[h=3]Comparison of Y-Chromosome and mtDNA Data[/h]Our identification of two major male migrations into the New World—one from southern Middle Siberia, bringing Y-chromosome haplogroups M45a and M3, and a second from eastern Siberia, bringing haplogroups M45b and RPS4Y-T—correlates well with previous conclusions about the maternal migrations that brought mtDNA haplogroups A, B, C, and D to the Americas. Since all Siberian migrations necessarily came through northwestern North America, the more southern distribution of the M45a and M3 lineages versus the M45b and RPS4Y-T lineages indicates that the southern Middle Siberian migration predated the eastern Siberian migration.
The Y-chromosome M45a and M3 lineages, together with the mtDNA haplogroups C and D and the Amerind sublineages of mtDNA haplogroup A, are all found together in southern North America as well as in Central and South America. Furthermore, the M45a Y chromosomes—which are the precursors to the Native American M3 lineage—and the mtDNA haplogroups C and D are at their highest frequencies in southern Middle Siberia, with the M3 lineage and the Amerind mtDNA haplogroup A sublineages both being present in Chukotka. Hence, the first Native American migration must have originated in southern Middle Siberia, traversed Chukotka, and entered the Americas. If we assume that the Amerind Y-chromosome lineages arrived together with mtDNA haplogroups C and D, then this migration occurred ∼20,000–30,000 years before present (YBP) (Schurr et al.
1999).
Similarly, the Y-chromosome haplogroups M45b and RPS4Y-T, along with the sublineage of mtDNA haplogroup A defined by the control-region sequence variant 16192T and the
RsaI polymorphism at np16392, are defining features of the Na-Dene of northwestern North America. Furthermore, the M45b and RPS4Y-T Y-chromosome lineages are found at their highest frequencies in the Lower Amur and Sea of Okhotsk regions of eastern Siberia, having originated earlier in Southeast Asia (B. Su and L. Jin, unpublished data). This implies that a major component of the Na-Dene migration arose in southeastern Siberia. Likewise, the precursor of the haplogroup A 16392
RsaI sublineage, defined by the control-region variant 16192T, has been observed in Chukotka and Kamchatka (Schurr et al.
1999), which border on the Sea of Okhotsk. Assuming that the mtDNA haplogroup A 16192T sublineage arrived in the Americas together with the Y-chromosome lineages M45b and RPS4Y-T, then this migration came from southeastern Siberia at ∼7,000–9,500 YBP.
In conclusion, there appears to be a striking correspondence between Siberian and Native American Y-chromosome and mtDNA haplogroup distributions, and, hence, they must have been associated during trans-Beringian migrations. The results strongly suggest that both males and females came to the New World in at least two coherent waves of migration, the first arising in southern Middle Siberia and the second arising later from southeastern Siberia.