British anthropologist Robin Dunbar's theory suggests humans can maintain only about 150 meaningful relationships at once. Known as Dunbar's number, this limit stems from the size of the neocortex relative to the body, which constrains social group complexity. The number appears consistently across historical and modern groups, from hunter-gatherer societies to offices and military units.
Dunbar's research, based on primate studies and human data, identifies nested layers within the 150 limit: a core of five loved ones, then 15 good friends, 50 friends, 150 meaningful contacts, 500 acquaintances, and 1,500 recognisable people. These layers are determined by the frequency of face-to-face interaction, with time being a limiting factor.
While some organisations, like the Swedish Tax Authority, have restructured around the 150-person threshold, critics question whether a single number can capture social complexity. However, anthropologist Cristina Acedo Carmona notes that such studies help measure variables influencing relationship limits.
Dunbar himself acknowledges the number is a range, with extroverts having larger, thinner networks and introverts smaller, thicker ones. Women typically have slightly more close contacts. The theory remains a useful framework for understanding social evolution and community dynamics.
