[katieHaylor (OP)]

Keith asks:

Is sexual orientation genetic?
Is choice a factor?

What do you think?

[chris]

This is controversial, but there is an association between regions on the X (Xq28) as well as the eighth chromosome, and being gay.

The claim holds water on evolutionary grounds because not only does it fit the inheritance pattern seen with a leaning towards homosexuality, but a woman carrying such a trait, which presumably enhances attraction towards men, could have twice the gene dosage (2 X chromosomes compared with a single one in a man). She might therefore be expected to be more strongly attracted to men compared with a women with one copy and hence more likely to reproduce.

However, the techniques used to pinpoint the genetic positions or "loci" associated with the trait are somewhat "old school"; a more modern genome-wide association-based approach to replicate and refine the results would be reassuring and necessary.

This report summarises and cites the work:

http://www.sciencemag.org/news/2014/11/study-gay-brothers-may-confirm-x-chromosome-link-homosexuality

[smart]

This is controversial, but there is an association between regions on the X (Xq28) as well as the eighth chromosome, and being gay.

Yay! Let's use CRISPR to knock down this alleged gay gene and control our sexual orientation from within the womb....

[Giles Farnaby]

Adding another angle to what chris wrote, I recommend you check:

Logistic regression analysis showed that homosexuality was positively correlated with the proband's number of older brothers but not with older sisters, younger brothers, younger sisters, or parental age at the time of the proband's birth. Each additional older brother increased the odds of homosexuality by 33%.

[puppypower]

Another way to look at this is male and female differ by an entire chromosome, and not just one gene. The Y-chromosome in men accounts for about 1% of all the genes in male cells, while the x-chromosome in females accounts for 5% of all the genes in female cells.

For the sake of argument, say there was a gay gene, wouldn't the 1% (200 genes) in male cells, or 5% genes in the female cells still dominate just one lowly gene? The gay gene theory, never made sense from a gene count POV, since the proportional strength does not add up. These proportions would also suggest that female homosexuality is less likely than male, from a physical POV, since the female gene count is five time more dominate than it is for the male.

One may argue and even show that one gene, out of sorts, can impact an entire range of genes. This may be true, but wouldn't the opposite also apply, with the 200 genes in males cells offering 200 ways to alter the impact of the gay gene.   The math still does not add up to a genetic trigger.

These ratios and logic is consistent with how the bible treats homosexuality. I have read through the bible, over the years, and based on recall, the homosexual taboo appears to be more geared toward gay men, but it is not explicitly against lesbians. For example,the story of Sodom and Gomorrah it is about a gang of violent gay males who will have sex with anything that moves. This image of gay is  violently compelled, analogous  to the modern construct of gay sex in a male prison. Circumstance is altering behavior.

On the other hand, King Solomon had 700 wives and 300 concubines. Yet there is no mention of a lesbian taboo in the wisdom of Solomon, even though his individual wives may go months without the King's company, even if the King could service 5 wives and a concubine per day. The King also had large and fierce castrated males, who would oversee and protect the wives, so the wives had no access to males beyond the King. The 5% female genes would make the wives more nurturing, therefore there was no need for the violence taboo.

I remember as a child, when culture was more divided down traditional male and female lines. It was considered socially normal for women/girls to hug, dance with each other, dress each other, hold hands, etc., with this never called lesbian. What today was branded lesbian was considered part of being a female. The males, on the other hand, were not socially allowed this type of behavior out of ancient taboo; 5% female vensus 1% male genes.

What that leaves is a psychological explanation that is more connected to the brain's firmware.

[Petrochemicals]

Adding another angle to what chris wrote, I recommend you check:

Logistic regression analysis showed that homosexuality was positively correlated with the proband's number of older brothers but not with older sisters, younger brothers, younger sisters, or parental age at the time of the proband's birth. Each additional older brother increased the odds of homosexuality by 33%.

Thats the older first born again. I wonder if it is to do with testosterone in the womb. The theory 9f nature veraus nurture has sort of been ruled out. There was a theory that the hormones encountered within the womb and the brain development at a very young age was what led to it.

[alancalverd]

Simple arithmetic rules. Over geological time, homosexual orientation cannot be propagated genetically because, being inherently sterile,  it will be consistently outbred by "heterosexual genes".

[puppypower]

Simple arithmetic rules. Over geological time, homosexual orientation cannot be propagated genetically because, being inherently sterile,  it will be consistently outbred by "heterosexual genes".

The idea that homosexuality is genetic puts a money wrench in the theory of evolution. In other words, for  natural selection to propagate to the future, the traits needs to be transferred through genetics, with homosexuality unable to make this genetic transfer. In other words, even if a homosexual person was selected as the big dog at any given point in time, the genes stop there.

If homosexuality is based on genetics then evolutionary theory is wrong and needs to be modified to include not genetic transfer. There would need to be another mechanism for how a behavior, that is not passed forward genetically, can nevertheless constantly appear in subsequent generations of genes.

The most obvious mechanism is the brain and learned behavior. In nature, mother lions are often indispensable for teaching her offspring how to hunt. If hunting was already written in the genes, this would not be necessary. She does not have to teach them how to walk and cry out of they are hungry, since this is in their genes. That learn behavior, if mastered can learn to natural selection.

A good example of a parallel in human populations is drug addiction. Most drug addicts are not born with a gene that attracts them instinctively to harmful drugs. That would not be a selection advantage. According to evolution this would not be selected and persist.

However, though exposure and the formation of habits, using the reward system of the brain, one can create a compulsive behavior that "looks" genetic based. The drug addict can't turn off their compulsive desire anymore than a homosexual can choose to be straight. Both are based on learning, that creates connected to the personality firmware that underlies the human personality. The firmware gives learned behavior, compulsive leverage, since the firmware is genetic based.

A good example of this affect is connected to fight and flight. If an animal was cornered and needed to survive, firmware would kick in that might give it exceptional speed and ferocity. Without that life-death stimulus, the same animal may not be able to willfully muster the same level of output. The reason is connected to firmware. The firmware needs certain triggers or internal cycles to become engaged. 

With humans having willpower and choice, it is possible to learn how to interface with aspects of the firmware to gain its compulsive animal like qualities. Homosexuality is a product of human willpower, interfacing middle level firmware, to modify its natural output.  Because it is firmware it appears and feels instinctive.

I am not making a parallel with the following. But rather is an illustration of the compulsive affects. A serial killer has an interface to firmware; lower level. They follow their compulsion because it feels instinctive. However, this is firmware that has been modified by willower such that the output becomes unnatural for the firmware; beast.

[Kryptid]

The idea that homosexuality is genetic puts a money wrench in the theory of evolution. In other words, for  natural selection to propagate to the future, the traits needs to be transferred through genetics, with homosexuality unable to make this genetic transfer. In other words, even if a homosexual person was selected as the big dog at any given point in time, the genes stop there.

If homosexuality is based on genetics then evolutionary theory is wrong and needs to be modified to include not genetic transfer. There would need to be another mechanism for how a behavior, that is not passed forward genetically, can nevertheless constantly appear in subsequent generations of genes.

This assumes that whatever genes influence homosexuality are responsible only for the development of homosexuality and not for other traits. For example, if a gene which increases the likelihood of a male being homosexual also increases the average number of offspring his heterosexual sister or mother produces, then there would be at least some selective pressure acting to keep that gene in the population. There is some evidence of that having some role in the maintenance of homosexuality in the population: https://link.springer.com/article/10.1007%2Fs10508-008-9381-6. That's probably not the whole story, of course.