Perhaps this is old news to most bayblabbers but I just found out about this recently.
Apparently, group size is a function of relative neocortical volume in nonhuman primates. Meaning larger brained primates hang out in larger numbers. This correlation was first described in 1990. It is thought that a larger brain size allows an individual to keep track of its social network to which it must use to the best of its ability in order to be as reproductively successful as possible. Social interactions among primates are maintained by social grooming. And the time devoted to social grooming is linearly related to group size among the Old World monkeys and apes.
So then based on my human brain size, how much time should I be grooming my friends and indeed how many friends can I have??
Awesome questions, answered by Dunbar, R.I.M. In a paper published in 1993, Dunbar explains how language enables us to more efficiently groom our friends, because based on our brain size, we should be grooming about 150 people. Especially with modern humans grooming obsession this would be extremely time consuming without just being able to chat. Dunbar suggests in fact that 60% of human conversations are about personal experiences and gossip, thus fulfilling its role as a social networking tool.
One hundred and fifty friends then is also known as Dunbar's number. I ran into a very interesting article that discusses the concept of Dunbar's number and how it applies to modern society. Apparently just through trial and error the military has been aware of Dunbar's number before it was proposed. And some companies, like Gore-Tex, use this number for company structuring.
An absolute KILLER blog entry at http://www.lifewithalacrity.com does an awesome job of discussing Dunbar's number and attempts to challenge it using data from online networks and massive multiplayer online games and their guild sizes. Check the ganked graph I ganked from that website.
On a podcast I remember stating that I thought that language evolution was all about the meme ie. being able to learn survival abstractly from others in the group and being able to pass on behaviors that can evolve faster than biology. I guess I was wrong and it's all about being able to gossip so that you can have a bigger group with which to beat down the smaller groups.