DAVID REICH NEXT QUESTION

Have humans been more violent last few thousands of years, or is there no research?

Reich's answer, classic avoidance of a question he undoubtedly knows a great deal about: Best research is from archaeology, where you can try to understand whether there is evidence of war. 

If population replacement, over the long term or the very short term, is shown by DNA evidence, regardless of what little archaeological evidence there happens now to be, how is that not also evidence of war, or the kind of localized guerilla conflict, call it tribal or clan feuds to the death, that was obviously widely prevalent in prehistory, especially between Neanderthals and modern humans?

Reich points out that war as we know it, large groups fighting each other, is a very recent phenomenon.

But, it's funny, he describes groups of dominant migrant males mating overwhelmingly with large groups, almost army sized groups, shall we say, of indigenous females. 

What were the indigenous males doing during this dominant migrant mixture male mating? Watching, applauding (The Allegory Of The Eunuch")? These seem rather unlikely.

One question, then, is: How recent is war, given the obvious example of the Yamnaya, using cart and horse technology for the first time, rapidly overrunning large areas of both Europe and Central Asia, overrunning very large numbers of early farmers and other preexisting hunter gatherers in a relatively short time. Reich poo poos the Yamnaya, but merely no stirrups is not a game breaker. 

Also, there apparently is archaeologtical evidence of large piles of their victims, the kind one would not see from isolated and episodic local small clan conflicts.