The immigrants from the steppes and their descendants. It's hard to interpret the fact that the majority and often 90% or more pre Indo European male lineages were replaced in Western and Northern Europe in any other way.

Sure it took many generations but it's hard to imagine that the violence wasn't culturally and racially motivated. Based on genetic evidence it's speculated that that there were more than 10 male migrants to every female coming from the steppe.

> The Yamnaya never made it out of the Ukraine.

I'm not sure what that means? Their descendants clearly did reach Iberia and Britain.