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.     
Testim® was evaluated in a randomized multicenter, multi-dose, active and placebo controlled 90-day study in 406 adult males with morning testosterone concentrations ≤ 300 ng/dL. The study was double-blind for the doses of Testim and placebo, but open label for the non-scrotal testosterone transdermal system. During the first 60 days, patients were evenly randomized to Testim 50 mg, Testim 100 mg, placebo gel, or testosterone transdermal system. At Day 60, patients receiving Testim were maintained at the same dose, or were titrated up or down within their treatment group, based on 24-hour averaged serum testosterone concentration obtained on Day 30.