Scientists have pieced together most of the DNA of a man who lived in Greenland about 4,000 years ago, a pioneering feat that revealed hints about his appearance and even an increased risk of baldness.
It's the first genome from an ancient human, showing the potential for what one expert called a time machine for learning about the biology of ancient people.
Analysis suggests the Greenland man probably had type A-positive blood, brown eyes, darker skin than most Europeans, dry earwax, a boosted chance of going bald and several biological adaptations for weathering a cold climate, researchers report in Thursday's issue of the journal Nature.
The DNA also indicated the man had dark, thick hair _ a trait the scientists observed directly, since that's where the genetic material came from.
More importantly, comparisons of his DNA with that of present-day Arctic peoples shed light on the mysterious origins of the man's cultural group, the Saqqaq, the earliest known culture to settle in Greenland. Results suggest his ancestors migrated from Siberia some 5,500 years ago.
It's not clear how or why they migrated, said Eske Willerslev of the University of Copenhagen in Denmark, an author of the paper. The analysis shows the now extinct Saqqaq were not direct ancestors of today's Inuits or Native Americans, he said.
The researchers nicknamed the man Inuk, which is Greenlandic for "human" or "man."
The DNA was recovered from a tuft of hair that had been excavated in 1986 from permafrost on Greenland's west coast, north of the Arctic Circle. The thousands of years in a deep freeze was key to preserving the genetic material. But most ancient human remains come from warmer places with less potential for preservation, and scientists said it's not clear how often DNA from such samples would allow for constructing a genome.
Willerslev said he believes many hair samples from around the world, perhaps from South American mummies or in collections, probably would be usable.
"I won't say it will become routine," he told reporters, but "I think it will be something we will see much more in the coming five years."
Over the past few years, scientists have reconstructed at least draft versions of genomes of other species from much older DNA. One used woolly mammoth DNA from about 18,000 years ago and 58,000 years ago, and a draft Neanderthal genome unveiled last year used 40,000-year-old DNA from three individuals.
For the new paper, the researchers identified particular markers in the man's DNA, and then turned to studies of modern-day people that have associated those markers with particular traits like eye color, blood type, and tendency toward baldness.
As scientists link more and more markers to biological traits in modern people, they will be able to apply those findings to learn more about the Greenland man, said Eddy Rubin of the Lawrence Berkeley National Laboratory.
"It's sort of a time machine," said Rubin, who studies Neanderthal DNA but was not connected to the new work. While the DNA-based picture is not definitive, it's a "pretty good guess," he said.
"I think it's a very important study," Rubin said. "We're really beginning to zoom in on physical characteristics of individuals which we'll never see."
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