Dunbar’s number

Posted by on Nov 9, 2006 in Uncategorized | No Comments


I was talking to the very smart (and charming) folk from 2CV today – a very interesting market research company (no, that’s not an oxymoron). I was talking about my Herd theory and trying to get them to work through what the implications might be of the basic assumption that (to paraphrase the Nobel Prize laureate, Thomas Schelling) each of us spends most of our lives responding to an environment which consists of other people responding to an environment which consists of other people people responding to an environment etc. In other words, we are first and foremost social creatures, primarily ‘designed’ (no creationism-lite intended, sorry) to interact with each other. A Super Social Ape, if you like.

In doing so, I showed them a graph from Robin Dunbar’s famous work on primate group size. In essence, through a study of human and other primates he managed to identify a strong correlation between brain size (in terms of the ratio of neocortex and body) and group size. Humans, it turns out, are able to live in groups of up to 150, while chimps get agitated once a group approaches 50; it all goes pear shaped, because the bonds that hold chimp society together can’t hold. Perhaps, the reason for this lies in the limits of our brains’ cognitive powers (one version of the Dunbar hypothesis). we just can’t handle the amount of information involved.

This, we agreed, explained why as small companies grow, they often reach a break point when internal politics takes over. My experience in such companies (and in larger ones) tells me that that number is around 100, maybe even less. Hence also why Jack Welch’s GE was repeatedly broken down into smaller business units (SBU’s) to enable folk to thrive. Dunbar’s explanation is that group size has shaped the size of our brains (as well as the structure of them). We are undoubtedly the primate most able to live peaceably in large groups.

Dunbar also goes on to point out that ‘grooming’ is the basis of relationship building in all primates, man included (hence the piccie on the post). And he sees this as the source of human language – hence the title of his fantastic book, (http://www.amazon.co.uk/Grooming-Gossip-Evolution-Language-R-I-M/dp/0571173977/sr=1-1/qid=1163105317/ref=sr_1_1/202-5287109-5832608?ie=UTF8&s=books)“>Grooming, Gossip and the Evolution of Language

However, I had an inkling that I might have not got the numbers quite right (Well, I did read Dunbar’s stuff at New Year on the beach in the West Indies…). 057117397701_aa240_sclzzzzzzz_

It was by visiting lifewithalacrity.com that I realised that I might indeed have misread Dunbar. Perhaps what he is saying is that 150 (that ol Dunbar number) is the maximum group size. Go check out the interesting example from tech innovation groups there. Beyond a much smaller group size, the folk spend too much time grooming each other to be properly co-creative.

I stand corrected (probably). But the principle remains the same (as Jimmy, Robert and the boys almost said). Even if the number is slightly different.