It's true enough that in the early 2000s one of my poli-sci professors devoted most of a course to the book War Before Civilization and kept hammering on the idea of prehistoric war being widespread and common as some kind of huge revelation and surprise.
I found such intense and sustained focus baffling, since the point seemed obvious (though the evidence was interesting, at least). I've since come to understand this as some "inside baseball" grad-level anthropology leaking through to the undergrad curriculum. We newbies didn't need to be convinced because we'd never strongly held the contrary view in the first place, but the field (and related ones) had only recently convinced itself so thought it worth spending a lot of time on.
It should be a revelation because war is a civilizational concept - it's a form of organized violence, 'organization' being the keyword here.
If you're living in scattered, small tribes, then at most you can get into small tribal scuffles and vendetta ... but war requires planning, organization, support, possibly diplomacy, marshalling of resources - so it's hard to have proper war without the mechanisms in place to support it.
> We had considered scenarios of raids, with small groups of young men killing and stealing food, but to imagine such a big battle with thousands of people is very surprising
So it's not so much the violence itself that's the surprise, as it is the scale of said violence
I found such intense and sustained focus baffling, since the point seemed obvious (though the evidence was interesting, at least). I've since come to understand this as some "inside baseball" grad-level anthropology leaking through to the undergrad curriculum. We newbies didn't need to be convinced because we'd never strongly held the contrary view in the first place, but the field (and related ones) had only recently convinced itself so thought it worth spending a lot of time on.