British researcher asks: How many friends can you have?

A British anthropologist says 150 friends are all the brain can actually take in, even if your Facebook page says you have more.

British anthropologist Robin Dunbar says human beings can have no more than 150 friends – that’s the upper limit the brain can absorb.

His conclusion comes from studying the social group size of monkeys and apes and how that size might relate to the brain.

Initially Dunbar was examining why primates groom each other. If the reason involved sexual bonding, it should correspond to “the social brain hypothesis” that the reason primates have a large brain is because of their social complexity.

In other words, you need a large brain to keep track of your relationships. Humans, he says, are no different.

Known as “Dunbar’s number,” the idea of an upper limit to friends is bound to cause some people – especially teens and young adults -- to raise their eyebrows, particularly in this era of social network sites where some people boast of having thousands of friends.

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Since first coming up with the number 150, Dunbar, who heads the Institute of Cognitive and Evolutionary Anthropology at Oxford University, has also looked at what the nature of the friendship is within that circle. And he found that the people within that circle were those that had a personal relationship based on history and a shared experience – be it family or friends.

Dunbar, whose book How Many Friends Does One Person Need? has just been published by Faber & Faber in England, describes a person’s friends akin to ripples in a pond – each ripple representing an ever increasing number of friends from 5 up to 150. Those closest to you are usually family, then close friends and eventually acquaintances.

“The other key thing is the 150 friends aren’t a homogeneous group of people, but rather they are rings of people or circles of friendship that expand outwards.”

The first five friends and or family you might be prepared to go to prison for, Dunbar said. The next layer of 10? You wouldn’t go to prison for all of them. “You’re less emotionally engaged with them,” Dunbar says. “You might lend them $100. The next layer out, which takes you to 50, your emotional engagement is less but still there. You might lend them $20. The next layer of 100, you might do them a favour.”

Everyone outside those 150 are people you may not even have a reciprocal friendship with, he added.

Dunbar said that once he had determined the upper range of friends, he examined a wide range of historical and contemporary settings to see if the number still applied. And it did – in everything from villages 100 years ago in which the population hovered around 150 to individuals’ social networking sites. Even the Gore-Tex fabrics factory keeps its employees at 150 at each of its sites, he said.


Some of Dunbar’s work on the magic number 150 is being used in other areas of research, including the development of mobile phones and how much storage is actually needed for people’s address books, as well as building the optimum organizational structure.

Even last year’s international banking crisis might have been averted if the number 150 had been applied, Dunbar said. If the banks units had been smaller, everyone might have known what was going on and felt more responsibility towards each other.