In it, [Thucydides] says that the motivations for us to go to war are fear, honor and interest. These three are all interpretations of evolutionary themes: fear of predation in order to simply survive to reproduce and rear the bearers of your genes; honor, pride or a sense of in-group protectionism to preserve the genes that related members carry; and interest in protection of resources that enable the survival of your genes, including territory, food and, for males, access to females. However, I am absolutely unwilling to offer these very sound evolutionary theories as any sort of moral justification for human warlike behavior. Though they superficially look like the same bases for going to war, it is intellectual folly and nonsense reductionism to attribute evolutionary principles to the extremely complex political and religious reasons that actual wars happen.
Here's my thing, though: what if our storytelling compulsion simply creates narratives that mask the same old evolutionary imperatives? We construct social groups and definitions that might have no bearing on reality—say, race—and declare who is an outsider, who is a threat. Then the same old “fear of predation”, “in-group protectionism”, and “protection of resources” drives us. The only difference is for other animals the instinct is bare. For us it's wrapped inside a story.
Once again, it's not that we are so elevated or so different from the primal instincts which evolved to drive any other animal. It's just that we've come to tell ourselves and each other stories about these things, stories which don't necessarily have to be about real threats from predators, threats to the group, or threats to resources.
Much like the stories we tell ourselves about our decisions and our emotions don't necessarily mean they happen in ways greater than the ways they happen for other animals, the stories we tell ourselves about our reasons for war and hate don't necessarily mean they happen in ways greater than the ways they happen for, say, chimpanzees and their “coalition violence”.
What if the biggest story we've told about ourselves, that we keep telling about ourselves—the story that we are so very, very different—is wrong.