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Genetics offers clues to human migration to Americas

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Nikkohl Gallant
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« on: January 12, 2009, 05:10:28 am »

Genetics offers clues to human migration to Americas
Updated Sun. Jan. 11 2009 10:54 AM ET




The Canadian Press

EDMONTON -- It's one of the great remaining questions of the ancient past -- and new research suggests the answer played out across the Canadian prairies.

Anthropologists have long thought the first humans came to the New World down the Pacific coast, but a paper published Thursday uses genetic analysis to argue that the eastern slopes of the Rocky Mountains and the plains of Alberta, Saskatchewan and Manitoba were also one of the main routes.

"For the first time, we can clearly see the route that these Paleo-Indians followed," Ugo Perego, lead author of the paper in Current Biology, said from Salt Lake City.

Humans first came to North America sometime between 17,000 and 15,000 years ago, crossing from Asia when the massive glaciers of the Ice Age lowered sea levels enough to create a land bridge between Siberia and Alaska.

Previous evidence has suggested that those early hunters migrated to their new land down the West Coast, along a glacier-free strip of land or in boats near the shore. But deep differences in aboriginal languages and tool-making styles have long hinted that there was more than one migration.

Perego and his team decided to use the same type of genetic analysis that has been used in other parts of the world to trace human migration over millennia. The technique is responsible for the "Out of Africa" theory, which suggests that humans originated on that continent and slowly spread over the planet.

Applying the method to aboriginal people across North and South America, Perego discovered that DNA material from a 10,000-year-old skeleton found in Alaska contained rare genes that were also present in contemporary aboriginals all the way down the Pacific Coast as far as Chile - and nowhere else.

A second type of rare DNA was found concentrated among Ojibwa people near Ontario's Manitoulin Island, as well as occasionally throughout continental North America, but nowhere south of the U.S.-Mexico border.

That suggests a separate group of migrants who would have moved into the new land by following a gap between the two great ice sheets that covered the northern part of the continent. They would have come diagonally southeast from Alaska to the eastern slopes of the Rockies, then across the plains to the Great Lakes.

"We could see a clear route coming down from Alaska all the way to the Great Lakes and kind of stopping there," Perego said.

"(The DNA) allowed us to follow in the footsteps of the Paleo-Indians. There were at least two different routes that were taken as the glaciers retreated after the last Ice Age."

The Pacific route was probably the most heavily used, his paper concedes. But the continental route was crucial how North America was peopled.

Perego noted that maps locating the different DNA types roughly correspond to different language groups as well as different tool-making styles.

"We have a signature, a legacy, that is still maintained in some people living today that is directly connected to that skeleton 10,000 years ago which is very close to that first arrival - which is really cool."

The next step will be to fine-tune his analysis using more commonly found DNA types, said Perego. But his current findings are a major step forward in understanding the prehistory of the entire New World, he suggested.

"Right now, there are three questions: How long ago did Paleo-Indians arrive in North America? How many waves of migration were there? How exactly did they arrive?"

Scientists have pretty good answers for the first two. Given the rarity of archeological sites from the era, Perego's paper may be the beginning of the answer to the third.

"We are very proud of this paper."

http://www.ctv.ca/servlet/ArticleNews/story/CTVNews/20090111/migration_genetics_090111/20090111?hub=SciTech
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