"Humans are often said to be intensely tribal. Indeed we are. But if “tribal” refers to a sense of solidarity with a large social group, the same is true of most primates. Tribalism does not distinguish us, nor does reactive aggression. It is coalitionary proactive aggression that makes our species and societies truly unusual.
Among our ancestors, coalitionary proactive violence directed at members of their own social groups enabled self-domestication and the evolution of the moral senses. Now it enables the functioning of states."
(Richard Wrangham: The Goodness Paradox: How Evolution Made Us Both More and Less Violent)