Settlement of The Americas - Genetics and Blood Type

Genetics and Blood Type

For more details on this topic, see Genetic history of indigenous peoples of the Americas.

By the 1920s studies indicated that blood type O was predominated in pre-Columbian populations, with a small admixture of type A in the north. Further blood studies combining statistics and genetic research were pioneered by Luigi Cavalli-Sforza and applied to population migrations predating historical records. This led Jacob Bronowski to assert in 1973 (in The Ascent of Man) that there were at least two separate migrations:

"I can see no sensible way of interpreting that but to believe that a first migration of a small, related kinship group (all of blood group O) came into America, multiplied, and spread right to the South. Then a second migration, again of small groups, this time containing either A alone or both A and O, followed them only as far as North America."

Modern Amerindian genetics studies focus primarily on Human Y-chromosome DNA haplogroups and Human mitochondrial DNA haplogroups. The genetic pattern emerging shows two very distinctive genetic episodes occurred, first with the initial peopling of the Americas, and secondly with European colonization of the Americas. The former is the determinant factor for the number of gene lineages, zygosity mutations and founding haplotypes present in today's indigenous Amerindian populations.

Genetics and blood studies indicate human settlement of the New World occurred in stages from the Bering sea coastline, with an initial layover on Beringia for the small founding population. The micro-satellite diversity and distributions of the Y lineage specific to South America indicates that certain Amerindian populations have been isolated since the initial colonization of the region. The Na-Dené, Inuit and Indigenous Alaskan populations exhibit haplogroup Q (Y-DNA) mutations, but are distinct from other indigenous Amerindians with various mtDNA and atDNA mutations. This suggests that the earliest migrants into the northern extremes of North America and Greenland derived from later migrant populations.