Where Did We Come From?

A Little History Of Science: Where Did We Come From?

Today we know that we share 98 per cent of our genome with our closest animal relatives, the chimpanzees. That’s an awful lot of similarity, but there are some crucial differences. While chimps do communicate they don’t talk together as humans do. And we can read and write. Take a step back and we find that humans and chimpanzees, together with the gorillas and orangutans, make up the family of Hominidae, often known as the ‘great apes’. We humans are less closely related to gorillas and orangutans, but at some point in the past all four of these groups shared a common ancestor, from which each group evolved. That was a long time ago, perhaps fifteen million years.

We find our great-ape ‘cousins’ fascinating and slightly disturbing. Those who wrote about them and studied them in the past did so too. They wondered where this brute animal, that seemed so like us and yet so different, fitted into creation. In 1699 an English anatomist, Edward Tyson (1651–1708), obtained the body of a dead chimpanzee. He carefully dissected this exotic animal and compared what he found with what he knew of human anatomy. It was the first time anyone had looked so closely at a chimpanzee. Tyson slotted it into Aristotle’s Great Chain of Being – just below us. It was natural, he argued, that some animal would smooth over the gap between humans and the rest of the animal kingdom. He didn’t say it, but Tyson had suggested the need for a ‘missing link’ in the chain, something that connects us to other animals. In Britain, Germany and France, a growing number of human artefacts such as flint arrows and axe heads were being uncovered.

This was exciting evidence of human presence going back millennia. These tools were often found in caves and fossil sites among the fossilised remains of extinct animals – the fearsome sabre-tooth tigers and giant woolly mammoths. These extinct animals and the Stone Age humans who had made the tools had obviously been alive at the same time. Humans had been on the earth for tens of thousands of years . . . not the much shorter period that most people believed. Not everyone agreed, of course, but Darwin’s friend Thomas Henry Huxley (1825–95) had no doubts. Huxley was excited by the discovery in 1856 of ‘Neanderthal man’ in a cave in the Neander Valley in Germany. He wrote about this fossil, and about modern humans and the great apes in his book Man’s Place in Nature (1863). We know now that this was the first fossil hominin that did not belong to our species, Homo sapiens, the biological name that Linnaeus gave us.

Hominin is the name now used for ourselves and for our extinct ancestors, and as more fossil evidence is uncovered, the group gets larger. The tree of life is growing, and gradually being filled in.

At the time, Huxley was cautious enough to recognise that a single find doesn’t tell you everything about a whole species, and so he kept Neanderthal man in the same species as modern humans. But he was confident that this was a very old specimen, one that had been around long enough for evolution to have taken place. There had certainly been some changes, for although Neanderthal man was similar enough to us, he was also different.

The skull had immense brow ridges and a much larger cavity for the nose. The proportions of the limbs and body were different to ours. It was even possible that this was a deformed body rather than another species. In time we would learn that the Neanderthals were the first hominins to bury their dead.

Huxley knew all about Darwin’s ideas on human evolution before the great man published two books in quick succession laying out his ideas and evidence for our ancestry. In 1871 The Descent of Man did what Darwin had avoided doing in On the Origin of Species: it focused his compelling account of our world upon the human race. In 1872, his book The Expression of the Emotions in Man and Animals, added an important psychological dimension to his argument. He based the book on his careful watching of his own children, their smiles and grimaces, among many other behaviours. Humans were part of life on earth, like all the other species of plants and animals. Darwin concluded that our ancestors had probably lived in Africa, where humans had first evolved.

Darwin’s depiction of evolution as a ‘tree of life’ meant that we could not be descended from modern apes. But it was the ‘ape man’ connection that immediately caught the public’s imagination. His ideas on evolution were first debated in public at a crowded meeting in Oxford, organised by the British Association for the Advancement of Science. The Association aimed to bring the latest scientific knowledge to everyone and held a meeting every year where scientists talked and debated what was new. The meeting in 1860 was full of drama, so sensational was the ‘ape man’ idea. The discussion of Darwin’s ideas on evolution was eagerly awaited, with Bishop Samuel Wilberforce leading the anti-Darwinians and Huxley the pro-Darwinians. Wilberforce, thinking he was clever, asked Huxley whether he was descended from the apes on his grandfather’s or his grandmother’s side. Huxley replied that he would indeed rather be descended from an ape than waste his time and brain on such a silly question: Wilberforce had quite missed the point. Wilberforce remained unconvinced, but Huxley and evolution came out on top that day.

The discoveries of mankind’s long existence on the earth encouraged naturalists, anthropologists (who study humankind) and archaeologists to ask the question: What had been the original condition of human beings? ‘Cave men’ emerged in this period from the discoveries in caves in Britain and Europe. It was clear that these cave dwellers had used fire. Weapons, stone tools and cooking utensils were all found. Anthropologists and explorers also discovered hunter-gatherer groups in Africa, Asia and South America, and suggested that all human societies had passed through common stages of social development. E.B. Tylor (1832– 1917) became the first professor of anthropology at Oxford. He used an idea of ‘survivals’ to put forward a grand path of human social and cultural evolution. By this he meant social and religious practices, superstitions and different ways of organising family relationships. According to Tylor, these survivals were frozen in the ‘primitive’ people of Africa, for instance, and gave clues to the common past of humankind. Tylor and others wanted to under- stand the origins of language and looked at gestures and other ways of communicating.

This early anthropology contrasted a dynamic Europe, North America, Australia and New Zealand with the presumed unchanging lives of ‘primitive’ peoples, or even the long- established and complex cultures of India and China. We now see it as arrogant. Applied to Western society, the idea of evolutionary competition and struggle seemed to explain why some individuals prospered and some didn’t. As industrial capitalism gained strength, ‘social Darwinism’ – evolution applied to human culture – began to be used to explain why some people were rich and others were poor, and some nations powerful and others not. Social Darwinism justified the triumph of strong individuals, races or nations over weaker ones.

While some people were debating social Darwinism, others were discussing biological evolution. Until the 1890s, all the fossilised human remains that were discovered were considered to be Homo sapiens. The status of Neanderthal man remained uncertain.

Then, a Dutch anthropologist, Eugène Dubois (1858–1940) went to the Dutch East Indies, looking for evidence of human evolution in the land of the orangutan. In Java (now Indonesia), he found the top of a fossilised skull belonging to a non-human creature that had walked upright. He called the creature ‘Java man’. Attention turned to Asia, as the place where humans must have evolved. Java man, along with another old human skeleton found in France at Cro-Magnon, stimulated questions about what had happened first.

Was it walking upright, on two legs? Or a large brain? Or language and living in societies? There have been many more discoveries of pre-human hominins in Asia. But in the twentieth century, it was Africa that proved how shrewd Darwin’s prediction had been. In 1924, a fossil was discovered by the Australian anatomist Raymond Dart (1893–1988). It became known as the ‘Taung child’, and its significance was championed by the South African doctor Robert Broom (1866–1951).

Tuang child had teeth like a human child but its brain was too ape- like to be considered human. Broom believed that Dart’s fossil (and several more found subsequently, including an adult) was an ancient ancestor of human beings. Dart named it Australopithecus africanus, literally, the ‘southern ape of Africa’. We now think it is between 2.4 million and 3 million years old. After Taung child, Africa yielded many other important fossils, helping piece together man’s evolutionary ancestry. Louis and Mary Leakey (1903–72; 1913–96) made the human story even more famous. They were working in the 1950s mainly in Olduvai Gorge in Kenya, and Louis Leakey stressed that early hominins were tool-makers. He called one of the fossil hominins that had lived 1.6 to 2.4 million years ago Homo habilis – the ‘handyman’. Mary Leakey discovered in the 1970s some footprints that were 3.6 million years old, preserved in volcanic ash that had hardened. The footprints were of three upright hominins, along with other animals, and suggested that walking on two feet came first, before hominins evolved with a big brain.

For the first half of the twentieth century, the study of human fossil bones was complicated by some curious finds in a gravel pit in the village of Piltdown, East Sussex, in southern England. The discoveries began in 1908. Then in 1912 a local amateur archaeologist, Charles Dawson (1864–1916), announced the recovery of a skull at Piltdown. The find generated tremendous excitement. ‘Piltdown man’ had a modern-looking human skull with a jawbone that was ape-like. It looked like a real missing link, a kind of ‘ape man’. A number of eminent scientists published papers on the strange fossil. But it was difficult to fit it into the emerging sequence of the new hominin and ancient ape fossils. Piltdown had always seemed fishy, and in the early 1950s dating techniques that had not been available in 1908 proved that it had been a huge forgery. Piltdown man combined a modern human skull with the jaw of an orangutan, soaked in chemicals to make them look old.

The teeth had also been filed down. No one is sure ‘whodunnit’ – there are several suspects but no definitive conviction. Dawson himself is high on the list of suspects. With Piltdown revealed as a hoax, the other fossil hominins could be placed in a more likely order, using radiometric dating to learn their age, and comparing their physical characteristics. One fossil in particular, nicknamed Lucy, has become a celebrity, going on tour and having her ‘biography’ written. Lucy was uncovered in Ethiopia in 1978, and her skeleton was more than half complete.

She had lived some three to four million years ago, long before the Taung child. Like the Tuang child, she is of the genus Australopithecus but is an earlier species, afarensis – ‘ape of Afar’. Lucy’s legs, pelvis and feet mean she could probably have walked upright and climbed in trees or on rocks. Her brain cavity was not much bigger than a modern chimpanzee’s, but her brain was larger than a chimp’s, in relation to the size of her body. (The brain-to-body ratio is a better guide to mental functions than mere size: elephants have larger brains than humans, but smaller brain–body ratios.

There are of course many other factors to ‘intelligence’ than simply brain size.) Lucy really did show ‘mixed’ characteristics, not yet even crudely ‘human’, but a successful creature in her own right.

Hundreds of fossil hominins from many parts of the world have allowed us to get a pretty clear idea of the evolutionary path that led to modern human beings. We can even tell what was eaten and what parasites infected our ancestors. The puzzle has many missing pieces, and there is much debate on details: what does this tooth tell us, or the shape of that thigh bone? There will be more surprises in store, too, because fossils are continually unearthed. In Indonesia in 2003, the Australian archaeologist Mike Morwood and his colleagues found fossils of small hominins on the island of Flores. They had lived as recently as 15,000 years ago, but are probably of an unknown species. The exact status of Homo floresiensis (‘Flores man’, nicknamed ‘the Hobbit’) is still uncertain. Attempts at DNA analysis (the most reliable way of establishing biological relationships) have so far been unsuccessful.

Working out how Neanderthals relate to modern humans is an exciting challenge, too. The species certainly lived at the same time as Homo sapiens in Europe, 50,000 or so years ago. We carry some of their genes. Did the coming of Homo sapiens, ‘modern’ man, contribute to the extinction of Neanderthals? We are not sure. Did they breed with each other? Probably. Both Neanderthals and Homo sapiens suffered from the very cold European temperatures the last time glaciers covered Europe, and the Neanderthals did not survive.

To reconstruct the human family tree from fossils of differing ages, and in different locations, we use the same tools and techniques as we do for other animals such as the horse or hippopotamus. Of course, there is much more emotion involved, when it’s humans rather than hippos. But the evidence is there, and palaeontologists, anthropologists, archaeologists and other specialists continue to put the pieces together. They have used the evidence to work out that hominins, including, at last, Homo sapiens, first lived in Africa and spread from there. There is still much we don’t know about the migrations of early hominins. Were there several movements out of Africa? What led to the rapid evolution of the large brain that sets our own species apart from our cousins? Science deals with the how, not the why. This seems especially true when we think about our ancestry and, as Huxley put it, ‘man’s place in nature’.