been of major importance. Few other den-dwelling mammals—and there are hundreds of species to pick from—have taken this step. Nevertheless, if nakedness was developed in some other connection, it might make it easier to remove troublesome skin parasites, a task which today still occupies a great deal of time for the hairier primates.
Another thought along similar lines is that the hunting ape had such messy feeding habits that a furry coat would soon become clogged and messy and, again, a disease risk. It is pointed out that vultures, which plunge their heads and necks into gory carcasses, have lost their feathers from these members; and that the same development, extended over the whole body, may have occurred among the hunting apes. But the ability to develop tools to kill and skin the prey can hardly have preceded the ability to use other objects to clean the hunters’ hair. Even a chimpanzee in the wild will occasionally use leaves as toilet paper when in difficulties with defecation.
A suggestion has even been put forward that it was the development of fire that led to the loss of the hairy coat. It is argued that the hunting ape will have felt cold only at night and that, once he had the luxury of sitting round a camp fire, he was able to dispense with his fur and thus leave himself in a better state for dealing with the heat of the day.
Another, more ingenious theory is that, before he became a hunting ape, the original ground ape that had left the forests went through a long phase as an aquatic ape. He is envisaged as moving to the tropical sea-shores in search of food. There he will have found shellfish and other sea-shore creatures in comparative abundance, a food supply much richer and more attractive than that on the open plains. At first he will have groped around in the rock pools and the shallow water, but gradually he will have started to swim out to greater depths and dive for food. During this process, it is argue, he will have lost his hair like other mammals that have returned to the sea. Only his head, protruding from the surface of the water, would retain the hairy coat to protect him from the direct glare of the sun. Then, later on, when his tools (originally developed for cracking open shells) became sufficiently advanced, he will have spread away from the cradle of the sea-shore and out into the open land spaces as an emerging hunter.
It is held that this theory explains why we are so nimble in the water today, while our closest living relatives, the chimpanzees, are so helpless and quickly drown. It explains our streamlined bodies and even our vertical posture, the latter supposedly having developed as we waded into deeper and deeper water. It clears up a strange feature—your body-hair tracts. Close examination reveals that on our backs the directions of our tiny remnant hairs differ strikingly from those of other apes. In us they point diagonally backwards and inwards towards the spine. This follows the direction of the flow of water prising over a swimming body and indicates that, if the coat of hair was modified before it was lost, then it was modified in exactly the right way to reduce resistance when swimming. It is also pointed out that we are unique amongst all the primates in being the only one to possess a thick layer of sub-cutaneous fat. This is interpreted as the equivalent of the blubber of a whale or seal, a compensatory insulating device. It is stressed that no other explanation has been given for this feature of our anatomy. Even the sensitive nature of our hands is brought into play on the side of the aquatic theory. A reasonably crude hand can, after all, hold a stick or a rock, but it takes a subtle, sensitised hand to feel for food in the water. Perhaps this was the way that the ground ape originally acquired its super-hand, and then passed it on ready-made to the hunting ape. Finally, the aquatic theory needles the traditional fossil-hunters by pointing out that they have been singularly unsuccessful in unearthing the vital missing links in our ancient past, and gives them the hot tip that if they would only take the trouble to search around the areas that constituted the African coastal sea-shores of a million or so years ago, they might find something that would be to their advantage.
Unfortunately this has yet to be done and, despite its most appealing indirect evidence, the aquatic theory lacks solid support. It neatly accounts for a number of special features, but it demands in exchange the acceptance of a hypothetical major evolutionary phase for which there is no direct evidence. (Even if eventually it does turn out to be true, it will not clash seriously with the general picture of the hunting ape’s evolution out of a ground ape. It will simply mean that the ground ape went through a rather salutary christening ceremony.) An argument along entirely different lines has suggested that, instead of developing as a response to she physical environment, the loss of hair was a social trend. In other words it arose, not as a mechanical device, but as a signal. Naked patches of skin can be seen in a number of primate species and in certain instances they appear to act as species recognition marks, enabling one monkey or ape to identify another as belonging to its own kind, or some other. The loss of hair on the part of the hunting ape is regarded simply as an arbitrarily selected characteristic that happened to be adopted as an identity badge by this species. It is of course undeniable that stark nudity must have rendered the naked ape startlingly easy to identify, but there are plenty of other less drastic ways of achieving the same end without sacrificing a valuable insulating coat.
Another suggestion along the same lines pictures the loss of hair as an extension of sexual signalling. It is claimed that male mammals are generally hairier than their females and that, by extending this sex difference, the female naked ape was able to become more and more sexually attractive to the male. The trend to loss of hair would affect the male, too, but to a lesser extent and with special areas of contrast, such as the beard. This last idea may well explain the sex differences as regards hairiness but, again, the loss of body insulation would be a high price to pay for a sexy appearance alone, even with sub-cutaneous fat as a partial compensating device. A modification of this idea is that it was not so much the appearance as the sensitivity to touch that was sexually important. It can be argued that by exposing their naked skins to one another during sexual encounters, both male and female would become more highly sensitised to erotic stimuli. In a species where pair-bonding was evolving, this would heighten the excitement of sexual activities and would tighten the bond between the pair by intensifying copulatory rewards.
Perhaps the most commonly held explanation of the hairless condition is that it evolved as a cooling device. By coming out of the shady forests the hunting ape was exposing himself to much greater temperatures than he had previously experienced, and it is assumed that he took off his hairy coat to prevent himself from becoming over-heated. Superficially this is reasonable enough. We do, after all, take our jackets off on a hot summer’s day. But it does not stand up to closer scrutiny. In the first place, none of the other animals (of roughly our size) on the open plains have taken this step. If it was as simple as this we might expect to see some naked lions and naked jackals. Instead they have short but dense coats. Exposure of the naked skin to the air certainly increases the chances of heat loss, but it also increases heat gain at the same time and risks damage from the sun’s rays, as any sun-bather will know. Experiments in the desert have shown that the wearing of light clothing may reduce heat loss by curtailing water evaporation, but it also reduces heat gain from the environment to 55 per cent of the figure obtained in a state of total nudity. At really high temperatures, heavier, looser clothing of the type favoured in Arab countries is a better protection than even light clothing. It cuts down the incoming heat, but at the same time allows air to circulate around the body and aid in the evaporation of cooling sweat.