BMAC: long term interaction between agricultural communities and steppe pastoralists in Central Asia

indo-european-indo-iranian-migrations

Interesting new paper Mixing metaphors: sedentary-mobile interactions and local-global connections in prehistoric Turkmenistan, by Rouse & Cerasetti, Antiquity (2018) 92:674-689.

Relevant excerpts (emphasis mine):

The Murghab alluvial fan in southern Turkmenistan witnessed some of the earliest encounters between sedentary farmers and mobile pastoralists from different cultural spheres. During the late third and early second millennia BC, the Murghab was home to the Oxus civilisation and formed a central node in regional exchange networks (Possehl 2005; Kohl 2007). The Oxus civilisation (or the Bactria-Margiana Archaeological Complex) relied on intensive agriculture to support a hierarchical society and specialised craft production of metal and precious stone objects for prestige display and long-distance exchange (Sarianidi 1981; Hiebert 1994). By c. 1800 BC (the local Late Bronze Age), the internal coherence of the Oxus civilisation began to break down, along with the inter-regional exchange networks; the settlement structure of the Murghab shifted from a tiered system of urban centres, villages and hamlets, to a more dispersed pattern of smaller-scale agricultural settlements (Salvatori 2008). Contemporaneous evidence for small campsites (with a distinct ceramic tradition) suggests an influx of mobile pastoralists from the Central Eurasian Steppe and foothills (Cerasetti 1998; Masson 2002; Cattani et al. 2008). This striking combination of the sites and material cultures of both late Oxus farmers and ‘steppe’ pastoralists spans more than 500 years of Murghab prehistory (Salvatori 2008; Rouse & Cerasetti 2017).

The mixed farmer-pastoralist archaeological record of the Murghab has influenced competing interpretations of Later Bronze Age socio-political and economic relationships. Some scholars argue that the ‘collapse’ of the Oxus civilisation was at least partly due to the hostile incursions of nomads (Marushchenko 1956; Kuz’mina&Lyapin 1984; Vinogradova & Kuz’mina 1996). Others suggest that pastoralists took advantage of the Murghab’s crumbling power structure by moving into the area, but occupying only marginal, agriculturally unsuitable zones (P’yankova 1993), or merging with the late Oxus farming populations (Masson 2002). These models broadly follow ‘trade or raid’ paradigms of farmer-pastoralist interaction, whereby the perceived shortages of pastoralist communities force them to rely on agriculturalists for subsistence, material and cultural inputs (Kroeber 1947; Ferdinand 2003; Potts 2014). Such models may explain certain cases of Near Eastern pastoral economic specialisation, or historical contact scenarios between Eurasian steppe and agricultural communities on China’s northern frontier (Lattimore 1979; Barfield 2001; Alizadeh 2009; Khazanov 2009). Near Eastern and Eurasian interaction paradigms, however, fit increasingly poorly with the archaeological evidence for early farmer-pastoralist encounters in southern Central Asia.

We present data from four Murghab pastoralist campsites dating to the third to second millennia BC, restricting our discussion to the materials and practices employed by Oxus-period pastoralists to navigate shifting social, political and economic networks. Our aim is to highlight how variable strategies broadly identified under the rubric of ‘agropastoralism’ can be teased apart to recognise mechanisms of social boundary-making. Individually, these four sites present chronologically and locally distinct snapshots of farmer-pastoralist interactions across different realms of exchange (e.g. subsistence, technology and ideology); they provide examples of how pastoralists and farmers mutually participated in each other’s material and social norms. Together, these sites reveal how varied farmer-pastoralist engagement with technology and material culture did not lead inevitably to the assimilation of the two groups; rather, they worked consciously within existing systems of cultural practice to maintain distinct ‘farmer’ and ‘pastoralist’ identities, potentially over a 900-year period.

oxus-bmac-pastoralism
Region of Central Asia as discussed in this article. Areas traditionally identified with farming-dependent Oxus communities and non-Oxus mobile pastoralists are shown, acknowledging that in both areas mixed agropastoral practices have occurred in the past and present.

Conclusions

(…)First, the results indicate a cultural model of ‘being’ a pastoralist that was maintained actively over hundreds of years, in part by its material difference from that of local farmers. Second, the variability of materials, technologies and practices shared at these campsites suggests that no hegemonic power controlled trade relationships or regulated economic dependency between Oxus farmers and non-Oxus mobile pastoralists in the Murghab. Indeed, current data indicate that pastoralist occupation in the Murghab intensified during the waning of Oxus political centralisation, suggesting that the loosening of state-level structures provided the opportunity for intercultural interactions, rather than interactions being promoted or facilitated from the top. Finally, in the removal of broad-brush narratives that polarise ‘the steppe’ and ‘the sown’, and the integration of evidence suggesting that mobile pastoralists influenced the crop systems of farmers in southern Central Asia (Spengler et al. 2014b), these four sites allow us to recognise the means by which farmers and pastoralists re-shaped cultural institutions while reinforcing the meaningfulness of the associated social categories. Current work in the Murghab complements detailed studies of pastoralists in other Eurasian contexts (e.g. Frachetti 2008; Rogers 2012; Honeychurch 2015) in beginning to unravel simplistic notions of broad cross-cultural exchanges in Eurasian prehistory and the political entities traditionally seen as directing them.

The whole article is very interesting, and the four sites studied and their relevance for the said interactions are described in detail, and in chronological order. If you have the opportunity, read it.

I found it interesting that the article mentions the traditional scholarly opposition of agriculturalists vs. pastoralists (‘civilised/barbarian’, ‘state/tribe’ and ‘centre/periphery’) as an idea of Eurasian origin, and having deep ‘Western’ roots. Reading what many OIT (or anti-AIT, as they like to call themselves) supporters write, it seems to me as though they have entirely accepted and in fact are eager to promote this ‘Western’ narrative from the mid-20th century…

Steppe MLBA

This is what Narasimhan et al. (2018) had to say about the BMAC – Steppe pastoralists interaction:

We document a southward spread of genetic ancestry from the Eurasian Steppe, correlating with the archaeologically known expansion of pastoralist sites from the Steppe to Turan in the Middle Bronze Age (2300-1500 BCE). These Steppe communities mixed genetically with peoples of the Bactria Margiana Archaeological Complex (BMAC) whom they encountered in Turan (primarily descendants of earlier agriculturalists of Iran), but there is no evidence that the main BMAC population contributed genetically to later South Asians. Instead, Steppe communities integrated farther south throughout the 2nd millennium BCE, and we show that they mixed with a more southern population that we document at multiple sites as outlier individuals exhibiting a distinctive mixture of ancestry related to Iranian agriculturalists and South Asian hunter-gathers.

yamna-steppe-emba-mlba-cloud
Narasimhan et al. (2018): “Modeling results.(A) Admixture events originating from 7 “Distal” populations leading 538 to the formation of the modern Indian cloud shown geographically. Clines or 2-way mixtures of 539 ancestry are shown in rectangles, and clouds (3-way mixtures) are shown in ellipses.

(…) The absence in the BMAC cluster of the Steppe_EMBA ancestry that is ubiquitous in South Asia today—along with qpAdm analyses that rule out BMAC as a substantial source of ancestry in South Asia (Fig. 3A)—suggests that while the BMAC was affected by the same demographic forces that later impacted South Asia (the southward movement of Middle to Late Bronze Age Steppe pastoralists described in the next section), it was also bypassed by members of these groups who hardly mixed with BMAC people and instead mixed with peoples further south. In fact, the data suggest that instead of the main BMAC population having a demographic impact on South Asia, there was a larger effect of gene flow in the reverse direction, as the main BMAC genetic cluster is slightly different from the preceding Turan populations in harboring ~5% of their ancestry from the AASI.

(…)between 2100-1700 BCE, we observe BMAC outliers from three sites with Steppe_EMBA ancestry in the admixed form typically carried by the later Middle to Late Bronze Age Steppe groups (Steppe_MLBA). This documents a southward movement of Steppe ancestry through this region that only began to have a major impact around the turn of the 2nd millennium BCE.

Related

Demographic history and genetic adaptation in the Himalayan region

Open access Demographic history and genetic adaptation in the Himalayan region inferred from genome-wide SNP genotypes of 49 populations, by Arciero et al. Mol. Biol. Evol (2018), accepted manuscript (msy094).

Abstract (emphasis mine):

We genotyped 738 individuals belonging to 49 populations from Nepal, Bhutan, North India or Tibet at over 500,000 SNPs, and analysed the genotypes in the context of available worldwide population data in order to investigate the demographic history of the region and the genetic adaptations to the harsh environment. The Himalayan populations resembled other South and East Asians, but in addition displayed their own specific ancestral component and showed strong population structure and genetic drift. We also found evidence for multiple admixture events involving Himalayan populations and South/East Asians between 200 and 2,000 years ago. In comparisons with available ancient genomes, the Himalayans, like other East and South Asian populations, showed similar genetic affinity to Eurasian hunter-gatherers (a 24,000-year-old Upper Palaeolithic Siberian), and the related Bronze Age Yamnaya. The high-altitude Himalayan populations all shared a specific ancestral component, suggesting that genetic adaptation to life at high altitude originated only once in this region and subsequently spread. Combining four approaches to identifying specific positively-selected loci, we confirmed that the strongest signals of high-altitude adaptation were located near the Endothelial PAS domain-containing protein 1 (EPAS1) and Egl-9 Family Hypoxia Inducible Factor 1 (EGLN1) loci, and discovered eight additional robust signals of high-altitude adaptation, five of which have strong biological functional links to such adaptation. In conclusion, the demographic history of Himalayan populations is complex, with strong local differentiation, reflecting both genetic and cultural factors; these populations also display evidence of multiple genetic adaptations to high-altitude environments.

himalayan-map
Population samples analysed in this study. A. Map of South and East Asia, highlighting the four regions examined, and the colour assigned to each. B. Samples from the Tibetan Plateau. C.Samples from Nepal. D. Samples from Bhutan and India. The circle areas are proportional to the sample sizes. The three letter population codes in B-D are defined in supplementary table S1.

Relevant excerpts:

Genetic affinity to ancestral populations

We explored the genetic affinity between the Himalayan populations and five ancient genomes using f3-outgroup statistics. Himalayans show greater affinity to Eurasian hunter-gatherers (MA-1, a 24,000- year-old Upper Palaeolithic Siberian), and the related Bronze Age Yamnaya, than to European farmers (5,500-4,800 years ago; Fig. 5A) or to European hunter-gatherers (La Braña, 7,000 years ago; Fig. 5B), like other South and East Asian populations. We further explored the affinity of Himalayan populations by comparing them with the 45,000-year-old Upper Palaeolithic hunter-gatherer (Ust’-Ishim) and each of MA-1, La Braña, or Yamnaya. Himalayan individuals cluster together with other East Asian populations and show equal distance from Ust’-Ishim and the other ancient genomes, probably because Ust’-Ishim belongs to a much earlier period of time (supplementary fig. S15). We also explored genetic affinity between modern Himalayan populations and five ancient Himalayans (3,150 1,250 years old) from Nepal. The ancient individuals cluster together with modern Himalayan populations in a worldwide PCA (supplementary fig. S16), and the f3-outgroup statistics show modern high-altitude populations have the closest affinity with these ancient Himalayans, suggesting that these ancient individuals could represent a proxy for the first populations residing in the region (supplementary fig. S17 and supplementary table S4). Finally, we explored the genetic affinity of Himalayan samples with the archaic genomes of Denisovans and Neanderthals (Skoglund and Jakobsson 2011), and found that they show a similar sharing pattern with Denisovans and Neanderthals to the other South and East Asian populations. Individuals belonging to four Nepalese, one Cambodian, and three Chinese populations show the highest Denisovan sharing (after populations from Australia and Papua New Guinea) but these values are not significantly greater than other South and East Asian populations (supplementary figs. S18 and S19).

himalayan-pca
Genetic structure of the Himalayan region populations from analyses using unlinked SNPs. A. PCA of the Himalayan and HGDP-CEPH populations. Each dot represents a sample, coded by region as indicated. The Himalayan region samples lie between the HGDP-CEPH East Asian and South Asian samples on the right-hand side of the plot. B. PCA of the Himalayan populations alone. Each dot represents a sample, coded by country or region as indicated. Most samples lie on an arc between Bhutanese and Nepalese samples; Toto (India) are seen as extreme outlier in the bottom left corner, while Dhimal (Nepal) and Bodo (India) also form outliers.

NOTE. The variance explained in the PCA graphics seems to be too high. This happened recently also with the Damgaard et al. (2018) papers (see here the comment by Iosif Lazaridis).

Similarities and differences between high-altitude Himalayan

The most striking example is provided by the Toto from North India, an isolated tribal group with the lowest genetic diversity of the Himalayan populations examined here, indicated by the smallest long-term Ne (supplementary fig. S5), and a reported census size of 321 in 1951 (Mitra 1951), although their numbers have subsequently increased. Despite this extreme substructure, shared common ancestry among the high-altitude populations (Fig. 2C and Fig. 3) can be detected, and the Nepalese in general are distinguished from the Bhutanese and Tibetans (Fig. 2C) and they also cluster separately (Fig. 3). In a worldwide context, they share an ancestral component with South Asians (supplementary fig. S2). On the other hand, the Tibetans do not show detectable population substructure, probably due to a much more recent split in comparison with the other populations (Fig. 2C and supplementary fig. S6). The genetic similarity between the high-altitude populations, including Tibetans, Sherpa and Bhutanese, is also supported by their clustering together on the phylogenetic tree, the PCA generated from the co-ancestry matrix generated by fineSTRUCTURE (supplementary fig. S10 and S11), the lack of statistical significance for most of the D-statistics tests (Yoruba, Han; high-altitude Himalayan 1, high-altitude Himalayan 2), and the absence of correlation between the increased genetic affinity to lowland East Asians and the spatial location of the Himalayan populations (supplementary figs. S12 and S13). Together, these results suggest the presence of a single ancestral population carrying advantageous variants for high-altitude adaptation that separated from lowland East Asians, and then spread and diverged into different populations across the Himalayan region. (…)

Recent admixture events

himalayan-admixture
Genetic structure of the Himalayan region populations from analyses using unlinked SNPs. C. ADMIXTURE (K values of 2 to 6, as indicated) analysis of the Himalayan samples. Note that most increases in the value of K result in single population being distinguished. Population codes in C are defined in supplementary table S1.

Himalayan populations show signatures of recent admixture events, mainly with South and East Asian populations as well as within the Himalayan region itself. Newar and Lhasa show the oldest signature of admixture, dated to between 2,000 and 1,000 years ago. Majhi and Dhimal display signatures of admixture within the last 1,000 years. Chetri and Bodo show the most recent admixture events, between 500 and 200 years ago (Fig. 4, supplementary tables S3). The comparison between the genetic tree and the linguistic association of each Himalayan population highlights the agreement between genetic and linguistic sub-divisions, in particular in the Bhutanese and Tibetan populations. Nepalese populations show more variability, with genetic sub-clusters of populations belonging to different linguistic affiliations (Fig. 3B). Modern high-altitude Himalayans show genetic affinity with ancient genomes from the same region (supplementary fig. S17), providing additional support for the idea of an ancient high-altitude population that spread across the Himalayan region and subsequently diverged into several of the present-day populations. Furthermore, Himalayan populations show a similar pattern of allele sharing with Denisovans as other South-East Asian populations (supplementary fig. S18 and S19). Overall, geographical isolation, genetic drift, admixture with neighbouring populations and linguistic subdivision played important roles in shaping the genetic variability we see in the Himalayan region today.

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