Mitochondrial DNA and prehistoric population movements in western North America

Ancient and modern DNA from populations in the Central Valley of California was examined to test specific hypotheses regarding the peopling and population structure of the region. Linguistic evidence suggests that a Penutian speaking population began replacing Hokan speaking populations in California's Central Valley approximately 4500 years before present (ybp). Archaeological data suggest substantial interaction among the peoples of California, the Great Basin, and the Columbia Plateau. However, it was not clear to what degree these interactions involved migrations and demic spreads and if so, which populations were involved.; The mitochondrial DNA (mtDNA) from virtually all modern Native Americans belongs to one of five maternal lineages or haplogroups (A, B, C, D and X) and the frequency of these haplogroups vary between populations. More closely related populations tend to possess similar distributions of haplogroups and, consequently, the frequency distribution of these haplogroups can be used to assess the relative relationships between groups as well as ancestor-descendant relationships between ancient and modern populations.; An analysis of mtDNA from modern Native American populations from western North America shows that while genetic differences increase with geographic distances, both Penutian and Hokan speaking populations show similarities across their respective geographic ranges indicative of common ancestry within the respective language phyla. MtDNA also indicates the possibility of a prehistoric migration along the Pacific coast, as populations from the Northwest closely resemble coastal peoples from southern California. Analyses of ancient mtDNA haplogroups from individuals from three burial sites in California's Central Valley do not support the hypothesis that the Penutian peoples replaced older Hokan speaking populations in the region 4500 ybp. Instead, the mtDNA haplogroup frequencies from prehistoric burials appear to be more closely related to modern Uto-Aztecan speaking peoples from southern California. DNA sequence data also broadly confirms this finding, however, there do appear to be some genetic ties between the ancient populations of the Great Basin and the prehistoric populations of the Central Valley and these relationships indicate admixture between the two regions at this time.