New Research: When It Comes to Social Groups, Size Matters

But not in the way you think. Contrary to the wisdom of high school cliques, bigger isn’t necessarily better. Primates lower on the pecking order maintain group size through grooming circles, but somewhere along the line we decided that talking was a more efficient way of maintaining group cohesion than ridding each other of lice.

Lower-order primates have a built-in limit to group size: how many other orangutans can one orangutan groom? Could it be that we humans have a similar upper limit on effective group size, despite our language and fancy large neocortexes?

British anthropologist Robin Dunbar says yes: He came up with a “group size” of 150 for humans and an intimate circle size of 12. Health writer and primal guru Mark Sisson notes that throughout history “the upper limit for human social cohesiveness was groups of about 150, and this tended to occur in situations involving intense environmental or economic pressure, like war (Roman maniples contained around 160 men) or early agriculture (Neolithic farming villages ran about 150 deep, and 150 members marked the point at which Hutterite settlements typically split apart). Any higher, and it’d be too costly and require too much social ‘grooming’ to maintain the group … If Dunbar is right, it [the limit to the number of people in a group] is an actual self-limiting brain mechanism forged 250,000 years ago that persists today.”

We may honor this size limit in our lives (the group of 12 would be family plus a few close friends, while the group of 150 would be acquaintances from your community, office, or place of worship) with one extra-large caveat: social media. Facebook users commonly have 1,500 or more friends, more than 10 times the upper limit Dunbar suggests.

Conclusions? Perhaps we’ve changed … or perhaps we’re fooling ourselves.