Evolutionary Psychology Chapter 5: PDF

136 ChALLENGES OF SEx AND MATiNG Figure 5.2 Logic of the Evolution of Standards of Attractiveness Standards of female attractiveness are hypothesized to have evolved to embody reliably observable cues to fertility or reproductive value. Beauty is in the adaptations of the beholder (Symons, 1995)....

136 ChALLENGES OF SEx AND MATiNG Figure 5.2 Logic of the Evolution of Standards of Attractiveness Standards of female attractiveness are hypothesized to have evolved to embody reliably observable cues to fertility or reproductive value. Beauty is in the adaptations of the beholder (Symons, 1995). Our ancestors had access to two types of observable evidence of a woman’s reproductive value: (1) features of physical appearance, such as full lips, clear skin, smooth skin, clear eyes, lustrous hair, good muscle tone, and body fat distribution; and (2) features of behavior, such as a bouncy, youthful gait, an animated facial expression, and a high energy level. These physical cues to youth and health, and hence to fertility and reproductive value, have been hypothesized to be some of the key components of male standards of female beauty (Symons, 1979, 1995; see Figure 5.2). Strong empirical support exists for the link between physical attractiveness and objective measures of health in a sample of roughly 15,000 Americans between the ages of 25 and 34 (Nedelec & Beaver, 2014). Psychologists Clelland Ford and Frank Beach discovered several universal cues that correspond with the evolutionary theory of beauty (1951). Signs of youth, such as clear, smooth skin, and signs of health, such as an absence of sores and lesions, are universally regarded as attractive. Cues to ill health and older age are less attractive. Poor complexion is always considered unattractive. Ringworm, facial disfgurement, and flthiness are universally undesirable. Even a super-white sclera, the whites of the eyes surrounding the iris, is key cue to health and evaluated as attractive (Provine, Cabrera, & Nave-Blodgett, 2013). Freedom from disease is universally attractive. Among the Trobriand Islanders in northwestern Melanesia, for example, anthropologist Bronislaw Malinowski reports that “sores, ulcers, and skin eruptions are naturally held to be specially repulsive from the viewpoint of erotic contact” (Malinowski, 1929, p. 244). The “essential conditions” for beauty, in contrast, are “health, strong growth of hair, sound teeth, and smooth skin.” Specifc features, such as bright, shining eyes and full, well-shaped lips rather than thin or pinched lips, are especially important to the islanders. Another cue to youth and health is the length and quality of women’s hair. One study interviewed 230 women at various public locations about their age, subjective health status, and relationship status and obtained observer measures of hair length and hair quality (Hinsz, Matz, & Patience, 2001). Hair length and quality were strong cues to youth: Younger women had longer hair of higher-rated quality than did older women. Hair quality was positively correlated with women’s subjective judgments of their own health. Skin quality is especially important in judgments of attractiveness. It provides a cue to a woman’s age and a partial record of her lifetime health (Sugiyama, 2005). Clear, unblemished skin signals an absence of parasites, absence of skin-damaging diseases during development, and possibly “good genes” to withstand disease and heal without infection (Singh & Bronstad, 1997). Skin quality is linked with perceived facial attractiveness (Fink & Neave, 2005). Female 5 MEN’S LONG-TERM MATiNG STRATEGiES faces with skin that has a homogeneous skin color distribution, not splotchy, receive higher attractiveness ratings and are perceived to be younger (Fink, Grammer, & Matts, 2006; Fink et al., 2008). Furthermore, more skin blood color in female faces enhances the perception of healthiness, perhaps corresponding to the subjective impression that some faces seem to “glow” (Stephen, Coetzee, Smith, & Perrett, 2009). This may also explain why some women use rouge as makeup, since it enhances perceptions of health and vitality. Femininity is another cue to attractiveness (Gangestad & Scheyd, 2005). Facial femininity includes cues such as full lips, relatively large eyes, thinner jaws, small chin, high cheekbones, and a relatively short distance between mouth and jaw. Female facial femininity is likely to be a marker of reproductive value for two reasons. First, as women age, their facial features become less feminine. Second, facial femininity is linked with higher levels of estrogen, the ovarian hormone that correlates with fertility (Schaefer et al., 2006). Third, facial femininity is linked to health and some aspects of disease resistance (Gray & Boothroyd, 2012). Meta-analyses reveal that facial femininity is one of the most powerful cues to women’s attractiveness (Rhodes, 2006). Feminine voices—relatively high pitched—are also found to be more attractive in women and provide cues to youth (Collins & Missing, 2003; Feinberg et al., 2005; Röder, Fink, & Jones, 2013). Another study using point-light methodology to measure biomechanical gait found that women who wear high heels are judged to be both more feminine (shorter stride length and increased rotation and tilt of the hips) and more attractive (Morris, White, Morrison, & Fisher, 2013). Facial symmetry is another correlate of female attractiveness (Gangestad & Scheyd, 2005; Rhodes, 2006). You may recall from Chapter 4 that symmetry is hypothesized to be a cue to developmental stability, a hypothesized sign of “good genes” and the capacity to withstand environmental insult. Symmetrical female faces are indeed judged to be healthier than less symmetrical faces (Fink et al., 2006). Facial symmetry is positively correlated with judgments of attractiveness, although the link is weaker than that of facial femininity (Rhodes, 2006). Facial averageness is another quality linked with attractiveness, although this may seem counterintuitive. Researchers created computer composites of the human face, superimposing faces on each other to create new faces (Langlois & Roggman, 1990). The new faces difered in the number of individual faces that made them up—4, 8, 16, or 32. The composite faces—the averages of the individual faces—were judged more attractive than the individual faces. And the more faces that went into the composite, the more attractive the face was judged to be. Two competing hypotheses have been advanced to explain why average faces are attractive. First, people may show a generalized cognitive preference for things that are easily processed, and stimuli that match an average prototype may be easier to process. People do indeed fnd averaged images of fsh, birds, and even cars more attractive than individual fsh, birds, or cars (Rhodes, 2006). Second, averageness may be a marker of genetic or phenotypic quality (Gangestad & Scheyd, 2005). Deviations from averageness may be cues to environmental insults such as disease, susceptibility to environmental insults, or genetic mutations. Leg length, especially long legs relative to torso length, has been hypothesized to be a cue to health and biomechanical efciency (Sorokowski & Pawlowski, 2008). Using silhouette stimuli that held overall height constant but varied leg length, researchers discovered that legs roughly 5 percent longer than average are viewed as maximally attractive in women (Sorokowski & Pawlowski, 2008). Other studies confrm that both sexes view relatively longer legs as more attractive in women (Bertamini & Bennett, 2009; Swami, Einon, & Furnham, 2006). Perhaps this explains why some women wear high-heeled shoes—they make legs appear to be relatively longer. Interestingly, a study of 9,998 Chinese found that women with longer legs had more ofspring, an association especially strong in women from lower socioeconomic backgrounds (Fielding et al., 2008). Lumbar curvature. Women face a critical adaptive problem no man has ever faced—a 9-month pregnancy. As the pregnancy progresses, it shifts women’s center of gravity forward, changing the strain or torque it puts on their spinal columns. Women have evolved somewhat diferent spinal structures—a wedge-shaped third-to-the last lumbar vertebra—that helps to solve this adaptive problem. David Lewis and his colleagues calculated the optimal degree of lumbar curvature that would minimize torque and predicted that men would fnd this optimum maximally attractive (Lewis, Russell, Al-Shawaf, & Buss, 2015). Two studies confrmed this 137 ChALLENGES OF SEx AND MATiNG 138 Figure 5.3 Lumbar Curvature and Standards of Attractiveness Note: Women with the optimal lumbar curvature are rated as maximally attractive (from Lewis et al., 2015, fgure 5.1, p. 346). hypothesis, highlighting a new discovery about evolved standards of beauty, guided by an evolutionary perspective (see Figure 5.3). Finally, a recent study of cue-based judgments of women in bikinis found that assessments of women’s attractiveness correlated nearly perfectly with assessments of women’s reproductive value (Andrews, Lukaszewski, Simmons, & Bleske-Rechek, 2017). This study, combined with the large body of empirical fndings just reviewed, provides strong empirical support for the evolutionary theory of women’s attractiveness shown in Figure 5.2. Beauty and the Brain Evolutionary psychologists are beginning to use neuroscience technology to identify the links between psychological mechanisms and specifc brain circuits. Exploiting the new technology of functional magnetic resonance imaging (fMRI), scientists Itzhak Aharon, Nancy Etcof, and their colleagues sought to identify the “reward value” of diferent images (Aharon et al., 2001). They exposed heterosexual male participants to four sets of faces difering in attractiveness, as determined by prior ratings: attractive females, average females, attractive males, and average males. While participants viewed these images, their brains were neuroimaged in six regions. The results proved to be dramatic. When men looked at attractive female faces, the nucleus accumbens area of the brain became especially activated. The nucleus accumbens is known to be fundamental reward circuitry, a pleasure center in the brain. This reward circuit fails to become activated when men look at either typical female faces or any of the male faces. Beautiful female faces, in short, are especially rewarding to men, psychologically and neurologically. This important fnding takes the feld a step closer to identifying the specifc brain bases of mating adaptations that have been well documented psychologically and behaviorally. Body Fat, Waist-to-Hip Ratio, and Body Mass Index Facial beauty is only part of the picture. Features of the rest of the body may also provide cues to a woman’s reproductive capacity. Standards for female bodily attractiveness vary somewhat from culture to culture. The most culturally variable standard of beauty seems to be in the preference for a slim versus a plump body build, and it is linked with the social status that build conveys. In cultures where food is 5 MEN’S LONG-TERM MATiNG STRATEGiES scarce, such as among the Bushmen of Australia, plumpness signals wealth, health, and adequate nutrition during development (Rosenblatt, 1974). In ecologies where food shortages are common, such as in Kenya, Uganda, and certain parts of Ecuador, men prefer women who are heavier and possess more body fat (Sugiyama, 2005). Even within cultures, men prefer heavier women during economic hard times (Pettijohn & Jungeberg, 2004), when hungry (Pettijohn, Sacco, & Yerkes, 2009), and when they feel poor (Nelson & Morrison, 2005). In cultures where food is relatively abundant, such as the United States and many Western European countries, the relationship between plumpness and status is reversed, and the wealthy distinguish themselves by being thin (Symons, 1979). Thus, although “body-weight preference varies across cultures and time, it does so in predictable ways” (Sugiyama, 2005, p. 318), suggesting context-dependent adaptations. One study revealed a disturbing aspect of U.S. women’s and men’s perceptions of the desirability of plump or thin body types (Rozin & Fallon, 1988). Men and women viewed nine female fgures that varied from very thin to very plump. The women were asked to indicate their ideal for themselves and their perception of men’s ideal female fgure. In both cases, women selected a fgure that was slimmer than average. When men were asked to select which female fgure they preferred, however, they selected the fgure of exactly average body size. So U.S. women think that men want them to be thinner than is in fact the case. A study of 7,434 individuals from 26 cultures in 10 world regions found the same pattern—men consistently prefer female bodies that are heavier in weight than women’s perceptions of what men prefer (Swami et al., 2010). Psychologist Devendra Singh has discovered one preference for body shape that may be universal: the preference for a particular ratio between the size of a woman’s waist and the size of her hips (Singh, 1993; Singh & Young, 1995). Before puberty, boys and girls show similar fat distributions. At puberty, however, a dramatic change occurs. Men lose fat from their buttocks and thighs, whereas the release of estrogen in pubertal girls causes them to deposit fat in the lower trunk, primarily on their hips and upper thighs. Indeed, the volume of body fat in this region is 40 percent greater for women than for men. Women with a low WHR (lef panel) are judged to be more attractive than women with a higher WHR (right panel). A relatively low WHR signals that the woman is young, healthy, and not pregnant. 139 140 ChALLENGES OF SEx AND MATiNG The waist-to-hip ratio (WHR) is similar for the sexes before puberty, in the range of .85 to .95. After puberty, women’s hip fat deposits cause their WHRs to become signifcantly lower than men’s. Healthy, reproductively capable women have WHRs between .67 and .80, whereas healthy men have a ratio in the range of .85 to .95. WHR is an accurate indicator of women’s reproductive status. Women with lower ratios show earlier pubertal endocrine activity. Married women with higher ratios have more difculty becoming pregnant, and those who do get pregnant do so at a later age than women with lower ratios. The WHR may also be an indication of long-term health status, although one recent review article casts serious doubt on this hypothesized link (Lassek & Gaulin, 2018a). One study found that women with a low WHR (as indicated by small waist) and relatively large breasts, compared to women from three groups with diferent combinations of body-shape variables, had 26 percent higher levels of the ovarian hormone oestradiol (E2), which is a good predictor of fertility and pregnancy success (Jasienska, Ziomkiewicz, Ellison, Lipson, & Thune, 2004). Oestradiol is a good index of reproductive value, since the oocytes are directly involved in producing it. All else equal, women with more oocytes left produce more oestradial. The link between the WHR and reproductive status may make it a reliable cue for ancestral men’s preferences in a mate. Nonetheless, one recent review article has failed to fnd direct links between WHR and fecundability (immediate odds of conception), which calls into question this hypothesis (Lassek & Gaulin, 2018b). Since WHR tends to increase with a woman’s age, however, it may be an indicator of reproductive value or future reproductive potential. Singh discovered that WHR is a powerful part of women’s attractiveness. In a dozen studies conducted by Singh, men rated the attractiveness of female fgures that varied in both WHR and total amount of fat. Again, men found the average fgure more attractive than either a thin or a fat fgure. Regardless of the total amount of fat, however, men fnd women with low WHRs the most attractive. Women with a WHR of 0.70 are seen as more attractive than women with a WHR of 0.80, who in turn are seen as more attractive than women with a WHR of 0.90. Studies with line drawings and with computer-generated photographic images produced the same results. The bodies of women who underwent surgery to remove fat from their stomachs and implant it on their buttocks—creating a lower WHR—were judged more attractive postoperation (Singh & Randall, 2007). Singh’s analysis of Playboy centerfolds and winners of U.S. beauty contests over 30 years confrmed the invariance of this cue. Although both centerfolds and beauty contest winners got slightly thinner over that period, their WHRs remained the same—roughly 0.70. A preference for a relatively low WHR has also been found in the United Kingdom, Australia, Germany, India, and Guinea-Bissau (Africa) and on the Azore Islands (Connolly, Mealey, & Slaughter, 2000; Furnham, Tan, & McManus, 1997; Singh, 2000). The crosscultural consensus on the link between women’s low WHR and attractiveness has been shown in Cameroon, Africa; Komodo Island, Indonesia; Samoa; and New Zealand (Singh, Dixson, Jessop, Morgan, & Dixson, 2010). A study of Venus fgurines covering 20,000 years of human history in Europe also supports a “deep time” consistency for the preference for a low WHR (King, 2013). A cross-cultural study of female “escorts” advertised online found that the average values of the stated WHRs, as calculated from reported body measurements of waist and hips, were .70, .75, .71, .76, and .69 in Europe, Oceania, Asia, North America, and Latin America, respectively (Saad, 2008). Another study found that online escorts who had a lower WHR and a younger age charged higher prices for their sexual services (Grifth, Capiola, Balotti, Hart, & Turner, 2016). Men blind from birth, when assessing female body shape through touch, prefer the low WHR mannequin models, suggesting that the preference for low WHR can develop in the total absence of visual input (Karremans et al., 2010). Eye-tracking studies discovered that men’s visual fxations occurred most often for female waists, hips, and breasts and that men rated women with a low WHR as most attractive, regardless of breast size (Dixon et al., 2011; Garza, Heredia, & Cieslicka, 2016). And another pair of studies of “adaptive memory” discovered that men remembered women with an attractive WHR much more than women with a less attractive WHR (Fitzgerald, Horgan, & Himes, 2016).