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The second theory is similar and is known as "evolutionary neuroandrogenic (ENA) theory of male aggression".   Testosterone and other androgens have evolved to masculinize a brain in order to be competitive even to the point of risking harm to the person and others. By doing so, individuals with masculinized brains as a result of pre-natal and adult life testosterone and androgens enhance their resource acquiring abilities in order to survive, attract and copulate with mates as much as possible.  The masculinization of the brain is not just mediated by testosterone levels at the adult stage, but also testosterone exposure in the womb as a fetus. Higher pre-natal testosterone indicated by a low digit ratio as well as adult testosterone levels increased risk of fouls or aggression among male players in a soccer game.  Studies have also found higher pre-natal testosterone or lower digit ratio to be correlated with higher aggression in males.     
But here’s what’s happening today. I’ve just described what normal health is. Now, what the problem is: As women are becoming more independent—and this is the whole trend of the last 30 years. More independent than ever before in the world. In our whole history, this has never happened, where women didn’t need men. So if you don’t need a man, how does your estrogen level go up? You become like a man, who should have lower estrogen levels. He should at least have 10 times more testosterone than any woman, and women should have at least 10 times more estrogen. And for her to be turned on to a man, like really turned on, she needs 20 times more estrogen than the man.