Dunbar's Number

Dunbar's number is a proposed cognitive limit on the number of people with whom one person can maintain stable social relationships, commonly cited as approximately 150. British anthropologist Robin Dunbar derived the figure in the 1990s from a correlation observed across primate species between neocortex size and typical social group size, then extrapolated the human neocortex's proportional size to predict a comparable ceiling for humans. Dunbar and others have pointed to historical and organizational groupings, such as hunter-gatherer bands and military companies, of roughly that size as supporting evidence, though the precise number and its universality remain debated.