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Four tufts of human hair found in the frozen ground of Greenland have yielded DNA from a man who lived 4,000 years ago. Scientists who analyzed the hair say this is the most complete reconstruction of ancient human DNA ever accomplished. And it reveals details not only of the man himself, but also where his people came from.

NPR's Christopher Joyce reports.

CHRISTOPHER JOYCE: The genetic snapshot of Inuk - that's what they're calling the 4,000-year-old man - almost didn't happen. Evolutionary biologist Eske Willerslev had gone to the Natural History Museum in Copenhagen asking for ancient human remains from the Arctic. They had some bones, but wouldn't part with them. So Willerslev went to northern Greenland to look for himself. He found nothing but ice and rock. Back at the museum, he met a scientist who said, wait a minute.

Professor ESKE WILLERSLEV (Evolutionary Biologist, University of Copenhagen): He said to me, well, I'm pretty sure, you know, there's some probably human hair in the basement of the national museum and was kind of 10 minute walk from where I'm living, we actually found the sample in the basement.

JOYCE: The hair had been collected in Greenland in the 1980s and forgotten. The hair contained DNA preserved by the cold, and very important, mostly free of contamination from bacterial and other foreign DNA. A team of scientists sequenced most of the chemical units in Inuk's DNA, and here's what they found.

Prof. WILLERSLEV: We can show, well, he was genetically adapted to cold temperatures. We can also show with a very high probability he had tendency to baldness, he had this blood type, you know, he had this skin color, et cetera.

JOYCE: Type A-positive blood to be exact, thick hair, brown eyes, dark skin and of the two types of earwax that humans inherit, Inuk had the dry kind - all this from hair.

Professor DAVID LAMBERT (Evolutionary Biologist, Griffiths University): Somebody would've told you 12 months ago, two years ago, certainly three years ago that this was impossible.

JOYCE: David Lambert is an evolutionary biologist at Griffiths University in Australia. He says superfast gene sequencing machines made the discovery possible.

Prof. LAMBERT: This is a remarkable feat, to say the least. And if you look at the people who did this work, it's quite a remarkable team as well.

JOYCE: What the scientists zoomed in on were single nucleotide polymorphisms. Yes, that's a mouthful. Just call them SNPs. They're tiny variations in the pattern of chemical units that make up DNA. Think of strings of multicolored beads with subtle variations from one string to the next. Brown-haired people have one set of beads; blonds, a different one. If you find a string and read its pattern, you know something about who was wearing it - the same with SNPs.

Willerslev says Inuk's SNPs reveal something else surprising: Inuk wasn't like the people now living in the North American and Greenland Arctic. His DNA closely matches people who now live in Siberia, thousands of miles to the West.

Prof. WILLERSLEV: It's most likely, you know, an independent migration that came into the New World Arctic around 5,500 years ago and it didn't really leave any present-day descendants in the New World.

JOYCE: Inuk's culture is called Saqqaq. Willerslev says his people must have crossed the Bering Strait from Siberia to North America and then to Greenland.

Willerslev says up till now, sequences of modern human DNA have revealed details of human evolution and migration, but that's just secondhand evidence of the past.

Prof. WILLERSLEV: And that's where I think ancient DNA becomes very powerful, because it gives you a direct look into the past.

JOYCE: The research appears in the journal Nature. Willerslev's next project at the University of Copenhagen: hair from 8,000-year-old South American mummies.

Christopher Joyce, NPR News.

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