Comment by archaeopteryx on March 18, 2012 at 2:44pm

But I think you're missing my point Sky,  or maybe I wasn't very clear inn the first place - if "gayness" is genetic, i.e., if there is a "gay" gene, how would it get passed on in the first place? Is it recessive (obviously, if it were dominant, the bearer would be gay and unlikely to pass it on), or recessive, in which case, it would take the meeting of two such recessive genes to create a "gay" person? If the latter were the case, wouldn't - according to Mendel's Laws of Heredity - there be a 25/75 ratio of gays to straights? (I use the two terms because they take up less space to type)

Understand we're not debating here, I'm genuinely curious.

Comment by Kris Feenstra on March 18, 2012 at 3:28pm

according to Mendel's Laws of Heredity - there be a 25/75 ratio of gays to straights? (I use the two terms because they take up less space to type)

Setting homosexuality aside for a moment, what you wrote is grossly inadequate when discussing genetics.  There are more variations that could conceivably be at play than I care to list, some of which are covered in entry level genetics units (such as multi-allelic traits, polygenic traits, and traits with multiple phenotypes).  While I'm not suggesting that homosexuality fits any of those categories (if it even is genetic in part or in while), when there are som any unknowns, conversations on genetics cannot be limited to such simple inheritance.

Comment by Arcus on March 18, 2012 at 4:30pm

@arch: It seems to be a mixture between biological predispositions and environmental factors. There was a fairly widely reported and comprehensive Swedish twin study which has now been added to Wiki:

A 2010 study of all adult twins in Sweden (more than 7,600 twins) found that same-sex behavior was explained by both heritable factors and individual-specific environmental sources (such as prenatal environment, experience with illness and trauma, as well as peer groups, and sexual experiences), while influences of shared-environment variables such as familial environment and societal attitudes had a weaker, but significant effect. Women showed a statistically non-significant trend to weaker influence of hereditary effects, while men showed no effect of shared environmental effects. The use of all adult twins in Sweden was designed to address the criticism of volunteer studies, in which a potential bias towards participation by gay twin may influence the results (see below).

Overall, the environment shared by twins (including familial and societal attitudes) explained 0–17% of the choice of sexual partner, genetic factors 18–39% and the unique environment 61–66%.

Comment by archaeopteryx on March 18, 2012 at 4:54pm

@ Kris - RE: "what you wrote is grossly inadequate when discussing genetics" - which is why, in both my posts on the subject, I indicated I was seeking information, rather than making definitive statements.

@Arcus - In a much earlier post on a different forum, in a similar discussion, I quoted my high school science teacher, who said that in an investigation of any physical condition, one could never entirely separate heredity from environment. My premise was shot down in favor of a strictly genetic explanation.

Comment by Arcus on March 18, 2012 at 5:21pm

@arch: By me? In that case I have not made myself entirely clear, as my opinion is that it is a mixture, though with the environment as the main factor. I usually get blasted since that position apparently implies that it would a conscious choice. A choice perhaps, but not conscious.

Comment by archaeopteryx on March 18, 2012 at 6:43pm

No Arcus - it happened a couple of months ago, and I honestly don't recall by whom. But definitely not you.

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