Dear experts, could some of you tell if there is a consensus among life-scientists on the reasons of homosexual attraction and\or behavour ?
I put this question into the "Evolution" category on purpose since there are many species of mammals and even birds that demonstrate this deviation, and not so rarely. It is not only humans that can be like that. Has it been already figured out why is it possible and what is the purpose?
The regularity of emergence of such individuals among intellectual social species probably raises a question of certain gene lines or typical mutations in charge of that. But the fact that such individuals typically never reproduce under normal conditions raises a question about how such a "gene" can survive from generation to generation and why - at least in humans - average number of such individuals is generally the same in any time and cultural group.
And another curious thing - has anyone ever wittnessed homosexual behavour in a species that lives strictly solitary life (like a leoprad for instance) or is considered to be a dull one (like a snake or a shrew). And what was it like?

I am asking because I am a boy who is attracted to men and I would like to understand what is the reason in the broader context.

Thank you.

It is not at all clear that homosexuality is wholly genetic.  If it is, it is unlikely to be determined by one single gene. 
Assuming that it is not an adaptive trait - much lower chance of passing on your genes if you are homosexual - why then does it persist?   The simplest explaination is that any alleles that contribute to homosexuality could also contribute to other adaptive behaviours or morphologies.  Perhaps these are genes that are most beneficial when one copy is "A" and the other is "a".  While "aa" may give an individual a 20% (say) probability of being homosexual, the benefits of being "Aa" could keep the "a" present in the population.

We can complicate this scenario with the possibility that homosexual relatives could be involved in childcare and/or family care, raising the survival rate of other individuals with whom they share DNA.  Similar hypotheses have been proposed to account for our survival long after the age of reproduction - old people can care for their grandchildren and help their own genes survive in the next generation.

Last edited by Ajna Rivera (19th Aug 2010 04:54:53)

I can't cite any sources, but I recall reading about a link between increased adrenaline in a pregnant mother and inhibition of testosterone-induced changes on the in utero male child. The study was done in rats and showed that male offspring of stressed mothers were more likely to display female-type behaviours.

The implication seemed to be that homosexuality (at least in men) isn't a genetic thing but is an environmentall-varied hormonal effect. Anyway, gay people do have children!

From an evolutionary point of view, it may persist as a form of population limitation or perhaps a mechanism for reduction of competition for mates between conspecifics, but no-one is really sure. As Ajna said, you can imagine that non-breeding memeber of a society do have valuable roles to play, for example in child care or feeding those who do have children.

Firstly: not all characters of an organism are there for a "reason". A large amount of features are likely non-adaptive, that is they are not due to natural selection, or they are a side-effect of other features.

As John mentioned, research is indicating that sexual orientation is strongly predisposed by the chemical environment a foetus grows up in (and, no, this is not intended to put yet more pressure on mothers); this implies that sexuality is actually hard-wired by birth, not a later 'choice'.

Indeed, sexuality is a very fluid aspect in many animals. Quite a few species can actually fully change from male to female, and vice versa during and individuals lifetime (independent of how many X or Y chromosomes they have).

As for the solitary species: my guess is that most of these are highly territorial, such a tigers, and a gay male would find it very hard to find another gay male, let alone aproach any other male.