From Friday's "Science News"--"Sex Roles Lose Their Universal Appeal"
Scientists at University of St. Andrews in Scotland are questioning the belief that men have evolved to be promiscuous, while women have evolved to be "choosy". After examining 18 societies (modern and traditional), reproductive success was observed with variation between "evolutionary normal" male and female roles. The distinct roles for male and female sexual tendencies were furthered by a 1948 experiment regarding fruit flies and the belief that it is more biologically "costly" to create an egg than sperm, so females must be more "choosy".
However, "in the last decade, studies of fruit flies and other animals have documented considerable variation in numbers of sexual partners and offspring for both sexes". Scientists from this study have noted this flexibility resulting in reproductive success, and suggest that a more detailed look at sexual roles should be examined.