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.     
Women can take testosterone as a cream, through a patch or in the form of pellet implants, which have the highest consistency of delivery. Synthesized from yams or soybeans, and compounded of pure, bioidentical testosterone, the pellets, each slightly larger than a grain of rice, are inserted just beneath the skin in the hip in a one-minute outpatient procedure. They dissolve slowly over three to four months, releasing small amounts of testosterone into the blood stream, but speeding up when needed by the body — during strenuous activities, for example — and slowing down during quiet times, a feature no other form of hormone therapy can provide.