The problem seems to be the size of our neocortex, the brain’s reasoning and communication department. British anthropologist Robin Dunbar noticed that in various animals, neocortex size corresponded to the maximum number of others of their species they could associate with without chaos and violence breaking out. Dunbar looked at the human neocortex size and predicted that humans would have the capacity to manage social interaction in societies with a maximum of 150 people (148.7, to be exact).
