You originally stated "For the vast majority of human (well, hominid) history, there is little to no evidence that humans fought each other at all."
And I remain correct.
If we're talking about the ancestral environment, then we aren't talking about homo sapiens. We're talking about earlier hominids such as homo erectus, who existed on this planet for at least 5 times longer than homo sapiens.
Pre-agriculture is a weird concept because there's no clear line between hunter gathering and agriculture, but I didn't talk about agriculture anyway. I didn't even claim violence was unheard of before the establishment of settlements (which homo sapiens have been doing pretty much from day one). However, there is a point in human evolution at which we start to find evidence of inter-group violence, and before that there is no such evidence. This strongly suggests that "tribalism" and inter group violence is not an inherent feature of human beings. It is not some ancient legacy from our animal past, it is not an instinct, it is a learned social behaviour which humans engaged in because it secured them an advantage.
I'd say it's only because of our intelligence that humans are so deadly.
It's common to think of humans as physically degenerate apes who rely completely on intelligence, but humans actually have some huge physical advantages. Humans are incredible at throwing, for example, partly because of our kinaesthetic intelligence, but also because our bodies are just mechanically designed for it in a way no other primate is. All the fancy tools in the world wouldn't have done anything without the physical dexterity to use them, and humans may lack strength, but they have physical dexterity in spades.
But if we're arguing whether humans are inherently violent, that's another matter. I've seen arguments for and against, and I can't really take any side.
I think it's missing the point.
I mean, what I said is true, organised conflict or group rivalry or "tribalism" is a thing that probably didn't exist at one point in human development, but at this point any characteristics inherent to humans are completely eclipsed by human intelligence, and have been for a long long time. From the very beginning, homo sapiens could choose whether to fight or cooperate with others based on the situation and their own individual thought processes and group culture. They weren't limited to a single strategy or evolutionary imperative.
This kind of pop-sociobiology often tries to present humans as werewolves, as superficially intelligent beings who are, in fact, driven and guided by
deep animalistic rage. It's true that being human can be confusing, and sometimes you don't feel in control of yourself, but that's not because of your brutish tribal instinct, it's because you are a complex, social, emotional being with a lifetimes worth of learned information. Whether it feels that way or not, you can entirely control whether you are racist, or whether you are violent, and if you (hypothetical you here) are these things, it is likely because you have weighed up the situation and decided that it benefits you in some way, even if that process wasn't conscious. That's what humans do, they learn and adapt. It's their most distinctive evolutionary feature by far.