Theory on Origin of Humans Put in Doubt : Fossils: Researchers say skulls found in China indicate that the species evolved there, not solely in Africa.
The “out of Africa” theory of evolution, which holds that modern humans arose on that continent and then spread throughout the globe, has been dealt a serious blow by an analysis by UC Berkeley and Chinese researchers of 350,000-year-old Asian fossil skulls with modern features.
The discovery of the two presumably male skulls, found on the Han River in Yunxian, China, is published in today’s edition of the British journal Nature. Some aspects of the craniums are associated with Homo erectus, a forerunner of Homo sapiens --modern humans. Most notably, the backs of the skulls are sharp and angular, similar to the end of a football.
But other elements, such as a broad, flat face and high cheekbones, are characteristic of the earliest Homo sapiens , indicating that there was a transition to modern humans taking place in Asia at the same time as in Africa.
The faces and teeth also have some distinctly Chinese features, said Dennis A. Etler, a doctoral candidate at UC Berkeley’s department of anthropology. He heard about the skulls while working in China, and teamed with their discoverer, Li Tianyun, of the Hubei Institute of Archeology, to analyze the finds and write the journal article.
“We think these finds . . . suggest that certain features of the modern anatomy were reached in Asia,” Etler said in a telephone interview. “The Asian features also suggest that this area was continuously occupied throughout prehistory by humans. There is no indication of a replacement of the more ancient Asians by more modern people from another part of the world.”
African fossils show a different path to modernity. Skulls of so-called “archaic Homo sapiens “ found in Africa had more primitive facial features than the Chinese skulls. But the rear of the head--the so-called “brain case”--was more rounded.
Asian fossils from later periods show the rounded brain cases while later African fossils show the more modern facial structures, Etler said.
He suggested that modern humans could have evolved in different regions independently, or they could be the result of interbreeding during large-scale movements of people around the world. In either case, Etler said, “it’s not a one-way street.”
“When I heard about these skulls, I thought, ‘I am glad I am not one of these Eve theory supporters today,’ ” said Milford H. Wolpoff, a University of Michigan anthropologist. “I would be very uncomfortable.”
The fossils, he said, provide “evidence that is stronger than I would have believed. . . . If all people originated in Africa we’d expect early humans to look more like Africans.”
Backers of the controversial Africa scenario said they are not ready to discard their theory. Nevertheless, they said that the new evidence raises important questions, especially because it comes on the heels of doubt cast on what had been a key argument for their side: the “African Eve” reported five years ago by three biologists who concluded that genetic material from a sub-Saharan woman living 200,000 years ago has been passed to everyone alive on Earth today. That study received widespread publicity.
A reanalysis earlier this year of the Eve data suggested that an important computer program had been misapplied. The Eve could have come from either Africa or Asia--or there could have been more than one. “What we’re left with is that the placement of the ancestor in Africa is still the best explanation, but we can’t rule out the others with a statistical certainty,” said Mark Stoneking, of Pennsylvania State University, who was involved in both the original work and the re-examination.
Stoneking, a biologist and anthropologist, declined comment on the Chinese fossils. “I’m not a paleontologist,” he said.
Others were not so reluctant. “My opinion is still that modern humans originated in Africa and spread from there,” said University of Chicago anthropologist Richard Klein. “What (Etler and Li) are saying is you start with people who are very different, they evolve differently and they turn out the same. I have trouble believing that.”
Klein added, however, that the finds “do require some explanations.”
The skulls, complete except for the lower jaws, were excavated in 1989 and 1990 on a high terrace overlooking the Han. Li traveled to Berkeley in 1991 to examine plaster casts of fossils of similar age found in Africa and Europe, and worked with Etler to study his finds.
The craniums were the most complete fossil skulls from the mid-Pleistocene to be found in Asia. Etler was struck by their size.
“These people had very low skulls, very long skulls and very broad skulls,” he said. “You wouldn’t want to meet them in a dark alley. They were pretty big and hulking people.”
