All primates, including humans, live in groups, and the groups are organized in terms of dominance hierarchies. However, humans have evolved beyond the simple hierarchical groups that characterize, for example, the chimpanzees, our closest primate relative. Humans have developed formal social organizations that allow them to accomplish sophisticated goals that are not attainable by individuals or mobs. The first significant social organizations were hunting bands and war parties; these groups, which initially must have resembled those formed by chimpanzees, were key elements in human survival. People evolved as group-living animals, and that has important consequences for understanding social behavior in general and leadership in particular—because people are prewired for group living.