150

As you no doubt all know, I am now listening to "The Tipping Point" by Malcolm Gladwell. He covers the fascinating concept of Dunbar's Number. Which is 150. Dunbar claims that 150 is the upper limit of people you can maintain social relationships with. Its the number of people you know well enough to feel comfortable sitting next to should you bump into them in a pub, say. Dunbar proposed this number is a direct function of neocortex size. The size of the neocortex in primates was once thought to be related to the complexities of their daily life (like the foods they ate, complexities of grooming etc). Primatologists then noted a direct correlation between the volume of the neocortex region of the brain of types of primates and the size of their social groups. When Dunbar did the math and related the size of primate neocortex with their social group size and projected this for human neocortex volume, he came up with 148 - usually rounded to 150.

The number 150 as a social group size seems to have had special historic significance. Various cultures through antiquity have maintained this size (neolithic farming villages, Hutterite settlements, army units in Roman and modern times). Christopher Allen has written a number of blog entries about Dunbar's number and how it relates to online communities (MMORPGs and Social Networking Sites). It's all rather cool.

So I sat down and tried to think of 150 people I could sit next to while enjoying a beer. Sadly I could only think of 7, but you are definitely one of them.