HUMAN FACIAL BEAUTY - AVERAGENESS, SYMMETRY, AND PARASITE RESISTANCE

It is hypothesized that human faces judged to be attractive by people possess two features-averageness and symmetry-that promoted adaptive m ate selection in human evolutionary history by way of production of of fspring with parasite resistance. Facial composites made by combining individual faces are judged to be attractive, and more attractive than the majority of individual faces. The composites possess both symmetr y and averageness of features. Facial averageness may reflect high ind ividual protein heterozygosity and thus an array of proteins to which parasites must adapt. Heterozygosity may be an important defense of lo ng-lived hosts against parasites when it occurs in portions of.the gen ome that do not code for the essential features of complex adaptations . In this case heterozygosity can create a hostile microenvironment fo r parasites without disrupting adaptation. Facial bilateral symmetry i s hypothesized to affect positive beauty judgments because symmetry is a certification of overall phenotypic quality and developmental healt h, which may be importantly influenced by parasites. Certain secondary sexual traits are influenced by testosterone, a hormone that reduces immunocompetence. Symmetry and size of the secondary sexual traits of the face (e.g., cheek bones) are expected to correlate positively and advertise immunocompetence honestly and therefore to affect positive b eauty judgments. Facial attractiveness is predicted to correlate with attractive, nonfacial secondary sexual traits; other predictions from the view that parasite-driven selection led to the evolution of psycho logical adaptations of human beauty perception are discussed. The view that human physical attractiveness and judgments about human physical attractiveness evolved in the context of parasite-driven selection le ads to the hypothesis that both adults and children have a species-typ ical adaptation to the problem of identifying and favoring healthy ind ividuals and avoiding parasite-susceptible individuals. It is proposed that this adaptation guides human decisions about nepotism and recipr ocity in relation to physical attractiveness.