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New York • Scientists have recovered the DNA code of a human relative recently discovered in Siberia, and it delivered a surprise: This relative roamed far from the cave that holds its only known remains.
By comparing the DNA to that of modern populations, scientists found evidence that these "Denisovans" from more than 30,000 years ago ranged all across Asia.
They apparently interbred with the ancestors of people now living in Melanesia, a group of islands northeast of Australia.
Scientists found evidence that in the genomes of people now living in Melanesia, about 5 percent of their DNA can be traced to Denisovans, a sign of ancient interbreeding that took researchers by surprise.
"We thought it was a mistake when we first saw it," said David Reich a Harvard University researcher and an author of the new paper. "But it's real."
And that suggests Denisovans once ranged widely across Asia, he said. Somehow, they or their ancestors had to encounter anatomically modern humans who started leaving Africa 55,000 years ago and reached New Guinea 45,000 years ago.
It's the second report in recent months of using a new tool, genomes of ancient human relatives, to illuminate the evolutionary history of humankind. In May, some of the same scientists reported using the Neanderthal genome to show that Neanderthals interbred with ancestors of today's non-African populations.
The existence of a new human relative was first revealed nine months ago from a sampling of DNA recovered from a finger bone discovered in the Denisova Cave in southern Siberia. Researchers proposed the informal name Denisovans in Thursday's issue of the journal Nature, in which they report the new results.
The researchers reported finding a Denisovan upper molar in the cave. Its large size and features differ from teeth of Neanderthals or early modern humans, both of which lived in the same area at about the same time as the Denisovans. Neither the finger bone nor the tooth can be dated directly, but tests of animal bones found nearby show the Denisovan remains are at least 30,000 years old, Reich said.
There's not enough evidence to determine whether Denisovans are a distinct species, the researchers said.
The genome, recovered from the finger bone, showed that Denisovans are more closely related to Neanderthals than to modern humans. That indicates that both they and Neanderthals sprang from a common ancestor on a different branch of the evolutionary family tree than the one leading to modern humans.