According to a recent study published in the journal PLoS ONE, researchers better understand why symmetry and sexual dimorphism are key variables that determine how attractive a face is.
Faces are important in transmitting social information among humans, and attractiveness is a quickly noted quality. Researchers have wondered why it is that these traits are attractive and what the link is between symmetry and sexual dimorphism – how masculine or feminine a face seems.
Researchers have postulated that symmetry and sexual dimorphism advertise genetic quality. That is, they are indicators of qualities such as fertility. Others believe that the preference for these traits is strictly a visual phenomenon, not a biological or reproductive one. To evaluate the idea of a face’s having the potential to advertise the quality of a mate, researchers looked at interrelationships between these two measures of quality.
Anthony Little (University of Stirling) and colleagues measured symmetry and sexual dimorphism in the faces of humans (both Europeans and African hunter-gatherers) and in a non-human primate (the macaque). The researchers found a relationship between the two measures in each group. Males and females with symmetric faces, in all samples, also had masculine and feminine facial proportions, respectively.
The authors write: “Our results indicate that symmetry and sexually dimorphic traits are related in male and female faces in humans, in a modern western society and in a different society living under conditions better approximating human evolutionary history, and across species, both in humans and a non-human primate. We found symmetry was related to sexual dimorphism using physical measurements of large numbers of faces and perceptual tests based on the perceived sexual dimorphism of faces that were most and least symmetric in our samples.”
According to the authors, the findings provide support for the idea that both sexual dimorphism and symmetry in faces advertise quality, and there must be some biological mechanism that links the two traits during development. They posit that having the symmetric and sexually dimorphic trains may be a characteristic of individuals who tend to be resistant to disease.
“Our finding of sex specific co-variation with symmetry, femininity for females, masculinity for males, indicates then that both sexual dimorphism and symmetry likely are signals advertising quality. We have shown such a relationship in diverse human cultures and in a monkey species, which suggests that signaling properties of faces are universal across human populations and that facial advertisements of quality may have arisen relatively early in the phylogeny of primates,” conclude the authors.
Symmetry Is Related to Sexual Dimorphism in Faces: Data Across Culture and Species
Little AC, Jones BC, Waitt C, Tiddeman BP, Feinberg DR, et al.
PLoS ONE (2008). 3(5): e2106.
doi:10.1371/journal.pone.0002106
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About PLoS ONE
PLoS ONE is the first journal of primary research from all areas of science to employ both pre- and post-publication peer review to maximize the impact of every report it publishes. PLoS ONE is published by the Public Library of Science (PLoS), the Open-access publisher whose goal is to make the world’s scientific and medical literature a public resource.
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Written by: Peter M Crosta