A Corded Ware-related Proto-Greek from the Pontic-Caspian steppe?

The recent Wang et al. preprint on the genetic prehistory of the Greater Caucasus features several supposedly already published ancient samples that, as far as I know, haven’t yet appeared anywhere. These include five Yamnaya samples from Hungary and two Neolithic samples from Greece. I’m guessing that they’re part of a paper that was scheduled to be released earlier this year, but was delayed, and will probably come out very soon.
Intriguingly, one of these new Greek samples, Greece_Neolithic I6423, appears to harbor an unusually high level of Yamnaya-related ancestry from the Pontic-Caspian (PC) steppe. So much, in fact, that in a Principal Component Analysis (PCA) he/she clusters amongst a pair of Corded Ware individuals from Northern Europe, and almost on top of a Varna Eneolithic outlier from Bulgaria, all of whom also pack a lot of this type of ancestry.
So if this isn’t some sort of an error, then I6423 might turn out to be a very important sample in the context of the population history of Greece, including in the search for the Proto-Greeks. That’s because the ancestors of the Corded Ware people are generally regarded to have been amongst the first Indo-European-speakers to migrate out of the PC steppe, and ancient steppe ancestry is now widely accepted to be a signal of early Indo-European expansions across Europe (including those that took Proto-Greek to Greece).

But note that I6423 also clusters near several Eneolithic samples from the North Pontic part of the PC steppe (look for the inverted gray triangles in the PCA). One of these samples is the Corded Ware-like Ukraine_Eneolithic I6561 from a burial associated with the Sredny Stog II culture, which is often said to have been a Proto-Indo-European archaeological culture. I’ve mentioned this sample on many occasions on this blog, including here.
Could it be, then, that the high level of ancient steppe admixture in I6423 is a signal of a surprisingly early Indo-European migration from the North Pontic region to the southern Balkans that led to the formation of the Proto-Greeks? I don’t see why not, especially when looking at this map of the spread of Corded Ware pottery and other typically steppe cultural traits into the region around 4,000 BC (sourced from Bulatovic 2014 here). In any case, I’m really looking forward to getting my hands on I6423, hopefully soon.

See also…
A Mycenaean and an Iron Age Iranian walk into a bar…
Graeco-Aryan parallels
Main candidates for the precursors of the proto-Greeks in the ancient DNA record to date

Source

https://xissufotoday.space/2018/07/a-corded-ware-related-proto-greek-from-the-pontic-caspian-steppe/