This entry was written by Emily Bender as part of a project done in BIAN 2133 ‘Human Reproductive Strategies’ at The Australian National University in 2019 Semester 2
Introduction
The Waist to hip ratio (WHR) is the ratio of the waist to hip measurement and in females has evolved to be a sign of fertility that males look for when selecting a potential mate. Certain waist to hip ratios are viewed as more attractive, because they signal greater fecundity to males, therefore it makes more sense for men to mate with women with that WHR. The evolutionary reason for the preferences for certain WHR as well as the association between it and fertility will be examined. Additionally, cultural differences in WHR preferences will also be discussed, and also how it interacts with other measurements of fertility.
Main Text
Why WHR is a signal of fertility
The WHR is regarded as a signal of fertility because it indicates higher levels of estrogen and other female hormones which is a factor of fertility. This is because in women with polycystic ovary syndrome, which have higher levels of androgens have a higher WHR, indicating that they are not as fertile (Singh, 1993). It has also been found that girls with a lower WHR have higher levels of early pubertal hormone activity. Additionally women with a lower WHR get pregnant more easily, compared to women with a higher WHR (Singh, 1993). This shows why males consider women with a relatively low WHR as more attractive, because they are more fertile. However, a preference for a higher WHR may be because it indicates that an individual is healthy. This is because a higher WHR, more specifically the distinct fat distribution associated with it has been linked with a lower risk of insulin resistance, type II diabetes and certain types of cancer (Singh, 1993). It has also been shown that lesbians rate a low WHR as more attractive, which makes sense as a low WHR indicates a potential mate is healthier (Singh and Singh, 2011). This shows that males and females’ attractiveness to low WHR evolved because women with it are generally more fertile and are also healthier, so would make ideal mates.
Cultural differences
In terms of WHR preferences there are cultural differences. In western societies studies have shown that a WHR of 0.7 is rated as optimal for attractiveness and for highest fertility (Singh, 1993). However, this WHR preference is not standard. For example, in Japan WHR is not valued as a measure of attractiveness and therefore fertility but body mass index is. Studies have shown that Japanese participants favour individuals with a low BMI which is believed to be due to sociocultural reasons (Swami et al., 2006). Another study that looked at the WHR preferences of the Hadza hunter gathers found that there was no preference for WHR but there was a strong preference for heavy or high BMI females (Wetsman and Marlowe, 1999). This shows that WHR is not a signal of fertility in all societies which is due to a variety of cultural and environmental reasons. High BMI may be used as an indication of fertility in some societies because food shortages may have occurred in the past, meaning that those who had stored excess calories as extra fat were preferred because they were more likely to survive and reproduce (Wetsman and Marlowe, 1999). Further studies such as Swami and Tovée (2005) have also indicated that BMI is a used measure of attractiveness and therefore fertility rather than WHR. The study also found that in both Britain and Malaysia BMI accounted for 75% of variance in levels of attractiveness not WHR (Swami and Tovée, 2005). This shows that the link between WHR and fertility may not be a strong as first thought, as it is found that females who are amenorrhoeic have a similar WHR to those that fertile (Swami and Tovée, 2005).Interestingly it was found that BMI preferences were not universal in one culture, with individuals from high socioeconomic areas preferring low BMIs whilst those from rural areas preferring higher BMIs (Swami and Tovée, 2005). This shows how WHR preferences differ from culture to culture. It also in some cultures how BMI instead signals fertility and that BMI and WHR preferences vary within cultures.
Effect of exposure to different cultures
However, individual preferences in BMI and WHR can be changed, when one is exposed to another culture. An example of this is comparing the BMI preferences of South African Zulus to Zulus that had emigrated to the UK and Britons who were of African descent . It was found that British born individuals of African descent had BMI and WHR preferences very closely aligned to that of British individuals of Caucasian descent (Tovée et al., 2006). On the other hand, South African Zulus displayed the opposite preference, instead of favouring a low WHR and low BMI, they favoured a higher WHR and a higher BMI. The UK Zulu group favoured a BMI and WHR between the two extremes showing that preferences do change (Tovée et al., 2006). This change may be due to different environments particularly the difference in amount of disease and availability of food. The change may also be caused by social interactions and exposure to western media, which espouses thin, low WHR female bodies as the most attractive (Tovée et al., 2006). This shows how WHR and BMI preferences can change with exposure to different cultures and how they change.
Conclusion
WHR is a signal of fertility because it indicates higher levels of female hormones necessary to successfully produce offspring. Additionally, preferences for a low WHR may have arisen because it correlates with lower risks for certain cancers and other diseases. This means that females with a lower WHR are more likely to survive and be able to care of offspring. Preferences for a low WHR are not universal however, with notable exceptions amongst the Hadza who favour a high BMI not a particular WHR. This is believed to be due to environmental and sociocultural differences. BMI and WHR preferences of individuals can also change when an individual is exposed to a different culture. This is due to a variety of cultural factors.
Literature Cited
Singh, D. (1993). Adaptive significance of female physical attractiveness: role of waist-to-hip ratio. J Pers Soc Psychol 65, 293–307.
Singh, D., and Singh, D. (2011). Shape and Significance of Feminine Beauty: An Evolutionary Perspective. Sex Roles 64, 723–731.
Swami, V., and Tovée, M.J. (2005). Female physical attractiveness in Britain and Malaysia: A cross-cultural study. Body Image 2, 115–128.
Swami, V., Caprario, C., Tovée, M.J., and Furnham, A. (2006). Female physical attractiveness in Britain and Japan: a cross-cultural study. Eur. J. Pers. 20, 69–81.
Tovée, M., Swami, V., Furnham, A., and Mangalparsad, R. (2006). Changing perceptions of attractiveness as observers are exposed to a different culture☆. Evolution and Human Behavior 27, 443–456.
Wetsman, A., and Marlowe, F. (1999). How Universal Are Preferences for Female Waist-to-Hip Ratios? Evidence from the Hadza of Tanzania. Evolution and Human Behavior 20, 219–228.