Why do we care about looking good? Attractive people are more likely to get jobs, receive higher salaries and more lenient sentencing. But what drives our obsession with beauty, and with idealized women’s bodies in particular? Former IAST biologist Jeanne Bovet adopts an evolutionary approach to understanding such behavior. Working with co-authors from economics, psychology, marketing and anthropology, her methods combine eye-tracking technology and analysis of ancient artworks to determine which female features are considered attractive and why.

WHAT DOES EVOLUTION HAVE TO DO WITH BEAUTY?

Individuals are often faced with a choice between a variety of potential partners with different mate values, defined (from an evolutionary point of view) as the degree to which an individual would promote the reproductive success of another individual by mating with him or her. Preferences for certain physical features can help increase the quantity or quality of descendants. This phenomenon – mate choice – is a major mechanism through which sexual selection influences evolution.

WHY DO WOMEN’S BODIES SPARK MORE INTEREST THAN THOSE OF MEN?

Women’s physical ability to have children varies more than it varies for men, requiring a larger investment. As this fertility is largely determined by a woman’s physical and physiological condition, men value physical cues in prospective mates more than women. Women appear to be sensitive to this preference and frequently try to amplify these cues, as indicated by the highly lucrative cosmetics and beauty industries.

WHAT PHYSICAL CUES WERE ANCESTRAL MEN LIKELY TO FIND APPEALING?

Not only is it dangerous to copulate with someone with a contagious disease, but older and unhealthy women cannot have as many children as young, healthy women. Pregnancy and breastfeeding are energetically demanding and usually require being in good health. As a consequence, ancestral men who were able to detect and prefer young and healthy women had more descendants, who inherited these preferences. Research shows, for example, that attractive faces are considered healthier and that men prefer partners younger than themselves. In fact, however old men are, they are sexually attracted to women with an age close to their fertility peak. Pregnant and lactating women are momentarily infertile, and each pregnancy decreases future reproductive potential. Thus, cues associated with reproductive status and parity (i.e., the number of previous pregnancies) are expected to be correlated with female sexual attractiveness.

FROM AN EVOLUTIONARY PERSPECTIVE, WHAT ELSE IS FEMININE BEAUTY MADE OF?

Studies have shown that facial features that indicate youth are more attractive to men, and the decline of facial attractiveness with age is stronger for women than for men. During puberty, androgens stimulate growth of the jaw, cheekbones, and brow ridges in boys; estrogens inhibit the development of these features among girls, and may also increase lip size. This facial femininity increases women’s attractiveness. Body shape also contains cues of age, health, reproductive status, and parity. Having a very low or high body mass index (BMI) can impact fertility. If a woman is too thin, she will stop ovulating or have insufficient resources for pregnancy or lactation. On the other hand, overweight and obesity are linked to disorders of the ovarian cycle and miscarriage. Feminine hormones like estrogens direct fat storage to the hips, while masculine hormones stimulate fat deposits in the abdominal region. This fat distribution can be measured with the waist-to-hip ratio (WHR). WHR seems to be a cue of age, reproductive status and parity. Many studies show that men find women with a low WHR more attractive [see panel].

Women are the only mammal with permanent breasts, and these are large compared to other female primates. Breast shape is linked to a woman’s age, current condition, and parity: high, firm breasts are associated with nubility, engorged breasts indicate lactation, “sagginess” increases with age and parity. There are many other physical features – such as hair, or leg length – known to have an effect on female attractiveness. And in almost every culture, beauty can be enhanced using dress, jewelry, tattoos, makeup or other techniques. When choosing a mate, men also use non-physical features, such as voice, smell, movements, and behavior, which can be linked to physical or physiological conditions, as well as personality, psychology, and social background. Such features, whether physical or not, are not all equally weighted in mating decisions, but they all likely contribute to the general evaluation of a potential partner.

HOW DOES THE MEDIA INFLUENCE CONTEMPORARY BEAUTY IDEALS?

When people see faces or bodies with a certain trait, they tend to prefer new faces or bodies that share this characteristic. For example, exposure to thin bodies makes people prefer thinner bodies. Individuals presented in the media do not correspond to the average population: among other things, they are generally more attractive. In one study, men previously exposed to women pictured in Playboy magazine judged “ordinary” young women as less attractive. Studies show that access to television or the internet also has an effect on preferences. For instance, in El Salvador, people without internet access prefer more feminine men’s faces, and more masculine women’s faces.

IS BEAUTY UNIVERSAL OR ‘IN THE EYE OF THE BEHOLDER’?

A complete understanding of beauty must combine both objective and subjective accounts. Many preferences for physical features appear to be the result of evolution and occur because these traits provide reliable cues about potential mates. However, these preferences are also plastic, varying between geographical regions and across time. This variation may be beneficial, enabling individuals to adapt to different conditions. For example, as fat represents caloric storage, a high BMI can be advantageous in environments where food supply is scarce and/or unpredictable. Populations where a preference for a high BMI has been observed have low and unreliable access to resources and a comparatively high prevalence of infectious diseases. A group’s socioeconomic status has also been shown to be a stronger determinant of body weight ideals than ethnicity.

> See www.jeannebovet.com

From IAST Magazine #15, Winter 2019 (read the whole magazine)