Steve Jones - The Language of the Genes

One of the earliest direct precursor of modern humans appeared between three and four million years before today in the Laetoli beds of Kenya. Australopithecus afar-ensis is named after the Afar region of Ethiopia, the Biblical Ophir referred to in the story of Solomon and Sheba. The most famous specimen is 'Lucy', so named because the discoverers were playing the Beatles' 'Lucy in the Sky with Diamonds' at the time. She was less than four feet tall, with a small skull. Australopithecus bones show that, like today's chimpanzees and gorillas, they went in for knuckle walking. The earliest bones which look as if they belong to our immediate ancestors, the genus Homo % come from Kenya and are dated at about two and a half million years old. The first stone tools appear at about the same time.

It is as difficult to classify fossils as to define artistic styles. Because they evolve one into another it is pointless to draw a line to show exactly when, for example, impressionist painting changed into post-impressionism. A certain arbitrariness is bound to creep in. In palaeontology things are even worse, as few specimens are found and their discoverers have a natural tendency to grace each with its own name. Even what is needed for promotion to that august genus, Homo is in dispute. A pint or so of brain, a grasping hand and a few simple stone tools are the minimum entrance requirements; but the pass mark depends on the whim of the examiner (some of whom are choosy enough to exclude the oldest member, Homo habilis> and to downgrade him to;i mere australopithecine).

However, mosl experts agree that there were at least tour species of Homo: the first. Homo habilis, ('handyman') from around 2.3 million years ago to its disappearance some seven hundred thousand years later; the second, Homo erectus^ emerging about 1.9 million years before the present, with the youngest reliably dated specimens at about 200,000 years old, and — in the end — our own species, Homo sapiens, which began to emerge about half a million years ago. Homo habilts is sometimes divided into two distinct species, habilis itself and Homo rudolfensis. Homo erectus, too, has been subdivided into two or more species; and the history of our species may be one of a series of close relatives who became extinct, leaving no trace of their presence. Habilis had a larger brain than its predecessors, its face jutted out less and for the first time there was a noticeable nose and a perceptible chin. An almost complete skeleton of an erectus boy has been found near Lake Turkana in Kenya. He had a brow ridge and a massive jaw, with long arms and legs. For much of the time more than one species of man-like beast existed at once. In Africa beasts which looked much like Lucy and her relatives lived for thousands of years alongside Homo habilts. For much of the time, several species of Homo may have lived together, a situation hard to conceive today.

Homo erectus was the first to escape from Africa and did so soon after it appeared. Erectus bones almost two million years old, mixed with those of sabre-toothed tigers and elephants, have been found in the the Republic of Georgia and this species soon spread, in modified form, to the Middle East, China, Java and Europe. Its remains include 'Java Man 1and 'Peking Man' (whose bones disappeared during the Japanese invasion of China) which had a static existence with almost no change in the skull over its long history.

The first Homo sapiens — some of which look rather like erectus — emerged in Africa more than four hundred thousand years ago. They were robust and would appear distinctly hostile to modern eyes, although some had brains larger than the average today. A half-million-yrnr-oid skull that may belong to this group was found M Knxgrove in Sussex. Within a couple of hundred of thousand years such populations of 'archaic Homo sapiens' wen* (omul throughout Europe.

The Neanderthals, who flourished for a hundred thousand years before they sank beneath a wave of modern humans, had larger brains than our own (albeit on a heavier body), with large noses and teeth. Their remains have turned up all over Europe and the Middle East, and have been found as far east as Iraq, but not in Africa or elsewhere. Once, they were assumed to be on the direct line to ourselves; but fragments of DNA extracted from mitochondria show them to have been so distinct that Neanderthals mark yet another dead end on the road to humankind.

Around a hundred and thirty thousand years ago, the first humans of modern appearance (light build, thin skull, large brain and small jaw) appear in Africa. Their remains have been found from Omo-Kibish in Ethiopia to the southern tip of Africa, thousands of miles south. Quite soon after they emerged, modern humans began a relentless expansion. Many of the earliest sites are near the coast: but in those distant days the sea was lower than it is today and broad coastal plains stretched in front of those ancestral caves. Stone tools have been found on coral reefs in the Red Sea (which was dry a hundred thousand years ago) so that perhaps our early ancestors walked along a now-drowned shoreline from Africa to Indonesia, leaving their archaic relatives, who were still around at the time, inland.

These early modern humnns had arrived in Israel, in the caves ol t)al/(.-li.ind Skhul, by a hundred thousand years.u;<>. Cro-Magnon man, the first modern European (who lived, like a sensible man, in the south of France) was there by forty thousand years before the present day. As in Africa, their antiquated relatives, the Neanderthals, held out for a time; and lasted in southern Spain for ten thousand years after the arrival of the newcomers.

This account of history is the 'out of Africa' model believed by most evolutionists. Some feel that humans emerged more or less at the same time over the whole world so that today's Chinese evolved from an ancient Chinese ancestor and Africans from a predecessor in their own land. The idea that the same species can evolve simultaneously in different places flies in the face of theories of the genetics of speciation. Some fossils might, perhaps, support the idea of local evolution. One, from the Han River in China, resembles Homo erectus, but has a flattened face which, to its discoverers, looks rather like that of a modern Chinese. Those in favour of local evolution make much of the 'shovel incisors' in fossil jaws from Asia. The teeth are scooped out at the back, as are those of some of today's Chinese. In some places in Europe, as well, a third of people have shovel incisors, so that this is not a forceful argument. So few fragments have been preserved that it seems that, too often, history is in the eye of the beholder. Africa was the centre in which most primates originated and there is no reason to suppose that humans came from anywhere else.

Another fossil controversy is the question of evolution by creeps or by jerks. Darwin felt that the origin of species was gradual and continuous. The past was no more than the present writ large. Because of the vast time available the enormous transformations which took place through the history of life could be explained by the slow and almost imperceptible changes that influences it today. His was a leisurely and Victorian view of the way the world worked; one of gradual and almost inevitable movement.

The opposing view (the theory of 'punctuated equilibrium' as it is known in its latest guise) has a more twentieth-century flavour. It sees evolution as boredom mitigated by panic. New species appear as the result of a sudden burst of revolutionary change. Between these historical disasters, life is tranquil. Punctuationists suggest that the origin of species has little to do with what happens to a species once it has originated and that the process of evolution today cannot tell us much about what went on in the past.