The Penguin History of the World

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.