July 12, 2012

Original American Settlers Arrived In Three Waves

redOrbit Staff & Wire Reports - Your Universe Online

The largest survey of Native American DNA ever conducted has revealed that people settled the New World in three distinct waves, not one as previously believed, various media outlets reported Wednesday.

According to Robert Lee Hotz of the Wall Street Journal, Harvard Medical School Geneticist David Reich and an international team of colleagues compared thousands of genetic variations among 52 contemporary Native American populations with 17 groups of Siberian origin in an attempt to locate evidence of genetic similarities and differences.

"The scientists used archived genetic samples collected for other reasons in recent decades and worked independently of any tribe or Native American group," Hotz said. "They found that Native Americans descend from three distinct streams of genes from Asia -- each the hereditary signature of a different ethnic group of intrepid settlers who began to arrive 15,000 years ago or more."

"Even so, most Native Americans from Canada to the tip of South America owe their ancestry to the first of those three migrations -- a group of restless Ice Age nomads the researchers call the 'First American' wave," he added. Previous DNA evidence had suggested that the Americas had been colonized by a single wave of migrants, but the authors of this latest research say that there was a second and a third migration, BBC News reported.

All three waves originated from Siberia between 5,000 and 15,000 years ago, according to AFP reports, and most Native Americans are descendants of the first group, which crossed into the New World from Asia using the Beringia land bridge near the end of the last ice age.

The other two waves were more closely related to Han ethnic Chinese, the French news agency said. Those ensuing waves impacted only Arctic populations whose languages belong to the Aleut family, and those in the Canadian Chipewyan who speak a language that belongs to the Na-Dene family, even though they, too, inherited most of their genome from the original migration, the BBC added.

Reich and his colleagues studied more than 350,000 genetic markers during their research, and published their findings Wednesday in the journal Nature.

"For years it has been contentious whether the settlement of the Americas occurred by means of a single or multiple migrations from Siberia," co-author Andres Ruiz-Linares, a professor at University College London (UCL), told BBC News. "But our research settles this debate: Native Americans do not stem from a single migration. Our study also begins to cast light on patterns of human dispersal within the Americas."

"There are at least three deep lineages in Native American populations," added Reich. "The Asian lineage leading to First Americans is the most anciently diverged, whereas the Asian lineages that contributed some of the DNA to Eskimo-Aleut speakers and the Na-Dene-speaking Chipewyan from Canada are more closely related to present-day East Asian populations."