“We conclude that irrespective of the Early Upper Paleolithic presence of anatomically modern humans both south and north of the Caucasus (Mellars 2006; Adler et al. 2008; Krause et al.2010),the combined autosomal and gender-specific genetic variation of the Caucasian 13populations testifies to their predominantly southern, Near/Middle Eastern descent. Y chromosomal variants under strong founder events, seen in particular among populations inhabiting the northern flank of the High Caucasus Mountain Range, appear to never have expanded to the East European Plain, while the nomadic people of the latter, once settled down predominantly on the northern slopes of the Caucasus, have likely preserved, to different extent, some oftheir earlier genetic heritage. In sum, though the Caucasus may well have served as a corridor for numerous invasive expeditions in the past,this has had only a minor influence on the largely sedentary core populations of the region, characterized by much greater autosomal uniformity than that might be expected from a region of deep linguistic and cultural diversity. This suggests that the core of the autosomal genetic structure of the Caucasian populations may have formed before its present-day linguistic diversity, including the language families autochthonous for the region, arose.”
'The Caucasus as an asymmetricsemipermeable barrier to ancient human migrations' By Yunusbayev et al. 2011
"Various Near Eastern groups invaded the Caucasus numerous times during the last two millennia including the occupation of Georgia by
Arab caliphs after 654 AD (Muskhelishvili 1977), the Seljuc Turks invasion of the South Caucasus in the 11th century (Muskhelishvili 1977), and repeated invasions by Turks and Persians (Muskhelishvili 1977 and references therein). Indeed, strong Y-chromosomal gene flow from
the Near East to the Caucasus has been clearly demonstrated for the interpolated maps of admixture proportions in a recent study of Central Asian populations (Zerjal et al.2002). Although these male-mediated invasions from the Near East might possibly explain why the Caucasian Y-haplogroups are of Near Eastern origin, they do not explain why mtDNA and Alu insertion polymorphisms group the Caucasus with Europe. A possible explanation for this latter result would be a common ancestry of Caucasian and European populations. This hypothesized common ancestry could date back to pre-Neolithic times, as suggested by Renfrew (1992) who considers Caucasian languages to reflect human dispersal before 15,000 years ago. On the other hand, it could reflect a route for Neolithic farmers
from the Near East to Europe via the Caucasus; there are several securely dated Neolithic sites in the Caucasus that are 6,000–7,000 years old (Masson and Merpert 1982; Muskhelishvili 1977). Analyses of additional autosomal markers are needed to verify this hypothesized common ancestry of Caucasian and European populations."
'Testing hypotheses of language replacement in the Caucasus:
evidence from the Y-chromosome' by Ivan Nasidze, Tamara Sarkisian, Azer Kerimov, Mark Stoneking