Are you allowed to talk about INAH-3 (third interstitial nucleus of the anterior hypothalamus)?
It is the part of the brain that governs sexual dominance in adulthood and is twice as large in straight men as it is in gay men and straight women
Asymmetric sexual divergence happens at age 5-10.
Science understands why and how this happens in rats, but I don’t think you are allowed to talk about it in humans.
I will say, evolution is a phenomenally powerful self regulating system. It has learnt to detect when a population is succeeding too much for its own good, and has also learnt to assert correcting pressure. 