Northeast Indian Population Genetics

Northeast Indian Population Genetics

Molecular Biology and Evolution
The Northeast Indian Passageway: A Barrier or Corridor for Human Migrations?
Richard Cordaux et al.
The northeast Indian passageway connecting the Indian subcontinent to east/southeast Asia is thought to have been a major corridor for human migrations. Because it is also an important linguistic contact zone, it is predicted that northeast India has witnessed extensive population interactions, thus leading to high genetic diversity within groups and heterogeneity among groups. To test this prediction, we analyzed 14 bi-allelic and 5 short tandem repeat Y-chromosome markers and hypervariable region 1 mtDNA sequence variation in 192 northeast Indians. We find that both northeast Indian Y-chromosomes and mtDNAs consistently show strikingly high homogeneity among groups and strong affinities to east Asian groups. We detect virtually no Y-chromosome and mtDNA admixture between northeast and other Indian groups. Northeast Indian groups are also characterized by a greatly reduced Y-chromosome diversity, which contrasts with extensive mtDNA diversity. This is best explained by a male founder effect during the colonization of northeast India that is estimated to have occurred within the last 4,000 years. Thus, contrary to the prediction, these results provide strong evidence for a genetic discontinuity between northeast Indian groups and other Indian groups. We therefore conclude that the northeast Indian passageway acted as a geographic barrier rather than as a corridor for human migrations between the Indian subcontinent and east/southeast Asia, at least within the last millennia and possibly for several tens of thousand years, as suggested by the overall distinctiveness of the Indian and east Asian Y-chromosome and mtDNA gene pools.
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