People have been killing each other since as long as there have been people. Yet organized warfare appears not to have sprung up until the Neolithic Age, when certain societies began farming and living in permanent settlements. Archaeological evidence suggests that Neolithic warfare progressed from small-scale clashes and massacres to longer and more sophisticated conflicts.
Early humans engaged in warfare in only the very broadest sense. “For most of our species’ history, it would have been very small, unorganized, decentralized raids very similar to what you see in chimpanzees,” says Luke Glowacki, an assistant professor of anthropology at Boston University, and an expert on the evolution of war. During this time, he says, “a group of individuals [might] encounter someone from another group and kill them.”