An international team of researchers has discovered well-dated human fossils in southern China that markedly change anthropologists perceptions of the emergence of modern humans in the eastern Old World. The discovery of early modern human fossil remains at least 100,000 years old in the Zhiren Cave of southern China by Eric Trinkaus of Washinton University of St. Louis (USA) and workers at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing provides evidence for the emergence of modern humans in eastern Asia - at least 60,000 years prior to previously known modern humans in the region.
     The Zhirendong fossils - a chin and related teeth - have a mixture of modern and archaic features that contrast with earlier modern humans found in east Africa and southwest Asia. This find indicates that the spread of modern human biology long preceded the cultural and technological innovations of the Upper Paleolithic and that early modern humans co-existed for many tens of millennia with late archaic humans further north and west across Eurasia.
     Popular theory states that Homo sapiens migrated out of Africa about 60,000 years ago, at which point modern humans quickly replaced early human species such as Homo erectus and Homo neanderthalensis across the world. The find of such an ancient example of modern human in China drastically alters this time line for human migration. It may also mean that modern humans in China were mingling - possibly even interbreeding - with other human species for 50,000 or 60,000 years. Erik Trinkaus said that the new findings mean "there was mating between these 'archaic' and 'modern' groups across Asia, and not just in Europe and the remainder of Africa."
     In addition, the find seems to suggest that anatomically modern humans had arrived in China long before the species began acting human. For example, symbolic thought is a distinctly human trait that involves using things such as beads and drawings to represent objects, people, and events. The first strong evidence for this trait doesn't appear in the archaeological record in China until 30,000 years ago.
     To date, genetic evidence largely supports the traditional timing of the "out of Africa" theory. But the newly described Chinese jawbone presents a strong challenge, said anthropologist Christopher Bae of the University of Hawaii, who was not associated with the find. "They actually have solid dates and evidence of, basically, a modern human," he said.
     Still, the jaw and three molars were the only human remains retrieved from the Chinese cave and the jaw is "within the range" of Neanderthal chins as well as those of modern humans, added paleoanthropologist John Hawks of the University of Wisconsin, Madison. "If this holds up, we have to reevaluate" the human migration time line, he said. "Basically, I think they're right, [but] I want to see more evidence," Hawks added. "I really, really hope that there can be some sort of genetic extraction from this [fossil]."
     In terms of what happened to the Asian Neanderthals, Trinkaus believes "that eventually they were partially absorbed into expanding modern human populations" around 40,000 years ago. He said, "We don't know why those modern humans expanded then, after remaining in Africa and southern Asia for 50,000 plus years."

Edited from Washington University in St.Louis, National Geographic News, Discovery News (25 October 2010)