. there is no evidence for that and that is not what modern isolated hunter gatherers do either.

I came across plenty of examples in my studies of anthropology. Of course it depends what you mean by "tribe". Really large scale violence requires a certain amount of technology. As an example"Yanomamo: The Fierce People" by Chagnon details some such incidents and suggests they were not unusual. Well actually the men and children were killed, the nubile women were kept alive for <reasons>.

See also the Torah / Old Testament for numerous genocides, though these were bronze/iron age people and also the historicity of the incidents is disputed.

This was not universal - the Kalahari Bushmen (now called the San people) did not do this, perhaps in part because their main weapon was a slow acting poison dart. An all-out war would kill everyone involved.

But rates of violent death among males were extremely high in hunter/gatherer societies often documented by early anthropologists (from reconstructing family trees) in the 30-50% range.