For a long time evolution scientists thought manly physiognomy to be the main attraction. But a slender body is even more enticing than an alpha-male face, according to a study co-authored by Indrikis Krams, a visiting professor at the University of Tartu.
Manly features indicate a high level of testosterone – the male sex hormone. This hormone debilitates the immune system, which is why macho men have to be really strong to compensate for its detrimental effects. Thus, just by looking at potential partners’ features, women could understand which had the best health.
Incidentally, the uber-male appearance doesn’t woo women as much as might be expected. Also, it hasn’t been proven that the most masculine looking men always have good health. The body’s fat content indicates bodily constitution much better than the features. Both overweight and underweight persons have a greater likelihood of health problems.
Women, too, may evaluate a potential partner’s immune system based on his weight, not the features. This hypothesis was tested by Krams with researchers from Daugavpils, Turku and Pretoria universities respectively in Latvia, Finland and South Africa.
The scientists hired 69 Caucasian men and took pictures of them in their underwear. Then they measured their testosterone levels and fat content. 65 per cent of the men were at a normal weight, 4 per cent underweight and the rest overweight. To test the strength of their immune systems, the men were vaccinated for Hepatitis B. Following the injection, the men with stronger immune systems had a larger number of antibodies against the hepatitis virus in their system.
The next step involved female students from Daugavpils University viewing photographs of the men’s faces and bodies. All the students were heterosexual, used no hormonal contraceptives and were in the fertile period of their menstrual cycles.
Also, a smaller group of Latvian women evaluated fat content based on photographs of the men’s faces and a group consisting of Finnish male and female students rated the volunteers’ manliness.
The results showed that the fat content of male faces was related to both the immune response and attractiveness. Pudgier men had weaker immune systems and fertile women liked them less.
A statistical analysis found no strong relations between a manly face and strong immune system or bodily attractiveness. Testosterone levels were more bound to body weight than manly features as well. Hence, a man’s body weight is a better indicator of his good health and physical attractiveness than masculine physiognomy.
Rantala, M., Coetzee, V., Moore, F., Skrinda, I., Kecko, S., Krama, T., Kivleniece, I., & Krams, I. (2012). Adiposity, compared with masculinity, serves as a more valid cue to immunocompetence in human mate choice Proceedings of the Royal Society B: Biological Sciences, 280 (1751), 20122495-20122495 DOI: 10.1098/rspb.2012.2495
Professor Indrikis Krams:
Masculinity is still a very important parameter, since it is one of the strongest sex-related signals. Our new study shows that masculinity is not enough, and that women value physical fitness and health over a masculine appearance. On the other hand, women also value resources, and this is often about within-sex competition: In a brutal world a more masculine (appearance, behaviour) man has more resources to share with his woman. This is why preferences for masculinity change across countries and cultures according to societal development index. Our resent results (resubmitted, Biology Letters) show that women prefer masculine men in poorly developed countries, while they avoid such men in highly developed countries – but this is another story!
It is important to note that women’s preferences for less masculine men might mean another challenge for men: Masculine men with high testosterone levels easily avoid adiposity problems because testosterone makes us more active and decreases appetite. So, if ladies avoid the “testosterone” type of men, sexual selection may favour “non-testosterone” men which are prone to increased adiposity. While “testosterone” men may have larger resources, they are also less faithful and more aggressive, or even dangerous to women (Domestic violence kills one Russian woman every hour). The main problem for fat men is their poor health, but this can be compensated by better medical services in highly developed countries. Perhaps the skin colour and other similar second-rate parameters (if adiposity level or masculinity are the first-rate ones) may become important when women have to choose among less aggressive, more faithful, but still not the best males…? However, it seems to be a great challenge for men to avoid adiposity and adiposity-related problems in highly developed countries, where access to food is not an everyday problem – where the main problem is how to avoid food! 🙂