Funny, Freud suggested something very similar in _Totem and Taboo_, and faced a lot of ridicule for it. Would be interesting if he were finally vindicated to some extent.
EDIT: I mean in academia; I suppose his ideas are still quite popular culturally.
WWI and WII basically selected to kill off Europe's bravest and most nationalistic men, those who immediately signed up to fight and were thrown in the meat grinder.
I'm partly convinced that's why America is so different from Europe, we managed to avoid most of the carnage of those wars
For about 1000 years, we know that west-european states executed about 1% of each generation. Assume it's the most violent 1%, and that violence is 50% heritable. Plugging these into standard formulas for animal breeding, and I believe the answer is that this explains about half the decline in the murder rate over this period.
Obviously there are some giant caveats here. But it's super-interesting that a back-of-the-envelope calculation gets you the right order of magnitude.
I'm dubious though of wars doing much. The big 20th C meat-grinder was largely conscripts. And anyway I'm not sure how correlated with blood-thirst most recruiting was. Whereas getting yourself hanged for murder in peacetime was pretty tightly correlated.
Much of that work is on its surface unremarkable today, though not at the time. But as it wasn't really central to his most influential work, it also hasn't been (IMHO) particularly influential
That Plato thought your mind transfers from your previous souls and this is called "evolution" is simply an accident of language.