My belief is that there is no gay gene or any combination of genes that creates a gay tendency.
My reasons are based on science:
As are mine...
1. Gays reproduce at a lower rate than straights. If there were a gay gene (or combination of genes) then the percentage of gays in society would decline with each succeeding generation.
Genetics don't quite work that way.
For example - some genetic mutations seem to crop up frequently - without being inherited. Sometimes this is due to a weak spot on a particular sequence that is more prone to damange or breaking, or maybe other matters. Cystic fibrosis is one such disease. Hence - despite the fact that (until recently) most patients did not survive into adulthood or reproductive age - the disease still kept showing up spontaneiously.
Second - not genes follow a mode of strict dominance/recessive patterns. If you have a polygenetic trait - the trait may not be expressed until a couple who happens to have all the necessary genes comes together and produces an individual that expresses the trait. That individual may not breed, but all the related individuals who do not express the trait might, thus keeping the genes in the gene pool. If you add environment to that - it further complicates things. All those traits may come together but - unless certain environmental factors (such as say, something in the pre-natal environment) trigger the expression - you might never know it.
Third - why do some genetic traits, seemingly destructive - continue to crop up? Maybe because they actually, at one time had a survival mechanism. For example cycle cell anemia. In a homozygous form, it is almost always eventually lethal. In a heterozygous form it offers protection against the malaria parasite thus conferring a survival benifit in those countries rife with malaria.
Fourth - group survival over individual survivial. In a cooperative species it might be beneficial to have a small number of non-breeding individual adults to take care of the young while other adults forage. In many highly organized cooperative species there is only one, or a few breeding pairs while the rest cooperate to raise the young. In that sort of situation there might be a survivial advantage to be gained by a small degree of homosexuality to reduce sexual tensions within the group. Who knows? The thing is though - it is not as simple as survivial and reproductive success of each individual or a straight dominant/recessive heredity.
2. If you believe in evolution, there is no reason for a gay gene to survive. Natural selection (survival of the fittest) provides for the welfare and survival of the population as a whole. Gays would be a liability to population survival with a lower birth rate. Therefore, a gay gene can't be defended by evolution.
See above. In a cooperative social species survival of the group becomes more important than reproductive success of each individual.
3. Genetic drift. I'm not an expert in this but the basic premise is that the frequency of competing genes may vary from generation to generation but one gene will emerge and the other competing gene will be eliminated over time. This has not happened and this is additional evidence there is no gay gene.
I'm not sure I understand how genetic drift would apply here. My understanding of the term is that it is the random change of the occurance of a particular gene in a population and it is thought to be one cause of speciation when a group is separated from its parent population.
4. Homosexuality is more common in prison that in the general population. Many enter prison straight and leave gay.
Homosexual
behavior maybe more common but I bet you once they leave, they go right back to being straight.
It is perfectly consistent with evolutionary theory for a "straight" gene to develop, as this provides the maximum chance for survival of the population.
I think a species reproductive success is more complicated then simply an individual's chances of reproducing.
No one has to chose to be straight. But those who are gay have chosen, consciously or unconsciously, to pursue a gay lifestyle.
One could say that one chooses, unconciously, to pursue a straight lifestyle.