Evolutionary Psychology ch 4_1-6.pdf

ChaPter 4 Women’s Long-Term Mating Strategies Learning Objectives Afer studying this chapter, the reader will be able to: ■ Explain the two major components of sexual selection theory. ■ Explain parental investment theory and analyze how parental investment infuences the components of sexual sel...

ChaPter 4 Women’s Long-Term Mating Strategies Learning Objectives Afer studying this chapter, the reader will be able to: ■ Explain the two major components of sexual selection theory. ■ Explain parental investment theory and analyze how parental investment infuences the components of sexual selection. ■ analyze the multiple adaptive problems potentially solved by women’s preferences for men with resources. ■ Evaluate why women have an evolved mate preference for cues to athletic ability. ■ summarize the evidence for the efects of women’s personal resources on their mate preferences. ■ Explain “mate copying” and provide one example from real life. ■ identify four fndings that illustrate how women’s mate preferences infuence actual mating behavior. Nowhere do people have an equal desire for all potential mates. Everywhere, some potential mates are preferred, others shunned. Imagine living as our ancestors did long ago—struggling to keep warm by the fre; hunting meat for our kin; gathering nuts, berries, and herbs; and avoiding dangerous animals and hostile humans. If we were to select a mate who failed to deliver the resources promised, who had afairs, who was lazy, who lacked hunting skills, or who heaped physical abuse on us, our survival would be tenuous, our reproduction at risk. In contrast, a mate who provided abundant resources, who protected us and our children, and who devoted time, energy, and efort to our family would be a great asset. As a result of the powerful survival and reproductive advantages reaped by those of our ancestors who chose mates wisely, many specifc desires evolved. As descendants of those winners in the evolutionary lottery, modern humans have inherited a specifc set of mate preferences. Scientists have documented evolved mate preferences in many non-human species. The African village weaverbird provides a vivid illustration (Collias & Collias, 1970). When a female weaverbird arrives in the vicinity of a male, he displays his recently built nest by suspending himself upside down from the bottom and vigorously fapping his wings. If the male impresses the female, she approaches the nest, enters it, and examines the nest materials, poking and pulling them for as long as 10 minutes. During this inspection, the male sings to her from nearby. At any point in this sequence, she may decide that the nest does not meet her standards and depart to inspect another male’s nest. A male whose nest is rejected by several females will often break it down and rebuild another from scratch. By exerting a preference for males capable of building superior nests, the female weaverbird addresses the problems of protecting and provisioning her chicks. Her preferences have evolved because they bestowed a reproductive advantage over other weaverbirds who had no preferences and who mated with any male who happened to come along. Women, like weaverbirds, also prefer males with “nests” of various kinds. Consider one of the problems that women in evolutionary history had to face: selecting a man who would be willing to commit to a long-term relationship. A woman in our evolutionary past who chose to ChALLENGES OF SEx AND MATiNG 102 mate with a man who was fighty, impulsive, philandering, or unable to sustain a relationship found herself raising her children alone and without beneft of the resources, aid, and protection that a more dependable mate might have ofered. A woman who preferred to mate with a reliable man who was willing to commit to her would have had children who survived, thrived, and multiplied. Over thousands of generations, a preference for men who showed signs of being willing and able to commit evolved in women, just as preferences for mates with adequate nests evolved in weaverbirds. Theoretical Background for the Evolution of Mate Preferences This section reviews two important theoretical issues that are key to understanding the evolution of mate preferences. The frst deals with the defnition of the two distinct types that exist in sexually reproducing species—males and females—and the related issue of the infuence of parental investment on the nature of mating. The second topic pertains to mate preferences as evolved psychological mechanisms. Parental Investment and Sexual Selection It is a remarkable fact that what defnes biological sex is simply the size of the sex cells. Mature reproductive cells are called gametes. Each gamete has the potential to fuse with another gamete of the opposite sex to form a zygote, which is defned as a fertilized gamete. Males are the sex with the small gametes, females the large gametes. The female gametes remain reasonably stationary and come loaded with nutrients; the male gametes are endowed with greater mobility. Along with diferences in size and mobility comes a diference in quantity. Men produce millions of sperm, which are replenished at a rate of roughly 12 million per hour. Women, on the other hand, produce a fxed and unreplenishable lifetime supply of eggs, of which perhaps a few hundred will be ovulated during the lifetime. Women’s greater initial investment per gamete does not end with the egg. Fertilization and gestation, key components of human parental investment, occur internally in women. One act of sexual intercourse that requires minimal male investment can produce an obligatory and energyconsuming 9-month investment by the woman. In addition, women alone engage in the activity of lactation (breastfeeding), which lasts as long as 4 years in some societies (Shostak, 1981). No biological law of the animal world dictates that females must invest more than males. Indeed, in some species such as the Mormon cricket, pipefsh seahorse, and Panamanian poison arrow frog, males in fact invest more (Trivers, 1985). The male Mormon cricket produces a large spermatophore that is loaded with nutrients. Females compete with each other for access to the high-investing males holding the largest spermatophores. Among these so-called sex-rolereversed species, males are more discriminating than females about mating. In particular, the females chosen by the males for depositing their spermatophore contain 60 percent more eggs than females who are rejected (Trivers, 1985). Among all 5,000 species of mammals and the 300 species of primates, however, the females—not the males—undergo internal fertilization and gestation. The great initial parental investment of females makes them a valuable reproductive resource (Trivers, 1972). Gestating, bearing, lactating, nurturing, protecting, and feeding a child are exceptionally valuable reproductive resources. Those who hold valuable resources do not give them away haphazardly. Because women in our evolutionary past risked investing enormously as a consequence of having sex, evolution favored women who were highly selective about their mates. Ancestral women sufered severe costs if they were indiscriminate: They experienced lower reproductive success, and fewer of their children survived to reproductive age. 4 WOMEN’S LONG-TERM MATiNG STRATEGiES In summary, Trivers’s (1972) theory of parental investment and sexual selection makes two profound predictions: (1) The sex that invests more in ofspring (typically, but not always, the female) will be more discriminating or selective about mating; and (2) the sex that invests less in ofspring will be more competitive for sexual access to the high-investing sex. In the case of humans, it is clear that women have greater obligatory parental investment. For longterm mating or marriage, however, both men and women typically invest heavily in children, and so the theory of parental investment predicts that both sexes should be very choosy and discriminating. Mate Preferences as Evolved Psychological Mechanisms Consider the case of an ancestral woman trying to decide between two men, one of whom shows great generosity to her with his resources and the other of whom is stingy. All else being equal, the generous man is more valuable to her than the stingy man. The generous man may share his meat from the hunt, aiding her survival. He may sacrifce his time, energy, and resources for the beneft of the children, aiding the woman’s reproductive success. In these respects, the generous man has higher value than the stingy man as a mate. If, over evolutionary time, generosity in men provided these benefts repeatedly and the cues to a man’s generosity were observable and reliable, selection could favor the evolution of a preference for generosity in a mate, especially if that generosity got directed specifcally to the woman doing the mate selection. Now consider a more complicated and realistic scenario in which men vary not just in their generosity but also in a bewildering variety of ways that are signifcant in the choice of a mate. Men difer in their physical prowess, athletic skill, ambition, industriousness, kindness, empathy, emotional stability, intelligence, social skills, sense of humor, kin network, and position in the status hierarchy. Men also difer in the costs they carry into a mating relationship: some come with children, a bad temper, a selfsh disposition, and promiscuous proclivities. In addition, men difer in hundreds of ways that may be irrelevant to women. From among the thousands of ways in which men difer, selection over hundreds of thousands of years focused women’s preferences, laser-like, on the most adaptively valuable characteristics. Women lacking specifc adaptively relevant preferences are not our ancestors; they were out-reproduced by choosier women. The qualities people prefer, however, are not static. Because preferences change over time, mate seekers must gauge the future potential of a prospective partner. A man might lack resources now but, as a medical student, might have excellent future promise. Gauging a man’s mate value requires looking beyond his current position and evaluating his future potential. In short, evolution has favored women who prefer men possessing attributes that confer benefts and who dislike men possessing attributes that impose costs. Each separate attribute constitutes one component of a man’s value to a woman as a mate. Each of her preferences tracks one critical component. Preferences that give priority to particular components, however, do not completely solve the problem of choosing a mate. In selecting a mate, a woman must deal with the problem of identifying and correctly evaluating the cues that signal whether a man actually possesses a particular quality. The assessment problem becomes especially acute in areas in which men are apt to deceive women, such as pretending greater status than they actually possess or feigning greater commitment than they are truly willing to give. Women also face the problem of integrating their knowledge about a prospective mate. Suppose that one man is generous but emotionally unstable. Another man is emotionally stable but stingy. Which man should a woman choose? Selecting a mate requires psychological mechanisms that make it possible to add up the relevant attributes and give each an appropriate weight to the fnal decision. Some attributes weigh more than others in arriving at the fnal decision about whether to choose or reject a particular man. Finally, wise women seek mates in their own mate-value range. Trying to attract a “10” if you are only an “8” is risky; even if 103 ChALLENGES OF SEx AND MATiNG 104 successful in the initial attraction stage, over time, the higher-mate-value partner is more likely to abandon the lower-mate-value partner. The Content of Women’s Mate Preferences With this theoretical background in mind, we turn now to the actual content of women’s mate preferences (summarized in Table 4.1). As the previous discussion implies, choosing a mate is a complex task, and so we do not expect to fnd simple answers to what women want. Preference for Economic Resources The evolution of the female preference for males ofering resources may be the most ancient and pervasive basis for female choice in the animal kingdom. Consider the grey shrike, a bird living in the Negev desert of Israel (Yosef, 1991). Just before the start of the breeding season, male shrikes begin amassing caches of edible prey such as snails and useful objects such as feathers and pieces of cloth in numbers ranging from 90 to 120. They impale these items on thorns and other pointed projections within their territories. Females scan the available males and choose to mate with those with the largest caches. When Yosef arbitrarily removed portions of some males’ stock and added edible objects to the supplies of others, females preferred to mate with the males with the larger bounties. Females entirely avoided males without resources, consigning them to bachelorhood. Table 4.1 Adaptive Problems in Long-Term Mating and Hypothesized Solutions adaptive Problem evolved Mate Preference Selecting a mate who is able to invest Good fnancial prospects Social status Slightly older age Ambition/industriousness Size, strength, and athletic ability Dependability and stability Love and commitment cues Positive interactions with children Size (height) Bravery Athletic ability Masculine body type Dependability Emotional stability Kindness Positive interactions with children Similar values Similar ages Similar personalities Physical attractiveness Symmetry Health Masculine features Selecting a mate who is willing to invest Selecting a mate who is able to physically protect her and children Selecting a mate who will show good parenting skills Selecting a mate who is compatible Selecting a mate who is healthy 4 WOMEN’S LONG-TERM MATiNG STRATEGiES Among humans, the evolution of women’s preference for a long-term mate with resources would have required two preconditions. First, resources would have to be accruable, defensible, and controllable by men during human evolutionary history. Second, men would have to difer from each other in their holdings and their willingness to invest those holdings in a woman and her children. Over the course of human evolutionary history, some women could garner more resources for their children through a single spouse than through several casual sex partners. Men invest in their wives and children with provisions to an extent unprecedented among primates. In all other primates, females must rely solely on their own eforts to acquire food because males rarely share those resources with their mates (Smuts, 1995). Men, in contrast, provide food, fnd shelter, defend territory, and protect children. They tutor children in sports, hunting, fghting, hierarchy negotiation, friendship, and social infuence. They transfer status, aiding ofspring in forming reciprocal alliances later in life. These benefts are unlikely to be secured by a woman from a casual sex partner, although some women develop “special friendships” with men that may ofer protection and resources during times of need or serve as “backup” mates should something happen to their regular mate (Buss, Goetz, Duntley, Asao, ConroyBeam, 2017; Smuts, 1985). So the stage was set for the evolution of women’s preferences for men with resources. But women needed cues to signal a man’s possession of those resources. These cues might be indirect, such as personality characteristics that signal a man’s upward mobility. They might be physical, such as a man’s athletic ability or health. They might include reputation, such as the esteem in which a man is held by his peers. The possession of economic resources, however, provides the most obvious cue. Preference for Good Financial Prospects Currently held mate preferences provide a window for viewing our mating past, just as our fears of snakes and heights provide a window for viewing ancestral hazards. Evidence from dozens of studies documents that modern U.S. women indeed value economic resources in mates substantially more than men do. In a study conducted in 1939, for example, U.S. men and women rated 18 characteristics for their relative desirability in a marriage partner, ranging from irrelevant to indispensable. Women did not view good fnancial prospects as absolutely indispensable, but they did rate them as important, whereas men rated them as merely desirable but not very important. Women in 1939 valued good fnancial prospects in a mate about twice as highly as men did, a fnding that was replicated in 1956 and again in 1967 (Buss, Shackelford, Kirkpatrick, & Larsen, 2001). Douglas Kenrick and his colleagues devised a useful method for revealing how much people value diferent attributes in a marriage partner by having men and women indicate the “minimum percentiles” of each characteristic they would fnd acceptable (Kenrick, Sadalla, Groth, & Trost, 1990). U.S. college women indicate that their minimum acceptable percentile for a husband on earning capacity is the 70th percentile, or above 70 percent of all other men, whereas men’s minimum acceptable percentile for a wife’s earning capacity is only the 40th. Personal ads in newspapers and online dating sites confrm that women who are actually in the marriage market desire strong fnancial resources (Gustavsson & Johnsson, 2008; Wiederman, 1993). In short, sex diferences in preference for resources are not limited to college students and are not bound by the method of inquiry. Nor are these female preferences restricted to America, to Western societies, or to capitalist countries. A large cross-cultural study was conducted of 37 cultures on six continents and fve islands using populations ranging from coast-dwelling Australians to urban Brazilians to shantytown South African Zulus (Buss et al., 1990). Some participants came from nations that practice polygyny (the mating or marriage of a single man with several women), such 105 106 ChALLENGES OF SEx AND MATiNG as Nigeria and Zambia. Other participants came from nations that are more monogamous (the mating of one man with one woman), such as Spain and Canada. The countries included those in which living together is as common as marriage, such as Sweden and Finland, as well as countries in which living together without marriage is frowned on, such as Bulgaria and Greece. The study sampled a total of 10,047 individuals in 37 cultures, as shown in Figure 4.1 (Buss, 1989a). Male and female participants rated the importance of 18 characteristics in a potential mate or marriage partner, on a scale from unimportant to indispensable. Women across all continents, all political systems (including socialism and communism), all racial groups, all religious groups, and all systems of mating (from intense polygyny to presumptive monogamy), placed more value than men on good fnancial prospects. Overall, women valued fnancial resources roughly twice as much as did men (see Figure 4.2). There are some cultural variations. Women from Nigeria, Zambia, India, Indonesia, Iran, Japan, Taiwan, Colombia, and Venezuela valued good fnancial prospects a bit higher than women from South Africa (Zulus), the Netherlands, and Finland. In Japan, for example, women valued good fnancial prospect roughly 150 percent more than men, whereas women from the Netherlands deem it only 36 percent more important than their male counterparts, less than women from any other country. Nonetheless, the sex diference remained invariant: Women worldwide desired fnancial resources in a marriage partner more than men. Figure 4.1 Locations of 37 Cultures Studied in an International Mate Selection Project Source: Buss, D. M. (1994a). The strategies of human mating. American Scientist, 82, 238–249. Reprinted with permission. Figure 4.2 Preference for Good Financial Prospect in a Marriage Partner N = sample size. p values less than .05 indicate that sex diference is signifcant. Source: Buss, D. M., & Schmitt, D. P. (1993). Sexual strategies theory: An evolutionary perspective on human mating. Psychological Review, 100, 204–232. Copyright © 1993 by the American Psychological Association. Adapted with permission.