Sunday, June 1, 2008

A clump of frozen human hair from northwest Greenland suggests that the first Eskimos in the New World did not descend from Native Americans as previously thought but came directly from Asia, a new study says. Furthermore, these pioneer settlers of the far north later died out and did not give rise to the Inuit living in Greenland today.

The research is based on DNA analysis of ancient hair from a so-called Paleo-Eskimo, which was found preserved in permafrost soil in the Disco Bay area in the 1980s.

The hair, which belonged to a male who lived some 4,000 years ago, has provided the first ever complete mitochondrial genome for an ancient human, according to a team led by Tom Gilbert of the Center for Ancient Genetics at the University of Copenhagen, Denmark.

Mitochondrial DNA is passed down from mother to child and thus gives a genetic marker to an individual's maternal ancestry.

In the ancient Greenland Eskimo's case, his hair revealed that his people came from Siberia, the study found.

The Paleo-Eskimo's genetic relatives survive today only in small pockets in northeastern Siberia and the Aleutian Islands, which stretch across the Bering Sea from Alaska to Russia, Gilbert said.

Challenging Theories

Previously, there were two main theories to explain the ancestry of the first Eskimos in Alaska, Canada, and Greenland, Gilbert said.

The theories held that they either descended from Native Americans who colonized North America at least 14,350 years ago, or they came from the same source area in Siberia that gave rise to modern Eskimos, such as those who have lived in Greenland for the past 1,000 years.

"Then there is a third idea that they were independent to both—and that's what it turns out to be," Gilbert said.

The new research, which appears tomorrow in the journal Science, suggests that the original Paleo-Eskimos of the New World were replaced by later colonizers, who spread eastward from Siberia.

"There would have been populations all the way from Alaska to Greenland, but then whole thing vanishes and another lot come in," Gilbert said. "A separate, new migration gave rise to the current Inuit."

Archaeological studies link the earliest Eskimos in Greenland to the Saqqaq culture, which appeared some 4,500 years ago, while the later Thule culture arose 1,000 years ago.

Tools associated with the two groups are very different.

For example, Saqqaq hunting equipment is described as "fly fishing tackle" compared to the much later, bulkier equipment, Gilbert said.

"Saqqaq culture is very distinctive, with finely made and precise tools such as lightweight harpoons and small [fishing] hooks," he said.

This archaeological transition in Greenland is now supported by the new DNA evidence, Gilbert added.

Eskimo Die-Off

Peter Forster, who studies archaeogenetics at Anglia Ruskin University in the United Kingdom, wasn't involved in the new study.

He said consensus among archaeologists had been that "the Paleo-Eskimos probably died out, but there's no means of knowing that for sure."

So this latest finding "makes beautiful sense" and "resolves an ongoing recent discussion in science," Forster said.

The distinct DNA signature of the frozen hair fits with Forster's own research, which indicated that no ancient Eskimo lineage survived in modern-day Greenland populations.

(Explore an atlas of the human journey.)

"It fits in exactly with what we predicted so I'm delighted," he said.

Lead author Gilbert and colleagues suggest that past ancient Eskimo populations succumbed to periods of climate cooling.

"Obviously it's an extremely tough environment up there, and it may be that the environments got so harsh that the populations got smaller and smaller and collapsed," he said.

Forster agreed, adding that the disappearance of Greenland's Paleo-Eskimos coincided with a cooling event that reached its peak 2,800 years ago.

Likewise a later cooling episode known as the little ice age, which lasted from A.D. 1350 to 1850, is credited with wiping out any modern genetic trace of Greenland's first European settlers—the Vikings, Forster noted

Source : nationalgeographic

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