Predatory land mammals are territorial, especially pack-hunters. Like lions, wolves and Homo sapiens, Neanderthals were cooperative big-game hunters. These predators, sitting atop the food chain, have few predators of their own, so overpopulation drives conflict over hunting grounds. Neanderthals faced the same problem; if other species didn't control their numbers, conflict would have.
This wasn't a blitzkrieg, as one would expect if Neanderthals were either pacifists or inferior warriors, but a long war of attrition. Ultimately, we won. But this wasn't because they were less inclined to fight. In the end, we likely just became better at war than they were.
It could be that Homo sapiens were overly aggressive, but 100,000 years of war and 1000s after that, work to make Homo sapiens, good for nothing, but over aggressive fighting and tribalism.
Being overly aggressive, does not keep people from be coming sheep, it does not help them think outside the box. So people are flawed and likely can't be fixed, unless we can stop fighting for 100,000 + years
Likely, people are domed to fight each other to death of the human race.
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