Helpful article, however, I will have to disagree with your comment about sprinting. Sprinting is a maximal effort exercise which constitutes the body’s reliance on predominantly carbohydrates and not fat. The fast catabolism of carbohydrates causes the lactic acid build up. The maximal exercise will actually not burn any fat but will boost testosterone levels. Also, the exercise can produce increased muscle mass, which can increase resting energy expenditure. Since your body burns predominantly fat at rest this can indirectly help you lose fat weight. If a person wants to become more efficient in metabolizing fat and lactic acid, they should focus on long duration (greater than 30 minutes) and low to moderate intensity exercises (~20-60% MHR)
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.     
Better still, with the evils of testosterone firmly established, the world may learn to appreciate older men. Around the age of 30, no longer “young, dumb and full of cum”, we typically find our testosterone levels declining, so that with every day that passes we become less aggressive, more rational and generally nicer. Your average 54-year-old – to pick an age entirely at random – can now boast that as well as decades of experience, he can draw on ever-larger reserves of self-control. Whether we’re trying to land a beautiful lover or a well-paid job, that should make us quite a catch.