A pair of late October 2021 papers have upset conventional paradigms about some of the details about the early spread of the Indo-Europeans, although most of the narrative remains intact.
Early Tarim Mummies Weren't From The Steppe
The Tarim Mummies ca. 2000 BCE were Paleo-Siberians who adopted herding and farming practices by cultural diffusion from neighboring populations.
Populations descended from the presumptively Indo-European Afanasievo people brought the Tocharian language eventually spoken in the Tarim Basin, which is a basal Indo-European language. They settled in the arid mountain ringed basin to the immediate North of the Tarim Basin, called Dzungaria ca. 3000 BCE (splitting off from the main steppe Indo-European population at that time). These people migrated to the Tarim basin, bringing their language with them, starting more than a thousand years later.
Indo-Iranian people came and admixed next which is why the Tarim basin people looked a lot like white people in art from ca. 500-1000 CE.
The paper that reported on the data from the famous “Tarim Mummies” is out. . . . it now looks that the Tarim populations from 4,000 years ago are among the last people who were mostly “Ancestral North Eurasian” (ANE), and, they had no connection to populations in Europe. . . .
the earlier remains from Dzungaria are mostly descended from Afanasievo populations with a minority of ANE ancestry. The authors conclude, correctly I think, that this points to the likely origins of the Tocharian languages from the Afanasievo, and the possibility (I bet) that the ancient Yamnaya language was similar to that of the Tocharians. The fact that the Tarim people seem to have been mostly very distant branches of [Y-DNA haplogroup] R1b illustrates the origin of the R lineage deep in Siberia during the Pleistocene. R and Q are clearly from the Paleo-Siberians. . . .
These results in this paper show that the core population 4,000 years ago in the region of the Tarim that was later home to the Tocharians was inhabited by an ANE/Paleo-Siberian population, with a minority component of ancestry derived from northern East Asians. This ancestry dates to the early Holocene, 10,000 years ago. The later Tocharians probably absorbed these people, but I believe they were a mix of post-Afanasievo populations and Iranians. The former gave the Tocharians their unique and very basal Indo-European language, and the latter were responsible for “European” physical features so noted by the Han Chinese chroniclers in the 1st millennium A.D.Note: the ANE are closer to West Eurasians than East Eurasians, but they are very distantly related to the former. Their ancestors seem to have diverged from European and West Asian hunter-gatherers 35,000 to 40,000 years ago.
Bernard's Blog explains (translation from French via Google):
[A]ncient individuals of Dzungaria have between 50 and 70% of Afanasievo ancestry, between 19 and 36% of an ANE / Tarim mixture and between 9 and 21% of ancestry from Lake Baikal. In addition, the ancient individuals of the Chemurchek culture have about two-thirds of the ancestry of the ancient individuals of Dzungaria and the rest from a mixture between Tarim / IAMC or BMAC.The ancient individuals of Tarim are the result of a genetic mix between an ANE population (72%) and ancient individuals from the Lake Baikal region (28%). They do not have Afanasievo ancestry. The date of this genetic mixture is estimated at 183 generations before the date of these individuals, i.e. between 8000 and 6000 BC.
The body text of the paper explains:
Within and around the Dzungarian Basin, pastoralist Early Bronze Age (EBA) Afanasievo (3000–2600 BC) and Chemurchek (or Qiemu’erqieke) (2500–1700 BC) sites have been plausibly linked to the Afanasievo herders of the Altai–Sayan region in southern Siberia (3150–2750 BC), who in turn have close genetic ties with the Yamnaya (3500–2500 BC) of the Pontic–Caspian steppe located 3,000 km to the west. Linguists have hypothesized that the Afanasievo dispersal brought the now extinct Tocharian branch of the Indo-European language family eastwards, separating it from other Indo-European languages by the third or fourth millennium BC. However, although Afanasievo-related ancestry has been confirmed among Iron Age Dzungarian populations (around 200–400 BC), and Tocharian is recorded in Buddhist texts from the Tarim Basin dating to AD 500–1000, little is known about earlier Xinjiang populations and their possible genetic relationships with the Afanasievo or other groups.
The paper and its abstract are as follows:
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 contentious. 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 Afanasievo or to have originated among the Bactria–Margiana Archaeological Complex or Inner Asian Mountain Corridor cultures. 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.
Zhang, F., Ning, C., Scott, A. et al. "The genomic origins of the Bronze Age Tarim Basin mummies." Nature (October 27, 2021) (open access).
Horses Came Late In Indo-European Expansion
Another not fully paradigm supporting result derived from modern and ancient horse DNA is that while horses were sporadically domesticated on the steppe ca. 3500 BCE, only with the Sintashta culture ca. 2000 BCE did domesticated horses (and wheeled chariots) explode from the steppe in the the Middle East and Europe.
Domestication of horses fundamentally transformed long-range mobility and warfare. However, modern domesticated breeds do not descend from the earliest domestic horse lineage associated with archaeological evidence of bridling, milking and corralling at Botai, Central Asia around 3500 BC. Other longstanding candidate regions for horse domestication, such as Iberia and Anatolia, have also recently been challenged. Thus, the genetic, geographic and temporal origins of modern domestic horses have remained unknown.
Here we pinpoint the Western Eurasian steppes, especially the lower Volga-Don region, as the homeland of modern domestic horses. Furthermore, we map the population changes accompanying domestication from 273 ancient horse genomes. This reveals that modern domestic horses ultimately replaced almost all other local populations as they expanded rapidly across Eurasia from about 2000 BC, synchronously with equestrian material culture, including Sintashta spoke-wheeled chariots.
We find that equestrianism involved strong selection for critical locomotor and behavioural adaptations at the GSDMC and ZFPM1 genes. Our results reject the commonly held association between horseback riding and the massive expansion of Yamnaya steppe pastoralists into Europe around 3000 BC driving the spread of Indo-European languages. This contrasts with the scenario in Asia where Indo-Iranian languages, chariots and horses spread together, following the early second millennium BC Sintashta culture.
Pablo Librado, et al., "The origins and spread of domestic horses from the Western Eurasian steppes" 598 Nature 634–640 (October 20, 2021) (open access).
Thus, the early phases of Indo-European expansion into Europe by the Bell Beaker and Corded Ware cultures that preceded the Sintashta culture were not driven mostly by utilization of the domesticated horse, as previously believed, but by advantages including their Bronze age metallurgy and superior agricultural practices.
This is of a piece with the increasing realization that the Corded Ware people further to the north of the steppe zone, were from lightly forested regions rather than open plain, and the lack of a strong association between the Bell Beaker people and horse. Both groups, however, would have had cattle herding and may have had occasional horses even though the presence of these horses wasn't a dominant military factor until the Sintashta horse riding and chariot utilizing accoutrements were added to the package.
But, the horse driven Sintashta cavalry driven expansion may have been instrumental in Indo-European expansion into the Balkans, Greece and Anatolia, and into Iran and South Asia. This was also probably pivotal in the arrival of steppe admixture into the Near East although, south of the Hittite empire, it did not give rise to language shift to an Indo-European language.