In a Tooth, DNA From Some Very Old Cousins, the Denisovans

A tooth fossil discovered in a Siberian cave has yielded DNA from a vanished branch of the human tree, mysterious cousins called the Denisovans, scientists said Monday.

Their analysis pushes back the oldest known evidence for Denisovans by 60,000 years, suggesting that the species was able to thrive in harsh climates for thousands of generations. The results also suggest that the Denisovans may have bred with other ancient hominins, relatives of modern humans whom science has yet to discover.

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The Denisovans are named after the cave where their bones were found in the Altai Mountains in southern Siberia. Every summer, a team of Russian scientists led by Anatoly Derevianko of the Russian Academy of Sciences explores the cave, unearthing thousands of bone fragments.

Before the latest discovery, Denisovans were known only from DNA in another tooth and a finger bone found in the cave in 2008. Analysis had shown them to be at least 50,000 years old.

In 2010, Dr. Derevianko and his colleagues reported that the genetic material in the bone and the tooth belonged to the same lineage of hominins, which they called Denisovans.

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Scientists estimate that Neanderthals and Denisovans diverged on the human family tree 400,000 years ago.

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The newest batch of Denisovan DNA comes from a tooth discovered in 2010. Svante Paabo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and his colleagues described it in the Proceedings of the National Academy of Sciences.

The new tooth, called Denisova 8, yielded only a modest amount of DNA. But the scientists gathered enough to draw some important conclusions.

Denisova 8, it turns out, is much older than the previously discovered remains. The researchers estimated its age at 110,000 years.

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{snip} Chunks of Denisovan DNA are found in Australian aborigines, New Guineans and Polynesians.

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