WASHINGTON • A trove of 47 fossil teeth from a cave in southern China is rewriting the history of the early migration of the human species out of Africa, indicating Homo sapiens trekked into Asia far earlier than previously thought and much earlier than into Europe.
Scientists announced on Wednesday the discovery of human teeth between 80,000 and 120,000 years old, which they say provide the earliest evidence of fully modern humans outside Africa.
The discovery could redraw the commonly accepted migration map for modern humans.
"The model that is generally accepted is that modern humans left Africa only 50,000 years ago," said Dr Maria Martinon-Torres, a researcher at University College London and a co-author of the study.
"In this case, we are saying Homo sapiens moved out of Africa much earlier," she told the journal Nature, which published the study.
Even though the route they took remains unknown, previous research suggests that the most likely path out of East Africa into East Asia was across the Arabian Peninsula and the Middle East.
The latest findings also mean that the first truly modern humans - who were thought to have emerged in East Africa some 200,000 years ago - landed in China well before they went to Europe.
The 47 teeth exhumed from a knee-deep layer of grey, sandy clay inside the Fuyan Cave near Daoxian in Hunan province closely resemble the dental gear of "contemporary humans", said the study.
They could have come only from a population that migrated from Africa, rather than one that evolved from another species of early man such as the extinct Homo erectus, the authors said.
Further, the scientists unearthed the remains of some 38 mammals, including specimens of five extinct species, one of them a giant panda larger than those in existence today.
"Judging by the cave environment, it might not have been a living place for humans," said lead author Wu Liu from the Chinese Academy of Science in Beijing.
The study also rewrites the timeline of early man in China.
Up until now, the earliest proof of Homo sapiens east of the Arabian Peninsula came from the Tianyuan Cave near Beijing, and dated from no more than 40,000 years ago.
The new discovery raises questions about why it took so long for Homo sapiens to find their way to nearby Europe.
"Why is it that modern humans - who were already at the gates - didn't really get into Europe?" asked Dr Martinon-Torres.
Dr Wu and his colleagues propose two explanations.
The first is the intimidating presence of Neanderthal man. Even though this species of early human eventually died out, they were spread across the European continent up until at least some 50,000 years ago.
"The classic idea is that Homo sapiens... took over the Neanderthal empire, but maybe Neanderthals were a kind of ecological barrier, and Europe was too small a place" for both, Dr Martinon-Torres said.
Another impediment might have been the cold. Up until the Ice Age ended 12,000 years ago, ice sheets stretched across a good part of the European continent - a forbidding environment for a new species emerging from the relative warmth of East Africa.
Dr Martinon-Torres also suggested that there might have been "different movements and migrations" out of Africa, not just one.
The cache of teeth nearly went unnoticed, Dr Wu said.
He and his Chinese colleagues discovered the cave's menagerie of animal remains in the 1980s, but had no inkling that it also contained human remains. While revisiting the site 25 years later, he had a hunch that they followed up on.
"By thinking about the cave environment, we realised that human fossils might be found there," he said by e-mail. "So we started a five-year excavation."