Robin Dunbar has ruined your life. Well, not him, really. And maybe not ruined, so much as complicated. And it probably isn't your whole life either.
Dunbar's number is an interesting concept, still being refined by scientists, but already useful to think of in vague terms. The basic idea is that there's a finite amount of brain in your head, a finite ability to process thoughts and so a finite portion of that you can spend on interpersonal relationships. So while you may know hundreds or thousands of people, and perhaps have a job that lets you interact with tens of thousands or even more, you probably only have one or two hundred friends you're comfortable and familiar with, really. That number of close friends is Dunbar's number.
And it's been pissing me off for the last few years. The improvement in social mechanisms on the internet has given us the ability to meet many more people than we could using offline methods alone. But this puts pressure on our Dunbar's, because presumably many of us (those old enough to pre-date social media) already had adequate social circles before. So now there's competition between interesting foreigners and convenient locals (I'd even hypothesise that there's probably a fairly predictable rank order most people will apply based on those three factors: interestingness, convenience and localness), and I've found I'm losing touch with great old friends, for no very apparent reason. Dunbar's number seems the most likely reason. I only have so many weekend hours to share, and while my week nights are pretty open, many other people will be more limited there, leaving little free overlap, and so it becomes impossible to fit everyone in logistically, even before they slip out of my brain too. And sometimes the decision of who to share my time with can be pretty petty; if you show me your boobs, for example, there seems to be a strong correlation with that and how much time I'll devote to you. Fucking reproductive instincts...
Now, perhaps this is normal and natural, and I'm sure kids born into such an internetty world will learn to treat it as such much more easily. But for a crotchety old man like me, I think it helps to be more aware of what's going on. I (and perhaps you) need to make a conscious effort to stay in touch with the people I value a lot, but who aren't so easily available or topless. It's a two way street, though, and I can certainly name friends who pushed me out of their lives (maybe intentionally, maybe not) by failing to match the effort I was making to keep in touch and display my boobs.
I guess that last paragraph was the main point I wanted to make. Now, a free bonus thought on how this relates to sex and dating.
What I consider my traditional social circle, basically my old high school friends and the outside friends we all have in common, has always (since 2000, at least) been in the habit of swapping partners. I don't mean we've had an intentional swinger thing going (the closest we ever got to that was Strip Rock-Paper-Scissors night), just that when A&B stopped dating and C&D stopped dating, it was considered perfectly normal for A&D to have a go next, and B&C too, if they liked. Some outsiders have expressed discomfort with this: Isn't it uncomfortable? Don't people get jealous? Surely that's a sick, incestuous way to do things? Well, fuck you, Mr Judgemental Outsider! But seriously, in hindsight it's worked out pretty well for us. Obviously we're mostly human, and jealousy and discomfort do happen. But like any emotions in life, learning to cope with these in a mature, responsible way makes them tolerable and makes us into better people. The individuals who couldn't adapt like that, whose jealousy and intolerance overwhelmed them, have tended to fall out of the group.
By sheer luck, I think it's also been a very convenient system in terms of Dunbar's number. If you always have to look for new people to date/shag, and friends are always off limits, then you've got to constantly add new people to your list of close people, which will eventually add strain to your older relationships, and now you're fighting Robin Dunbar (with shivs, in a broom closet). Instead, the sharing and re-sharing of genitals means that everyone already knows each other, the numbers remain fairly constant, and Dunbar's bloody cleaver stays out of the picture. I don't think it's at all coincidental that our group stayed close for so many years after school, while everyone else reported losing touch with most of their former social circles quite quickly. If I'm right about this, I'd be fascinated to see how it applies to friendship circles from single-sex schools. (It may also have added incentive to take STD prevention seriously, as anything transferred is going to go to someone you all know and love, not some faceless, distant stranger.)
Of course, outward expansion of our network was inevitable once we left school and (in some cases) got jobs. I once drew up a diagram of our whole canoodling network (which caused great unhappiness among those who mistook it for me being judgemental, rather than merely geeky), and while I haven't updated it in years, I'm willing to bet that the friends who've stayed in my life longest are, to some extent and depending on exact definitions, the ones who kept themselves in that network the best. So in conclusion, if you want to be friends with me, we'd better have sex?