It is a naturally occurring anamoly. Normally benign until the anamoly is accepted as normal.
It's interesting, I did the math, if you flip the demographics, and instead of 90% + being hetro, and made that Population (and all future generations) 90% homosexual, the population of human beings in the United States would be zero within 11 generations.
That's also giving those populations every benefit. Each hetro female having 4 children and no hetro female dies before they too had 4 children.
It was actually a chilling excersize.