Genetic diversity in Svaneti and its implications for the human settlement of the Highland Caucasus.

Abstract

In this study, we characterized genetic diversity in the Svans from northwestern Georgia to better understand the phylogeography of their genetic lineages, determine whether genetic diversity in the highland South Caucasus has been shaped by language or geography, and assess whether Svan genetic diversity was structured by regional residence patterns. We analyzed mtDNA and Y-chromosome variation in 184 individuals from 13 village districts and townlets located throughout the region. For all individuals, we analyzed mtDNA diversity through control region sequencing, and, for males, we analyzed Y-chromosome diversity through SNP and STR genotyping. The resulting data were compared with those for populations from the Caucasus and Middle East. We observed significant mtDNA heterogeneity in Svans, with haplogroups U1-U7, H, K, and W6 being common there. By contrast, ∼78% of Svan males belonged to haplogroup G2a, with the remainder falling into four other haplogroups (J2a1, I2, N, and R1a). While showing a distinct genetic profile, Svans also clustered with Caucasus populations speaking languages from different families, suggesting a deep common ancestry for all of them. The mtDNA data were not structured by geography or linguistic affiliation, whereas the NRY data were influenced only by geography. These patterns of genetic variation confirm a complex set of geographic sources and settlement phases for the Caucasus highlands. Such patterns may also reflect social and cultural practices in the region. The high frequency and antiquity of Y-chromosome haplogroup G2a in this region further points to its emergence there.