Some 25 or 30 million years ago, as desiccation began to reduce the area of the forests, competition for diminishing forest resources became fiercer. Environmental challenge and opportunity appeared where the trees and the grasslands met. Some primates, not powerful enough to hold on to their forest homes, were able, because of some genetic quality, to penetrate the savannahs in search of food and could meet the challenge and exploit the opportunities. Probably they had a posture and movement marginally more like that of men than, say, that of the gorillas or chimpanzees. An upright stance and the capacity to move easily on two feet make it possible to carry burdens, among them food. The dangerous open savannah could then be explored and its resources withdrawn from it to a safer home base. Most animals consume their food where they find it; man does not. Freedom to use the forelimbs for something other than locomotion or fighting also suggests other possibilities. We cannot confirm what the first ‘tool’ was, but primates other than man have been seen to pick up objects which come to hand and wave them as a deterrent, use them as weapons, or investigate and expose possible sources of food with their aid.
The next step in the argument is enormous, for it takes us to the first glimpse of a member of the biological family to which both man and the great apes belong. The evidence is fragmentary, but suggests that some 15 or 16 million years ago a very successful species was widespread throughout Africa, Europe and Asia. Probably it was a tree-dweller and certainly specimens were not very large – they may have weighed about forty pounds. Unfortunately, the evidence is such as to leave it isolated in time. We have no direct knowledge of its immediate forebears or descendants, but some kind of fork in the road of primate evolution seems to have occurred to its later relatives, often called hominids, around 5 million years ago. While one branch was to lead to the great apes and chimpanzees, the other led to human beings. This line has been named ‘hominin’. It is likely that the separation of these groups was a relatively slow process, occurring over millions of years, with episodes of interbreeding taking place. During that time big geological and geographical changes must have favoured and disfavoured many new evolutionary patterns.
The earliest surviving hominin fossils belong to a species which may or may not provide the ancestors for the small hominids which eventually emerged over a wide area of east and south-east Africa after this huge period of upheaval. They belong to the family now called Australopithecus. The earliest fragments of their fossils have been identified as over 4 million years old, but the oldest complete skull and a nearly complete skeleton found near Johannesburg in 1998 are probably at least half-a-million years ‘younger’ than that. This is not very different (allowing for the generous stretches of time and approximation available in prehistoric chronology) from the dating of ‘Lucy’, formerly the most complete specimen of Australopithecus discovered (in Ethiopia). Evidence of other species of ‘australopithecines’ (as they are usually termed), found as far apart as Kenya and the Transvaal, can be dated to various periods over the next 2 million years and has had a great impact upon archaeological thinking. Since 1970, something like 3 million years has been added to the period in which the search for human origins goes on, thanks to the australopithecine discoveries. Great uncertainty and much debate still surround them, but if the human species have a common ancestor it seems most likely that it belonged to a species of this genus. It is with Australopithecus, though, and with what, for want of a better word, we must call its ‘contemporaries’ that the difficulties of distinguishing between apes, man-like apes and other creatures with some human characteristics first appear in their full complexity. The questions raised are still becoming in some ways more difficult to deal with. No simple picture has yet emerged and discoveries are still being made.
We have most evidence about Australopithecus. But there came to live contemporaneously with some australopithecine species other, more man-like creatures, to whom the genus name Homo has been given. Homo was no doubt related to Australopithecus, but is first clearly identifiable as distinct about 2 million years ago on certain African sites; remains attributed to possible ancestors, however, have been dated by radioactivity to some 1½ million years before that.
Where specialists disagree and may be expected to go on arguing about such fragmentary evidence as we have (all that is left of 2 million or so years of hominid life could be put on a big dining-table), laymen had better not dogmatize. Yet it is clear enough that we can be fairly certain about the extent to which some characteristics later observable in humans already existed more than 2 million years ago. We know, for instance, that the australopithecines, though smaller than modern humans, had leg-bones and feet which were man-like rather than ape-like. We know they walked upright and could run and carry loads for long distances as apes could not. Their hands showed a flattening at the fingertips characteristic of those of men. These are stages far advanced on the road of human physique, even if the actual descent of our species is from some other branch of the hominid tree.
It is to early members of the genus Homo, none the less, that we owe our first relics of tools. Tool-using is not confined to men, but the making of tools has long been thought of as a human characteristic. It is a notable step in winning a livelihood from the environment. Tools found in Ethiopia are the oldest which we have (about 2½ million years old) and they consist of stones crudely fashioned by striking flakes off pebbles to give them an edge. The pebbles seem often to have been carried purposefully and perhaps selectively to the site where they were prepared. Conscious creation of implements had begun. Simple pebble choppers of the same type from later times turn up all over the Old World of prehistory; about 1 million years ago, for example, they were in use in the Jordan valley. In Africa, therefore, begins the flow of what was to prove the biggest single body of evidence about prehistoric man and his precursors and the one which has provided most information about their distribution and cultures. A site at the Olduvai Gorge in Tanzania has provided the traces of the first identified building, a windbreak of stones which has been dated 1.9 million years ago, as well as evidence that its inhabitants were meat-eaters, in the form of bones smashed to enable the marrow and brains to be got at and eaten raw.
Olduvai prompts a tempting speculation. The bringing of stones and meat to the site combines with other evidence to suggest that the children of early hominins could not easily cling to their mother for long foraging expeditions as do the offspring of other primates. It may be that this is the first trace of the human institution of the home base. Among primates, only humans have them: places where females and children normally stay while the males search for food to bring back to them. Such a base also implies the shady outlines of sexual differentiation in economic roles. It might even register the achievement of some degree of forethought and planning, in that food was not devoured to gratify the immediate appetite on the spot where it was taken, but reserved for family consumption elsewhere. Whether hunting, as opposed to scavenging from carcasses (now known to have been done by australopithecines), took place is another question, but the meat of large animals was consumed at a very early date at Olduvai.