Central Asia: genetics and archaeology

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Central Asia: genetics and archaeology Ron Pinhasi and Evelyne Heyer

This chapter discusses human migrations in Central Asia, with particular reference to the genetics of the Indo-Iranian- and Turkic-speaking populations and the archaeological record of pastoralism on the Steppes, from the Caspian Sea to the Tian Shan Mountains.

The evolutionary history of modern humans has been characterized by range expansions, colonizations and recurrent migrations over the last 100,000 years (CavalliSforza et al. 1994). Some regions of the world served as natural corridors between landmasses and are of particular importance in the history of human migrations. Central Asia was probably at the crossroads of several such migration routes (Nei & Roychoudhury 1993). It encompasses a vast territory, stretching from the Pamir and Tian Shan mountains in the east to the Caspian Sea in the west; limited to the north by the Russian taiga and to the south by the Iranian deserts and Afghan mountains. The rather uniform low-relief, treeless topography of the Eurasian steppe, mostly unsuitable for rain-based agriculture, facilitated potential contact and movements between human groups. But the archaeological record of this region indicates that the movements and contacts varied in type, intensity, and nature during different prehistoric epochs (Sherratt 2003). The nature and timing of the emergence and spread of agriculture in Central Asia differed from that in other regions such as the Near East and southeast Europe. This is partly due to the nature of the steppe – a vast open region which is generally not suitable for rain-based agriculture – and partly due to a unique set of socioeconomic, technological, and cultural circumstances. Two of the main processes associated with the emergence of agriculture in Central Asia were the development of pastoralism and the domestication of the horse. In this chapter we review the main genetic and archaeological associations of these processes.

The Encyclopedia of Global Human Migration, Edited by Immanuel Ness. © 2013 Blackwell Publishing Ltd. Published 2013 by Blackwell Publishing Ltd. DOI: 10.1002/9781444351071.wbeghm822

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Genetic diversity in Central Asia Most previous studies, based on classical markers (Cavalli-Sforza et al. 1994), mitochondrial DNA (mtDNA) (Comas et al. 1998, 2004; Perez-Lezaun et al. 1999), or the non-recombining portion of the Y-chromosome (NRY) (Hammer et al. 2001; Wells et al. 2001; Zerjal et al. 2002; Chaix et al. 2007), have shown that genetic diversity in Central Asia is among the highest in Eurasia. NRY studies suggest an early settlement of Central Asia by modern humans, followed by subsequent waves of colonization out of this region (Wells et al. 2001). Some mtDNA studies point to an admixed origin from previously differentiated eastern and western Eurasian populations (Comas et al. 2004), and several recent analyses of mtDNA data identify east-to-west expansion waves across Eurasia in the late Pleistocene–Holocene (Derenko et al. 2007; Rootsi et al. 2007; Chaix et al. 2008). We have conducted an extensive autosomal study of more than 20 populations from this area, in which we have found a high level of autosomal genetic diversity, consistent with previous observations and higher than in Europe, the Middle East, or East Asia (Martinez-Cruz et al. 2011). We propose that the observed genetic diversity is due mainly to the differentiation of one ancestral gene pool into two major population clusters. The first includes Indo-Iranian-speaking populations (Tajiks and three Uzbek populations) who are genetically closer to populations from western Eurasia. The second includes Turkic-speaking populations (Karakalpaks, Kazakhs, Kirgiz, and two other Uzbek populations) who are closer to eastern Asian populations (with the exception of the Turkmen, who are closer to western Eurasian populations). (See Figure 24.1 for the locations of some of these groups.) This study sheds new light on the putative origins of the Indo-Iranian and Turkicspeaking populations. Most Indo-Iranians belong to two clusters that mostly do not occur in other modern Middle Eastern or European populations. One of these includes populations from Pakistan as well as Central Asia. Altogether, the significant pairwise genetic distance (i.e. FST) between almost all pairs of Indo-Iranian-speaking populations, their high levels of diversity and the variable level of admixture from putative parental populations seem consistent with the premise that Indo-Iranian speakers were already in the region during the Neolithic. Brunet’s (1998) hypothesis that some of the Neolithic populations of Central Asia have a high antiquity in the region is consistent with our genetic data, which point to an early settlement by ancestral Tajik (Indo-Iranian) people compared to the Turkic groups. However, it is not yet possible to assess the pre-Neolithic ancestry of either of these Asiatic populations. Our results simply indicate a lower genetic differentiation among Turkic speakers, despite their wide geographic distribution, which suggests a more recent common origin for them. Most Turkic-speaking individuals sampled belonged to one Central Asian cluster, only overlapping to a very small extent with the East Asian cluster, thus confirming the results of Li et al. (2009) for the Turkic-speaking Uyghur, Kazakh, and Khanty. This pattern likely reflects the existence of an ancestral group of Turkic speakers, genetically differentiated from East Asian populations, historically and linguistically believed to have originated from the Altai region or

central asia: genetics and archaeology 3 Mongolia (see chapter 23). We see no evidence for a strong Southeast Asian genetic contribution to these Central Asian populations, and an ancient DNA study on skeletal samples from Kazakhstan dated before the 7th century bce by Lalueza-Fox and his colleagues (2004) revealed a majority of west Eurasian mtDNA haplotypes, in accordance with the affinities of the Indo-Iranian-speaking populations.

The emergence of agriculture The transition to a fully Neolithic agro-pastoral economy did not occur in the steppe region until several millennia after such a transition occurred in the Fertile Crescent and southeast Europe. Unlike the Near East and Anatolia, where sedentism preceded the development of agricultural societies, the transition to agriculture in the steppe region was a product of contact with, and migration by, Fertile Crescent and southeast European Neolithic communities. Until the late 1980s, Western researchers had limited information about the Neolithic, Eneolithic, and Bronze Age cultures of eastern Europe and the Soviet regions of Europe and central Asia. Soviet archaeologists assumed that the emergence of Neolithic cultures equated with the first evidence of pottery in the archaeological record, in contrast with Western archaeologists, who viewed the Neolithic more as an economic, technological, and social transition (Telegin & Potekhina 1987; Telegin et al. 2002). Here, we differentiate three “Neolithic” economies in the Eurasian steppe as follows: (1) pottery using hunter-fisher-gatherers; (2) sedentary agro-pastoralists whose subsistence contained only a limited contribution from wild resources; and (3) hunterfisher-gatherers who incorporated some agro-pastoral elements into their subsistence, either through indigenous development or by trade/exchange with neighboring fully agricultural Neolithic groups. However, the allocation of different archaeological “cultures” into these three categories is not always straightforward. Recent research has highlighted the inadequacy of many chronologies and cultural definitions by typological attributes such as pottery style (Lillie 1998). Emphasis is therefore placed here on well-defined archaeological entities that reveal evidence for a transition to agriculture. A maritime Early Pre-Pottery Neolithic B dispersal with domesticated crops, sheep, and goats from the Levant/Anatolia to Cyprus (c.8300 bce, see chapters 17 and 20) is now well documented. This initial dispersal was followed by one or more migrations from northwest Anatolia into Turkish Thrace and further into southeast Europe. It seems plausible that one or more of these westward migrations was also paralleled by the spread of farming eastward to the eastern flanks of the Fertile Crescent and further east into central Asia. In northeastern Iran, western Turkmenistan and central Asia, foundation dates for the Neolithic, which includes pottery, are towards the end of the 7th millennium bce. Examples are Tepe Sialk and Tepe Chakmak in eastern Iran (c.6300 bce) and the Jeitun culture in Turkmenistan at c.6000 bce (Harris 1998, 2010; Fuller 2006). Local Mesolithic sites in these regions do not show evidence of being the progenitors of the Jeitun culture, and it seems most likely that there was a spread of Neolithic agricultural elements from the Fertile Crescent (Harris & Gosden 1996).

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In other parts of Central Asia, north of Afghanistan and southeast of Tajikistan, Neolithic cultures began up to half a millennium later, represented for example by the Kelteminar complex of Kazakhstan, the Hissar culture of Tajikistan, the Central Ferghana of Uzbekistan and the Neolithic levels of the Oshkona site in Tadjikistan (Brunet 1998). However, most of these cultures lack archaeological evidence of domesticated plants and animals, and hence may have been associated with pottery-using hunterfisher-gatherers (Fuller 2006). In the western zone of the Central Asian steppe, agriculture and animal husbandry were first introduced from Eastern Europe by the Criş culture at about 5800 bce (Anthony 2004). Further east, in the forest steppe regions of the Dniester and Bug rivers, local Bug-Dniester foragers began to produce pottery in the northwestern Black Sea littoral around 6200–6000 bce, prior to contact with southern farmers. Around the same period, the Surska-Dnieper culture in the Lower Dnieper area and the Rakushechnyi Yar of the lower Don river provide similar evidence for early pottery making (Telegin et al. 2002). Evidence for hunter–farmer contact is apparent in stylistic elements in Bug-Dniester pottery, and percentages of domesticated cattle and pig bones increase in Bug-Dniester occupational phases a few centuries later (c.5800–5700 bce; Anthony 2007). The North Pontic societies east of the Dniester continued to hunt, gather and fish until about 5200 bce (Anthony 2004, 2007), and the Dniepr Rapids region further east was also populated by hunting-foraging-fishing populations who adopted pottery. Around 5100–4900 bce, the fully Neolithic Cucuteni-Tripolye and Gumelniţa cultures dispersed eastward into the Dniester and southern Bug valleys.

The origins of pastoralism and horse domestication As pointed out by Renfrew (2001) and by Khazanov (1984), steppe pastoralism involved a nomadic lifestyle distinct from Near Eastern agro-pastoralism. Nomadic pastoralism entailed periodic mobility in which all the community must move, in contrast to transhumance where only herdsmen moved in and out of permanent settlements. However, identification of pastoralism in the archaeological record is not straightforward because neither the faunal nor the settlement records are sufficiently detailed. For instance, evidence of some wild resources in the diet need not mean that a particular group was not truly pastoralist. It should be pointed out that pastoral economies in Asia are offshoots of a farming economy (Renfrew 2001), since sheep, goats, and cattle were domesticated by earlier agro-pastoral communities. However, the horse is a special case since it was domesticated in regions of Central Asia where mixed farming developed late and where hunting and gathering remained dominant. The introduction of both cattle and horse breeding are taken to be major developments of the 5th/4th-millennium bce on the Russian/Ukrainian steppes. Many archaeologists today typically identify the archaeological cultures involved as Indo-European (Lamberg-Karlovsky 2002; Anthony 2007), following Marija Gimbutas (1977), who combined data from linguistic paleontology and archaeology in an attempt to locate the “homeland” of the Proto-Indo-European

central asia: genetics and archaeology 5 (PIE) speakers and to explain their rapid and extensive spread. Gimbutas defined the term “Kurgan culture” to refer to pastoral communities documented from the 5th millennium bce onwards in the steppe environments of the Volga-Ural-Caspian region. She suggested that these peoples spoke Indo-European languages, maintained a patriarchal society and were militant, mobile horse-riding pastoralists. This was in contrast to the matriarchal, peaceful, and sedentary European (Neolithic, Eneolithic) societies. She also proposed three major incursions or infiltrations of “Kurgan” peoples from the Pontic steppe into Europe, which took place between 4500 and 2500 bce. However, since the 1990s, Gimbutas’ model has lost popularity due to the limited archaeological and genetic evidence for migration from the Steppes into Europe on the required scale at this time (see chapter 18). The recovery of horse bones from the Eneolithic (Copper Age) settlement of Dereivka on the Lower Dnieper River was once believed to offer the first material evidence for early horse domestication and for the movement of nomads from the east. But Anthony (2007) has shown that the only Dereivka horse teeth displaying evidence of bit wear date to the medieval period. More recently, new evidence has emerged from DNA analysis of modern horses to suggest multiple centers of origin for horse domestication, and not a single center as was previously assumed (Jansen et al. 2002; McGahern et al. 2006). A more recent study by Outram et al. (2009) examines bit wear, metrics of horse limb bones, and organic residues in pottery from several Botai culture sites in Kazakhstan (3500–3000 bce). Horse bones here often comprise 99 percent of total faunal assemblages, suggesting that the Botai groups were utilizing horses in several different ways, for meat, milk, and perhaps riding. By 2500 bce, a different mobile pastoralist strategy dominated the steppes as dependence shifted from horses to domesticated sheep/goats and cattle (Benecke & von Een Driesch 2003). It appears that the emergence of nomadic pastoralism in some regions of Central Asia occurred well after the agro-pastoral economy documented, for instance, in the Jeitun culture at c.6000 bce. In some regions, such as the Botai culture, nomadic pastoralism developed directly from nomadic hunting-gathering.

Conclusion Lack of geographic barriers to gene flow within the Central Asian steppe allowed relatively easy mobility of human populations, especially during the last 10 kya, following the onset of a milder Holocene climate. Gene flow should perhaps have resulted in a homogenization of genetic diversity, but in fact there is a great degree of heterogeneity which should perhaps be attributed to cultural rather than to geographic barriers. The main divide was between nomadic herders who relied on pastoralism and consumption of livestock, and agriculturalists who relied on domesticated crops with variable livestock dependence (mainly sheep and goats, also some cattle). The emergence of nomadic pastoralism was probably associated with the domestication of the horse, although further research is required on whether this lifestyle was initially developed by nomadic hunter-gatherers or introduced by eastern Fertile Crescent agriculturalists. Further research on ancient DNA in Neolithic, Chalcolithic, and Bronze Age skeletons

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is also required in order to provide a more holistic outlook on the complex interplay between the biological and cultural history of Central Asia. SEE ALSO: 17 Anatolia and the Balkans: archaeology; 19 Europe and western Asia: IndoEuropean linguistic history; 20 Europe: Neolithic colonization; 23 Northern and northeastern Asia: archaeology; 24 Northeastern and Central Asia: “Altaic” linguistic history

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