Is homosexuality a natural response to large populations?

The short answer to your question is "no". It does not have any scientific validity. Adaptive traits arise to benefit individuals, not an entire species.The genetic components to homosexuality are far from certain; and the selective effects are likewise far from certain. If there was any selective benefit to a predilection for homosexuality, it would have to be expressed as a benefit related to the individual. For example, it might be a speculative possibility that having some small proportion of homosexual offspring gives a benefit for helping to raise a family, in some contexts. But this is sheer speculation. It is just as likely that the effect not selected, but a natural consequence of the complexity of human behaviour and the diversity of individuals.Also, I think you misunderstand the term "recessive". A recessive trait is (in the simplest case) one which is controlled by two alleles, and is only expressed if both of them carry the trait. A dominant trait is one which is expressed if either carries the trait.It has nothing to do with being a hidden potential to be expressed when circumstances require it.Cheers -- Sylas