Despite the boundless reach of social media, our brains are wired to juggle no more than about 150 meaningful relationships—a social ceiling rooted in our evolutionary past, according to British anthropologist Robin Dunbar. His research comparing primate brain sizes and social groupings—published as far back as 1993, per the Independent—led to a figure now known as "Dunbar's Number," a proposed limit of about 150 stable social relationships per human, supported by observations from various periods and cultures, going back to hunter-gatherers. Other researchers argue modern humans, no longer bound by basic survival needs, might support larger networks. But as Dunbar tells the Wall Street Journal, he's sticking with his theory even in the face of long lists of Facebook friends.
Dunbar believes humans can likely recognize about 1,000 faces beyond their network of 150 (think public figures). He also acknowledges people may have hundreds of acquaintances, but he argues these connections are usually one-sided. "The key to the 150 and the layers within is that they're reciprocated," Dunbar tells the Journal. He describes an inner circle made up of the five closest people to you, followed by 10 good friends you contact less regularly, a broader group of about 50 people, and finally the full 150, who are familiar but less central—the people you might invite to your wedding.
If you lose touch with someone, they tend to drift out of these circles over time, says Dunbar. He argues this remains true even in the age of social media. Digital interaction helps to keep people in our networks longer, but doesn't fundamentally expand the number of meaningful relationships, he notes. Most people seem to prefer in-person contact for deeper emotional support, he adds, noting, "it's difficult to get emotional support from somebody you can't actually hang on to physically and put your arms around."