The genomic origins of the Bronze Age Tarim Basin mummies

Abstract

The identity of the earliest inhabitants of Xinjiang, in the heart of Inner Asia, and the languages that they spoke have long been debated and remain contentious1. Here we present genomic data from 5 individuals dating to around 3000–2800 bc from the Dzungarian Basin and 13 individuals dating to around 2100–1700 bc from the Tarim Basin, representing the earliest yet discovered human remains from North and South Xinjiang, respectively. We find that the Early Bronze Age Dzungarian individuals exhibit a predominantly Afanasievo ancestry with an additional local contribution, and the Early–Middle Bronze Age Tarim individuals contain only a local ancestry. The Tarim individuals from the site of Xiaohe further exhibit strong evidence of milk proteins in their dental calculus, indicating a reliance on dairy pastoralism at the site since its founding. Our results do not support previous hypotheses for the origin of the Tarim mummies, who were argued to be Proto-Tocharian-speaking pastoralists descended from the Afanasievo1,2 or to have originated among the Bactria–Margiana Archaeological Complex3 or Inner Asian Mountain Corridor cultures4. Instead, although Tocharian may have been plausibly introduced to the Dzungarian Basin by Afanasievo migrants during the Early Bronze Age, 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, which allowed them to settle and thrive along the shifting riverine oases of the Taklamakan Desert.

Bronze and Iron Age population movements underlie Xinjiang population history

“…These results, based on a broad sampling across the region, point to BA populations in the Tarim Basin containing a deep ANE-related ancestry ( 16 ), with Northeast Asian ancestry similar to that from the EBA Lake Baikal region appearing at least in the north and west. We also report additional movements and admixtures along the IAMC with Afanasievo- and BMAC-related populations, validating aspects of both the Steppe and Bactrian oasis hypotheses for the settlement of Xinjiang.…”

“…S26) ( 21 ). QpAdm models revealed the primary source of East Asian ancestry found in BA Xinjiang to be similar to the Northeast Asian ancestry common among Neolithic Mongolia (Mongolia_N), Lake Baikal (Shamanka_EN), and Yellow River (YR_MN) populations (tables S3 and S4) ( 16 ). By contrast, the East Asian components of IA populations are more diverse.…”

“…Beginning with ancestral sources traced to indigenous ANE-derived and BA western and eastern Steppe populations, Xinjiang population structure can be characterized by waves of incoming gene flow and admixture from surrounding populations adding to the extant ancestry. The BA Xinjiang region contained four major ancestries, which included Tarim_EMBA1 (Xinj_BA1_TMBA1) (16), Afanasievo (Xinj_ BA5_oAfan), Northeast Asian (Xinj_BA7_oEA), and BMAC (Xinj_BA6_aBMAC), with Tarim_ EMBA1 possibly being indigenous to the region given its presence among diverse BA individuals (Fig. 3B).…”

“…S29 and tables S3 and S4) ( 21 ). Additionally, models with more contemporaneous potential ancestral sources portray BA populations from northern and western Xinjiang as a mixture of four major ancestry sources derived from ancestry present in the BA Tarim Basin mummies at the Xiaohe site Xinj_BA1_TMBA1 (8 to 85%) ( 16 ), Afanasievo (57 to 100%), Shamanka_EBA (10 to 92%), and Gonur1_BA (BMAC) (~43%) (Fig. 3A and tables S5 and S6) ( 21 ).…”

“…3A, table S5, and fig. S14) ( 21 ) may be traced to Tarim_EMBA1 ancestry, ~72% of which could be derived from the Upper Palaeolithic individual AG3 ( 16 ). ANE ancestry in present-day populations from South America (e.g., Surui and Karitiana), Europe, and Siberia may explain the affinity for BA Xinjiang with these populations, as shown in the PCA and outgroup- f3 results (figs.…”