Quote Originally Posted by Ygorcs View Post
I see, but, I mean, how likely is it that a R1b BB and a R1a CWC from, say, around 2500 BC would still have a very close match with a 5th millennium Bulgarian individual even after so intensive migrations, cultural changes and certainly lots of mixing with the local peoples (who, especially in the case of BB, they didn't seem to replace overwhelmingly)? Would very little mixing and autosomal change have happened in more than 1500 years even as the Bulgarian Suvorovo spread to lands very far away and already densely inhabited? I'd be very surprised if that did happen. I think the fact that the BB and CWC do not match as well as with the Sredny Stog and the Yamnaya samples may just result from the very likely and plausible fact that those were still "steppe proper", pre-expansion societies with much less admixture with the ANF+WHG mix dominant especially to the west of the Dniester.
We do not know how much people admixed until we examine the data. If we look at the R1a-M417 sample from circa 4,000 BC, for example, it differs little autosomally from the R1a-M417 samples in Corded Ware 1,500 years later. I would suggest this indicates that extant M417 admixed very little during this period, just as its females seemed to admix almost exclusively with M417 men. This is surely a more likely explanation than that it changed autosomally through admixture with Sredny Stog and Yamnaya before changing back to pretty much the same autosomal mix that it had before.

Sredny Stog and Yamnaya look to me like red herrings. They had different autosomal mixes from each other, and neither of their Steppe DNA mixes match the mixes in the Steppe components within BB or CW.