Darwin’s ideas were largely ignored by psychologists for about a century. Then about 60 years ago a group of researchers in the new field of evolutionary psychology began to apply Darwin’s theory of sexual selection to human mating behavior. They focused on two mechanisms believed to guide evolutionary change: preferred characteristics in a mate and competition for a mate.

David Buss, a pioneer in this field, initiated a series of cross-cultural studies of mate selection. One of these studies involved interviewing more than 10,000 people from 37 cultures around the globe. The results revealed striking sex differences in heterosexual mate preferences. Across cultures, men consistently place more value on a potential mate’s physical attractiveness, youthfulness, and health. Women consistently place more value on attracting mature, dominant, affluent, powerful mates; women also want mates who will make a long-term investment in their offspring.

Less is known about mate preferences in gays and lesbians, but several studies have found differences between lesbians who describe themselves as “femme” (who place more emphasis on the financial resources of a potential partner) and those who describe themselves as “butch” (who place less value on a partner’s willingness to commit to a long-term relationship).

LEONELLO CALVETTI / Science Photo Library / Getty Images