What are the biological and environmental determinants for sexual orientation?

[shmogie]

The youngest male having older male siblings also seems to have an affect, in that the youngest is more likely to be homosexual because of earlier male births. Is this not relevant evidence?

Yes, it could be. But if this is the case, why ?

 

[Dawnofhope]

This review is a couple years old, but it summarizes the evidence for the biological basis of sexual orientation pretty well. Anyone who thinks there's no biological basis at all is just ignorant of the research. Granted, there are still plenty of unanswered questions with regard to the details. Sexual orientation is a complex psychological trait, and like all complex traits it appears to have a multi-faceted origin.

I don't think anyone here is arguing there's no biological basis for sexual orientation. I agree with your statement that sexual orientation involves complex psychology and has multifaceted origins.

The conclusion from the useful paper you provided reads:

The preponderance of evidence from sexual orientation research strongly suggests that human sexual orientation has biological underpinning and that it is tightly regulated at the molecular level. Although the “gay genes” are yet to be identified, there is little doubt that genetics plays a role in this trait. Epigenetics appears to be another important contributor, particularly in mediating environmental effects, such as the intrauterine milieu. However, much work remains to be done on both fronts to identify which genes are involved in the control of sexual orientation.

 

[Left Coast]

I don't think anyone here is arguing there's no biological basis for sexual orientation.

I disagree? Isn't that exactly what @shmogie is saying? :

My belief is that there is no physiological reason for homosexuality.

Perhaps I misunderstood?

 

[Dawnofhope]

I disagree? Isn't that exactly what @shmogie

Perhaps I misunderstood?

@shmogie can defend his own position. You may want to ask him specifically about the likelihood of genetic and/or prenatal factors. My position is what science says. There is a strong likelihood such factors contribute.

 

[shmogie]

@shmogie can defend his own position. You may want to ask him specifically about the likelihood of genetic and/or prenatal factors. My position is what science says. There is a strong likelihood such factors contribute.

There is no homosexual gene. There may be a number of factors, yet there is no consensus theory on why homosexuality exists.

Science is proposing ideas, without the evidence to establish any of them.

 

[SomeRandom]

There is no homosexual gene. There may be a number of factors, yet there is no consensus theory on why homosexuality exists.

Science is proposing ideas, without the evidence to establish any of them.

To be fair, there’s no heterosexual gene either.

 

[Left Coast]

Science is proposing ideas, without the evidence to establish any of them.

This is flatly contradicted by the actual scientists whose work has been posted in this thread. Multiple lines of evidence falsify the assertion that genes play no role in determining sexual orientation. They clearly play some role; the question is the exact mechanism by which they do so and in what way they're likely mediated by epigenetic factors.

 

[shmogie]

This is flatly contradicted by the actual scientists whose work has been posted in this thread. Multiple lines of evidence falsify the assertion that genes play no role in determining sexual orientation. They clearly play some role; the question is the exact mechanism by which they do so and in what way they're likely mediated by epigenetic factors.

"they clearly play some role". yet the how is not known. How then do they "clearly play some role" ?

I stated that there is not a gene identified as the one that causes homosexuality, a homosexual gene.

Are you saying there is ?

There very well may be genetic factors, however, can you point me to a theory that establishes what genes they are and how they work related to causing homosexuality ?

 

[shmogie]

To be fair, there’s no heterosexual gene either.

There are chromosomes however.

 

[Left Coast]

"they clearly play some role". yet the how is not known. How then do they "clearly play some role" ?

Because there is no plausible explanation of the available evidence that does not implicate genetic influence.

I stated that there is not a gene identified as the one that causes homosexuality, a homosexual gene.

Are you saying there is ?

Of course not. Are you saying that because there's not a single gene that's been solely identified as causal (because, in fact, multiple are likely involved) that therefore genes are not a factor?

If you're not saying that, then why ask such an obviously simplistic and irrelevant question?

There very well may be genetic factors, however, can you point me to a theory that establishes what genes they are and how they work related to causing homosexuality ?

See above. Also, read the paper I posted, as the authors do actually discuss this.

 

[SomeRandom]

There are chromosomes however.

Those determine the sexes, though. That’s not really the same as sexual orientation. Of any variety. And even then there are “oddities.”
XX, XY, XYX, XXY, XXYY, XXYX and XXXX, if I recall high school biology correctly.

 

[Mock Turtle]

Yes, it could be. But if this is the case, why ?

Wherever the effect comes from, it most certainly doesn't come from choice it seems:

Fraternal birth order and male sexual orientation - Wikipedia

 

[shmogie]

Wherever the effect comes from, it most certainly doesn't come from choice it seems:

Fraternal birth order and male sexual orientation - Wikipedia

That is a pretty emphatic statement. If the reason is not known then one possibility cannot be eliminated till another is proven.

Does birth order represent a physiological or environmental ? Or, something else ?

 

[shmogie]

Those determine the sexes, though. That’s not really the same as sexual orientation. Of any variety. And even then there are “oddities.”
XX, XY, XYX, XXY, XXYY, XXYX and XXXX, if I recall high school biology correctly.

Yes, oddities. However, as you state, they have nothing to do with what someone thinks about their sexuality.

 

[shmogie]

Because there is no plausible explanation of the available evidence that does not implicate genetic influence.



Of course not. Are you saying that because there's not a single gene that's been solely identified as causal (because, in fact, multiple are likely involved) that therefore genes are not a factor?

If you're not saying that, then why ask such an obviously simplistic and irrelevant question?



See above. Also, read the paper I posted, as the authors do actually discuss this.

You accused me of being in error when I stated there was no homosexual gene. Therefore I wanted a clarification of what you said. I asked the question because your response to my statement was unclear.

Genetic influence may be involved. Your paper implies genetic involvement, it does not establish it.

Some believe that birth order is a strong determining factor. I don't see any genetic determination in that, unless the factor is a male child instead of a girl, since sisters don't seem to apply to the birth order hypothesis.

 

[Mock Turtle]

That is a pretty emphatic statement. If the reason is not known then one possibility cannot be eliminated till another is proven.

Does birth order represent a physiological or environmental ? Or, something else ?

Yes, I suppose there could just as well be environmental factors - interactions with brothers, variable treatment by parents, etc.

Except this quote in the Wiki article:

Secondly, the fraternal birth order effect operates through a biological mechanism during prenatal life, not during childhood or adolescence

 

[Shad]

It should be natural "all humans are equal", still "many men see themselves more equal than women (or slaves, other color, other (non) religion)".

That isn't natural though. People are not equal otherwise there would be no geniuses nor people with disabilities just to point out extremes. Do not conflate application of law and principles with nature.

 

[Shad]

. If it was natural it would not need so much political manipulation and forced conformity.

You know there are things called laws which made it illegal for homosexuals to marry for decades. There is a political element which was created not by homosexuals but rabid religious believers.

 

[Left Coast]

You accused me of being in error when I stated there was no homosexual gene.

No, I didn't. I accused you of being in error for claiming there is no genetic basis for homosexuality at all. You actually went even further and made the even more absurd claim that there's no physiologic basis for homosexuality.

Genetic influence may be involved. Your paper implies genetic involvement, it does not establish it.

From the paper:

The preponderance of evidence from sexual orientation research strongly suggests that human sexual orientation has biological underpinning and that it is tightly regulated at the molecular level. Although the “gay genes” are yet to be identified, there is little doubt that genetics plays a role in this trait.

Now, if you disagree with this assessment by the researchers who study this for a living, please offer an alternative hypothesis that accounts for all existing evidence wherein genetics play no role whatsoever.

Some believe that birth order is a strong determining factor. I don't see any genetic determination in that, unless the factor is a male child instead of a girl, since sisters don't seem to apply to the birth order hypothesis.

You're confused. Birth order is hypothesized as as epigenetic effect on testosterone levels in utero (which explains why sisters are not correlated), not a genetic effect.

 

[tas8831]

You accused me of being in error when I stated there was no homosexual gene. Therefore I wanted a clarification of what you said. I asked the question because your response to my statement was unclear.

Genetic influence may be involved. Your paper implies genetic involvement, it does not establish it.

Some believe that birth order is a strong determining factor. I don't see any genetic determination in that, unless the factor is a male child instead of a girl, since sisters don't seem to apply to the birth order hypothesis.

Tell us all about your biology background and genetics expertise such that your opinions on such matters have any merit.