The web is abuzz over a new publication in PLoS Genetics about a single main migration across Bering Strait. From what I can tell, this new paper, “Genetic Variation and Population Structure,” coincides with a recent publication in PLoS One that sampled mtDNA and figured out people moved in waves, but first they spent some time in Beringia.
Both of these papers use microsattelites or SNPs in genes from native American populations to answer the question, did a small population from Siberia trek across the Bering Strait land bridge some 12,000 years ago and give rise to the native peoples of North and South America? Or did people come from other parts of Asia or Polynesia, arriving in multiple times, at several places on the two continents, by sea as well as by land, in successive migrations that began as early as 30,000 years ago?
To answer this question, the authors picked out 678 markers in the DNA of present-day members of 29 Native American populations across North, Central and South America. They also analyzed data from two Siberian groups. The figure to your right is from the publication, which illustrates who and where the populations sampled are from.
They figured out that a unique genetic variant, which is part of a noncoding region, is widespread in Native Americans across both American continents and it originated in Siberia. This implies that the first populations came into the Americas came from a single migration or multiple waves from a single source. This rules out the possibility that people came in waves of migrations from different sources. The following graph documents this:
Furthermore, the genetic diversity, as well as genetic similarity is very close to the Siberian groups tested. This supplements to existing archaeological and genetic evidence that the ancestors of native North and South Americans came by the northwest route.
Additional findings that are also interesting are that populations in the Andes and Central America are genetically similar. And populations from western South America showed more genetic variation than populations from eastern South America. And to appease the linguists out there, the populations more similar linguistically were also more similar genetically. Pretty cool, huh?