BG was right about the female brain, I think. Still, whatever the mechanisms are for wiring our brain according to our biological sex, they're not foolproof. They often don't snap into place quite as well as they should, and there are many, many people who wind up with their brains partially wired like the opposite sex. Sometimes, you'll get a guy who wants to get married and only have sex with one woman for his entire life. Sometimes, you'll get a guy who is attracted to other guys. And sometimes you'll get a woman who likes having sex with a lot of different guys without necessarily having low self-esteem. This variation contributes a lot to our diversity, and I think this is a good thing.