Still from the supplementary materials :
"
2.1.4 LATEST ADNA RESULTS AND ALTERNATIVES TO THE STEPPE HYPOTHESIS
Recently published aDNA findings in Europe significantly update and refine the first major results (16). Notably,
populations of the Yamnaya culture on the Pontic-Caspian Steppe no longer appear as the whole or even main
source of the new ancestry component that spread into Central Europe from c. 5000 BP, from further to the east.
The ancestry predominant in aDNA samples from early Corded Ware contexts has recently been reported (39) to
have originated not on the Pontic-Caspian grassland steppe, but further to the north in the ‘forest steppe’ of the
Middle Dnepr region, and towards the Baltic (85). The ancestry predominant in Yamnaya samples entered Central
Europe via the Danubian corridor in a separate expansion further to the south. This conclusion has been challenged
in (23), arguing that the Yamnaya culture on the Pontic-Caspian cannot be excluded as a primary source for Corded
Ware samples, within the limits of the statistical resolution of their analysis. That inference, however, is a function
of the low resolution of their chosen analysis, and of the fact that both Yamnaya and Corded Ware ultimately derive
from a very similar Eneolithic ancestry background that formed c. 7000 BP once CHG ancestry spread north across
the Caucasus.
Recent aDNA results have also more clearly identified an additional, earlier east-to-west expansion, which brought
into the Eastern Mediterranean and the Balkans a quite different ancestry component, predominantly CHG/Iranian
(86, 44, 87). The homogenization of Anatolian and Iranian Neolithic ancestry is attested in Anatolia and the Near
East around 8500 BP (22), from where the mixed ancestry spread westward c. 7000 BP, which is best explained by
continued contacts with the eastern Mediterranean during the Chalcolithic and early Bronze Age (86, 44, 87).
Notably, the westward dissemination of CHG/Iranian, albeit in mixed form and not as a distinct migration event,
predated the expansions from the forest and grassland Steppe by approximately two millennia.
These updated aDNA findings open up potential correlations with processes of expansion and divergence attested
in the topology of the Indo-European language family. By the time that distinct forest vs. grassland steppe
ancestries were expanding westwards deeper into Europe (after c. 5000 BP, by the radiocarbon dating of the aDNA
samples), the linguistic chronology we report here has one already existing split, estimated around 6370 BP (4940-
7860 BP), between branches that make for at least a prima facie rough geographical and chronological fit: the Balto-
Slavic clade as opposed to the joint clade of Germanic+Celtic+Italic. Further south, the expansion of CHG/Iranian
ancestry into the eastern Mediterranean and Balkans, without passing through the Steppe (48) and thus without
major admixture with EHG ancestry, presents a closer chronological and geographical match with the remaining,
deeper European branches in our topology, namely Albanian, Greek and Armenian. (To these might be added other
‘Paleo-Balkan’ branches, known of and identifiable as some form of Indo-European, but long since extinct and too
scantily documented to be placed reliably within the Indo-European topology.)
Ancient DNA evidence from the Fertile Crescent (46, 47) has already pointed to a scenario for the origins and
spread of agriculture that is more complex than the original farming hypothesis in which Indo-European languages
spread with the first farmers both westwards into Balkan Europe and eastwards to the Indus. The hybrid
hypothesis, in which some branches of Indo-European reach (Northern) Europe via the steppe as a secondary
homeland, fits with aDNA evidence that starting from c. 7000 BP, populations of the Pontic-Caspian steppe derived
approximately half of their ancestry from a source first found from the southern Caucasus to north-western Iran
(48). On the route by which this CHG/Iranian ancestry reached the Steppe, aDNA evidence is not yet sufficient to
exclude a route via Central Asia, i.e. first eastwards and then north and westwards, counter-clockwise around the
Caspian, as hypothesized in (54). Nonetheless, the more parsimonious explanation, also given the aDNA record for
time-transects through the Caucasus (48), would be a far shorter route directly northwards through the Caucasus,
in line with corresponding expansions in material culture in the archaeological record (48, 88).
Recent aDNA results from the Fertile Crescent and Western Asia more widely (21, 22, 23) find no intrusion of
Steppe ancestry into the region that spoke the Anatolian branch of Indo-European, as entailed by the Steppe
hypothesis. They do detect, however, “an admixture event that biologically connected” regions from Western
Anatolia to the Zagros in northern Iran, admixed into a common “Anatolian/Iranian ancestry cline” (22). Possible
scenarios include population movements westwards and eastwards out of the northern Fertile Crescent, which
could correlate with the early splits to the Anatolian and Indo-Iranic branches in a hybrid hypothesis for Indo-
European origins. This admixture event has been dated to c. 8500 BP (22)."
https://www.science.org/doi/suppl/10.1126/science.abg0818/suppl_file/science.abg0818_sm.pdf