Steinhauer, view post
#193, I added a new paragraph and linked back to the original lecture where the excerpt is from. Hope that will explain why we won't be able to find answer for homosexuality at the present date.
Lifeforms don't devolve. They don't necessarily evolve from simple to more complex. One species isn't superior or inferior to another. They evolve, but they don't necessarily regress.
Many plants have more complex and longer strands of DNA, and they have more chromosomes than we do. Does that make them more advanced? It depends on how one looks at it.
Evolution favour stable populations. If the environment changes and it destablize the population, it shifts the frequency of the alleles. Certain alleles regulate different type of expressions. So the ones that are best adept to the change in environment are the most stable.
For example, with Africans, they have a serious bout with malaria. They have a sickle-cell mutation. SS (or non-sickle cell) are prone to being attacked by malaria. Heterozygous (Ss) resists malaria better. Unfortunately, ss, or sickle-cell amenia causes sickness. Now, as long as mosquitoes still transmit malaria, Ss and ss will always be selected for.
If you take the same group of people and stick them in a place where there is no malaria, SS is preferred because there is no selection pressure for Ss to be maintained; and ss is not favourable for the population. So over time, the ss genotype will be completely phased out through genetic drift.
This is vastly oversimplifying because it is ignoring thousands of other loci and the hundreds of different selection pressures acting all at once.