The migration of North America's first residents across the Bering Strait thousands of years ago has proved to be one of science's long-standing mysteries. Who arrived first? How was the Arctic region settled? Why did these people leave Eurasia in the first place?

Now researchers have completed the largest-ever genetic analysis of the Arctic peoples using DNA from ancient human remains and comparing it to DNA from contemporary residents of the region from Alaska to Greenland. This new study reveals the history of a strange group of people -- known as the Dorset people or Paleo-Eskimos -- who lived by themselves for more than 4,000 years.

This group of about 2,000 to 3,000 people were not related to Eskimos, Inuit or Native Americans. They were wiped out by the others, either by design or disease about a thousand years ago, before the arrival of Viking raiders from Scandinavia.

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"I was surprised that there was no mixing of paleo-Eskimos and (early) Native Americans," said Eske Willerslev, director of the Center for GeoGenetics at the University of Copenhagen's National Museum of Natural History in Denmark and an author on the study appearing today in the journal Science. "Usually, they might be fighting each other but they also have sex with each other and that doesn’t seem to be the case here. From a genetic point of view, the lack of mixture between those two groups was a big surprise."

This lost tribe of early Arctic residents made simple flaked stone tools, lived in micro-villages of two or three families, followed migrations of seals and caribou. They avoided bigger, stronger, more populated groups, such as the Thule culture that swept from Alaska to Greenland. With so few in number, they were also probably inbred.

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"Dorsets were the hobbits of the eastern Arctic, a strange people that we are just getting to know," said William Fitzhugh, director of the Arctic Studies Center at the Smithsonian National Museum of Natural History in Washington, D.C.

The Dorset people arrived some six thousand years ago from Northeast Asia, probably Siberia. They followed their own wave of migration, separate from the three other waves that archaeologists have until now documented.

Fitzhugh said these small tribes survived for four millennia in the harsh environment of the Arctic tundra. But eventually they became easy prey for the more powerful Thule, who are ancestors of modern-day Inuit.

Wooden dolls were used by prehistoric Bering Sea Eskimos in ceremony and religion, but were also sometimes made as children's toys.University of Aberdeen/Qanirtuuq, Inc.

"The Thule people came with larger villages and dogsleds and boats and had come from a militaristic background," Fitzhugh said. "The Dorsets had no bows and arrows; they were sitting ducks. They were pushed into the fringes or were annihilated."

Their demise came around 1300 to 1400 A.D., before the arrival of Norse seafarers from Europe. After looking at the genetic data, it appears that no living groups are related to this extinct society, the authors say.

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Anthropologists and archaeologists say there are still many more questions to answer about who settled North America, the planet's last continent to be colonized by humans.

"The picture that emerges is interesting and supports some of the things we are doing with y- chromosome analysis," said Theodore Schurr, professor of anthropology at the University of Pennsylvania who was not part of the study. "It does add some nuance to sequence of expansions coming out of the (Siberia) and some clarity of relationship between paleo-Eskimo and neo-Eskimo. It raises some interesting questions about cultural continuity."

Schurr says understanding how the Dorset, Inuit and other groups adapted to their environment thousands of years ago is also important as a model for modern-day Arctic residents who now are dealing with increased temperatures, shrinking sea ice and changes in wildlife migrations as the result of global climate change.