Summary: Researchers investigate why men generally find women with lower waist-to-hip ratios (WHR) more attractive and sexually appealing.
Source: Frontiers
Male turkeys famously try to mate with a head on a stick. In the same spirit, male preferences can sometimes be reduced to a single visible cue. How far can human ideals of an attractive sexual partner be simplified?
Even though human attraction includes many subtle and personal elements, researchers have identified consistent patterns across cultures and studies.
Waist-to-hip ratio (WHR) is one of the strongest predictors of female physical attractiveness. The preferred WHR varies between studies and cultures, but men consistently favor values that are lower than typical male WHR or the average female WHR. In a review published in Frontiers in Psychology, Dr. Jeanne Bovet of Stony Brook University (SUNY) asks a direct question: why do men show these preferences?
Euphemisms and the problem of vague hypotheses
Over the past 25 years, the literature on WHR and attractiveness has grown substantially. However, many evolutionary accounts reduce the meaning of a low WHR to broad, catch-all terms like “health” and “fertility” without specifying the precise mechanisms that would make a preference adaptive. Bovet argues that this tendency leads to “just-so stories” that explain patterns after the fact rather than testing clearly defined evolutionary pathways.
To address this, Bovet systematically reviewed the hypotheses linking WHR to mate value. She framed two core questions for each hypothesis: can a man reliably perceive the trait from WHR, and would choosing a mate with that WHR increase the number or quality of his descendants?
What WHR reliably signals
Bovet concludes that WHR provides several straightforward pieces of information that men can infer visually: a person’s sex, approximate age, current pregnancy status, and parity (number of children previously given birth to).
Children and men generally have higher WHRs than adult women. In women, WHR typically falls with puberty and remains lower through early adulthood, then tends to rise again with age and with each childbirth. A visibly increased waist is also a reliable cue of ongoing pregnancy. In this way WHR tracks aspects of reproductive potential: it is noninformative or null for prepubertal girls, pregnant women, and postmenopausal women; it tends to peak in women in their twenties; and its predictive power declines for women with many children or none.
Fat distribution and offspring brain development
Among the traits associated with WHR, one stands out with particularly strong supporting evidence: the role of gluteofemoral fat (fat stored on the hips, thighs, and buttocks) in supplying essential nutrients for fetal and infant brain development.
Although pelvic bone size influences childbirth, the pelvis is constrained by the mechanics of walking on two feet, which limits how large it can become. Most variation in WHR therefore reflects differences in fat distribution rather than pelvic dimensions. Importantly, fat on the hips and thighs behaves differently from abdominal fat: it is metabolically conserved during periods of caloric restriction and is preferentially mobilized during late pregnancy and lactation. That fat supplies long-chain polyunsaturated fatty acids (LCPUFAs) that are critical for early brain growth. By contrast, abdominal fat reduces the activity of enzymes such as Δ-5 desaturase that are necessary to synthesize these fatty acids.
Consistent with this mechanism, some studies have reported that women with lower WHRs—and their children—score higher on cognitive tests. Birth order effects that show reduced cognitive scores for later-born children may align with the progressive depletion of gluteofemoral fat with each pregnancy.
Multiple hypotheses and a moving target
Bovet emphasizes that a preference for low WHR could have evolved via several different pathways, and that not all plausible hypotheses have been tested equally. Candidates include WHR as a cue to health, fecundity, current pregnancy, parity, hormone-driven sexual behavior, or even parasite load. Some widely cited explanations (for example, WHR as a simple shortcut for “health and fertility”) are not necessarily the best supported by theoretical reasoning or empirical data, while other promising hypotheses (such as WHR indicating parity or current pregnancy) have been underexamined.
It is also possible that WHR’s association with attractiveness is an indirect effect: men might actually prefer another correlated feature, such as hip size alone or waist-to-height ratio, and WHR would then be an imperfect proxy. Cultural change and reproductive technologies could alter the strength or direction of these preferences over time. Conversely, a process of “runaway selection” might exaggerate traits that once conveyed reproductive advantage, intensifying preferences for certain body shapes in future generations.
Source:
Frontiers
Media Contacts:
Jeanne Bovet – Frontiers
Image Source:
The image is in the public domain.
Original Research: Open access
“Evolutionary Theories and Men’s Preferences for Women’s Waist-to-Hip Ratio: Which Hypotheses Remain? A Systematic Review.” Jeanne Bovet. Frontiers in Psychology. doi: 10.3389/fpsyg.2019.01221
Abstract
Evolutionary Theories and Men’s Preferences for Women’s Waist-to-Hip Ratio: Which Hypotheses Remain? A Systematic Review
Over the past 25 years, researchers have investigated men’s preferences for women’s physical traits and the possible evolutionary benefits of those preferences. This field has become controversial in part because many evolutionary hypotheses are imprecise or incomplete. This review focuses on the extensive literature about men’s adaptive preferences for female WHR and highlights theoretical weaknesses that have contributed to confusion and debate. Specifically, the literature often lacks clear definitions of key evolutionary concepts—reducing female mate value to vague notions like “health and fertility”—and tends to test WHR effects without systematically distinguishing among different evolutionary routes (for example, fecundability versus offspring quality). Unsound theoretical foundations produce weak predictions and hinder proper testing, sometimes leading to premature rejection of evolutionary explanations. This paper provides a comprehensive review of existing hypotheses linking WHR to mate value, evaluates their theoretical credibility, identifies which hypotheses are plausible, and suggests directions for future research to strengthen the theoretical basis of evolutionary studies of human mate choice.