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While the authors are justified in arguing that they found five significant results, some of their other claims are harder to defend. Smith points out that there’s a difference between a statistically significant result and a practically significant result. Two runners can have different times without one having a significant competitive advantage over the other. And while most in the track and field community would consider the two-second difference found between low-T 800 meter runners and high-T 800 meter runners to be significant, that’s only the authors’ best guess for the time difference—it could be a difference as small as a fraction of a second, or as large as four or five seconds. As Smith says, “the broader implications are unclear.”
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.