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Facial asymmetry tracks genetic diversity among Gorilla subspecies

McGrath, Kate; Eriksen, Amandine B; Garcia-Martinez, Daniel; Galbany, Jordi; Gomez-Robles, Aida; Massey, Jason S; Fatica, Lawrence M; ... Heuze, Yann; + view all (2022) Facial asymmetry tracks genetic diversity among Gorilla subspecies. Proceedings of the Royal Society B: Biological Sciences , 289 (1969) , Article 20212564. 10.1098/rspb.2021.2564. Green open access

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Mountain gorillas are particularly inbred compared to other gorillas and even the most inbred human populations. As mountain gorilla skeletal material accumulated during the 1970s, researchers noted their pronounced facial asymmetry and hypothesized that it reflects a population-wide chewing side preference. However, asymmetry has also been linked to environmental and genetic stress in experimental models. Here, we examine facial asymmetry in 114 crania from three Gorilla subspecies using 3D geometric morphometrics. We measure fluctuating asymmetry (FA), defined as random deviations from perfect symmetry, and population-specific patterns of directional asymmetry (DA). Mountain gorillas, with a current population size of about 1000 individuals, have the highest degree of facial FA (explaining 17% of total facial shape variation), followed by Grauer gorillas (9%) and western lowland gorillas (6%), despite the latter experiencing the greatest ecological and dietary variability. DA, while significant in all three taxa, explains relatively less shape variation than FA does. Facial asymmetry correlates neither with tooth wear asymmetry nor increases with age in a mountain gorilla subsample, undermining the hypothesis that facial asymmetry is driven by chewing side preference. An examination of temporal trends shows that stress-induced developmental instability has increased over the last 100 years in these endangered apes.

Type: Article
Title: Facial asymmetry tracks genetic diversity among Gorilla subspecies
Location: England
Open access status: An open access version is available from UCL Discovery
DOI: 10.1098/rspb.2021.2564
Publisher version: https://doi.org/10.1098/rspb.2021.2564
Language: English
Additional information: © 2022 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited.
Keywords: Science & Technology, Life Sciences & Biomedicine, Biology, Ecology, Evolutionary Biology, Life Sciences & Biomedicine - Other Topics, Environmental Sciences & Ecology, asymmetry, great apes, geometric morphometrics, inbreeding, stress, VOLCANOS NATIONAL-PARK, VIRUNGA MOUNTAIN GORILLAS, FLUCTUATING ASYMMETRY, GEOMETRIC MORPHOMETRICS, BERINGEI-GRAUERI, POPULATION, PATTERNS, SYMMETRY, GROWTH, FRAGMENTATION
UCL classification: UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS
UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS > Dept of Anthropology
UCL > Provost and Vice Provost Offices > UCL SLASH
URI: https://discovery.ucl.ac.uk/id/eprint/10145514
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