Genetic basis of homosexuality and Republicanism

Simply put, is there better evidence for the role of genetic variation in shaping variation in sexual attraction when compared to the evidence for the role of genetic variation in party affiliation?

On a related note, do you believe it is nonsensical to ask questions about genetic variation biasing behavior?

I don’t believe there is any significant role of genetic variation in the development of sexual attraction at all. I think whatever biases us toward a given sexual orientation occurs so early and so unconsciously in our development that it seems like it should be in our genes, but it isn’t.

On the other hand, there is apparently a subdiscipline of behavior genetics called genopolitics. If you read the Wikipedia article you will see that studies are generally focused on biases like Liberalism versus Conservatism and do not necessarily deal with the actual choice of one political party versus another.

So overall, although neither field is very well developed, I believe there is better evidence for genetic variation’s role in biasing political orientation than sexual orientation.

This is the result of a side discussion in this thread: here.

I am not a geneticist.

I think your hypothesis is reasonable, but I don’t have any hard information to confirm or contradict it. Not sure the bio people do yet, either.

I am under the impression that

a) it somehow became established political-social belief that IF sexual orientation were genetic in origin, it would be more widely accepted. (I personally call bullshit on this notion. There have been plenty of pogroms and hate campaigns against people who were believed to be innately different)

b) there’s a wide band of pressure to conform ideologically among the socially progressive, wherein people get tired of re-explaining the majority-among-progressives position to any who have a different notion and become intolerant of it, with an attitude of “you’re not merely wrong but offensive if you believe that”; and that the embrace of biological origin for sexual orientation is among these canonical beliefs

c) there are some twin studies and similar research that seems to indicate a greater tendency to have the same sexual orientation as someone sharing biological makeup but different social environment growing up; these do tend to point towards the possibility of biological components of sexual orientation, but my impression of them is that they are neither conclusive in establishing that much nor do they give sufficient reason for concluding beyond that point that therefore biological components are the only meaningful variables in sexual orientaton.

I don’t think there’s a “gay gene” if that’s what you mean. And my evidence for that is that it often happens that when one identical twin is gay, the other is not. If there were a gay gene then identical twins would almost always either both be gay or both be straight. Since that doesn’t happen, there is no gene that makes you gay.

However, it is true that if your identical twin is gay, you are much more likely to be gay than a random person. It’s also true that if your identical twin is gay you are much more likely to be gay than if your fraternal twin is gay. So if your fraternal twin is gay you are somewhat more likely to be gay, but if your identical twin is gay you are much more likely to be gay.

And this means that it can’t just be “environment” or “choice”. Your hypothesis that there is no genetic role in the development of sexual attraction can’t be right, because if you were right then identical twins and fraternal twins would have the same co-incidence of homosexuality. Again, this doesn’t mean there’s a gay gene, any more than there’s a gene for liking musical theater or leather pants or spicy food. Just that certain people tend to like certain things, and identical twins often have much more similar tastes in lots of ways compared to fraternal twins.

Can you cite the scientific studies on which you are biassing that proposition? I mean, it’s incredibly interesting that you “believe” that and all, but I’d like to know why you believe it.

I am basically with Lemur866 on this. That there is some genetic basis for sexual orientation is kind of beyond doubt. I also agree that there is no “gay gene” but probably a suite of genes that make it more likely given certain environmental conditions.

Your own wiki cite specifically dismisses party affiliation being genetic so I’m not sure why you included it in your title.

For some context, this came out the thread on abortion and whether folks would abort a fetus if it might be gay. But that doesn’t even need to come down to genes. Suppose we learn that certain environmental factors in the womb predispose a fetus to turning out gay. You could still abort. Or, you could opt for a surrogate if it were determine that you had a “gay producing womb”.

Given the consensus that sexual orientation is innate (that is, set at birth), the issue of aborting fetuses to prevent having gay children is not, per this OP in the other thread “unrealistic”.

Of course behavior has a genetic component. If it didn’t, how could different species have different behaviors?

Right. Chimpanzees don’t vote Republican but humans do, the difference between humans and chimpanzees is genetic, therefore there is a genetic component to voting Republican. QED.

problem with twin studies is they don’t just mean almost identical genes, they also mean almost identical pre-natal environments, so epigenetics, hormones and other factors will also be the same. Are there any twin studies on identical twins birthed by separate mothers (say, by IVF)?

OK, I should have said that some behaviors must have a genetic component.

It’s almost certainly true that some specific behaviors are wholly environmental (like which religion you practice, pardon the pun).

But, bottom like, it is NOT “nonsensical to ask questions about genetic variation biasing behavior”.

Sure, but that’s why ideal twin studies compare identical twins to fraternal twins. Of course even sharing the same womb doesn’t mean your environment is identical, only that’s as close as we can get.

Ideal twin studies compare identical twins raised together vs those raised apart.

I don’t think you can produce identical twins in separate mothers via IVF. Unless I don’t understand your question.


I was only being a little bit silly, but it certainly is true that certain unique human behaviors can only exist because humans have a particular genetic inheritance. It probably isn’t true that there’s a genetic component to voting Republican, but it certainly is true that Chimpanzees don’t vote Republican. So there is something about human beings that allows them to vote Republican while other animals can’t. But there probably isn’t a genetic difference between humans who vote Republican and those who don’t.

Not sure who you are asking, but there is no reason you couldn’t produce identical twins via IVF. We can separate the “clump of cells” shortly after they begin dividing with little fear of damage to the resulting embryo. Then implant them in different mothers.

It would no the ethical to do this for purely research, but it wouldn’t be technically difficult to do.

Let’s back up a bit. Chimps can’t vote Republican, but they can challenge the prevailing social order or try and re-enforce it. They can be overbearing and tyrannical, or more tolerant. They can be good mothers or bad mothers.

And there might be genes that predispose individuals to go with the flow or be more of a challenger to the social order, and would therefore predispose someone to being “conservative” vs “progressive”, where progressive = working for change.

I don’t think anyone is currently intentionally trying to create identical twins, but the procedure would be straightforward. Identical twins are formed when an embryo develops into two embryos. So you could split a very early IVF embryo, see if it develops into two viable embryos and then implanting both.

The problem is that the odds of success for any one embryo implantation is pretty low, that’s why they do multiple embryos and hope one survives. So attempting this would have very low odds of success, you’d have to do it multiple times to get one success. And for what? Fertility clinics aren’t allowed to create living children just do do genetic studies, they only create children for parents that want them.

In other words, it could be done, but nobody would do it.

The ideal is both types of studies happening, as womb environment is somewhat taken out of the equation with fraternal twin comparison and “nurture” and childhood development environment is taken out by being raised apart.

We know that common chimpanzees and bonobos are very closely related, genetically. But their behavior is significantly different. The former is patriarchal, territorial, and prone to waging wars on their neighbors, while the latter are matriarchal, welcoming to strangers, and have never been observed to wage war.

It’s been postulated that part of the reason is the bonobo environment has more abundant food sources, but it’s unlikely that explains the entirety of the difference in behavior.

Although my understanding of it was never something I delved into very deeply, my impression of the research is not much different than yours.

Heritability studies are the basic evidence for the role of genetic variation in human behavioral variation within a population, and the results are neither very reliable nor do they show a very strong signal for male and female sexual orientation. Especially when compared to other types of behaviors.

This Swedish study is the most recent twin study, its abstract starts out with “There is still uncertainty about the relative importance of genes and environments on human sexual orientation”, it goes on to show some pretty modest heritability estimates, and then state “Although wide confidence intervals suggest cautious interpretation…”. I imagine the article fleshes all that out quite a bit more. This isn’t anything like what you would see for twin and adoption studies for any number of other behavior patterns like various aspects of cognition, affect or personality.

Studies based on candidate gene approach and linkage analyses haven’t really provided reliable results. Or even when they have some replication, weasel words like “approaching significance” are used. So its not a replicated result.

Against the weakness of this work, there’s the strength of studies like those showing birth order effects on male sexual orientation.

Now with political ideology (which I am taking as an assumption will strongly influence party affiliation), you have twin studies like this where similar heritibility estimates are obtained but they are more stable across many populations and this is only the latest in many studies cited by the authors. Ok, their genome wide association study didn’t work out, but when comparing twin studies on political orientation versus twin studies on sexual orientation its pretty clear the former has a much stronger set of results.

There isn’t any strong evidence suggesting that homosexuality has a direct genetic basis.

I’d look for a better cite but I’m on my phone so it’s quite annoying.