There was a huge die off of humans tens of thousands of years ago where only 1600 humans survive... if 50% or even 15% was gay, we would be fucked and went extinct. Basically genetic bottle neck where we are genetically extinct because eventual inbreeding. If humans back then were super gay or cut off their dicks with stone axes, problem wouldve been worse. But... luckily cro magnons and homo erectus had sexy time and merged to create modern humans.