Scientists have reconstructed the genome of an ancient human from a tuft of hair that had been preserved in the Arctic permafrost for 4,000 years.
Genetic analysis of the thick, dark hairs revealed that they belonged to a young man with dark skin, brown eyes and shovel-shaped teeth, whose metabolism and build were well adapted to life in a cold climate.
The DNA encased in his frozen locks also revealed his blood group (A+), his risk of developing certain diseases, that he faced a high likelihood of going bald, and perhaps most improbably, the dry consistency of his earwax. Other tests on the hair suggest the man survived on a marine diet of seals and seabirds.
"Because we found quite a lot of hair from this guy, we presume he died quite young," said Eske Willerslev, who led the study at the Centre of Excellence in GeoGenetics at the Natural History Museum in Copenhagen.
"He's genetically adapted to living in the Arctic, although it was not that many generations ago that his ancestors came to the New World," he added.
The work, a tour de force of modern genetic technology, is the first to piece together an almost complete genome of an ancient human. The feat is exceptional because DNA degrades over time, making it difficult to read and reassemble into a meaningful genome.
The hairs were recovered from the permafrost in the Qeqertasussuk region of Greenland and are from an individual the scientists have named "Inuk", meaning man or human in Greenlandic. Inuk was part of the Saqqaq culture, the first known people to inhabit Greenland.
The origins of the culture are hotly debated by scientists, though most believe the Saqqaq's ancestors were migrants from neighbouring populations, such as the Na-Dene of North America or the Inuit of the New World Arctic.
Detailed analysis of Inuk's genome allowed the scientists to compare his genome with that of several surrounding populations. To their surprise, they found that Inuk was most closely related to three Old World Arctic populations, the Nganasans, Koryaks and Chukchis of far eastern Siberia.
The discovery suggests that there was a wave of migration from Siberia into the New World some 5,500 years ago that was independent of those that gave rise to modern Native Americans and the Inuit. The study is published in the journal Nature (vol 463, pp 757-762).
At the time, there was no land bridge over the Bering Strait, so Inuk's ancestors must have reached Greenland by boat or crossed in the winter when it was frozen over, said Willerslev.
The migration is curious since the climate to the south was warmer and more hospitable, though that land might have been dominated by other groups. "Maybe these guys who were adapted to marine hunting and a life in the high Arctic didn't see it as we do – as a very hostile place – but in fact a place full of opportunities," Willerslev said.
Willerslev mounted an expedition to the high Arctic to look for human remains in 2006, after hearing that the local museum held only four tiny fragments of bone from Greenland, which could not be released for genetic analysis.
"I was freezing my butt off up there in the high Arctic to try and recover human remains to do DNA on and I came back without anything," Willerslev said. Soon after returning, however, he heard that some long-forgotten human hairs from the same spot in Greenland were lying in a drawer in the basement of a museum no more than a few streets away.
The work raises the prospect of studying the origins of other fallen cultures and ancient migrations by recreating the genomes of individuals from remains held in museums around the world. The major technical hurdle will be reading genetic material from remains uncovered in more temperate climates, where DNA will not have been preserved in ice.
Last year, anthropologists at the Max Planck Institute for Evolutionary Biology in Leipzig, Germany, reconstructed the genome of a Neanderthal from strands of DNA plucked from a 38,000-year-old fossilised leg bone unearthed in a cave in Croatia.
A year earlier, a Russian-American team sequenced the genetic code of a woolly mammoth from hairs taken from two mammoths recovered from the permafrost in Siberia. The work prompted speculation that scientists might be able to resurrect the extinct species, but most researchers are doubtful this could be achieved in the foreseeable future.