Heterosexuals: did you choose your sexual orientation?

[umop_ap_sdn]

Left-handedness is genetic, and it influences your behavior, doesn’t it? And maybe it’s a stereotype, but left-handedness is usually associated with certain tendencies, like an interest in or aptitude for the arts, etc.

I will admit that a person’s chances of being left-handed jump from 10 percent to 40 percent if both parents are left handed, and that more men are left handed than women. But until I see a study that proves handedness is genetic, I will be somewhat skeptical.

Being artistic, on the other hand, is a personality trait and when you try to draw genes->left-handedness->artistic you’re stretching it pretty thin, IMO.

Genes are chemical, not physical.

I’m not sure what this means.

What I mean is genes primarily direct the sequences of peptides (proteins, etc) which are pretty much left to themselves to fold up into a functional unit. We can see how a genetic vaiation inserts the wrong amino acid into the string and results in a nonfunctional protein, but still the line from genes->protein folding->behavior still seems tenuous.

There’s no maybe about it, genes direct the growth of your brain and everything else. We’re sentient, but that doesn’t mean genes don’t affect our behavior. It’s not an either/or thing.

Indirectly. But it’s such a complex system that tracking down genetic influences would be phenomenally complex. A person has approximately 30,000 genes and, assuming you’re right, for all we know half of them could be involved. That’s why:

That’s because there is gay gene.

I don’t believe it. Out of all those genes, the concept that one gene and one gene only would have such a definite effect on behavior, without any associated “side effects” for lack of a better term.

Let me use an analogy: a computer is made of several parts - memory, CPU, video circuitry, sound card, etc., and each of these parts is made of silicon and various other materials. If there was a change in the composition of the silicon, it would tend to affect all the components and functions equally. Okay, you say, but genes are more complex than silicon and are expressed in specific areas. So in my analogy a variation might specifically affect the CPU, or the memory, or the video circuitry.

Now suppose somebody came along and announced that their computer had a variation that rendered it unable to run any kind of word processor. Runs calculator programs, flight simulators, paint-type programs, educational software, development environments, but no word processors, even ones written by the user. Wouldn’t that be a stretch?

I don’t know if there’s a correlation. But then, I didn’t say homosexuality was passed from parents to kids. Most gay people probably have straight parents because (1) more people are straight than gay, and (2) straight people are more likely to have kids.

You have a point. However, if it were genetic there would be a clear and indisputable correlation, such as the 40% left-handedness I cited above. (Even then, genes are not the only possible explanation.) I was just asking if you knew of such a correlation.

What else is there? You’re not leaving anything else except choice, which few people (here or elsewhere) think is the case. And even choice is shaped by genes and environment.

Okay. And of course we make choices on subconscious levels too. But where does choice come from? This conversation is going back to the age old question, “who am I why am I here” which of course is well outside the scope of this thread.

[Marley23]

Out of all those genes, the concept that one gene and one gene only would have such a definite effect on behavior, without any associated “side effects” for lack of a better term.

Again, I never said it was one gene. I would be a dope if I suggested there was a “gay gene.” Look for annaplurabelle’s posts on this thread, she knows more about it than I do. scm1001 also offers a few links. Studies have been done that indicate genetics are a factor to some extent: a study done in 1991 by Bailey and Pillard showed that 52% of identical twins of gay men were also gay, for example. Linkyness.

As far as ‘side effects’ go, I think homosexuality in men is correlated with a larger than normal hypothalamus. And a recent study showed lesbians were more likely to get at least one type of cancer than straight women. That may be linked in the same thread.

However, if it were genetic there would be a clear and indisputable correlation, such as the 40% left-handedness I cited above.

Not if we didn’t know what the correlation was yet. I said it already, but just because homosexuality is (in part) genetic doesn’t mean it’s based on one gene and is obviously inherited from family.

Looking at the old thread again, I’d be wrong to say it’s just genetics. Prenatal hormone levels appear to be a large factor.

In the thread, annaplurabelle cites a couple of studies, including one that says: “In men, sexual orientation is also highly correlated with the number of older brothers in the gay man’s family. Each additional older brother increases the odds of homosexuality by approximately 33% (Blanchard and Bogaert 1996).” My example was a coincidence, but she also mentions that handedness is also apparently developed in utero.

[umop_ap_sdn]

*Originally posted by Marley23 *
**Again, I never said it was one gene. I would be a dope if I suggested there was a “gay gene.” **

Yes, and citing The Onion makes it clear what a ridiculous claim that would be. Seriously, I thought you said there was such a gene - yo seem to have left a word out of the sentence, leaving it open to interpretation. So we agree on this statement.

a study done in 1991 by Bailey and Pillard showed that 52% of identical twins of gay men were also gay, for example.

Okay but identical twins share more than just genes. They share the same fetal development environment, for one, and IIRC they start out as one fertilized cell. Plus I don’t have any cites to give you but supposedly identical twins raised in separate households tend to develop the same habits, give their pets the same names, etc (any identical twins here who can confirm this or tell me it’s a bunch hot air?) so just because a correlation exists between twins doesn’t make it genetic.

And if it were genetic, Mendelian genetics would come into play, and you would see a few families (more than chance alone would dictate) where the hereditary pattern clearly obeys the Mendelian laws for the simple matter that however many genes could be involved, somebody out there must be getting the same of all but one from each parent.

As far as ‘side effects’ go, I think homosexuality in men is correlated with a larger than normal hypothalamus. And a recent study showed lesbians were more likely to get at least one type of cancer than straight women. That may be linked in the same thread.

Okay but how do we know the big hypothalamus causes homosexuality and not the other way around? Maybe they’re 2 different effects of the same cause? (And who says the cause is genetic?) What size is the hypothalamus in bisexuals, and how much overlap is there between the biggest straight man hypothalamus and the smallest gay hypothalamus?

As for cancer, I don’t know what to believe. There are so many carcinogens out there it’s silly, and roughly a year ago there was a big scare about eating potato chips because of their acrylamide content (incidentally, I still wolf down those things as much as ever).

Looking at the old thread again, I’d be wrong to say it’s just genetics. Prenatal hormone levels appear to be a large factor.

Well it’s hard to argue with that since hormones are central to pubescence. And yes, that’s a chemical factor which as I said in one of my other posts is under the influence of genes. But is there a study that correlates hormone levels of men to their sexual orientation?

In the thread, annaplurabelle cites a couple of studies, including one that says: “In men, sexual orientation is also highly correlated with the number of older brothers in the gay man’s family. Each additional older brother increases the odds of homosexuality by approximately 33% (Blanchard and Bogaert 1996).” My example was a coincidence, but she also mentions that handedness is also apparently developed in utero.

Okay, here’s a clue - and I’m not going to do the math right now because it’s 1:30 AM but according to you and others in this thread:

• A person with an identical twin who is gay has a 52% statistical chance of being gay;
• A person with an older brother who is gay is 33% more likely to be gay than one without (and since it seems to increase with each brother, I have to strongly suspect the home environment here);
• 10% of men are gay

Now since identical twins share (in theory) 100% of their DNA and nonidentical siblings share an average of 50%, we should see that the siblings should be half as likely to inheret a genetic characteristic. 52% is a 420% increase from 10%, so based on my hasty late-night math, that means the siblings should receive a 210% increase over the 10% which would mean statistically 31% of all men who have gay brothers should be gay.

That looks close but - if I am to interpret your cite correctly, then it’s a 33% increase from the 10% baseline - since 33% of 10% is 3.3%, that should mean that they actually found 13.3% of men with one gay brother are themselves gay.

Of course that’s oversimplifying the baseline as being 10% which, given that some of that is already accounted for, would actually be a little lower, and it’s assuming that 50% average genetic similarity would mean 50% of the statistical likelihood, and of course the influence of having a gay brother, whether he is open about it or not, would also lower that number, etc…

So in conclusion I don’t see any numbers to back up the theory that sexual orientation is genetic.

Which goes back to the OP’s question, to paraphrase, do we choose our orientation? My initial reply was to the effect that I was probably born straight but not because of genes. (Both of my parents are bi). If I was born straight then it was so long ago that I just don’t remember if I chose it or not.

[Marley23]

Okay but identical twins share more than just genes. They share the same fetal development environment, for one, and IIRC they start out as one fertilized cell. Plus I don’t have any cites to give you but supposedly identical twins raised in separate households tend to develop the same habits, give their pets the same names, etc (any identical twins here who can confirm this or tell me it’s a bunch hot air?) so just because a correlation exists between twins doesn’t make it genetic.

There have been some studies like that; I don’t know how much weight they carry. But the point of those studies, generally, is that personality IS somewhat genetic and that it doesn’t ALL come from one’s environment. And it also would seem to be heavily influenced by that fetal environment. Either way, it doesn’t support the notion that people choose their sexual orientation.

Regardless of the number games, which I can neither confirm nor deny, there seems to be correlation at work here - unless you’re chalking everything up to coincidence.

[umop_ap_sdn]

*Originally posted by Marley23 *
**There have been some studies like that; I don’t know how much weight they carry. But the point of those studies, generally, is that personality IS somewhat genetic and that it doesn’t ALL come from one’s environment. **

Show me a study where clones that were not originally part of the same egg grow up with the same personality traits.

It’s a shame president Clinton outlawed human cloning; it could tell us a whole lot about these matters.

[Marley23]

Show me a study where clones that were not originally part of the same egg grow up with the same personality traits.

Not only can I obviously not do that, I’m not sure how it’s relevant. Identical twins are as close to clones as you’re going to get, and if a number of studies demonstrate that they can grow up somewhat alike even if they’re raised totally separately, what else are you going to say it indicates?