Humans
Though the differences are less pronounced than among many other mammals, considerable anatomical and behavior evidence indicates that men have been subject to stronger sexual selection pressure than women.
Men are larger than women. Boys reach sexual maturity later than girls, and men age more rapidly than women.
Aggression and violent competition among males is more common and pronounced than it is among females. Male sexual coercion is far more frequent than the reverse. Rape and sexual assault by men remain common in almost all modern societies.
Polygyny is much more common than polyandry. Women are typically more selective than men in their choice of sexual partners.
In one respect, humans reverse the usual pattern between more and less sexually selected genders: men are more concerned than women with the physical attractiveness of a potential sexual partner.
The physical beauty of the female receives more explicit consideration than does the handsomeness of the male. The attractiveness of the man usually depends predominantly upon his skills and prowess rather than upon his physical appearance. ~ American anthropologist Clellan Ford & American ethologist Frank Beach
There is an evolutionary reason for the strong appeal of men to a woman’s physical attractiveness: it correlates well with fecundity. Owing to menopause, there is much more age-related variance in fertility among women than men. The sexiest women are those in their prime child-bearing years.
Menopause is somewhat common among invertebrates, fish, birds, and mammals. According to the grandmother hypothesis, menopause serves to lengthen a female’s life so that she may assist her descendants, thus enhancing her legacy prospects. This has been observed in women and orcas. More broadly, having experienced females about may enhance group survival prospects.
