But not compared to American English … oh, wait, you didn’t mean the Scottish National Party.
These examples (that I made up) helped me understand the situation. Suppose there’s a condition that’s entirely due to the womb environment; in that case, identical twins would be perfectly correlated, and so would fraternal twins. For a condition that’s entirely genetic, identical twins would again be perfectly correlated, but fraternal twins would be correlated significantly less (50%?). For a condition that is partially genetic and partially due to womb environment, the correlation of identical twins would still be 100% but the fraternal twin correlation would be between 50% and100%.
(as another example, consider a condition that’s due entirely to post-womb environment: then, the correlation for identical twins raised separately would be the same as the correlation for fraternal twins raised separately).
Please let me know if I’ve got any of this wrong…
One study I perused (or perhaps I was just looking at a report on the study) said that they were using the 0~6 Kinsey scale, where 0=het, 3=bi, 6=gay, with shades of bisexuality-with-a-preference in between. I believe the ratings were self-reported, where they ranked any 3+ as being in the gay category.
People who consider sexual behavior/preference to be fairly straightforward are not really taken seriously by people who study genetics, behavior and/or sexuality. I tend to think that most people are not 0 or 6 on the Kinsey scale but identify strongly with their scale bias and so identify in a binary way.
Then, of course, we have the religion issue, which wants to paint any non het-norm behavior as wrong. Take away the “moral” pressure and no one will have much interest in the origins of homosexuality, because it would not even matter where or not it is a choice. That, I think, is a more desirable goal than trying to find an elusive biological origin.
To complicate matters, I need to point out something that’s easily overlooked…
The environment that twins experience in utereo isn’t the same. Twins don’t get equal measures of their mother’s blood supply, nutrition, or hormones, which is why even identical twins have noticeable disparities in their sizes at birth. From the moment the two embryos split off from each other, their respective environments diverge, which means their gene expression is different from the moment they are conceived. Yes, technically they will have the same blueprint. But each blueprint gets read differently because they exist in individuals inhabiting different environments.
So it is quite possible for a cause to occur in the womb, and only “hit” one twin and not the other. Maybe the unaffected twin has a gene that confers resistance . Or maybe the affected twin, through sheer coincidence, received a heavier dose of “cause”.
Good point.
I just think human beings are incredibly complicated and have an enormous potential for learning various behavior patterns and something like sexual orientation is much more of a nebulous concept than some people would like to think it is. This is why I think the role of the environment should not be underestimated.
I am not an expert by any means in this field, but I don’t think this is a useful way of looking at things. There are indeed two areas to look at, feelings and actions. You can refuse to act on same-sex attraction, either by faking it with the opposite sex or by being celibate. You can be bi-sexual and only perform sexually with one or the other sex. But you have whatever feelings you have, and those feelings define your sexual orientation (in my opinion) much more than your actions do. If there is a spectrum of however-finely-distinguished degrees of difference, you are somewhere on that spectrum at any point in time. Your position on the spectrum may change over time, although probably not much after adulthood.
Not to me, just because it seems so unlikely. In any case, more or less as you noted, all they could do would be to increase the likelihood not to guarantee it, just as changing the conditions in the other direction would probably reduce the likelihood rather than eliminate it.
I’m not sure I see the relevance of most of these observations. The term “sexual orientation” is shorthand, but that doesn’t make it necessarily limited. You can think of it like a compass, not all north or south, but anyplace on the dial in between. Or like a radio dial. Or any other metaphor for a condition that can have nearly infinite variations.
All the comments about the limitations of 23andme’s research are gratefully received. They just make me wonder why they bothered to post the findings at all, and then I remembered that they are, en fine, a commercial enterprise.
I would say that twin studies show that there is no genetic determination of sexual orientation because a pair of twins may consistent of one gay person and one straight person. I know such a pair of twins. I’m not sure why beyond that it makes a difference in an ideal world. I realize this world is less than ideal but in an ideal world I would consider that it doesn’t matter why someone would act or identify as homosexual. Although it’s not something to appeals to me I don’t like the idea that I couldn’t be gay if I wanted to be for any reason at all and that somehow I’d have to have certain genes to be considered such. However, as I noted above, I know a pair of twins with different sexual orientations, each say they’ve always known what their sexual orientations were (i.e. ‘born that way’). I haven’t checked their medical records myself but they say that doctors have confirmed they are identical twins, not fraternal. So starting with the same genes they have ended up with different sexual preferences and if there is any physical cause for either of their sexual orientations it is not based solely on their genetic structure.
That’s kind of totally misunderstanding what the twin studies showed. There are still disagreements, but what they showed to varying degrees was it was more likely for identical twins to have the same sexual orientation than fraternal twins. If all identical twins always had the same sexual orientation then that would be good evidence that it is purely genetic. The fact that it was only a higher chance leads researchers to think it is only partially genetic.
Which is what I said. There may be a genetic component, but it doesn’t by itself determine sexual orientation since two people with identical genes may not have the same sexual orientation.
I don’t know of recent well-run polling on this. My anecdote is that that I have never in all my life experience, having met in person at least 2,000 transgender persons and I don’t know how many online, found a transgender person who said “I always wanted/hoped I would be transgender.”
The debate of “if there was a magic pill you could take and not have to be trans” comes up at everything from Sunday morning brunches to late-night club talk. I’d say about a third of us would take a pill to magically make us cisgender in our original gender presentation. Most would not, or else would want to be cisgender in our new gender presentation. It kinda trends with support levels. Those who are unemployed, newly divorced, ostracized by family, friends, church, the victims of abuse - most of them would take the pill. Those with less abuse in their lives are more likely not to. Those who found strong support in their lives (a small population) are militantly against the magic pill.
I wouldn’t take the pill. As an intersex transgender person, I really have gained a unique perspective on the two main sexes and two main gender presentations in society, which I think has really opened my eyes to humanity in general. However, sometimes I do think I might have taken the pill…I do feel isolated and lonely sometimes, even when I’m among transgender persons, because I’m still not exactly like them. I stand out because I look cisgender female, even with no makeup and wearing boy clothes. Ironically, one of my friends who I cannot stand much of the time because she’s often a total bitch, who is also intersex and transgender, is someone I feel most “comfortable” around. 
On a similar note, I know of a pair of identical twins, kept and raised in the same environment by the birth family, where one twin is normal and the other pretty severely autistic.
There is a gene for right-handedness. If you don’t have the gene, you have a 50% chance of being right handed, and a 50% chance of being left-handed. People who don’t have the gene are no less left handed than people with the gene are right-handed-- or for that matter, people without the gene who are right-handed are no less right-handed than people with the gene. Also, it doesn’t seem to matter whether you have one or two copies.
This suggests to me that it might be a mistake to look for a gene for gayness. Maybe we should be looking for a gene for being straight. If 80% of the population had the gene, and those people were straight, while 20% of the people did not have the gene, and those people were somewhere on the Kinsey scale, we’d have the situation we have now, where about 10% of the population reports being gay at any one time, while a larger number reports “experimentation,” or “previous phases,” but is straight at the time of the reporting, and a smaller number report being bisexual. (A lot of people who are bisexual report being gay or straight based on the long-term relationship they ended up in, even though they know they are really bisexual. Just ask me.)
Anyway, if that were true, the gene spread, 80%, would be the same as the gene for right-handedness. It might even turn out that having one gene is advantageous in some way, but having two genes is not, like in Tay-Sachs where one gene protects from TB, or Sickle Cell anemia where one gene protects from malaria (although obviously not that serious or we’d have stumbled on it by now).
I think you have been able to gain such unique and fascinating perspective on humanity, one that I have little doubt you would never trade for anything in the world. This is despite, or maybe at least in part because of the pain and struggle you had to experience to arrive at such a perspective. I don’t really know exactly what I’m trying to say here, other than I recognize, from my own perspective, the unique wisdom your life experiences have provided you. I deeply respect you. If I ever had the chance to meet you, which I know I won’t, I’d buy you a drink. 
ETA: sorry for the hijack!
(TriPolar, probably would have been clearer if you had initially stated “not exclusive genetic determination of sexual orientation” rather than “no” but be that as it may.)
Yes, the identical to fraternal twin analysis technique can, at best, estimate a likely level of genetic contribution to a particular phenotype. So for example the technique allows one to estimate the degree that autism is genetic, which is high even though not all identical twins will be concordant. Few people would describe the fact that there are identical twins in which one twin does and one twin does not have autism as demonstrating that such shows that there is no genetic determination of autism.
For autism there are many alleles that have, not always consistently, been found linked to some degree of increased risk but most of them are also commonly present in the general population. The prevailing belief is that various so far not well determined combinations of different alleles results in autism. But the relatively heritability of autism was well established and accepted before those alleles were identified.
This study does not contradict the conclusion of a fairly strong heritable component to gayness. It does however state that the mechanism of the heritability is not by way of any of the SNPs on the 23andme v4 chip, likely not for SNPs highly linked to those SNP, to a level of impact that the study was powered to find. There are (to an 80% confidence) as of yet no SNPs that have been identified that increase the odds of gayness in males by 30% and females by 70%. The study would identify SNPs that individually contributed less than that increased risk and would not identify other heritable mechanisms (such as epi-marks). The reputed 50% of the variance of sexual orientation being heritable seems to work in ways more complex than that.
Just to add to the argument that this is absence of evidence rather than evidence of absence: the study has used the standard level of statistical significance of 5% per test which is adjusted for the number of tests (1 million) to 5 x 10-8. So by that measure they have to conclude that no significant associations were found.
This doesn’t mean that there are no genetic variants associated with sexual orientation (the NKAIN3 SNP is close enough that it would be worth following up). Larger cohorts or finer division of the phenotype could turn something up.
Previous GWAS studies of complex traits have been relative failures at fully identifying genetic causes, often turning up many variants that account for only a small fraction of genetic contribution. This is unlikely to be different.
That’s interesting. Thanks!
DNA sequence is not the only component of genetics. Epigenetics no doubt has a role; Lamarck wasn’t so wrong afterall. The idea that there would be some identifiable “gay gene” that would fit into a Punnet square was always naive.
I had a pair of identical twin roommates in college. One very straight and one very gay and neither was fooling themselves either way. And I have no doubt that it was biological nonetheless.
Sorry CarnalK. I see that I did word that poorly. Tx for restating that** DSeid**.