The Tarim Basin Bronze Age horizon: Isolated Paleo-Siberians or recent colonists from the West ?

I’m an admirer of the works contributed to the scientific community by Cui, Jeong & the various other contributors of the paper The genomic origins of the Bronze Age Tarim Basin mummies. (https://www.nature.com/articles/s41586-021-04052-7/figures/3). The Tarim mummies are of course well known in popular culture.

They concluded that ‘we find that the earliest Tarim Basin cultures appear to have arisen from a genetically isolated local population that adopted neighbouring pastoralist and agriculturalist practices ”. That begs the question – where are the pre-2200 BC sites in the Tarim basin ? Is it mere coincidence that the horizon became established ca 2200 BC, during the so-called 4.2 kiloyear phenomenon, when much of Eurasia was experiencing a complex and inter-connected series of demographic and socio-cultural shifts ?

As such, I thought I’d take a look into these individuals. This glimpse into the Tarim basin is a preliminary section into what I hope some day might be a more formalised synthesis and re-assessment of ‘steppe cultural dynamics’ which hopes to collate the growing body of data and assess it via a common pipeline, so to speak.

In looking at the Tarim#1 cluster, the successful model offered by the study entailed a 2-way admixture between Kolyma_mesolithic (~ 30%) and Afonotova-Gora (~ 70%). If true, then this would indeed support the hypothesis of ‘relictual Siberian population’. Their p-value was 0.219. Their finding of high ROH does lend support to the existence of a bottle-necked population,

(What I also have issues with is the modelling of clusters such as Kumsay & Botai- which date to ca 3000 BC- on the basis of Tarim 2200 BC. Whilst we sometimes have to accept ‘dyschronological’ models for the sake of hypothesis building, this approach is contingent on some unwarranted assumptions (such as the primordialism of the said Tarim basin population)).

However, there is also this possibility.

p-value 0.412936

left pops:
Tarim_EMBA1
BZK002 (Bazhaka)
Kazakhstan_Kumsay_EBA

best coefficients: 0.394 0.606 (SEs 0.09)

tail prob 0.39

right pops:

Cameroon_SMA.DG
Pinarbasi
MA1
Israel_PPNB
Brazil_LapaDoSanto_9600BP
Kostenki14a
Tianyuan
Iran_GanjDareh_N
Mongolia_North_N
Russia_HG_Karelia
Satsurblia_HG
Villabruna_HG
Hungary_EN_Starcevo_1

Also interesting is the uniparental data. The Tarim_BA males feature R1b-Ph155. R1b is so-far missing in pre-Copper/Bronze Age remains from central, ‘inner’ and northern Asia, as well as the parts of Siberia from where the Kolyma individual was found. Instead, its links to other ‘basal’ R1b lineages such as R1b-V88 and V3616 in Eastern Europe, having branched out ca 18,000 BP according to YFull. This is the start of climactic amelioration following the LGM.

For me, the evidence suggests that the Tarim _EBA horizon was neither completely isolated nor ‘local’ to the Tarim. Instead, they probably arrived from regions to the north/ northwest (? central/west Siberia, the Mountain corridor, Kazakh steppe). Of course, this is consistent with archaeological observations of early forms of pastoralism developing in Central Eurasia (e.g Frachetti), and we are beginning to understand that they engaged in complex forms of interaction across the steppe from ca 3000 BC, if not earlier.

Since then, a new study (care of Prof. Fu’s team) has come out covering the Iron Age. During this period, the basin becomes a lot more heterogeneous, with groups bearing Northeast Asian and Bactrian-related ancestry also appearing. What is also intriguing is the prevalence of Andronovo-related R1a-Z93 in the the Dzhungar basin but also a sample from the (southern) Tarim; not suprising given the expansion of Andronovo communities into the Dhzungar region (e.g. Jie et al )

Whilst I’m not going to get into historical linguistic details for now, these data provide conclusive evidence of western steppe herder presence in the vicinity of attested Tocharian speakers. Exactly with which group ‘pre-proto-Tocharian’ arrived is more difficult to answer. However, it might not be a simplistic case of Afansievo=Tocharian, Sintashta/Andronovo= proto-Indo-Iranian (requiring the introduction of concepts from the fields of contact & socio-linguistics). More data from the Tarim basin is required to synthesise a holistic framework.