Some scientists argue that Chinese genes originate from an African female, believed to be the ancestor of human beings who emerged two million years ago. But, the truth is not that simple, as new evidence shows.

In a cave southwest of Beijing city, scientists have unearthed fragments of an early modern human skeleton dating back approximately 40,000 years, indicating that the African dispersal theory of modern humans may be more complex than previously thought.

The new finding, jointly conducted by researchers both at the Institute of Vertebrate Paleontology and Paleonanthropology (IVPP) under the Chinese Academy of Sciences and Washington University, is published this week online in the US journal Proceedings of the National Academy of Sciences.

The excavation was completed in 2004, but it was not until recently that scientists finished examination of the 34 pieces of human remains found in Tianyuan Cave, six kilometers from the Peking Man Site at Zhoukoudian, famous for the finding of an ape man skull.

The remains go back 42,000 to 38,500 years, making them the oldest modern human remains from eastern Eurasia, and one of the oldest modern humans from the region, according to researchers.

"It was an older individual with an estimated age of between 40 and 60," said Erik Trinkaus, professor of Washington University and co-author of the paper. "We are thinking the human being was 1.5 to 1.6 meters in height."

Owing to the lack of a skull and pelvis of the Tianyuan human, Trinkaus and his Chinese colleagues cannot draw a conclusion about its gender.

More significantly, the anthropologists traced mixed features of both modern humans and late archaic humans, suggesting that modern humans in this region inherited genes of both archaic Africans and the local population in East Asia.

The specimen provides secure documentation of a suite of derived modern human characteristics in eastern Asia at this time, including the strongly projecting tuber symphyseos which suggest the development of a "chin", according to the published research report first authored by Shang Hong with IVPP who, however, was not available for any comment by press time.

At the same time, it also exhibits several features that place it closer to the late archaic humans or between them and early modern humans.

"It has relatively large teeth and big finger tips compared with modern humans," said Trinkaus. "Its body proportion suggests it came from a more tropical area than modern China, probably from Southeast Asia or Africa."

The mix of modern and archaic human features thus constitutes strong evidence against the Out of Africa Hypothesis, which has dominated the European scientific community for decades.

While anthropologists have reached consensus that Homo erectus dispersed from the eastern African continent across the world some two million years ago, a controversy remains about modern human origins.

The Out of Africa or African Replacement Hypothesis contends that every living human being has descended from a small group in Africa, which then dispersed into the wider world totally displacing earlier forms such as the Neanderthals. The theory was bolstered in the early 1990s by research on mitochondrial DNA studies which suggest that all humans ultimately descended from one female: the Mitochondrial Eve.

It is challenged by a multi-regional theory, which holds that Homo erectus populations evolved into modern humans in many regions, and that these groups later bred with each other and with groups that emigrated from Africa.

According to the Out of Africa Hypothesis, the archaic human population spread to China from Africa some 60,000 years ago and totally replaced earlier local population. Though Chinese anthropologists have always cast doubts about it, they failed to uncover enough and intact fossil specimen to argue with the hypothesis.

"The Tianyuan skeleton is the earliest and the first secured dated fossil of modern humans across eastern Eurasia," said Wu Xinzhi, an academician with the IVPP. "The finding provides strong evidence that such entire replacement was impossible."

Along with the skeleton, the researchers also excavated some mammalian fossils from the Tianyuan Cave, but with no stone artifacts or other cultural remains.

Tong Haowen, a researcher at IVPP who studies mammalian evolvement, also participated in the excavation and said: "Our study also shows there are few common features between ancient mammals in Eurasia and in Africa in the late Pleistocene (around 50,000 years ago)."

This also proof against the Out of Africa Hypothesis, Tong said.

Professor Trinkaus, who has led several researches into modern human skeleton specimens collected in Europe, added that the Tianyuan fossil skeleton can help anthropologists have a better idea about what was going on in Asia after the archaic African landed on the continent.

"One of our problems is that we have few fossils of archaic humans in this region, so we can only conduct comparative studies generally," he said. "But we will find more fossils."

There is an ongoing debate about how similar or different people and races are. Hence, an analysis of early modern humans can improve the understanding of "in which minor way we are different from each other," added Trinkaus.

The American professor will come to Beijing in May to conduct more joint research with his Chinese anthropologists at IVPP into the Tianyuan skeleton's biological details.

(China Daily April 3, 2007)