Anthropologist Robin Dunbar is most famous for his research-based determination of the number of stable social relationships a single person can maintain (the aptly named Dunbar’s number is 150). He also found that the strongest predictor of brain size across species is the size of the typical social group. The human brain is uniquely large relative to body size, which Dunbar attributes to the fact that our species is highly social. Put simply: You are social because you are human, and you are human because you are social.
