Schizophrenia is the price we pay for minds poised near the edge of a cliff

Do men and women both have the coding for male/female attraction, with one typically disabled ? This perhaps seems most likely, in same way both sexes have nipples, etc. Without knowing exactly how this all works we can only speculate how male/female genes can combine to create same-sex attraction. Obviously it's not so simple as inheriting a gay gene from one of your parents!

Typical is putting in a lot of work in that sentence. I could rephrase it with the same truth content and make it much more ambiguous.

"Many phenotypical sexual differences in humans are obviously genetic. Some very common differences in sex-specific sexual attraction are likely genetic as well. For large swaths of sexual attraction, we have absolutely no evidence of a genetic link."

What's funny is that the one example you facetiously picked (a curve detector) is extremely culturally dependent. Trying to tie elements of human sexuality to evolutionary just so stories is usually pseudoscience. When we start isolating genes for the things that we think of as natural, if we ever do, I bet you $100 the mapping from our social experience of these traits to some kind genetic reality is muddled to the point of total detachment.

Actually, it wasn't intended as facetious! I'd bet money that male attraction to females is indeed based on curve and jiggle detectors! If not this, then what - it has to be based on some (simple, perceptual) physical characteristics. I realize that female ideals vary a lot between cultures, and time periods, but the differences are more about things like fat percentage and distribution than the underlying characteristics that visibly differentiate men from women.

Sure - it seems there may be a large degree of imprinting as well, but homosexuality does seem to be an important special case given that it typically means lack of descendants. Of course evolution is really about sub-populations and gene-pools, not individuals, and it seems there has to be some benefit at that level otherwise this trait would have been out-competed in the population.

For much of human history, that has been false. In many societies, there has been strong pressure to (heterosexually) marry, arranged marriages - with the result that most individuals with a homosexual orientation end up participating in heterosexual reproduction-so homosexuality is much less of an evolutionary disadvantage than you’d assume.

Modern Western society puts great emphasis on marrying for love, marrying on the basis of actual attraction rather than social pressure or political calculation, being “true to yourself” - and in such a society, a homosexual orientation does significantly reduce the odds of participation in classical heterosexual reproduction. But modern Western society isn’t normal in world-historical terms, what we consider “normal” is actually rather novel