[LeftIsSinister]

I don't want to pick a dog in this fight yet, but just to address the possibility, consider that if it's genetic, maybe it's a recessive gene.

[Area Freeper]

Typically recessive genes such as sickle-cell anemia serve some purpose that continues to perpetuate them. There is no conceivable explanation for the origination of a homosexual gene or its perseverance.

[King Prout]

or a combination of multiple recessive factors.

*shrugging*