The rather artistic PCA below shows genetic clines which run through West Eurasia, and thus potential routes of ancient migrations across the region. It suggests that Europe and the Caucasus were populated by similar populations from the Near East, but didn't mix much after that. There appears to be some Russian influence in a few samples from the Caucasus, but no significant admixture from the Caucasus in Ukraine or Russia.
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.
Bayazit Yunusbayev et al., The Caucasus as an asymmetric semipermeable barrier to ancient human migrations, Mol Biol Evol (2011) doi: 10.1093/molbev/msr221 First published online: September 13, 2011