The Dunbar Number is the upper limit on the number of other people with whom one can have interpersonal relationships. This restriction is purely cognitive, a result of evolutionary pressures, and it tops out at about 150 people. Robin Dunbar gave a great presentation on his work, and Cracked magazine has a brilliant exposition on it, calling it The Monkeysphere. Dunbar's number is all about relationships: the number we can maintain in our heads. It's about the same size as a human tribe before the invention of civilizations with uniform laws; it's also the maximum size of most family's Christmas card lists.
150 people seems to be the maximum number we can treat as people rather than as abstract human beings that need categorizing and simplification in order to manage. Laws treat human beings simply, as categories rather than as people. So do companies bigger than 150 people. We need these abstractions to marshall large numbers of people to accomplish things that require so many, but down inside our brains we're still dealing with the same simple small number of real people.
One the things that occurred to me this morning is that writers might have their monkeysphere slots filled with their own characters. This might be one of the reasons we're all so famously isolationist and loner: our slots of friendship capability are limited to those not currently occupied by the characters that haunt our stories. And I say this because I've recently felt as if Ken Shardik, Aaden, and P'nyssa haven't been as much of my monkeysphere as the rest of the world. Part of that is because they've been pushed out by circumstance: they don't have twitter feeds and Facebook accounts, they're not part of the rest of my family's world. I didn't have to keep them away from Omaha, but the kids don't need to know about them, so dealing with them is a bit like having an affair these days. I have to go to cafe's and long train rides to have long conversations with them, catch up on their lives, and push the stories forward.
There are, of course, exceptions: Jay Lake seems to have pretty solid characters and yet maintains a huge monkeysphere of friends. A skilled politician often has a prodigious memorys and can glad-hand thousands of people, making each feel as if she is a member of his tribe at least long enough to vote for him. I seem to have a less-than-well-endowed monkeysphere, myself. It kinda bothers me, but I'm dealing.
So, if you're a writer: do you believe that your characters take up treasured positions in your Dunbar number of friends?