No matter how utterly charming you are, there is apparently a natural limit to how many friends you can have: 150.
It’s known as “Dunbar’s number” because British anthropologist Robin Dunbar came up with the figure. Dunbar defines a friend as “the number of people you would not feel embarrassed about joining uninvited for a drink if you happened to bump into them in a bar,” and back in the 1990s, he asserted that people can only maintain 150 social relationships that stable at any given point in time.
Dunbar went on the claim that we devote 40% of our social time to the five people who are closest to us. The next 20% is devoted to the next closest 10.
These numbers are now widely accepted in social science. Some companies, like W. L. Gore and Associates (the producers of Gore-Tex) even limit the size of their offices to 150 employees.
Dunbar’s number didn’t appear out of thin air; he came up with it by studying primates. He found that primates with bigger brains were able to track more social relationships, and from his research he predicted an average human social network size of 148 based on the size of the human brain.
Then he rounded up.
Not all social scientists agree with Dunbar. But the 150 figure is consistent with other figures throughout history, such as the estimated size of neolithic farming villages and the average size of army units from Roman times to the present day.
So, the next time you want to gently turn down a new friend, just tell ’em you’ve already reached your Dunbar number.