Why Sex Matters
Females in the few polyandrous species are usually a little bigger, and sometimes a bit more brightly colored, than males. Because much of the selection on displays is preference by the choosing sex rather than relative survival enhancement, sexual selection on expensive—and possibly dangerous—displays can 'run away.'
Thus, males in polygynous species are likely to grow antlers, or large horns, or bright feathers, or long decorative tail feathers—all costly, and sometimes risky, displays that may do nothing more than advertise a male's ability to take these risks: the 'Handicap Principle.' The message is: I am so fit that I can support this expensive handicap, which would kill a lesser individual. And when females prefer these costly displays, they work. For example, female European swallows prefer to mate with longer-tailed males: these males more often get mates, and get them sooner, than other males. The success of longer-tailed males is high—but these tails carry a cost in terms of survivorship; long-tailed males die sooner.
Most nonhuman examples, including those given at the beginning of this chapter, principally involve male physical (energetic) resources, even when, as in Bower Birds (for whom the criteria are the number and color of decorations on the bower), the display is not simply a physical part of the displayer's body. In contrast, humans invent, augment, and change signals; and females do a great deal of signaling. Bras make our breasts look large and/or young, girdles can imitate an ideal waist-hip ratio, shoulder pads mimic good physical condition, makeup reflects light and hides wrinkles, cheek and lip color make us look healthy and sexually interested. Our manipulations have sometimes been intrusive: in the nineteenth century, for example, some women underwent surgery to remove their floating ribs in order to have a small waist; today we have facelifts and liposuction. These manipulations imitate signals of youth and health.
Cross-culturally, cultural augmentation of sexual signals or ornaments is virtually universal, favored for the same reasons selection favors physical ornaments and displays in other species. Remember the old adage, 'If you've got it, flaunt it.' Males and females profit by signaling or flaunting different attributes. Humans are actually rather paradoxical with regard to sexual selection and sexual displays: most scholars agree that human evolutionary history, like that of most other primates, is polygynous: 83 percent of societies for which we have information are polygynous. All of these patterns suggest that in humans, males should be the 'ornamented' sex, yet most people talk about women's adornments. But ornaments can be what either sex advertises.
Because of our polygynous history, men's and women's cultural augmentation of sexual signals should give information about different characteristics. Men are likely to signal wealth and power status, and members of cultural subgroups with limited real resources seem likely to concentrate those resources in highly visible signals. Sociological studies of wealth and status signals among contemporary poor groups, for example, find the 'ghetto Cadillac' phenomenon common. Because humans show male parental investment, a woman's reproductive value becomes important; thus, women should signal reproductive value, things that reflect youth and health. Today, billion-dollar industries exist to do just that: makeup and cosmetic surgery, for example, are designed to signal youth, health, and sexual interest—the products and processes are aimed at making the skin tauter and less wrinkled. Though a few men indulge themselves this way, most clients are women, who get facelifts, and undergo liposuction to obtain an attractive waist-hip ratio. In the nineteenth century, women put belladonna in their eyes, dilating their pupils, ordinarily a strong signal of sexual interest. Women use rouge to make the cheeks rosy, indicating they have either been exercising or are sexually aroused, and lipstick to mimic the dark, blood-engorged state of the lips during sexual excitement. The specifics change across time and societies, but the desired result does not.
Women, like females of other species, can signal interest and availability behaviorally. Patterns of eye contact in flirting appear to be virtually universal and invariant in widely differing societies. The facts that women frequently wear signals of 'unavailability' (e.g., wedding rings, styles of clothing or hair worn only by married women), and that in some cultures they undergo treatment that may decrease their general health and vigor (foot binding, clitoridectomy) are suggestive. Men and women's interests often conflict, and women are at least sometimes manipulated by men, (for example by proclaiming unavailability in return for parental investment, or undergoing foot binding to get a mate). Such ornaments of unavailability should be more common in societies in which women are more dependent on men for resources.