The research, published in the journal Science Advances, represents the first large-scale study of ancient DNA from early Americans.
The findings suggest that people from Siberia were isolated for around 2400-9000 years in what is now the Bering Land Bridge region (referred to as "Beringia" and including parts of Russia and Alaska) before entering North America 16,000 years ago. They traveled down the Pacific coastline, with some reaching southern Chile 14,600 years ago.
One of the descendants of these first Native Americans was "La Doncella," The Maiden, a 13-year-old girl who died during a ritual sacrifice at Mount Llullaillaco, Argentina, 500 years ago. Her frozen body, discovered in 1999, was hailed as being one of the best-preserved mummies ever found.
Bastien Llamas, a senior research associate with the University of Adelaide's Australian Center for Ancient DNA (ACAD), told Discovery News that "it seems that her mitochondrial lineage did not survive until today, and that this pattern is not unusual."
Mitochondrial DNA represents maternal genetic lineages. It was the focus of the new study. The fact that such DNA for La Doncella has not yet been found in existing Native Americans suggests that she has no direct living relatives. The researchers also could not make a modern match with the other 91 analyzed pre-Columbian remains.
Llamas said, "The fact that none of the 92 pre-Columbian mitochondrial lineages survived to today is due to a combination of factors: 1- indigenous populations were fragmented and groups lived isolated from each other; 2- some of these isolated groups became extinct following European contact; 3- many modern genetic lineages have not been surveyed yet."
It is known that many early Native Americans succumbed to diseases brought over by Europeans for which many had evolved no immunity. Such illnesses included syphilis, smallpox, measles, mumps, and the bubonic plague.
Nevertheless, Alan Cooper, who is the director of ACAD, suspects that at least some of the ancient genetic lineages did survive to modern times and will eventually be found in current populations, once enough individuals are analyzed.
Cooper explained that "demographic results show that the Beringian population was relatively small -- probably as few as 10,000 individuals -- which is consistent with what we estimate the resources in Beringia could have sustained."
He continued, "At 16,000 years ago, the population suddenly increased massively, and then kept increasing for several thousand years after that. This population increase could not occur in Beringia because of the limited resources, however, the timing coincides with a slight retreat of coastal glaciers along the northwest Pacific coast, providing a route around the ice sheets and into North America proper."
Once in the Americas, the groups appear to have splintered off, but generally migrated following the coastline. Some, via multiple generations, remarkably traveled the entire length of North, Central and South America in just 1400 years.
Carles Lalueza-Fox, a scientist at the Spanish National Research Council, told Discovery News that the new study "not only tackles the loss of genetic diversity in the current Amerindian populations as compared to the ancient, but also narrows down the date of a population expansion that is only compatible with a coastal migration route and not with the ice-free corridor that opened thousands of years later."
He suspects that the noted loss of genetic diversity could be tied to the epidemics brought in by Europeans. For example, he said that the survivors might have "had some rare resistance genetic variants," which those who perished lacked. The disease aftermath then might have reduced or eliminated some early Native American lineages in favor of others.
Read more at Discovery News
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