Stone tools recovered from an excavation in China suggest that our evolutionary forerunners trekked out of Africa earlier than we thought.
Until now, the oldest evidence of human-like creatures outside Africa came from 1.8 million-year-old artifacts and skulls found in the Georgian town of Dmanisi. But the new find pushes that back by at least 250,000 years.
"It's absolutely a new story," said archaeologist Michael Petraglia of the Max Planck Institute for the Science of Human History in Jena, Germany, who did not participate in the study. "It means that early humans were getting out of Africa way earlier than we ever realized."
That exit came long before our own species, Homo sapiens, even appeared. The researchers believe the tools were made by another member of the Homo evolutionary group.
The items included several chipped rocks, fragments and hammer stones. The 96 artifacts were dug up in an area known as the Loess Plateau, north of the Qinling mountains, which divide the north and south of China.
Some of them were as old as 2.1 million years, according to the study in Wednesday's journal Nature.
"We were very excited," said Zhaoyu Zhu, a professor at the Guangzhou Institute of Geochemistry, who led the field work. "One of my colleagues suddenly noticed a stone embedded in a steep outcrop. After a short while, more artifacts were found — one after another."
The tools were distributed throughout layers of dirt, suggesting our unidentified ancient relatives came back to the same site over and over, possibly following animals to hunt. Researchers also found bones of pigs and deer, but were not able to provide proof that the tools were used for hunting.
Some experts not involved in the research think that the findings need to be taken with caution.
"I am skeptical," said Geoffrey Pope, an anthropologist from William Paterson University in New Jersey. "I suspect this discovery will change very little."
The problem, he said, is that sometimes nature can shape stones in a way that they look as if they were manufactured by hand. Scientists know, for example, that rocks smashed together in a stream can acquire sharp edges.
But Sonia Harmand, an archaeologist at Stony Brook University in New York, disagrees.
"This could be, frankly, one of the most important (archaeological) sites in the world," said Harmand, who studies stone tools.
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