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.     
In a clinical study conducted to evaluate the effect of hand washing on the residual amount of testosterone, 36 healthy male subjects received 50 mg of testosterone from 5 g of testosterone gel on a hand and applied testosterone gel to the upper arm and shoulder of one side. Subjects washed their hands with liquid soap and warm water immediately after drug application. Then the hand was allowed to air dry or patted dry with a cloth towel. A skin swab sample was collected and analyzed for testosterone content. A mean (SD) of () to () µg of residual testosterone (., 99% reduction compared to when hands were not washed) was recovered after washing hands with liquid soap and warm water.