Cranial shape changes with age in male and female adults of Papio
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Date
2021
Authors
Quintanilla, Andrea
Johnson, Jyhreh
Journal Title
Journal ISSN
Volume Title
Publisher
University of Oregon
Abstract
Ontogenetic changes to skull shape from juveniles to adults have been well researched and studied, but those that occur during adulthood are less well known. In this study, we collected 45 3D landmarks with a Microscribe 3DX digitizer of 345 wild-collected baboon (Genus Papio) crania representing all six currently recognized subspecies. As a proxy for age, we visually scored maxillary third molars for degree of wear. Landmarks were superimposed with generalized Procrustes analysis using MorphoJ. Procrustes coordinates were regressed against natural log-transformed upper third molar wear stage using multivariate tests for significance. We used Landmark editor to warp a surface scan to show the shape changes correlated with increased molar wear. Results demonstrated a significant effect of molar wear stage on cranial shape, even after accounting for size, but it is a subtle effect that accounts for approximately 4.5% of shape variance. As the skull ages, the face seems to get longer while the orbitals and zygomatics shift posteriorly. The sexes do not differ in the pattern of shape changes and their regression slopes are parallel, meaning that the sexes do not age differently in their cranial shapes. The degree these shape changes are a consequence of genetics or bone remodeling due to strain experienced during life is unclear. Nonetheless, if this pattern is consistent across papionins, then it may help better to diagnose fossil taxa represented by small samples where it is unclear if differences are taxonomic or due to age.
Description
1 page.
Keywords
Primatology, Ontogeny, Geometric Morphometrics, Morphology and Biomechanics, Growth and Development