For one thing, before the 20th century, there were plenty of genocides. We tend to forget about them, partly because they weren't as well documented and partly because, until recently, people didn't care. We used euphemisms like 'sackings' and 'sieges' instead of calling them 'genocides.'
Steven PinkerCognitive psychology tells us that the unaided human mind is vulnerable to many fallacies and illusions because of its reliance on its memory for vivid anecdotes rather than systematic statistics.
Steven Pinker[Napoleon deployed] every available resource to inflict all-out defeats on [his] enemies.
Steven PinkerAfter their return from Babylon, the practice of human sacrifice died out among the Jews, but survived as an ideal in one of its break-away sects, which believed that God accepted the torture-sacrifice of an innocent man in exchange for not visiting a worse fate on the rest of humanity. The sect is called Christianity.
Steven PinkerI don't think aggression works like thirst or sleep. I think aggression is more elicited by particular situations. I think it can be mitigated.
Steven Pinker