“In humans, faces are an important source of social information. One property of faces that is rapidly noticed is attractiveness. Research has highlighted symmetry and sexual dimorphism (how masculine or feminine a face is) as important variables that determine a face’s attractiveness. […]
In all samples, symmetric males had more masculine facial proportions and symmetric females had more feminine facial proportions.
The findings therefore support the claim that sexual dimorphism and symmetry in faces are signals advertising quality by providing evidence that there must be a biological mechanism linking the two traits during development. For example, individuals resistant to disease may be able to grow both symmetric and sexually dimorphic.”