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Article

Fluctuating Asymmetry and Sexual Dimorphism in Human Facial Morphology: A Multi-Variate Study

1
Evolutionary Ecology Group, Department of Biology, University of Antwerp, 2610 Antwerp, Belgium
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Department of Electrical Engineering, ESAT/PSI, KU Leuven, 3000 Leuven, Belgium
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Medical Imaging Research Center, UZ Leuven, 3000 Leuven, Belgium
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Department of Human Genetics, KU Leuven, 3000 Leuven, Belgium
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Department of Anthropology, Pennsylvania State University, University Park, PA 16801, USA
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Center for Craniofacial and Dental Genetics, Department of Oral and Craniofacial Sciences, University of Pittsburgh, Pittsburgh, PA 15261, USA
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Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261, USA
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Department of Biology, Indiana University Purdue University Indianapolis (IUPUI), Indianapolis, IN 46202, USA
*
Author to whom correspondence should be addressed.
Academic Editor: John H. Graham
Symmetry 2021, 13(2), 304; https://doi.org/10.3390/sym13020304
Received: 8 December 2020 / Revised: 2 February 2021 / Accepted: 8 February 2021 / Published: 10 February 2021
(1) Background: Fluctuating asymmetry is often used as an indicator of developmental instability, and is proposed as a signal of genetic quality. The display of prominent masculine phenotypic features, which are a direct result of high androgen levels, is also believed to be a sign of genetic quality, as these hormones may act as immunosuppressants. Fluctuating asymmetry and masculinity are therefore expected to covary. However, there is lack of strong evidence in the literature regarding this hypothesis. (2) Materials and methods: In this study, we examined a large dataset of high-density 3D facial scans of 1260 adults (630 males and 630 females). We mapped a high-density 3D facial mask onto the facial scans in order to obtain a high number of quasi-landmarks on the faces. Multi-dimensional measures of fluctuating asymmetry were extracted from the landmarks using Principal Component Analysis, and masculinity/femininity scores were obtained for each face using Partial Least Squares. The possible correlation between these two qualities was then examined using Pearson’s coefficient and Canonical Correlation Analysis. (3) Results: We found no correlation between fluctuating asymmetry and masculinity in men. However, a weak but significant correlation was found between average fluctuating asymmetry and masculinity in women, in which feminine faces had higher levels of fluctuating asymmetry on average. This correlation could possibly point to genetic quality as an underlying mechanism for both asymmetry and masculinity; however, it might also be driven by other fitness or life history traits, such as fertility. (4) Conclusions: Our results question the idea that fluctuating asymmetry and masculinity should be (more strongly) correlated in men, which is in line with the recent literature. Future studies should possibly focus more on the evolutionary relevance of the observed correlation in women. View Full-Text
Keywords: fluctuating asymmetry; 3D morphometrics; sexual dimorphism fluctuating asymmetry; 3D morphometrics; sexual dimorphism
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MDPI and ACS Style

Ekrami, O.; Claes, P.; Van Assche, E.; Shriver, M.D.; Weinberg, S.M.; Marazita, M.L.; Walsh, S.; Van Dongen, S. Fluctuating Asymmetry and Sexual Dimorphism in Human Facial Morphology: A Multi-Variate Study. Symmetry 2021, 13, 304. https://doi.org/10.3390/sym13020304

AMA Style

Ekrami O, Claes P, Van Assche E, Shriver MD, Weinberg SM, Marazita ML, Walsh S, Van Dongen S. Fluctuating Asymmetry and Sexual Dimorphism in Human Facial Morphology: A Multi-Variate Study. Symmetry. 2021; 13(2):304. https://doi.org/10.3390/sym13020304

Chicago/Turabian Style

Ekrami, Omid, Peter Claes, Ellen Van Assche, Mark D. Shriver, Seth M. Weinberg, Mary L. Marazita, Susan Walsh, and Stefan Van Dongen. 2021. "Fluctuating Asymmetry and Sexual Dimorphism in Human Facial Morphology: A Multi-Variate Study" Symmetry 13, no. 2: 304. https://doi.org/10.3390/sym13020304

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