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.     
Myth: Testosterone-Propionate is not as powerful for bulking as long ester base forms. Truth: The active hormone testosterone is the same in all forms and the mode of action and its very nature is no different in Testosterone-Propionate than it is in Testosterone-Cypionate or any other form. However, this myth gets more ridiculous as on a milligram for milligram basis Testosterone-Propionate is stronger than other commonly used ester based testosterones. For example, 100mg of Testosterone-Propionate will yield approximately 83mg of testosterone, the rest of the total mass being comprised of the Propionate ester. Conversely, 100mg of Testosterone-Cypionate, because the Cypionate ester takes up more mass in the total compound will yield approximately 70mg of active testosterone per 100mg. Granted, you can receive the same dose of active testosterone by simply adjusting where needed but in the end the benefits and results will be the same with Testosterone-Propionate or any form assuming all things remain constant, . dosing, duration of use, diet and training.