Undressing in front of each other is just cultural... and guys do that too, haha. Locker rooms, anyone ?

And how about public bath houses - still common in other countries today.

I don't think either one is more or less natural. Other species do both, anyway.

I think that it is a lot more common for women to be openly bisexual than men, and I agree that it's a cultural thing. It's a lot easier to imagine a bisexual or even homosexual woman being completely feminine, but for some reason most people have a harder time seeing a bisexual or homosexual man as still being just as masculine as anyone else. This is obviously false, I've known plenty of bi or gay guys who were just as manly as straight guys, and not even in a fake "I have something to prove" kind of way. It really is just plain a cultural thing. In society's eyes, a girl can be bisexual, or even bi-curious, or experimenting, or there was just that one time when I was drunk, or whatever the case may be, and it's perfectly fine. But if a guy were in that situation, there's no coming back from it. He's gay in the eyes of almost everyone he knows who happens to know about the situation. I think this can become a pretty complex topic depending on how many people get involved, but that's just a little bit of my take on the subject.

Bi-sexual erasure is something men seem to face more frequently. There's a lot of back ground behind, but it is definately something that is a construct of our society.