Episcopalian,
"Sexual gratification" is just the most obvious aspect of human sexuality, not the most important. Of course, from an evolutionary perspective, the primary purpose of sex is reproduction... but it also has the secondary purpose of driving pair-bonding behavior that is indirectly advantageous to any offspring. As for your implied question: in some people, sexual desire is mapped to the evolutionarily "wrong" sex. And in some people, it isn't there at all.
So what? Evolution dictates reproduction; morality does not. There is no reason for asexual people to have sex if they don't have the desire to. There is no reason for homosexual people to have sex with people they have no desire for -- nor to refrain from it with those they do desire, if the circumstances are appropriate. No reason, that is, until you bring religion into the equation... but that's a personal matter, to be decided by the individual, not the state.
I don't believe you've replied to my thread on gay marriage, now on the members-only board. I'd certainly be interested in your response, if you have the time.
Crystal,
I think it's generally more a matter of "in-between," rather than "both." I saw a show on intersexed people a while back. It seemed like most of them had a fairly clear gender identity... although not necessarily the one that matched their genetic sex, or the sex they'd been assigned. There were also one or two that were more androgynous.
The real problem is, parents want their baby to have a definite sex, and doctors tend to oblige with surgical "assignments" that may-or-may-not match the gender identity the kid's going to grow up to have. There just isn't much space in society for parents to be saying "well, we're not sure if it's a boy or a girl yet, we're going to let it grow up a bit so it can tell us." And there isn't much space for a kid to grow up and say, "well, actually, neither." Most people think of gender as binary, an either-or question... but speaking as someone who would prefer to say "neither," I think it's a bit more complicated than that.