Determining the link between facial appearance and immunity in an African population

Abstract

Facial appearance is thought to indicate immunity in humans, but very few studies have tested this relationship directly. The aim of the work in chapter 2 was to test the relationship between direct measures of immunity, apparent facial health and attractiveness, and facial cues in African men. In chapter 2 we show that men with a stronger cytokine response are considered significantly more attractive and healthy. Men with more masculine, heavier facial features (i.e. muscular appearance) have a significantly higher cytokine response and appear significantly healthier and more attractive, while men with a yellower, lighter, “carotenoid” skin tone, have a marginally higher immune response and are also considered significantly healthier and attractive. In contrast, more symmetrical, skinnier looking men appeared more attractive and healthier, but did not have a stronger cytokine response. These findings shed new light on the “androgen-mediated” traits proposed by the immunecompetence handicap hypothesis (ICHH). Finally, we build on previous evidence to show that men’s facial features do indeed reveal aspects of immunity, even better than more traditional measures of health, such as body mass index (BMI). The major histocompatibility complex (MHC) is one of the best studied genetic mating systems which is referred to as the Human Leucocyte Antigen (HLA) in humans and is an indirect measure of immunity. The aim of the work in chapter 3 was to test the relationship between two HLA based mating preferences (preference for HLA heterozygosity and a preference for common HLA alleles), facial cues (e.g. masculinity, symmetry) and overall facial appearance (attractiveness and health) in African men. We show that an HLA-associated SNP (rs2524079 in the HLA-C region) which has been linked to lymphocyte count is positively associated with facial appearance in an African population. Our results also show that the relative contribution of different aspects of immunity might differ between different populations. While HLA heterozygosity has been positively associated with facial attractiveness in British and Australian men, specific common HLA-associated alleles seem to play a larger role in African men.