If homosexuality is innate/genetic, how has it survived evolutionary selection, given that a homosexual couple produces no offspring? Wouldn't an evolution-based standpoint argue that homosexuality is developmental?

Oh, there are so many aspects to it that I don’t even know where to begin…

For starters, homosexuality is not as disadvantageous as it seems.

Humans are social species that originally used to live in packs of around thirty members and cooperated to get food.

Since food was scarce, having too many babies in the pack was very dangerous: it might seem counter-intuitive that an animal wouldn’t want to breed as much as possible, but that’s how it was. If too many people decided to reproduce at the same time, everyone could die from starvation! The entire pack!

In that light, homosexuality was quite useful: if a minor percentage of the pack didn’t breed, it greatly relieved it from pressure. Homosexuals could then spend their time helping taking care for their siblings (with whom they share approximately 50% of the genes, same amount as they would’ve with their children) or children of siblings (with whom they share circa 25% of the genes).

As the result, their effort was 25% efficient — as opposed to the alternative of 0% (remember — if the pack bred too much, everyone dies).

Next, the same genes could be acting differently in two sexes: e.g., the genes that make boys homosexual could be responsible for making girls super-sexy or super-horny, thus giving advantage to the entire family line. Or genes that make girls homosexual could make boys more horny or competitive. Remember: there are two sexes in humans that are considerably different from each other, and yet use virtually the same genes. As the result, men have to put into use the genes that originally evolved to accommodate the women’s needs, and vice versa. Sometimes with unexpected results.

If you are into reading about sex of fruitflies — here’s a research on the topic.

Q: C’mon, even if it was true, it would take every sister of a gay to produce twice as many offspring just to compensate for her gay sibling and keep up with other women!

Exactly!

Which is why homosexuality is a minority trait.

For a trait to disappear completely, it must be absolutely devastating in every way — because if there is a loophole to turn a disadvantageous trait into an advantage, some individuals will exploit it.

Here’s a real example:

Those are moths called Biston betularia, the majority of which were whitish-grey in colour. Such colouration allowed them to camouflage against light-coloured tree bark and lichens, while black colouration was too conspicuous to predators and effectively deadly.

However, after the Industrial Revolution, many lichens disappeared, and tree bark was darkened by soot. Immediately, black colouration became advantageous, and in a matter of decades, black moths thrived and bred, while lighter ones were eaten out by predators:

The new advantage brought by the Industrial Revolution allowed those two blacks out of a hundred whites to become more successful.

But one thing doesn’t make sense: How the fuck were there any blacks at all before the Industrial Revolution?

I mean, you can understand why those two blacks have taken the population over after the revolution, but they should’t’ve existed in the first place — they were at a disadvantage and dying like flies.

And yet, somehow…

You might be seriously underestimating the hardship of driving every individual with a certain trait into extinction — even when that trait is not very helpful. As long as at least a few individuals are capable of surviving and reproducing, the trait will likely persist as a minority trait.

Homosexual genes might make reproduction more difficult. But apparently, not difficult enough to stop at least some individuals from passing their genes on. So their existence is not so surprising.

Remember: it’s a minority trait! We don’t need to explain why it’s so damn good for survival of the population — because it probably isn’t: all we need to explain is how at least some homosexuals are capable of working around it, or how it can give some advantage at least in some situations. It doesn’t have to be super-duper good.

But let’s imagine the worst. Let’s imagine that homosexual genes don’t give any advantages to opposite sex. Let’s imagine that no human could use help from their gay sibling. Let’s even imagine that none of gay people ever get raped by opposite sex or ever try mating with opposite sex even once out of curiosity or because of circumstances.

Even then, getting rid of homosexuality genes completely would’ve been almost impossible.

Because there’s such a thing as homologous genes.

You see, the status of being sexually reproducing creatures obliges us to carry not one, but two copies of every gene. Two copies of haemoglobin gene. Two copies of the eyecolour gene. Two copies that get expressed at the same time and do the same thing.

Sometimes, genes get broken: for example, the gene that makes the embryonic brain sensitive to testosterone (and thus enables the development of sexual attraction to women in men) might mutate and stop doing its job. In that case, the second copy of that gene might back it up, and homosexuality won’t develop.

Yes, a person is literally carrying a homosexuality gene and yet remains heterosexual. It’s quite possible that you carry homosexuality genes right now. You just don’t know about it, because it’s backed up by another gene that nullifies its effect. But your children might become homosexual — if your partner happens to carry a copy of this “broken” gene too.

And again, here’s a real example: haemophilia.

It’s a disease that impairs the blood’s ability to coagulate, so any scratch or bruise becomes a potential death sentence to the affected human. It’s a genetic disease that passes on from generation to generation. And it exists even nowadays.

But you may wonder: But how come such a monstrosity wasn’t ripped out by natural selection, root and stem? That gene should’ve gone extinct long before humans have left the caves!

It should’ve. But the thing is: not all people that carry it are sick!

To become sick, you need every copy of that gene to be broken — otherwise, the functional one would back up the broken one. And if you aren’t sick but carry the gene, it’s safe from natural selection within you.

(if you’re interested — here’s a huge write-up on homologous genes from me)

Basically, if some eugenicist bigot decided to exterminate homosexuality, not only would he/she have to exterminate all homosexuals, but also a good deal of heterosexuals who just happen to carry a suppressed copy of homosexuality gene — and I don’t mean bisexuals or something, but indeed a part of perfectly heterosexual population. Because otherwise, even with all homosexuals gone, they’ll inevitably pop up in the next generation.

Finally, even if he/she eradicated homosexuality genes for good, there’s still a matter of mutations. Even if all carriers of gay genes without exceptions suddenly failed to reproduce, a small number of homosexuals would still be born because mutations happen, and new errors constantly arise in genes.

Bottom line is: to eradicate homosexuality for good, all sexually reproducing animals must go extinct.

By the way, did I mention that it’s not only genetics — saying that it’s always innate is an overly simplistic, even politically correct view. Most likely, some homosexuals are indeed made rather than born (as well as some heterosexuals are made) — our brain is very plastic, and environmental factors can affect it to great extent. But there are genes that contribute to it majorly, and more importantly — there’s an explanation to how such genes could preserve in the population.

Update: apparently, my example about moths is not entirely accurate, because the black moths have appeared for the first time at the beginning of the Industrial Evolution — meaning that they didn’t have to survive for long in disadvantage, but became advantageous immediately after the mutation has occurred (which makes them a good example of how mutations can create new traits, by the way).

Thanks to Keith Robison for pointing it out.

There are other, proper examples though: black panthers as the minority of jaguars, and black squirrels as the minority of ordinary squirrels (thanks to Tamara Vardo for the example). I’ll probably see which example fits better into the narrative and update my answer later — meanwhile, be informed.