less aggressive parents Parenthood is a state that controls the character, a recent study reveals that makes men less aggressive. Research, conducted jointly by doctors at Harvard University and Nevada, Unites States, specialists assessed the responses from a questionnaire administered to 130 men, and at the end thereof they took a saliva sample. Singles revealed a higher level of testosterone that married, at a rate almos 50%. One conclusion is that, due to the male animal nature, it generates testosterone when looking reproduced, while the decline in these levels can be caused when the man withdrows from the competition, which makes it more controllable temperament. Notably testosterone levels also decline with age.