Homo sapiens' Chinese footprint

By Amina Khan

Forty-seven human teeth dug up out of a cave in southern China reveal that our species, Homo sapiens, may have arrived in China 80,000 years ago - long before humans were able to leave their mark on Northern China and Europe.

The findings, published in the journal Nature, may compel researchers to reconsider the current view of human migrations out of Africa - and could hint that Neanderthals may have been a much greater barrier to Europe than previously thought.

"It's opening a new period of understanding and more creative thinking about the other possibilities of long-established models," said paleoanthropologist María Martinón-Torres of University College London, who co-led the study with researchers from the Chinese Academy of Sciences.

Scientists believe that Homo sapiens first emerged in East Africa somewhere between 190,000 and 160,000 years ago, spread into the eastern Mediterranean around 100,000 to 60,000 years ago but then were replaced by Neanderthals after that, according to Robin Dennell of the University of Exeter.

New discovery

Scientists say they've discovered a new member of the human family, revealed by a huge trove of bones in a barely accessible, pitch-dark chamber of a cave in South Africa.

Fuyan Cave in Hunan Province, where these teeth were found, has an ideal mix of features that allowed scientists to pin down the fossils' age. (Teeth often are the best-preserved remains in an acidic environment like a karst cave because enamel is the hardest tissue in the human body, and dentin, while not quite as hard, is still harder than bone.)

For such fossils, understanding their context - where they were located, how deep they were buried - is vital because each layer of rock represents a different epoch in time. The deeper the objects were found, the older they are. So if those layers are disturbed in any way, it becomes very difficult for excavators to tell the true age of those fossils.

Luckily, in Fuyan Cave, a layer of flowstone had grown over the layer that held the human teeth, sealing them in and preventing them from being disturbed. Over the flowstone grew a stalagmite, which was dated to at least 80,100 years old - which means all the material below it, teeth included, must be older.

Beneath the flowstone, the scientists also found mammalian fossils from 38 species as well as five extinct large mammals, including Stegodon orientalis (a relative of mammoths and elephants) and Ailuropoda baconi(an ancestor of the giant panda). These animals must have come from a period of time known as the Upper Pleistocene, about 125,000 to 10,000 years ago.

Mammalian fossils

Together, the stalagmite and the mammalian fossils allowed researchers to put an upper limit on the age of the human teeth. Their owners must have lived sometime between 80,000 and 120,000 years ago.

Taken together, these teeth look remarkably like those of contemporary humans; they're smaller and smoother than those of earlier human species, such as Homo erectus.

"The fact that the teeth resemble those of Upper Pleistocene Europeans and modern humans implies that the population they came from were immigrants and not the outcome of local evolution from H. erectus," Dennell wrote in a commentary on the study.

"To place these finds in their continental context, the Fuyan teeth indicate that modern humans were present in southern China 30,000 to 60,000 years earlier than in the eastern Mediterranean and Europe."

"We should not rule out the possibility that H. neanderthalensis was for a long time an additional barrier for modern humans' expansion, who could only settle in Europe when Neanderthal populations started to fade," the study authors wrote.

There could be other explanations for the delay in getting to Europe, others said.

"The predominantly colder winter conditions of the enormous landmass between Europe and northern China may better explain the earlier colonization of southern zones," Dennell wrote.

Either way, it opens up a lot of questions about whether, and how, this migration into southern China relates to the human population today," Martinón-Torres said.

- LA Times