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.     
This web site is a repository of publicly available information, and is not intended to form a physician-patient relationship with any individual. The content of this website is for informational purposes only. The information presented on this web site is not intended to take the place of your personal physician’s advice and is not intended to diagnose, treat, cure or prevent any disease. Discuss this information with your own physician or healthcare provider to determine what is right for you. All information is intended for your general knowledge only and is not a substitute for medical advice or treatment for specific medical conditions. The information contained herein is presented in summary form only and intended to provide broad consumer understanding and knowledge. The information should not be considered complete and should not be used in place of a visit, call, consultation or advice of your physician or other health care provider. Only a qualified physician in your state can determine if you qualify for and should undertake treatment.
In men, low testosterone levels in the body can be supplemented by hormone replacement with testosterone. Testosterone replacement therapy can be prescribed as an intramuscular injection usually given on a biweekly basis; as a patch or gel placed on the skin, or as putty that is applied to the gums of the mouth. Each of the treatments has its risks and benefits. The decision as to which form of testosterone to use depends upon the clinical situation. Discussions between the patient and health care professional often helps decide which medication to use.
In the United States there are currently no preparations that are FDA approved for testosterone replacement for women.