Since human evolutionary history involved a greater competition among males for females that vice versa, it is not surprising that men exhibit a much greater desire for sex-partner variety than women (Symons 1979;Buss 1994; Townsend 1998). The male evolutionary ancestors of humans males who outreproduced other males in human evolutionary history were individuals who were willing and able to copulate with many females, especially young adult females at the peak of their fertility and/or reproductive potential. Men’s greater eagerness to compulate and their greater interest in and satisfaction with casual sex evolved because those traits promoted high sex-partner number in evolutionary historical settings (Symons 1979;Buss and Schmidt1993; Townsend 1998).

Randy Thornhill and Craig T. Palmer