Another random thought (gee I hope I'm not forcing them):

caveat: don't even try to think about the thought process involved in this one.

So there's this book I read a while ago in which Neanderthals came to be the dominant species and not homo sapiens or whatever we were back then. [Did you know that, according to this book anyway, its possible that home erectus (we) killed off the Neanderthals? Isn't that crazy? Our first case of genocide.] Anyway, in this other reality, all the women lived together in the center of town and the men only visited for a couple days a month. It wasn't that the men couldn't go to visit the females, but everyone just led different lives. The men all went when the women were ovulating and could concieve chilren...yeah anyway. 'Cause the women were all on the same cycle because they all lived together. So the point is that, while men could go visit the women, if they went during that one week a month...they couldn't get any taxis to take them and buses diverted their routes and stuff.

And I was thinking, dude, that must suck for the women to all be PMSing at the same time! And then I was thinking, dude, that's what happens here. And the men all do it too.