First; there's plenty of evidence to suggest we are related to quadrapedal animals. Heck, there's plenty of evidence to syggest we're related to radishes. It's called DNA. That does not negate the Christian position on sex outside the male-female bond ....for the Christian, Spud. It's not on...whether with a man, woman, chicken oy lamp post. It is, indeed, sin. So are a lot of things. But suggesting it can be a lifestyle choice, or can be 'cured' is on a par with suggesting I can cure the fact that I don't have a left eye. I can't. I can, however deal with it. I get really fed up with my fellow evangelicals who throw a wobbly every time the gay thing comes up. It happens in the animal kingdom as well; not a disability, not a lifestyle choice; just a thing. That's where faith comes in; faith to cope with the situation in the light of Scripture. You know as well as I do the attitude in most ancient cultures - Israel included - to disability in general, and blindness in particular. It was a mark of shame; some thought it was a mark of sin...though Jesus told them where to go as far as that went. Yet many, myself included, believe that Paul himself was suffering from extremely poor eyesight at the time of his trial before the Sanhedrin and his subsequent imprisonment...yet God chos to continue to use him in ways which changed, and still change,lives. Did God remove his visual impairment? Not that we can discern. Did this 'mark of shame' stop him in any way? Not a bit of it! Did he learn to live with it in the light of Scripture? Look for yourself. Same with sexuality, whether homosexual, heterosexual or promiscuity. Faith is the answer...not condemnation.
Thanks.
In case you think that same sex attraction is unchangeable: I know someone who has been open with me about having same-sex attraction in the past, but recently told me that a friend of his has unwittingly said something that enabled him to change his orientation.
I note that this person I know hasn't practiced homosexuality, except once as a teen. This makes me think it's possible that those who do practice it may in time become less able to change orientation later on. At some point I may be able to ask him what was said. I just thought I would mention it, as it may be that same sex attraction is not unchangeable, despite the insistence of many that it is.
You are right that for the Christian, sex should be between a husband and wife. People other than Christians also believe this, though, simply out of respect for it as the bond on which the family is based or just through knowledge of anatomy and physiology.