Magazine article Science News

Details of Migration into the Americas Revealed in DNA: Analysis of Genetic Material from Modern People Shows Three Distinct Waves of Arrival

Magazine article Science News

Details of Migration into the Americas Revealed in DNA: Analysis of Genetic Material from Modern People Shows Three Distinct Waves of Arrival

Article excerpt

The early inhabitants of the Americas entered the New World in three stages and by three distinct routes, a new genetic analysis of living Native Americans suggests.

About 15,000 to 18,000 years ago, the first migrant wave spilled from Asia down the Pacific coast and then pushed inland, eventually peopling the land from "the tip of South America all the way to Hudson Bay," says Andrew Kitchen, a genetic anthropologist at the University of Iowa who was not involved in the new research. That first migrant wave contained the ancestors of all South and Central American tribes, and North Americans, too. Later migrations changed the genetic mix of North Americans, a team of researchers has discovered.

The scientists examined the DNA of mitochondria, tiny power plants within cells that get passed down from mother to child. Scientists use mitochondrial DNA from living populations to decipher ancient movements of their ancestors. Most studies have examined only a small part of the mitochondria's circular piece of DNA. Now, Antonio Torroni, a geneticist at the University of Pavia in Italy, and his coauthors have compiled complete mitochondrial genomes from 41 native North Americans and combined that data with information from previous studies.

The result is the clearest picture yet of the complicated movements of people into the Americas, says Theodore Schurr, a molecular anthropologist at the University of Pennsylvania.

The analysis, published August 12 in the Proceedings of the National Academy of Sciences, supports the widely accepted notion of an initial coastal migration wave. A second wave of migration probably left Siberia only a couple thousand years after the first wave. Instead of trickling down the coast, the second group slipped through an ice-free corridor running from Alaska into what is now southern Canada, the team found. …

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