Born Gay?

Alexander McCobin, in the link above, did a nice job. I liked his tone and attitude and I liked the fact that he used the term “advocate freedom,” rather than the much more common (and incorrect) “advocate for freedom.”
Didn’t like the fact that people kept booing Sorba though. One short “boo” is enough to let him know where you stand and then let him speak uninterrupted.

It’s exactly as you say–genetics doesn’t work the way he seems to think that it does.

Moreover, even if you could demonstrate that genetics plays a very very weak role in the whole thing, it still wouldn’t be enough to demonstrate that homosexuality isn’t biological–because it could be a trait that emerges as much developmentally (due to conditions in the womb and whatnot) as it does from some specific gene(s).

Greg Cochran explains it’s not genes, it’s germs.

We have to be careful about what heritable means. It refers to the amount of variation in phenotype (an observable trait like sexual orientation) that is associated with variation in genetic makeup. So it’s defined at the level of a population.

It does not mean what role if any genes play in mechanistically producing the phenotype. That refers to the building process within an individual, not the process that distinguishes on individual from another within a population.

The mechanistic process producing the phenotype could be only the function of genes and have no environmental or chance inputs, but if everyone in the population has the same genetic variants or if everyone has the same phenotype, the trait has a heritability of 0.

Conversely, we could have a phenotype that had no mechanistic influence of genes at all, but that was still perfectly associated with genetic differences across the population. This trait would be 100%. Suppose that instead of Social Security numbers, we had a number — a really long number — that identified us by what values we had across our genome. Obviously this is a social convention that genes don’t mechanistically produce, but differences in genes perfectly predict differences in the phenotype.

Strictly speaking, heritability doesn’t tell us that genes are involved in causing the particular phenotype to show up or not. They might if there’s a mechanism, like finding genes that code for proteins related to bone growth would make us suspect that the heritability of height was picking up on the mechanistic action of genes.

But there’s not going to be such a mechanism for genes causing a male to be preferentially homosexual because these will get weeded out by natural selection. (Google “cochran gay germ” for the basic logic and arithmetic.) To make it more intuitive to folks here: why would a firm not only refuse to seek out customers but also actively turn away any customers that did show up? Obviously that firm will get driven out of business.

Random mutations don’t happen at a high enough frequency to produce about 3% of the male population that’s gay. And inclusive fitness arguments don’t work because the cost they incur by nearly not reproducing would have to be compensated for by raising scores of nieces and nephews, not just acting warmer than a straight male toward his siblings.

@ Tim,

You forget that women aren’t supposed to enjoy sex in the first place! 🙂

There’s also evidence that fraternal birth order (the number of older male siblings a male has) influences the likelihood that he will be gay, and that this effect seems to exist even in sons not raised by their birth-mother, implicating some in-utero cause. See this article for an overview.

I’ve read a few months ago that there seem s to be a connection between pheromone receptors and homosexuality. Specifically, gay men have male pheromone receptors, making them sensitive to male pheromones, and lesbians have female pheromone receptors, making them sensitive to female pheromones.

I have also read that male homosexuality seems to be linked genetically to their mothers.

Add these two together, and you get a connection between sexual orientation and the sex chromosomes themselves — something we should perhaps not be all that surprised about.

My wife has a gay friend whose brother is also gay, who has a gay uncle on his mother’s side, and many gay and lesbian cousins — again, on his mother’s side. This seems to argue in favor of the genetic linkage to the mother. This got me thinking about the possible genetics behind this.

It seems likely that male pheromone receptors are on the X chromosome, and female pheromone receptors are on the Y chromosome. I’m guessing that Y chromosome also has a way of blocking the production of male pheromone receptors. We can make sense of the cause of same-sex sexual orientation with a simple phenomenon: a chromosomal recombination that placed a female pheromone receptor on the X chromosome.

How does this make sense? Through the fact that sometimes, when you add another gene to a chromosome, instead of making more of the gene, it shuts the genes off. As a consequence, the presence of the female pheromone receptor on the X would turn off the gene on the Y, meaning only male pheromone receptors would be made. This would explain the sexual orientation of gay men. It would then suggest that having an X chromosomes having this gene would make a woman a lesbian, since one of the X chromosomes would be acting like a Y.

If true, this should be fairly easy to prove.

It might be interesting to know if a genetic basis exists, but since the ultimate purpose of this discussion is to ground moral norms, both sides – to the degree that they count on the result – failed before they began by attempting to infer a moral norm from genetic fact. Even if a theory of naturalist moral normativity is brought in, one would still need to argue why our raw genetics are more fundamentally explanatory than, say, our ability to reason and form cooperative bonds. After all, what our genes “want” is for us to engage not only in reproductive sex (to the exclusion of all other kinds) but to engage in it at every conceivable moment. Sorba, like the rest of us undoubtedly, does not hold this up as the “good life.”

Interesting post, it helps to show that the argument in and of itself is more complicated than many people make it out to be.

Also, as a guy who is taller than both of my parents, I’d like to thank my parents for both their genes and what they fed me. I totally know this first generation American who’s taller than either of his parents, who emigrated here from a much poorer country, and they were able to feed him much better quality food in higher quantities than they had.

Those who argue for abuse as a major source of homosexual behavior have to also explain why non-human animals also express homosexual behaviors (bighorn sheep, dolphins, and especially bonobos). Most notably, our closest genetic relatives, bonobos, exhibit homosexual behavior as a way of social bonding. Bonobos are basically bisexual. It may be that humans are basically bisexual, but our awareness of the relation between reproduction and sex pushed us culturally toward more heterosexual behavior (and the wide taboo on homosexual behavior in many cultures).