In the early 1990s, a British anthropologist named Robin Dunbar argued that humans can’t handle more than 150 stable relationships based on the size of the human brain’s neocortex and observations of other primate groups socializing. Now, a team of researchers in Sweden say that number is bunk.
The team argues that Dunbar’s number—really a set of numbers that define different circles of intimacy and their sizes, with the 150 number for casual friends being the most cited—is not a reasonable way of decrypting human sociality. Their study is published today in the journal Biology Letters.
The researchers conducted the same analyses as Dunbar, but with new methods and updated data from the now-30-year-old dataset. They found that the average maximum group size among primates was actually lower than 150 individuals, but the number was in a gulf of statistical uncertainty, which put the actual maximum group size number between two and 520—hardly a range to go on.
“What we did was to replicate Dunbar’s original analysis but with more data and updated statistical methods,” said Patrik Lindenfors, a zoological ecologist at the Institute for Futures Studies in Stockholm, in an email. “Our main point is that the 95% confidence interval is way too large to make it possible to state any one number, as Dunbar did.”
Dunbar’s 150 was really the midpoint of a range; one person could have about 100 to 200 of these stable relationships. But that range doesn’t fit the new analysis, either. Dunbar’s other groupings were 1,500 (the total number of people you can name), 500 (the most acquaintances a person could have), 150 (stable relationships, a nebulous concept basically meaning people you have regular social contact with), 50 (friends, but not your inner circle), 15 (maximum close friends), and then the elite five (or so—these are your best friends and loved ones). But Dunbar said that there was fluidity to these groups; counts could slightly vary and people could drift in and out of these spheres.
According to Lindenfors, there’s more than just biology undergirding our social capacities; in other words, it doesn’t come all down to the neocortex and our innate tendencies as human creatures.
“Most people reading this article know more than 20,000 words,” he said. “People learn all sorts of things. Why would we not be able to use this ability on social relationships?”
Dunbar came up with his numbers in the nascent days of the World Wide Web. Since then, we’ve developed social networks that have reshaped what it means to be a “friend.” Previously, with the Dunbar number in mind, Wired checked in with 1,000 Facebook friends, with some interesting (and mixed) results, reminding us how little one can interact with so-called friends in a social network.
“Culture affects everything from size of social networks to whether we can play chess or if we like hiking,” said co-author Johan Lind, a cognitive scientist at Stockholm University, in a university release. “Just like someone can learn to remember an enormous number of decimals in the number pi, our brain can be trained in having more social contacts.”
Of course, we’ve come a long way even from the dawn of social media. Perhaps the pandemic reminded you of the relationships that matter most in your life or helped you split from the friends of convenience. Maybe you never want to see 150 people in the same video call again, much less in real life. Like a lot of “rules,” Dunbar’s number may not hold up in the face of humanity’s huge diversity.