"The more competitive nature of men is a consequence of sexual selection. Men have evolved to live dangerously because success in competition or battle used to lead to more or better sexual conquests and more surviving children. Women who live dangerously merely put at risk those children they already have. Likewise, the intimate connection between female beauty and female reproductive potential (beautiful women are almost by definition young and healthy; compared with older women, they are therefore both more fertile and have a longer reproductive life ahead of them) is a consequence of sexual selection acting on both men’s psyches and women’s bodies. Each sex shapes the other. Women have hourglass-shaped bodies because men have preferred them that way. Men have an aggressive nature because women have preferred them that way (or have allowed aggressive men to defeat other men in contests over women—it amounts to the same thing)."