This entry was written by Rebecca Johnston as part of a project done in BIAN 2133 ‘Human Reproductive Strategies’ at The Australian National University in 2019 Semester 2
Introduction
Female waist-to-hip ratio (WHR), the ratio of the waist (the narrowest area between the ribs and iliac crest) and the hips (the widest point from the buttocks) (Singh, 1993 p.294), is one factor that has been proposed by evolutionary biologists as significant in male mate preferences. In particular, a low WHR is suggested to be attractive in women and selected for by males, as it indicates high mate value and subsequently, increased reproductive success. Within this essay, a brief overview of WHR will be explored, in addition to the hypothesis of its adaptive nature and finally supportive and opposing evidence of WHR as an attractive trait will be discussed.
Main Text
WHR
The WHR is an anthropometric measure of android and gynoid fat distribution (Singh, 1993). Prior to puberty, females and males have similar WHR as fat deposition is alike, however when puberty is reached, testosterone and estrogen differentially affect fat distribution. For males, testosterone prompts the fat deposition in the abdominal area and constrains deposition in the gluetoalfemoral area, whereas in females, the rise in estrogen has the opposite effect, causing fat deposition around the hips and thighs, rather than the abdominal area. As a consequence, women typically have a lower WHR then men, although a similar ratio arises with menopause.
Hypotheses for the adaptive value of WHR
It has been suggested that WHR can be used as a measure of a woman’s physical attractiveness, in particular, a low WHR is indicative of high mate value and subsequently increased reproductive success for males (Bovet, 2019). However, the exact value that WHR conveys is contested and many hypotheses have been proposed. Bovet (2019) conducted a systematic review of published material that explored an evolutionary approach of male preferences for women’s WHR. It was found that 87% of the material stated a low WHR indicates a woman’s good health, as a high WHR indicates potential health issues including, cardiovascular disease, stroke, hypertension, and diabetes. However, the evidence used in support is largely based on elderly individuals and the diseases linked to a high WHR are chronic conditions, thus cannot be passed on to descendants and are largely associated with contemporary lifestyle. Consequently, it is argued that this hypothesis may only be valid in contemporary western societies and does not account for the evolutionary basis for the preference for a low WHR.
The next most common hypothesis is that WHR is a signal of fecundity, with 54% of material arguing that WHR provides information about a woman’s ability to reproduce (Bovet, 2019). The basis of this hypothesis being that men aim to select high fecundity as this increases reproductive success in both short term and long-term relationships. Evidence supporting this hypothesis arises from studies that show a greater likelihood of conception in women with lower WHRs, however, more recent studies find limited support for this relationship (Bovet, 2019).
The third major hypothesis appearing in 43% of papers, is that WHR is an indicator of age (Bovet, 2019). This hypothesis arising out of the similarities and differences in men and women’s WHR prior to puberty, after puberty and following menopause. Hence, it is suggested that WHR is a reliable indicator for men to identify the start of a woman’s reproductive period and subsequently, peak of fertility, which will increase a male’s reproductive success. However, studies in perceived age and WHR have been inconclusive.
Other less supported hypotheses include that WHR provides a cue of current pregnancy, pelvis size and ability to obtain resources (Bovet, 2019). Therefore, overall it is suggested that WHR provides a visual cue for mate value information that can aid in mate selection.
WHR as an attractive trait
The preference for a low WHR has found support from numerous studies. Singh (1993) found that when men observed line drawings of women with different WHRs, 0.7 was considered the most attractive, healthiest and most capable of having children. However, the methodology used has been criticised, as changes to the waist or hip width of the line drawing models, also altered the perceived body mass, thus it is difficult to determine if the attractiveness preferences were representative of WHR or BMI (Donohoe, von Hippel & Brooks, 2009). Although criticised, the preference for 0.7 has been supported by others. Examinations of Playboy magazine centrefolds and contestants from the Miss America contest found a WHR of 0.68 to 0.7 was favoured (Bovet & Raymond, 2015; Singh, 1993). Similarly, Bovet and Raymond (2015) examined the WHR of 216 artworks representing Greek or Roman women from 500 BCE to the present. It was found that a preference for a mean WHR of 0.74 was constant from 500 BCE to 400 CE, before the ideal WHR began to decrease from 1400CE, resulting in a preference of 0.68 contemporarily. Although, these findings may arise due to a limited number of artworks or from imitation in art styles.
However, this support for a low WHR as an attractive trait has largely been found in western societies, consequently, cross-cultural studies have been undertaken to determine the universality of the WHR and female attractiveness. A study undertaken with the Hadza of Tanzania, found that WHR was not a significant aspect for mate preference, rather weight was a more important factor in judging female quality. It is suggested that this preference is likely representative of the foraging lifestyle of the Hadza in which surplus food is rarely available, thus weight rather than WHR is a better predictor of fertility (Marlowe, Apicella, & Reed, 2005). Conversely, in the Amazonian Tsimané society, men preferred a low WHR, although they did not link WHR with age, health or fertility (Sorokowski et al, 2014). Thus, preferences in WHR attractiveness are not universal but vary between societies.
Conclusion
Therefore, a women’s WHR plays a significant role in male mate selection as it is suggested that it indicates high mate value. The exact adaptive value of WHR is contested, with numerous hypotheses proposed, with cues of good health, fecundity or reproductive age most widely supported. The preference for a low WHR, particularly around 0.7, has found support with numerous studies (Bovet & Raymond, 2015; Singh, 1993). Although, the universality of this claim has been tested and the attractiveness does vary between societies, in particular, the Hadza of Tanzania, do not consider WHR to be an attractive trait. Overall, it is evident that the adaptive nature, the preferences and evolutionary origin of WHR is a complex matter.
Literature Cited
Bovet, J. (2019). Evolutionary theories and men's preferences for women's waist-to-hip ratio: Which hypotheses remain? A systematic review. Frontiers in Psychology, 10, 1221-1221.
Bovet, J., & Raymond, M. (2015). Preferred women's waist-to-hip ratio variation over the last 2,500 years. PloS One, 10(4), e0123284-e0123284.
Donohoe, M. L., von Hippel, W., & Brooks, R. C. (2009). Beyond waist-hip ratio: Experimental multivariate evidence that average women's torsos are most attractive. Behavioral Ecology, 20(4), 716-721. doi:10.1093/beheco/arp051
Marlowe, F., Apicella, C., & Reed, D. (2005). Men's preferences for women's profile waist-to-hip ratio in two societies. Evolution and Human Behavior, 26(6), 458-468. doi:10.1016/j.evolhumbehav.2005.07.005.
Singh, D. (1993). Adaptive significance of female physical attractiveness: Role of waist-to-hip ratio. Journal of Personality and Social Psychology, 65(2), 293-307.
Sorokowski, P., Kościński, K., Sorokowska, A., & Huanca, T. (2014). Preference for women's body mass and waist-to-hip ratio in tsimane' men of the bolivian amazon: Biological and cultural determinants. PloS One, 9(8), e105468-e105468.