Throwing light on the lineage of indigenous Americans, a new international study found that the native population originated from at least three waves of migrations. Nevertheless, majority of the natives in the Americas descended from a single group of migrants, the study report published in the Nature journal says.
Exploring more than 300 thousand gene variations, the broader genetic investigation concluded that the first migrations was through now submerged 'Berengia land bridge' created by deep glacial ice between Siberia in Eurasia to Alaska in North America. The first migration might have occurred around 15,000 years ago in the last ice age.
Probably settling debates on the number and composition of lineage diversities within the Americas, researchers examined the single nucleotide polymorphisms or SNP, among the population groups. SNP represents a difference in a single DNA building block, called a nucleotide. This helped them uncover the genetic similarities and differences between the various Native American groups. The international team analyzed samples from 52 Native American and 17 Siberian groups.
David Reich, professor of genetics at Harvard Medical School, who led the team of scientists said, "There are at least three deep lineages in Native American populations." According to him, the Asian lineage leading to First Americans is the most anciently diverged, whereas the Asian lineages that contributed some of the DNA of Eskimo-Aleut speakers and the Na-Dene-speaking Chipewyan from Canada are more closely related to present-day East Asian populations.
The study thus shows that most of the indigenous Americans have their genetic make-up from first migrants. The two subsequent migrations into the Americas had an impact only on the Arctic populations that spoke Eskimo-Aleut languages and the Canadian Chipewyan people who spoke a Na-Dene language. This indicated the fact that migrants mixed with Native Americans already present on the continent. It is observed that Eskimo-Aleut speakers had half of their genome from first Americans, while the Chipewyan had almost 90 percent.
Once in the Americas, the population moved southward along the coast, branching off at places. After that there was no mixing of genes among the Native American groups, especially in South America.
There were, however, two exceptions to this movement of people. This included the Central American Chibchan-speakers who had a mixed ancestry from both North and South America. This indicated back-migration from South America. The Naukan and coastal Chukchi people from Northeastern Siberia carried 'American' DNA. This meant that Eskimo-Aleut speakers migrated back to Asia, taking with them Native American genes.
by RTT Staff Writer
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