The Caucasus as an Asymmetric Semipermeable Barrier to Ancient Human Migrations

The Caucasus, inhabited by modern humans since the Early Upper Paleolithic and known for its linguistic diversity, is considered to be important for understanding human dispersals and genetic diversity in Eurasia. We report a synthesis of autosomal, Y chromosome, and mitochondrial DNA (mtDNA) variation in populations from all major subregions and linguistic phyla of the area. Autosomal genome variation in the Caucasus reveals significant genetic uniformity among its ethnically and linguistically diverse populations and is consistent with predominantly Near/Middle Eastern origin of the Caucasians, with minor external impacts. In contrast to autosomal and mtDNA variation, signals of regional Y chromosome founder effects distinguish the eastern from western North Caucasians. Genetic discontinuity between the North Caucasus and the East European Plain contrasts with continuity through Anatolia and the Balkans, suggesting major routes of ancient gene flows and admixture.