Research has highlighted symmetry and sexual dimorphism -- how masculine/feminine a face appears -- as important variables that determine a face's attractiveness.

Anthony Little of the University of Stirling in Scotland and colleagues show that measurements of symmetry and sexual dimorphism from faces are related in humans, both in Europeans and African hunter-gatherers and in a non-human primate.

In all samples, symmetric males had more masculine facial proportions and symmetric females had more feminine facial proportions.

The study, published in the journal Plos One, supports 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.

Individuals resistant to disease may be able to grow both symmetric and sexually dimorphic, Little said.