Doctoral Dissertation Improvement: Causes of Sexual Size Dimorphism in Primates

University Of Texas At Austin, Austin TX

Investigators

Abstract

The purpose of this study is to investigate the causes of sexual size dimorphism (SSD) in primates. SSD is the presence of differences in mean overall body size between males and females. These differences are meaningful because they are often related to social structures and group compositions present in primates, and thus are useful in deducing the ways in which extinct primate species organized themselves. It is important to understand the strength of the correlation between SSD and these other factors when drawing inferences about extinct populations. The proposed study differs from earlier work in which analyses across species of SSD indices and categorical data (e.g., mating system, dietary type, substrate type) were compared to theoretical predictions. Instead, a quantitative model is used to generate predictions for populations of continuous data. Predictions are based on initial conditions that correspond to mechanisms that can potentially produce SSD - mechanisms that predict high correlation between SSD and certain social structures, and other mechanisms that do not. Data from primate populations will be compared to model predictions using analyses that take into account degree of relatedness between species to determine which mechanisms produce SSD in those primates. This study has multiple areas of significance. First, it tests the validity of an alternative technique for determining body size of skeletal specimens. Second, it introduces a new technique for testing the influence of particular forces on SSD in primates. Third, it will identify the forces that affect SSD within particular primate groups, as well as across the Order Primates. Finally, reconstructed values of ancestral size and distribution parameters can be compared with values of known fossils, furthering understanding of the relationships between fossil primates, ancestral primates, and living primates.