Human Paternal Lineages, Languages, and Environment in the Caucasus

Abstract

Publications that describe the composition of the human Y-DNA haplogroup in different ethnic or linguistic groups and geographic regions provide no explicit explanation of the distribution of human paternal lineages in relation to specific ecological conditions. Our research attempts to address this topic for the Caucasus, a geographic region that encompasses a relatively small area but harbors high linguistic, ethnic, and Y-DNA haplogroup diversity. We genotyped 224 men that identified themselves as ethnic Georgian for 23 Y-chromosome short tandem-repeat markers and assigned them to their geographic places of origin. The genotyped data were supplemented with published data on haplogroup composition and location of other ethnic groups of the Caucasus. We used multivariate statistical methods to see if linguistics, climate, and landscape accounted for geographical differences in frequencies of the Y-DNA haplogroups G2, R1a, R1b, J1, and J2. The analysis showed significant associations of (1) G2 with well-forested mountains, (2) J2 with warm areas or poorly forested mountains, and (3) J1 with poorly forested mountains. R1b showed no association with environment. Haplogroups J1 and R1a were significantly associated with Daghestanian and Kipchak speakers, respectively, but the other haplogroups showed no such simple associations with languages. Climate and landscape in the context of competition over productive areas among different paternal lineages, arriving in the Caucasus in different times, have played an important role in shaping the present-day spatial distribution of patrilineages in the Caucasus. This spatial pattern had formed before linguistic subdivisions were finally shaped, probably in the Neolithic to Bronze Age. Later historical turmoil had little influence on the patrilineage composition and spatial distribution. Based on our results, the scenario of postglacial expansions of humans and their languages to the Caucasus from the Middle East, western Eurasia, and the East European Plain is plausible.

Y-DNA haplogroup diversity is most commonly used to analyze ancestry of individual ethnic groups or linguistic families (Kayser et al. 1997; Brisighelli 2012), because Y-DNA haplogroups generally show more distinct ethnogeographic patterns than does matrilineally inherited mitochondrial DNA (Comas et al. 2000; Nasidze et al. 2003, 2004a), most likely because of higher dispersal rates of women (Seielstad et al. 1998; Oota et al. 2001; Nasidze et al. 2004b), the effects of selective pressures on the mitochondrial genome (Mishmar et al. 2003), and/or sex ratio in favor of women causing more genetic drift in males (Dupanloup et al. 2003). Moreover, there is a popular nomenclature of the haplogroups linked to a well-established phylogenetic pattern (Underhill et al. 2001; Y Chromosome Consortium 2002; Karafet et al. 2008; Chiaroni et al. 2009).

The Caucasus is among the most linguistically and culturally diverse regions of Eurasia (Comrie 2008; Nasidze et al. 2004a; Marchani et al. 2008; Balanovsky et al. 2011; Yunusbayev et al. 2012). Currently, the region hosts dozens of languages that are grouped into three language families (Comrie 2008): Caucasian, Indo-European, and Turkic. The Caucasian language family traditionally includes Adyghean, Vainakh, Daghestanian, and Kartvelian languages (Catford 1977), although the common origin of these languages is disputed (Starostin 1989). A recent study by Pagel et al. (2013) shows that the Kartvelian and Dravidic language families are the most basal in relation to the other Eurasian language families. Diakonoff and Starostin (1988) suggest that Vainakh and Daghestanian (i.e., Northeast Caucasian languages) are related to extinct Hurro-Urartian. Armenian and Ossetian languages belong to the Indo-European language family, and Oghuz and Kipchak subgroups of the Turkic language group are spoken in the Caucasus as well (Catford 1977; Comrie 2008). Linguistic differences, along with the differences in political history, influence (but do not determine) the ethnic identities of the people inhabiting the region. Some ethnic boundaries (e.g., that of Armenians or Ossetians) coincide with the linguistic boundaries, but those of the other ethnic groups do so only partly. Some groups speaking several mutually unintelligible but related languages consider themselves to be part of a single ethnos (e.g., Georgians...