Abstract
The idea that symmetry in facial traits is associated with attractiveness because it reliably indicates good physiological health, particularly to potential sexual partners, has generated an extensive literature on the evolution of human mate choice. However, large-scale tests of this hypothesis using direct or longitudinal assessments of physiological health are lacking. Here, we investigate relationships between facial fluctuating asymmetry (FA) and detailed individual health histories in a sample (n = 4732) derived from a large longitudinal study (Avon Longitudinal Study of Parents and Children) in South West England. Facial FA was assessed using geometric morphometric analysis of facial landmark configurations derived from three-dimensional facial scans taken at 15 years of age. Facial FA was not associated with longitudinal measures of childhood health. However, there was a very small negative association between facial FA and IQ that remained significant after correcting for a positive allometric relationship between FA and face size. Overall, this study does not support the idea that facial symmetry acts as a reliable cue to physiological health. Consequently, if preferences for facial symmetry do represent an evolved adaptation, then they probably function not to provide marginal fitness benefits by choosing between relatively healthy individuals on the basis of small differences in FA, but rather evolved to motivate avoidance of markers of substantial developmental disturbance and significant pathology.
Highlights
Fluctuating asymmetry (FA; small random deviations from perfect symmetry in bilateral traits) has been proposed, and is commonly used, as an index of developmental stability: i.e. the ability of an organism to buffer against developmental stressors and perturbations [1,2]
All data were sourced from the Avon Longitudinal Study of Parents and Children (ALSPAC), an on-going cohort study initially involving over 14 000 British families with children born in 1991/ 1992 and with approximately 5500 children participating in data collection aged 15–16 [22]
We found no evidence of associations between facial FA and longitudinal health measures, which suggests that gross facial asymmetries may be associated with specific pathological processes and injuries, subtle variations in facial symmetry (i.e. FA) are not associated with variations in general health during childhood
Summary
Fluctuating asymmetry (FA; small random deviations from perfect symmetry in bilateral traits) has been proposed, and is commonly used, as an index of developmental stability: i.e. the ability of an organism to buffer against developmental stressors and perturbations [1,2]. The use of FA as an index of developmental stability has been popular in evolutionary models of human mate choice and evolutionary psychological studies of sexual preferences, providing a compelling functional explanation for consistent demonstrations that facial symmetry predicts attractiveness in both males and females [6]. This conceptual framework has generated a large literature on preferences for symmetry, and studies of FA in humans fall. While concentrating on faces alone is not the strongest test of the developmental instability hypothesis (single traits will have a noisy relationship with developmental instability [3]), the very large representative sample of young people in South West England [22] that we employ, coupled with the excellent longitudinal health history data and high-quality three-dimensional scans of the faces from this cohort go some way to ameliorate this concern and provide for a robust test of associations between health and facial FA
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