What this suggests to me is that the Kurgan cultural horizon was not genetically homogeneous. I suspect that Kurgan groups closer to the Balkans carried significantly higher levels of Near Eastern Neolithic farmer ancestry, and were thus much darker than those in the more temperate northerly regions. However, it seems that at some point, the Neolithic farmer DNA was diluted enough by continuous movements of light pigmented groups from the north and east, possibly made up mostly of males, that there was a major shift in pigmentation traits from Near Eastern-like to North European-like across most of Eastern Europe. This scenario actually fits very nicely with the latest on the genetic origins of Europeans see here.We won’t know what really happened until we see at least a few complete ancient genomes from Eastern Europe. But for now, I’d have to suspend my disbelief to accept that present-day Eastern Europeans are, by and large, descendants of these exceedingly brunet prehistoric people of the Pontic-Caspian steppe.
Eurogenes Blog: Extreme positive selection for light skin, hair and eyes on the Pontic-Caspian steppe…or not