Humans are social creatures; we live in family groups, socialise with friends, and work with colleagues both in person and online. Yet, how many friends do you really have?

Evolutionary psychologist Professor Robin Dunbar says it won’t be more than 150. Proposed in the 1990s, ‘Dunbar’s number’ puts a limit on the number of stable relationships humans can maintain at any given time, and his ‘social brain hypothesis’ suggests that brain size is directly related to social group size in mammals. In short, the bigger the group, the bigger the brain.

In this interview with our sister publication, Research Outreach, we find out how Dunbar’s education moved from philosophy to psychology and how his research moved from primates to people, as well as why size matters when it comes to social groups and evolution.

Read more in Research Outreach