Testosterone is significantly correlated with aggression and competitive behaviour and is directly facilitated by the latter. There are two theories on the role of testosterone in aggression and competition.  The first one is the challenge hypothesis which states that testosterone would increase during puberty thus facilitating reproductive and competitive behaviour which would include aggression.  Thus it is the challenge of competition among males of the species that facilitates aggression and violence.  Studies conducted have found direct correlation between testosterone and dominance especially among the most violent criminals in prison who had the highest testosterone levels.  The same research also found fathers (those outside competitive environments) had the lowest testosterone levels compared to other males. 
Mike, thanks for the research. I am 44 and never had a flat belly in my life. I have lifted on and off but am fairly regular since the last year. I am seeing gains but my belly is seeing gains too. I just started fasted cardio in mornings and increased my activity levels. What can I do to get a flat belly (forget a 6 pack). It seems no matter what i do my body fat is on the rise. My eating habits are OK. I used to eat lots of soy but have completely cut down on that. Should i try some T supp? or your fat burners? I feel i can get the muscle easily but the belly fat is so annoying. Oh never smoke and no alcohol for almost a year.