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.     
You will note that all of the products I recommend are either unflavored or chocolate, there is a very good reason for that. A lot of times its the flavors that add incredible amounts of artificial junk and a nasty aftertaste which is the reason that I always choose unflavored or chocolate. Chocolate is easy, you just add natural cocoa powder. Cocoa powder is virtually nonfat, its natural, and its good flavoring – easy peasy. Unflavored whey also tastes really good but note that unflavored does NOT mean vanilla. Vanilla typically tastes horrible in my experience and almost always has a horrible aftertaste, again, because of the artificial flavors. Back to unflavored whey, it tastes amazingly good. Unflavored, unsweetened whey has a very pleasant neutral flavor that is slightly sweet and if you add it to water it tastes a lot like … well, milk. Milk that is 90% protein instead of 5% protein. The fruit flavors like strawberry and banana are virtually always artificial and pack a really nasty aftertaste so choose those only after very careful inspection of the ingredients list. Flavors that sound like candy bars should be avoided like the plague as they are always artificial – “toffee bar crunch”? Nope, pass.