The Peopling of North America from a Molecular Anthropological Perspective  

Historically our knowledge concerning the peopling of North America was informed by archaeological, geographic, and ethnographic evidence. This evidence argued that the ancestors of today's American Indians migrated into the Americas from north Asia some 15,000-13,000 years ago, shortly after the end of the Pleistocene time period. With the development of new technologies, however, new evidence has emerged that at times challenges long held anthropological theories. Such a restructuring of our understanding of the early peopling of the Americas is currently taking place. This new understanding of American Indian's time depth in the Western Hemisphere is largely the result of the advent of molecular genetic methods and theories that have been applied to questions concerning the early peopling of the Americas.

Two types of data are the basis for the molecular genetic evidence, which argues that the initial migration into the Americas originated somewhere in south-central Siberia between 35,000-20,000 years before present. These dates are much earlier than previous estimates based on radiocarbon analysis of archaeological material, although new sites such as Gault in Texas may date to this time period. Using the frequency of genetic markers found in either mitochondrial DNA (mtDNA) or Y chromosome DNA, the new understanding of the peopling of the Americas argues that the first migrants followed what has come to be called the Northwest Coast route. These early north Asian migrants, it is hypothesized, moved along the Northwest coast of North America until they were south of the Pleistocene glacial ice sheets that covered much of Canada, at which point they expanded into all continental regions. These early American Indians are hypothesized to have brought mtDNA haplogroups A-D and Y chromosome haplogroup P-M45a and Q-242/Q-M3 haplotypes. A second migration is also hypothesized to have entered the Americas either at the same time or at a somewhat later date, bringing mtDNA haplogroup X and Y chromosome haplogroups P-M45b, C-M130, and R1a1-M17. A third and final migration is hypothesized to have taken place after the last glacial maximum in northern North America.

Based on this genetic evidence, it has also been possible to geographically position the area in north Asia where these early migrants most likely came from. For example, the major Y haplotype present in most American Indians has been traced back to recent ancestors common with Siberians, namely, the Kets and Altaians from the Yenissey River Basin and Altai Mountains, respectively. Going further back, the next common ancestor in the genetic lineage gave rise also to Caucasoid Y chromosomes, probably from the central Eurasian region. The mtDNA evidence argues for a similar conclusion, although it places the homeland of the north Asian first Americans somewhere between contemporary Mongolia and Siberia, most likely around present-day Tibet and Ulan Bator. This is based on evidence indicating that all mtDNA lineages can be found in Siberia except lineage B, which is found in the Ulan Bator region of north Asia.

No molecular genetic evidence has been found to support theories that argue Pleistocene Europeans, ocean going Polynesians, sea-faring Persians, or other cultural groups migrated to the Americas. In fact, the molecular genetic evidence is fairly conclusive: today's American Indian, Alaskan Native, and First Nation people's ancestors originally migrated to the Americas from north Asia. The exact times when these migrations took place are still under dispute, but the molecular genetic evidence strongly argues for a greater time depth of human occupation in the America than historically held.

About the Author

I am Director of the Bauu Institute and Press, which conducts research and publishes books in the environmental, psychological, and social sciences. I have written numerous articles and books, includingAmerican Indian mtDNA, Y Chromosome Genetic Data, and the Peopling of North America.