An anthropologist of original insights

Where did humankind come from? PETER CALDER looks at the latest twists in one of science's most fascinating arguments.

He's 62,000 years old but, says the man who's examined him as closely as science will permit, he wouldn't look out of place in a modern group of Australian Aborigines.

He rejoices in the name Mungo Man, but his mates wouldn't have called him that. He picked up the moniker from the place where he - or rather his fossilised skeletal remains - turned up in 1974, Lake Mungo in far western New South Wales, north of Mildura and south of Broken Hill.

"It's dry country out there," says Dr Alan Thorne, the Australian palaeoanthropologist who led the research team which successfully extracted the 600-century-old DNA from Mungo Man. "But as little as 40,000 years ago there were large lakes."

The results of Thorne's research have sparked fierce and often bitter debate in the scientific community because, says the genial and soft-spoken anthropologist, they deal a body blow to the so-called "Out of Africa" theory of human evolution.

It's an idea which has held sway in academic circles since the mid-80s: that Homo sapiens emerged, like his evolutionary predecessor known as Homo erectus, in Africa and "progressively went around the world killing off and replacing all the others."

Thorne never liked the idea because, as he puts it, it didn't fit the facts.

"We used to call them 'killer Africans' and my opponents didn't like that," he says with a low chuckle.

Thorne, who gave a public lecture at the University of Auckland this week, marvelled at the serendipity of a rash of recent discoveries which have upended anthropology and our understanding of where we came from.

First, a skull found in Central Java of a woman prosaically known as SM3 shows clear evidence of brain structure close to that of modern humans. The skull, something between 100,000 and 800,000 years old, has torn a gaping hole in the theory that Homo sapiens arrived, as a killer horde, only 150,000 years ago and displaced Homo erectus.

At the same time, research at the University of Michigan at Ann Arbor compared ancient and modern skulls from Australia and from central Europe. The local family resemblances in both cases were more striking than the similarities between specimens from opposite sides of the world, which, the research concluded, was powerful evidence of what Thorne calls "regional continuity."

"It's been a fantastic year," he says with obvious excitement. "A lot of evidence has come forward in the last few months, new dates, new fossils which make it clearer. There are two groups of scientists - anatomists, archaeologists, neurologists, even some linguists, and anthropologists - and the one thing we all agree on is that one side is absolutely wrong."

On one thing all anthropologists are agreed. Humanity - the genus Homo - emerged in Africa. That's because chimpanzees and gorillas, our closest relatives, are African and are found nowhere else.

The warring factions also agree that about 2 million years ago some humans - the conventional term is Homo erectus, a category Thorne disputes is even valid - began to leave Africa.

"They are in Java and China and the ancestors of Neanderthal Man in Europe. That's not a problem; even at 50km a generation, getting to China from Africa is a doddle."

But the group of which Thorne is a leading light does not hold with the idea - embodied in the so-called Eve hypothesis developed in the mid-1980s - that Homo sapiens emerged as a new species who killed off Homo erectus.

He says primitive man behaved like modern man - interbreeding and evolving in various places at the same time.

"In other words the way I see the [prehistoric] world is the way it is now. As man moves out of Africa, populations mix and meet, a bit of bonking goes on, genes are flowing from Algiers to Capetown. When they get out into the Levant and Europe and China the same things are happening.

"That's why a person from anywhere in the world can meet someone from anywhere else in the world and they'll produce children. It doesn't matter if they're from Tierra del Fuego and Finland. All humans can interbreed with all other humans.

"At the same time we're making adaptations to different environments - from high altitudes, to deserts, to jungles and that's why we've got black Africans and pygmies and white, yellow and black people.

"What a European person looks like today is not what he used to look like, and the same goes for Africans.

"So what we think of as local variants may look different but we have evidence that some skull types continue the same for a very long time. We have very good evidence, for example, about what we call Java Man, that what distinguishes him from all other people at the time are exactly the same anatomical features as distinguish living Australian Aborigines from all other people living in the world today. That's why we call it regional continuity."

Thorne reckons his theory, "which starts from what we know about the way humans are and works back", was lent enormous weight by the DNA extracted from Mungo Man.

"Neither his skeleton nor his DNA had any links with human ancestors from Africa found in other parts of the world.

"This man is 60,000 years old and would disappear into a tribe of modern Aborigines. He doesn't look African at all. And if he did leave Africa 100,000 or 150,000 years ago, he's got to get around to Australia. Now either he's evolving while he's pedalling his bicycle to Singapore to get the boat to Australia - or he never was in Africa. His predecessors came out of Africa two million years ago but his ancestors came out of China where there are fossils who look just like him."

The notion that Homo sapiens prospered by exterminating his predecessors might seem likely to minds raised on the ideas of Darwin or Nietzsche. But that's exactly where Thorne finds fault with it.

"It's old-fashioned Eurocentrism. It's Marx and Engels, winners and losers."

Homo erectus, Thorne and the multi-regionalists argue, never existed.

"It's just an old-fashioned term for the early part of us. It says there were Neanderthals and Cro-Magnon and they went extinct. We have this notion that if people's physical features disappear, they've become extinct. But that's not true.

"One of the things that humans are good at is gene flow. We are very sexy creatures. The Tasmanians didn't become extinct; they just became part of a new population. Hitler couldn't manage it with modern technology; how could hunter-gatherers with a boomerang and a spear do it? The best way of wiping out a population is to take it over."

The successful extraction and analysis of DNA, which has only been possible since the mid-1990s, is revolutionising the science of anthropology and marrying it with biology into a powerful new discipline. Thorne and his colleagues have so far been working with what he calls "infinitesimal samples, but as techniques improve we will work out how to get other bits and pieces."

But he doubts that the argument, which has at times been bitter, will soon be settled.

"I don't imagine I'll ever sway my opponents. They'll go down with the ship. But there are a large number of my colleagues who are sitting on the fence waiting to see what happens."