Check out this thought-provoking piece in the NYT about the social and biological reality of swinging both ways (or not) and how the world perceives those of us who aren't especially dogmatic about the gender of our partners. Did you know that's a thought crime in some circles? Lol, if you've lived through the past two decades, of course you do. I found myself nodding fit to bust over the bit about gender as well as sexual identity and all the questions that little doozy raises, and am pleased young folks are questioning received wisdom in that direction.
Where do we get off personally? The Lovely R's straight as the straightest thing on earth and identifies as strongly male as far as gender goes. I'm bi, and mentally sort of come down in the middle between the boy-girl polarities, gender-wise. The fact that I've always attracted super-straight, overtly male men has long been mysterious to me, since I've never felt especially/conventionally girly and just assumed I'd end up with another ambiguous weirdo. But I look very female and it turns out my tits have been trolling for straight action whether I liked it or not. And another thing... I'm not attracted to butch girls, but my massively straight partner is while considering me pretty femme. WTF. Complicated, isn't it?
I think it's safe to say we're not getting to the bottom of this shit any time soon. Do read the article though; it might give you somewhere to start and it'll definitely give you something to argue about.