Evolutionary Anthropologist Robin Dunbar is the author of How Many Friends Does One Person Need? (Faber) and he has just been interviewed by The Guardian’s Aleks Krotoski on the subject of how we came to be modern humans. His findings say a lot about why cities and villages work best at high density, and why suburbia is disastrous for humanity.
What does your work tell us about the way we interact socially?
The way in which our social world is constructed is part and parcel of our biological inheritance. Together with apes and monkeys, we’re members of the primate family - and within the primates there is a general relationship between the size of the brain and the size of the social group. We fit in a pattern. There are social circles beyond it and layers within - but there is a natural grouping of 150. This is the number of people you can have a relationship with involving trust and obligation - there’s some personal history, not just names and faces.
And this is the Dunbar number!
Yes.
You're a lucky man, with a number named after you. How did you come up with this concept?
Looking at the Machiavellian intelligence theory, I was working on the arcane question of why primates spend so much time grooming one another, and I tested another hypothesis - which says the reason why primates have big brains is because they live in complex social worlds. Because grooming is social, all these things ought to map together, so I started plotting brain size and group size and grooming time against one another. You get a nice set of relationships.
It was about 3 in the morning probably, and I thought, hmm, what happens if you plug humans into this? And you get this number of 150. This looked implausibly small, given that we all live in cities now, but it turned out that this was the size of a typical community in hunter-gatherer societies. And the average village size in the Domesday Book is 150 [people]. It’s the same when we have much better data - in the 18th century, for example, thanks to parish registers. County by county, the average size of a village is again 150.
Can we grow the Dunbar number?
We’’re caught in a bind: community sizes were designed for hunter-gatherer- type societies where people weren’t living on top of one another. Your 150 were scattered over a wide area, but everybody shared the same 150. This made for a very densely interconnected community, and this means the community polices itself. If you step out of line, somebody else will wag a finger at you, maybe granny or great-granny.
Our problem now is the sheer density of folk - our networks aren’t compact. You have clumps of friends scattered around the world who don’t know one another; now you don’t have an interwoven network. It leads to a less well-integrated society. How to re-create that old sense of community in these new circumstances? That’s an engineering problem. How do we work around it?
The alternative solution, of course, is that we could evolve bigger brains. But they’d have to be much bigger, and it takes a long time.
To see this interview in full, visit www.guardian.co.uk/video
And keep it dense! Dr Dunbar's studies certainly point to the advantages of avoiding overcrowding, but equally they highlight the necessity for communities to be physically interconnected.
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