The New Penguin History of the World (4 page)

Some twenty-five or thirty 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 The dangerous open savannah could then be explored and its resources withdrawn from it to a safer home base.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 fifteen or sixteen 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 had occurred. While one branch was to lead to the great apes and chimpanzees, the other led to human beings. This line has been named ‘hominid’. But the first hominid fossils (found in Kenya and Ethiopia) are dated only some four and a half to five million years ago, so that for about ten million years the record is obscure. During that time big geological and geographical changes must have favoured and disfavoured many new evolutionary patterns.

The earliest surviving hominid 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 four 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 two million years and has had a great impact upon archaeological thinking. Since 1970, something like three 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 surrounds them, but if the human species has 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’ of other species, that the difficulties of distinguishing between apes, manlike 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 manlike 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 two million years ago on certain African sites; remains attributed to one of his species, however, have been dated by radioactivity
to some million and a half years before that. But, to make confusion worse, the remains of an even bigger hominid have turned up near Lake Rudolf in northern Kenya. About five feet tall, with a brain about twice the size of a modern chimpanzee’s, he has the undignified name of ‘1470 man’, that being the number attached to his relics in the catalogue of the Kenya museum where they are to be found.

Where specialists disagree and may be expected to go on arguing about such fragmentary evidence as we have (all that is left of two million or so years of hominid life could be put on a big 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 two million years ago. We know, for instance, that the australopithecines, though smaller than modern humans, had legbones and feet which were manlike rather than apelike. 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
(sometimes distinguished as
Homo habilis
), 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 two and a half 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 one 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 hominids 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.

Yet such exciting evidence only provides tiny and isolated islands of hard fact. It cannot be presumed that the East African sites were necessarily typical of those which sheltered and made possible the emergence of humanity; we know about them only because conditions there allowed the survival and subsequent discovery of early hominid remains. Nor, though the evidence may incline that way, can we be sure that
any
of these hominids is a direct ancestor of humanity; they may all only be precursors. What can be said is that these creatures show remarkable evolutionary efficiency in the creative manner we associate with human beings, and suggest the uselessness of categories such as ape-men (or men-apes) – and that few scholars would now be prepared to say categorically that we are not directly descended from
Homo habilis
, the species first identified with tool-using.

It is also easy to believe that the invention of the home base made biological survival easier. It would have made possible brief periods of rest and recovery from the hazards posed by sickness and accident, thus sidestepping, however slightly, the process of evolution by physical selection. Together with their other advantages, it may help to explain how examples of the genus
Homo
were able to leave traces of themselves throughout most of the world outside the Americas and Australasia in the next million or so years. But we do not know for certain whether this was through the spread of one stock, or because similar creatures evolved in different places. It is generally held, though, that tool-making was carried to Asia and India (and perhaps to Europe) by migrants originally from East Africa. The establishment and survival in so many different places of these hominids must show a superior capacity to grapple with changing conditions, but in the end we do not know what was the behavioural secret which suddenly (to continue to talk in terms of prehistoric time) released that capacity and enabled them to spread over the landmass of Africa and
Asia. No other mammal settled so widely and successfully before our own branch of the human family, which was eventually to occupy every continent except Antarctica, a unique biological achievement.

The next clear stage in human evolution is nothing less than a revolution in physique. After a divergence between hominids and more ape-like creatures, which may have occurred more than four million years ago, it took rather less than two million years for one successful family of hominids to increase its brain size to about twice that of
Australopithecus
. One of the most important stages of this process and some of the most crucial in the evolution of humanity were already reached in a species called
Homo erectus
. It was already widespread and successful a million years ago, and had by then spread into Europe and Asia. The oldest specimen of the species so far found may be about half a million years older than that, while the last evidence for its survival (from Java) suggests members of it were still living between thirty and fifty thousand years ago.
Homo erectus
therefore successfully exploited a much bigger environment than
Homo habilis
and did so for much longer than has
Homo sapiens
, the branch of hominids to which we belong. Many signs once more point to an African origin and thence to a spread through Europe and Asia (where
Homo erectus
was first found). Apart from fossils, a special tool helps to plot the distribution of the new species by defining areas into which
Homo erectus
did not spread as well as those into which he did. This is the so-called ‘hand-axe’ of stone, whose main use seems to have been for skinning and cutting up large animals (its use as an axe in the usual, hafted sense seems unlikely, but the name is established). There can be no doubt of the success of
Homo erectus
as a genetic product.

When we finish with
Homo erectus
there is no precise dividing line (there never is in human prehistory, a fact it is only too easy to overlook or forget), but we are already dealing with a creature who has added to the upright stance of his predecessors a brain approaching that of modern man in magnitude. Though we still know only a little of the way in which the brain is organized, there is, allowing for body size, a rough correlation between size and intelligence. It is reasonable, therefore, to attribute great importance to the selection of strains with bigger brains and to reckon this a huge advance in the story of the slow accumulation of human characteristics.

Bigger brains meant bigger skulls and other changes, too. An increase in antenatal size requires changes in the female pelvis to permit the birth of offspring with larger heads, and another consequence was a longer period of growth after birth; physiological evolution in the female was not sufficient to provide antenatal accommodation to any point approaching
physical maturity. Human children need maternal care long after birth. Prolonged infancy and immaturity in their turn imply prolonged dependency: it is a long time before such infants can gather their own food. It may be with the offspring of
Homo erectus
that there began that long extension of tolerated immaturity, whose latest manifestation is the maintenance of young people by society during long periods of higher education.

Biological change also meant that care and nurture came gradually to count for more than large litters in ensuring the survival of the species. This in turn implied further and sharper differentiation in the roles of the sexes. Females were being pinned down much more by maternity at a time when food-gathering techniques seem to have become more elaborate and to demand arduous and prolonged cooperative action by males – perhaps because bigger creatures needed more and better food. Psychologically, too, the change may be significant. A new emphasis on the individual is one concomitant of prolonged infancy. Perhaps it was intensified by a social situation in which the importance of learning and memory was becoming more and more important and skills more complex. About this point the mechanics of what is going forward begin to slip from our grasp (if, indeed, they were ever in it). We are somewhere near the area in which the genetic programming of the hominids is infringed by learning. This is the beginning of the great change from the natural physical endowment to tradition and culture – and eventually to conscious control – as evolutionary selectors, though we may never be able to say where precisely this change occurs.