What scares me though are the numbers. I can take some brain mutations, thats all a part of being an organism some evolve differently. But what I don't get is how this gene keeps passing on on the rate it does. Something like 1/10 people are gay (a lot of people seem to think...Ive also read 1/100). But will we all be gay eventually and our race will cease to exist or will it always be the same numbers? Will we hit a maximum ammount of gayness. Or will we eventually destroy the gene through genocide or other scientific matters?
I've got a theory based on absolutely no scientific fact that when any creatures' population reaches a critical mass, that the genetic mutation (I say that in a respectful and positive way) for homosexuality increases, in an attempt to level off the population. Bi-sexuality is included as it opens up the number of available sexual partners while hypothetically "halving" the odds that the sexual encounters will (or could) result in offspring.
Could explain why captive animals (especially those in herds) tend to get their same sex freak on more often (though is could just be documented more since they're captive animals) and why big cities have higher gay populations (I know a lot of that is migration, but is it all?)
Phobic much?
For starters, genes normally aren't fast enough for this. I highly suspect that those things are simply changes in REPORTS, not changes in actual population. But for a moment hypothetically assuming that something like this were to happen, then i can only think of two ways:
1. Culture and mental evolution. Culture fixes everything that genes don't do, humans just haven't figured that out, because they are too busy with rejecting responsibility for who they are, and genes are an easy scapegoat ( A
wizard gene did it!
2. A way to drastically change natural selection, depending on the population size. The problem here is: how does biology know? I can only think of one approach here: Let us assume, that choice of sexual partner is not "atomic", and that it is instead a bias on a spectrum of possibilities (i.e., a 2D grid, with the corners representing hetero, homo, bi, and "neither"). Then, lets assume that when life is harsh, the highly heterogenous ones get the best chance of getting a partner (with the more moderate ones getting less spread). That way, heterogenous sexuality would be escalated. Now, lets say life gets less harsh, and the density of population increases. Then, more variety can survive without getting overly marginalized.
Still, the result of 2. can never be "the gays and asexuals killed humanity!". I mean, come on! If this is gene stuff, the choice of partners influence the offspring. Meaning: You can only get so many gays and asexuals until a soft balance is created - reason: gays and asexuals do not make children

(ignoring more fancy tricks, i'm talking old-school here
So no, there cannot be some homo/asexual menace that kills off humanity - if that ever happens, then it will have been done on purpose by humans messing around with stuff. Number one way for humans to get killed off, is by doing it themselves - and they're constantly inventing more variety in how to bring on doomsday.