Group Sex?

Over at weaverluke, Luke Razzell considers the possibility of a genetic explanation to why human's generally like to hang around those that think like ourselves

a man and woman who share a point of view are presumably more likely to reproduce together than a man and woman who do not.

Luke's theory offers no explanation as to why both men and women seek out similar-minded people of the same sex. If reproductive success isn't necesary to explain why males seek out other males (or females seek out other females) that share their point of view, why should we to attribute to it the same phenomena when it occurs between males and females?

Luke goes on to wonder

Could there be a genetic component in the formation of communities of thought?

I expect that any link between reproductive success and the tendency of humans to form into groups is less direct. If you aren't in a group you are on your own. In our evolutionary past, being alone would almost certainly have had an impact on your ability to pass genes on - starving when food is scarce, being swallowed by a lion or speared by another tribe would surely have cramped your moves on Friday night down at the pub.