To improve the AAS research, biochemists have created an objective to alter the molecules to be "more anabolic and less androgenic" than testosterone, in which makes it possible to take orally, and have a reduce effect on the HPG axis (Stephen Kishner, page 3). According to an article called, Anabolic Steroids Use and Abuse, by Stephen Kishner, "AASs is developed from 3 compounds: testosterone, dihydrotestosterone, and 19-nortestosterone", (Kishner, page 3). (Testosterone and 19-nortestosterone is a very similar compound, very much alike except 19-nortestpsterone doesn't include the 19th carbon).
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.