Re: Different dojo populations...
Yeh, you're right not to have too much faith in this information Sarah (polls are almost always biased towards some agenda). I've heard it on Radio 4 (a good quality radio station in the UK) and I've read it somewhere as well, maybe it was New Scientist? Another survey I've seen (on a political news programme) gave figures for women and mens pay. In the UK men get paid higher, but men also work far longer hours. The pay per hour for men was actually lower than for women (though I wasn't really convinced about these statistics). As I have said, it is very wrong to compare average values between sexes.
I suppose my point is, there is sexual competition in many ways, and we are probably unaware of much of it. For example, male squirrels secrete a mucus plug to stop other squirrels fertilsing their mate, but females scape this out.