Fluctuating asymmetry and preferences for sex-typical bodily characteristics

Abstract

Body size and shape seem to have been sexually selected in a variety of species, including humans, but little is known about what attractive bodies signal about underlying genotypic or phenotypic quality. A widely used indicator of phenotypic quality in evolutionary analyses is degree of symmetry (i.e., fluctuating asymmetry, FA) because it is a marker of developmental stability, which is defined as an organism's ability to develop toward an adaptive end-point despite perturbations during its ontogeny. Here we sought to establish whether attractive bodies signal low FA to observers, and, if so, which aspects of attractive bodies are most predictive of lower FA. We used a 3D optical body scanner to measure FA and to isolate size and shape characteristics in a sample of 77 individuals (40 males and 37 females). From the 3D body scan data, 360°videos were created that separated body shape from other aspects of visual appearance (e.g., skin color and facial features). These videos then were presented to 87 evaluators for attractiveness ratings. We found strong negative correlations between FA and bodily attractiveness in both sexes. Further, sextypical body size and shape characteristics were rated as attractive and correlated negatively with FA. Finally, geometric morphometric analysis of joint configurations revealed that sex-typical joint configurations were associated with both perceived attractiveness and lower FA for male but not for female bodies. In sum, body size and shape seem to show evidence of sexual selection and indicate important information about the phenotypic quality of individuals.3D morphometrics ͉ body shape ͉ developmental stability ͉ sexual dimorphism ͉ sexual selection I n humans, as in other species, sex differences in size and shape are attributed to divergent effects of morphology on the survival or reproductive success of each sex (1-10). For human females, smaller waist relative to hips (WHR), larger breasts, and longer legs relative to height have been attributed to fecundity selection and are perceived as attractive by males (8,11,12). In human males, greater height, larger size, and shorter legs relative to height are believed to have arisen through sexual selection by enhancing success in male-male rivalry (6, 7) and by being more attractive to females (6, 12). In addition, pronounced secondary sex characteristics may be preferred because they are signals of a pathogen-resistant genotype (13). However, recent theoretical models suggest that high-quality signalers may be more resistant, equally resistant, or less resistant to pathogens, depending on life history trade-offs between reproductive effort, survival, and fecundity (14, 15). For example, high-quality males that produce costly signals may compromise their future survival but nonetheless be more fit than their low-quality competitors.If sex-typicality of body size and shape are attractive to the opposite sex because they indicate phenotypic quality, then these conspicuous sex-specific signals are expected to correlate negativ...

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Cross-cultural effects of color, but not morphological masculinity, on perceived attractiveness of men's faces

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Three-Dimensional Facial Asymmetry in Attractive and Normal People from Childhood to Young Adulthood

“…Facial asymmetry is better appreciated using a three-dimensional approach that allows a direct measurement of the two facial halves [6,7,13,14], because the visual, qualitative assessment is often insufficient. For instance, skeletal asymmetries of less than 3% are not clinically discernible [5,15].…”

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