I believe this is true, there are changes that can occur that do not have an advantage. Those nonadvantage changes present themselves in a physical way.
Actually, no, or to be more precise, not obviously. Many mental illnesses are apparently caused by subtle changes in brain or blood chemistry; I believe there is at least one with a genetic component predisposing (not precisely
causing) it. In my personal case, I'm subject to occasional depression attributable to post-cardiac depression syndrome -- if you have had a heart attack, it's likely (not certain) to have caused microscarring of neural tissue leading to a form of organic depression. (This is not genetic, but an example of a mental/emotional condition with a subtle physiological cause -- and while I'm not calling homosexuality a mental illness, I'm suggesting that as an emotional condition, it may have physiological causes which may in turn be genetic in origin.)
A couple of points worth considering: "male-bonding" -- the trait that makes men, irrespective of sexual orientation, form friendship/comradeship bonds and work together for common purposes, from going hunting to running political parties -- probably has its origins in a survival characteristic. Oog the loner would go out and hunt the wild boar, coming home the hero who has enabled his tribe to feast. But if Oog misses just once, he gets gored by the boar. On the other hand, Og, Ugh, and Agg male-bond and go hunting together. None of them is the hero, but they stand a better chance of surviving a hunt, on average. Guess which gene is preferentially preserved, to the point that "I'm gonna get together with the guys and watch the Super Bowl" is a common characteristic? Now, suppose that male-bonding works like malaria resistance and sickle-cell anemia. Heterozygosity leads to a survival characteristic, which gets selected for. That homozygosity results in a trait that does not reproduce, is acceptable evolutionarily for the benefit of the heterozygous condition.
I'm not saying that
is the genetic explanation of homosexuality -- but it's one that demonstrates how it could be persistent in the gene pool.
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It is not, by the way, the prostate gland itself, but a nerve ganglion closely associated with it anatomically, which produces the erogenous sensations mentioned by earlier posters. And the fact that this exists is evident to almost any man who has had a prostate examination -- in a percentage of men far larger than the gay/bisexual population, digital stimulation of the prostate (actually of that ganglion during a prostate exam) leads to an involuntary erection.
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But, if I may be allowed the privilege of ranting a bit, the issue here is
not gay sex and/or its morality. We are presented with the case of Lawrence King, a 15-year-old, who expressed his romantic interest in a classmate by giving said classmate a Valentine, and in consequence was shot twice in the head and killed. It appears to me that a fair number of people posting in this thread about the immorality of gay sex, instead of addressing the issue of why gay people cannot be left alone to lie their lives with equal rights under the law, are in effect saying that one boy giving another boy a Valentine constitutes grounds for justifiable homicide. Because focusing on homosexual cts and what the Bible may have to say about them is pretty clearly saying, "Well, he was one of them thar quaaars and not someone God loves, so he didn't deserve to live." It might be useful if people stopped turning this into "the Bible says being gay is bad" thread #10984, and look at the facts: one boy is dead, for being publicly gay and daring to show his attraction in a socially acceptable way; one boy is due to spend the rest of his life behind bars, for having gotten the message somewhere that it's OK to kill gay people.
Guess where he probably got that idea!!!
IMO, there's some repenting of sin and incitement to sin that needs to be done. And not necessarily by gay people.