Native Americans descended from a single ancestral group

April 30th, 2009 - 4:01 pm ICT by ANI  

Washington, April 30 (ANI): In a new research, an international team of scientists has determined that the Native Americans, who came to the New World, descended from a single ancestral group.

“Our work provides strong evidence that, in general, Native Americans are more closely related to each other than to any other existing Asian populations, except those that live at the very edge of the Bering Strait,” said Kari Britt Schroeder, a lecturer at the University of California, Davis, and the first author on the paper describing the study.

“While earlier studies have already supported this conclusion, what’s different about our work is that it provides the first solid data that simply cannot be reconciled with multiple ancestral populations,” he added.

The research team, which was headed by Noah Rosenberg at the University of Michigan, scrutinized DNA samples of people from 31 modern-day Asian populations, 19 Native American, one Greenlandic and two western Beringian populations.

The team’s work follows up on earlier studies by several of its members who found a unique variant (an allele), dubbed the “9-repeat allele,” of a genetic marker in the DNA of modern-day Native American people.

They found that in each sample that contained the 9-repeat allele, short stretches of DNA on either side of it were characterized by a distinct pattern of base pairs, a pattern they seldom observed in people without the allele.

“If natural selection had promoted the spread of a neighboring advantageous allele, we would expect to see longer stretches of DNA than this with a similarly distinct pattern,” Schroeder said.

“And we would also have expected to see the pattern in a high frequency even among people who do not carry the 9-repeat allele. So we can now consider the positive selection possibility unlikely,” he added.

The results also ruled out the multiple mutations hypothesis.

If that had been the case, there would have been myriad DNA patterns surrounding the allele rather than the identical characteristic signature the team discovered.

“There are a number of really strong papers based on mitochondrial DNA - which is passed from mother to daughter - and Y-chromosome DNA - which is passed from father to son - that have also supported a single ancestral population,” Schroeder said.

“But, this is the first definitive evidence we have that comes from DNA that is carried by both sexes,” he added. (ANI)

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