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.     
Nandrolone decanoate in the form of the Organon product, Deca-Durabolin, has been around for over 30 years. It has anabolic, androgenic, progestogenic and erythropoietic activity. The steroid maintains the anabolic activity of testosterone but the androgenic action is markedly diminished. The anabolic/androgenic quotient after 2 weeks of treatment has been shown to be 12 times that obtained with testosterone decanoate. Nandrolone decanoate has been shown to influence calcium metabolism positively and to increase bone mass in osteoporosis. Androgenic effects are relatively uncommon at the recommended therapeutic dosages.