Primitive humans may have ventured out of Africa earlier than previously thought, new evidence suggests.
Stone tools found during an excavation in China are thought to be about 270,000 years older than the previous earliest evidence of a human presence outside Africa.
Chinese and British researchers believe the tools were made by another member of the homo evolutionary group, rather than homo sapiens, as much as 2.1 million years ago.
Until now, the oldest evidence of human-like creatures outside the continent came from 1.8 million-year-old artefacts and skulls found in Dmanisi in Georgia.
The newly discovered artefacts were found on a plateau north of the Qinling mountains and include several chipped rocks, fragments and hammer stones.
The research, published in the journal Nature, also suggests that the ancient humans returned to the same site repeatedly, possibly for hunting.
Bones of pigs and deer were discovered at the site but the scientists could not prove definitively that the tools were used for hunting.
Zhaoyu Zhu, a professor at the Guangzhou Institute of Geochemistry, said the team was "very excited" about the findings.
"One of my colleagues suddenly noticed a stone embedded in a steep outcrop. After a short while, more artefacts were found – one after another."
However some other experts have said the findings should be taken with caution.
An anthropologist from William Paterson University in New Jersey, Geoffrey Pope, said he is "skeptical" and that the discovery will "change very little".
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He explained that sometimes nature can shape stones in such a way that it appears they have been carved by hand.
But Sonia Harmand, an archaeologist at Stony Brook University in New York, said: "This could be, frankly, one of the most important (archaeological) sites in the world."