For decades, anthropologists have tried to trace the patchy trail left by the earliest modern humans out of Africa. But they have been stymied by gaps in the fossil record or unreliable dates, especially in East Asia. Now, Chinese anthropologists report 47 teeth of Homo sapiens from a cave in southern China, dated to 80,000 to 120,000 years ago. If the dating is accurate, the discovery pushes back the appearance of our species in Asia by at least 30,000 years, wiping out a long-standing picture in which modern humans swept out of Africa in a single wave 50,000 to 70,000 years ago.
“This changes everything. It’s the best evidence we have for modern humans in East Asia this early,” says archaeologist Michael Petraglia of the University of Oxford in the United Kingdom, who was not part of the work but has long advocated an early migration out of Africa. Others question the dates. “This case is better than the previous similar claims, but it is not fully convincing,” says paleoanthropologist Yousuke Kaifu of the National Museum of Nature and Science in Tokyo.
Most researchers agree that modern humans arose in Africa and first ventured out of that continent into the Middle East about 120,000 to 90,000 years ago, as shown by skulls from Israel. But H. sapiens remains don’t appear in Europe, East Asia, and Australia until 40,000 to 50,000 years ago. Older fossils in Asia proposed as H. sapiens are controversial. Genetic studies, too, suggest that humanity’s great global expansion began just 50,000 to 70,000 years ago.
But Petraglia and others have unearthed sophisticated stone tools from the Arabian Peninsula and India, persuading him that modern humans left Africa as long ago as 125,000 years, settled in a then-wet Arabia, then pushed into India and eastward (Science, 29 August 2014, p. 994). Skeptics counter that other archaic humans could have made the tools, and that fossils are needed as proof.
Hence the excitement about the teeth reported this week in Nature, from Fuyan Cave in Daoxian in southern China, about 600 kilometers northwest of Hong Kong. A team led by Wu Liu and Xiu-Jie Wu of the Chinese Academy of Sciences’ Institute of Vertebrate Paleontology and Paleoanthropology in Beijing found small teeth with slender roots that barely differed from modern Chinese teeth. Indeed, the wear pattern and shape of the teeth are so modern that some wonder how they could be so old.
The dates come from a small stalagmite, part of a flowstone that capped the layer holding the teeth. The team used the radioactive decay of uranium to thorium to date this stalagmite to 80,000 years ago—a minimum age for the teeth. Fossils of extinct elephants, hyenas, and pandas in the hominin layer are 120,000 years old at most, so the team concluded that the teeth are 80,000 to 120,000 years old, says co-author Maria Martinón-Torres of University College London.
But the dated stalagmite came from a different trench than the teeth, and may be of a different age, says paleoanthropologist Russell Ciochon of the University of Iowa in Iowa City: “The actual dates reported for Fuyan Cave are probably good but I doubt that the teeth are that old.”
The authors insist that the stratigraphy in the cave is clear. Liu even argues that the find supports the radical—and minority—view that our species was born in China, not Africa. The discovery is likely to spur “a lot of debate,” Martinón-Torres says, “and force a new look at other alleged [H. sapiens] sites in China.”