Date of Graduation

5-2025

Document Type

Thesis

Degree Name

Master of Arts in Anthropology (MA)

Degree Level

Graduate

Department

Anthropology

Advisor/Mentor

Plavcan, Joseph M.

Committee Member

Delezene, Lucas K.

Second Committee Member

Villaseñor, Amelia

Keywords

Comparative Morphology; Evolution; Primatology; Sexual Dimorphism

Abstract

Since Darwin, the evolution of sexual dimorphism connects to different evolutionary mechanisms reflecting both natural selection and sexual selection. In primates, body size dimorphism has been attributed to multiple factors, including sexual selection, fecundity selection, ecological selection, and other factors. In contrast, canine tooth size dimorphism has been primarily associated with sexual selection in males with minor change in females, with other factors playing only a secondary role. This suggests that the degree to which body size dimorphism and canine size dimorphism covary, controlling for phylogeny, should reflect the strength of sexual selection. Conversely, the magnitude of divergence between the two dimorphism measures should indicate number of other factors that impact sexual size dimorphism. A key factor that is difficult to tease apart is how the measure of changes in either male or female canine tooth size or body size might impact the magnitude of sexual dimorphism. This study evaluates covariation in body mass dimorphism and canine height dimorphism, and the relative contribution of males and females to the evolution of sexual dimorphism. Tooth size and body mass data were gathered from the literature. The analysis includes PGLS-corrected linear regressions and independent contrasts, and linear parsimony reconstructions. The results of these analyses suggest that sexual selection through the mechanism of male competition is indeed the dominant factor underlying the evolution of both sexual size dimorphism and sexual canine dimorphism, but that other factors impact sexual size dimorphism disproportionately as compared to sexual canine dimorphism. Thus, the use of sexual size dimorphism as a proxy for sexual selection should be approached with caution.

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