Symmetry

Studies have shown that facial symmetry is one of the best observational indicators of good genes and healthy development, and that these traits are what we mean when we say someone is attractive⁴. Preference for symmetric faces is an evolutionary adaptation to identify high-quality mates. More symmetric males tend to have more sexual partners. Since symmetry signals superior genes, female preference for a more symmetric male face is heightened at the periods of peak fertility during the menstrual cycle⁴.

Averageness

In the late 1870s, Sir Francis Galton, who was a cousin of Charles Darwin, conceived the idea to develop an image of the prototypical ‘face of crime’ by creating composite photos of men convicted of serious offenses. Galton overlaid multiple images of faces onto a single photographic plate so that each individual face contributed roughly equally to a final composite face. To his surprise, the composite image was more attractive than the component faces. Averageness theory, developed by Langlois and Roggman⁵, claims that evolutionary pressures and natural selection generally favour average rather than extreme population features. Therefore, people who look different from the norm are generally regarded as less attractive.

Scientists believe that average faces are easier for the brain to recognise, since they are prototypic, and thus acknowledged. When a collection of computer-averaged faces and real female faces were submitted to a famous modelling agency for comments, 80% of the computer‑generated faces were selected as having potential to be a model. The rationale behind this is that by blending together a number of faces, unpleasant asymmetries and defects are also blended and become less pronounced⁵.

Sexual dimorphism

Dimorphism comes from two Greek words, ‘di’ meaning two and ‘morph’ meaning form, and refers to systematic differences in form between individuals of different sexes in the same species. Examples of sexual dimorphism in nature include larger male animal size, and differences in colouration and presence, versus absence of certain body parts such as horns or display feathers.

In humans, signs of femininity include evenly toned skin, full lips, narrow eyebrows, full hair, high cheek bones, and narrow nose⁶. In addition, child-like facial features increase the female’s attractiveness. Evolutionary biologists argue that men prefer younger-looking women as mating partners since they have a long period of fertility ahead of them.

Characteristics of male attractiveness include ‘tanned’ and evenly-toned skin, prominent supraorbital ridges (frontal bossing), flatter eyebrows, slightly narrower eyes, slightly thinner lips (especially upper lip), and square and prominent lower jaw and chin^7, 8. During puberty, the lower part of the face develops differently in males under the influence of testosterone. Men who develop broader chins are perceived as more dominant, as they have probably had higher levels of the male hormone. Women seem to choose sexual partners on the basis of a male’s ability to protect and provide for his partner and their offspring. Dominance is associated with higher resource-providing potential; therefore, women are more attracted to dominant males. Those with broad chins do better in military hierarchy, they are more successful socially, and have greater reproductive success.