First "same sex" genes discovered.

[sukumvit boy]

https://www.sciencemag.org/news/2018/10/giant-study-links-dna-variants-same-sex-behavior


https://geneticliteracyproject.org/2018/10/26/there-is-no-gay-gene-but-study-suggests-genetics-may-play-role-in-choosing-same-sex-partner/ (https://www.sciencemag.org/news/2018/10/giant-study-links-dna-variants-same-sex-behavior)

[Stavros]

Fascinating links, but I wonder what you think about it? You are an intelligent man and must have an opinion, notably on the question that links DNA to emotional as well as physical behaviour, as noted in the Scientific American link above-

the findings reinforce the idea that human sexual behavior is complex and can’t be pinned on any simple constellation of DNA. “I’m pleased to announce there is no ‘gay gene,’” Ganna said. “Rather, ‘nonheterosexuality’ is in part influenced by many tiny genetic effects.” Ganna told Science that researchers have yet to tie the genetic variants to actual genes, and it’s not even clear whether they sit within coding or noncoding stretches of DNA. Trying to pin down exactly what these DNA regions do will be among the team’s difficult next steps.

There is a lot to consider here, because two people who become emotionally close may extend it to become physical even though they would not identify as gay.

More intriguing is the possibility that we have inherited ideas from Plato that have percolated through two millenia of debate and argument that suggest humans were once one sex. Although this sounds absurd, it surely reflects the likelihood that same-sex behaviour is as old as time but may have different explanations. The argument I first encountered in The Symposium but is also referred to I think in the Timaeus and is briefly discussed here-

http://global.oup.com/us/companion.websites/9780199315468/student/ch5/wed/plato/

It is a stretch I suppose, but I think we are trying to understand how ancient societies dealt with procreation, where they may have believed -as Gilbert Herdt claims with regard to a tribe in Papua New Guinea- that men store semen in their body and thus consider it a waste to masturbate to ejaculation, a prohibition that can also be found in the Old Testament. It would thus give weight to the prohibition of male same-sex behaviour not due to any enjoyment, but the waste of a finite resource that is needed for the survival of the group. Thus social attitudes can be derived from basic rules of survival much as societies realised at some point in history that sexual relations between fathers and daughters, brothers and sisters leads to degeneration and collapse. But, such is the force of desire, societies may have speculated on the origins of the human to find a way of permitting same sex behaviour thus creating a tension between obligation and desire, establishing the complexity of moral judgement which we continue to wrestle with today.

[filghy2]

According to natural selection, genetic evolution should be related to gaining advantages in survival and reproduction of the species. I wonder what the biological advantage of a same sex gene would be? Could it be to make men more inclined to risk themselves to defend other men outside of their immediate family?

[broncofan]

I read a while back that one theory was that homosexuality may be the result of many genes. Having some (but not all) of the genes may provide an advantage that increases the odds of reproducing but having all of the genes would reduce it based on sexual preference.

Another theory was based on kin selection ie. that it increases the probability of offspring for all siblings but not necessarily the individual who possesses the gene. I can't remember the other theories but I think there were a few more.

[broncofan]

I just looked at the wiki on the subject and the kin selection theory is expounded upon in a section called the "gay uncle hypothesis".

They say it's the most plausible explanation. Without having read too much about the issue I think it makes at least as much sense that sexual orientation is determined by many genes and that certain combinations increase the probability a person is attracted to members of the same sex. Other combinations of these genes might provide various reproductive and survival advantages that would ensure the propagation of these gene variants in the gene pool even if there exist specific combinations that reduce fitness.

Always an interesting subject. Thanks for the articles.

[broncofan]

Sukumvit Boy, I should have read the article more carefully before posting. This part was towards the end. Apologies! This theory always made the most sense to me. Not quite what I was saying because it implies that the four alleles don't completely determine sexual orientation, but similar idea.

"
The abstract for Ganna’s talk referenced another provocative result: Heterosexual people who possess these same four genetic variants tend to have more sexual partners, suggesting associated genes might confer some mating advantage for heterosexuals. That could help explain why these variants might stick around in populations even if people attracted to the same sex tend to have fewer children than heterosexuals. Ganna did not touch on that finding in his talk, citing lack of time."

[Stavros]

I will stick with the cultural explanation of a chemical process -that is, that in ancient societies there was an assumption that semen was a finite resource that should not be wasted. I should also note that a long time ago I read of an anthropologial study of the Andaman islands where it was argued men engaged in anal sex on a regular basis but did not appear to be what we would call homosexuals -they were all fathers in married families. This would also fit with the idea that semen is a finite resource contained inside the body, and just as Herdt has argued that young boys increase their store of semen through fellating older boys and men, anal penetration would be another means. But does this mean there is a genetic explanation for it? After all, homosexuality may refer to same sex activity, but does it account for the essential ingredient in a relationship, namely love?

[sukumvit boy]

Thanks all for the thoughtful and provocative additions to this post.
Interesting stuff.
I've often wondered , I had a gay uncle.....

[sukumvit boy]

Hey flighty2 , you raise another interesting question that biologists are currently exploring , that is , 'altruistic behavior' and it's widespread persistence accross many different orders of animals , despite it's apparent violation of the principles of Darwinian evolution.

https://en.wikipedia.org/wiki/Altruism_(biology)