Measures of Man; Men: The Scientific Truth; Scientific American Presents; by Staff Editor; 2 Page(s)

Athletes, actors, entrepreneurs and high-ranking politicians shape our definitions of male gender. Mark McGwire, Denzel Washington, Bill Gates and Bill Clinton. Heroes of summer and screen, the self-made billionaire and the self-destructive philanderer. This typology of our transmillennial culture marks only one measure of what it means to carry a Y as well as an X chromosome. Whether muscleman or nebbish, the male of the species fulfills a destiny shaped not just by batting average and bank balance but by genes, hormones and psyche.

Biology and psychology both confirm and deny the prevailing stereotypes. Statistically, men do live up to expectations as tough guys: killing and being killed, drinking, sleeping around and generally ignoring what ails them. Testosterone, the hormone that defines the essence of maleness, may foster life-threatening recklessness-and may also raise the risk of heart disease and stroke. If only the strong survive, then men are the weaker sex. Dying like a man in the U.S. means to expire, on average, six to seven years earlier than the opposite sex.