Trading Genes along the Silk Road: mtDNA Sequences and the Origin of Central Asian Populations

Abstract

Central Asia is a vast region at the crossroads of different habitats, cultures, and trade routes. Little is known about the genetics and the history of the population of this region. We present the analysis of mtDNA control-region sequences in samples of the Kazakh, the Uighurs, the lowland Kirghiz, and the highland Kirghiz, which we have used to address both the population history of the region and the possible selective pressures that high altitude has on mtDNA genes. Central Asian mtDNA sequences present features intermediate between European and eastern Asian sequences, in several parameters-such as the frequencies of certain nucleotides, the levels of nucleotide diversity, mean pairwise differences, and genetic distances. Several hypotheses could explain the intermediate position of central Asia between Europe and eastern Asia, but the most plausible would involve extensive levels of admixture between Europeans and eastern Asians in central Asia, possibly enhanced during the Silk Road trade and clearly after the eastern and western Eurasian human groups had diverged. Lowland and highland Kirghiz mtDNA sequences are very similar, and the analysis of molecular variance has revealed that the fraction of mitochondrial genetic variance due to altitude is not significantly different from zero. Thus, it seems unlikely that altitude has exerted a major selective pressure on mitochondrial genes in central Asian populations.

A Genetic Focus on the Peopling History of East Asia: Critical Views

“…Altogether, these results indicate that the genetic pool of NEAS is related to that of CAS and exhibits signatures of gene flow from multiple sources, while that of SEAS indicates greater isolation and population subdivision, although with a low level of differentiation among populations. Another crucial result related to these observations is the very high level of genetic diversity found in Central Asian populations (Comas et al 1998(Comas et al , 2004Hammer et al 2001;Quintana-Murci et al 2004;Wells et al 2001;Zerjal et al 2002), compatible with their connection to NEAS through gene flow, Central Asia being considered either as a source or as a receiver (Comas et al 1998(Comas et al , 2004Quintana-Murci et al 2004;Zerjal et al 2002) of human migrations.…”

Ancient links between Siberians and Native Americans revealed by subtyping the Y chromosome haplogroup Q1a

“…[2][3][4][5][6][7] The presence of West-Eurasian genetic components in North and East Asia can be interpreted either as the evidence of ancient migration via the northern route 8 or simply as the reflection of recent population admixture. 9,10 However, results of mtDNA analysis in northern Eurasian populations do not support a northern Asian migration route out of Africa, but they do predict that there were at least two migrations into South Siberia, one from East Asia and one from West Eurasia. 6 West Eurasian mtDNA haplogroups found in gene pools of South Siberians (for example, N1e, I4, J1b2, N1a, U4 and X2e) demonstrate an obvious link between populations of Siberia and those of West Asia, the Caucasus and East Europe.…”

Northwest Siberian Khanty and Mansi in the junction of West and East Eurasian gene pools as revealed by uniparental markers

“…This emphasize the complex background of Northwest Siberian genetic diversity, shaped by recurrent founder effects, admixture and drift in these indigenous populations. Figure 5 Median-joining networks for Eurasian (a) mtDNA U4 sequences (colors for the U4 network are the following: gray (original Khanty and Mansi data with additional reference populations 40,44,45 ); white (Northeast European populations 16,25,46 -48 ) and black (South Siberian populations 12,15,49 grouped with Central Asian populations 50,51 and Central Siberia Yakuts 52 )) and Y chromosome (b) N3 (the N3 network corresponds the following colors: gray (original Khanty and Mansi data); white (Northeast European populations 28,53 ) and black (Central Siberian Yakuts 54 )) and (c) N2 Y-short tandem repeat (STR) haplotypes (nine loci) (the N2 network corresponds the following colors: gray (original Khanty and Mansi data); white (Northeast European populations 11,28 ) and black (South Siberian populations 11 grouped with Northeast Siberian Eskimos 11 )).…”