Doctoral Dissertation Improvement: Craniodental Form, Functional Convergence, and the Evolution of Dietary Preferences

Northwestern University, Evanston IL

Investigators

Abstract

Researchers have long sought to understand the environmental variables underlying behavioral and anatomical evolution in early primates. While disagreement persists over which factors were of greatest significance, diet is widely thought to have played an important role. Therefore, efforts to illuminate trends in early primate evolution will require the ability to reconstruct diet from fossils. To this end, investigators over the past two decades have attempted to identify features of the skull and dentition that can be used to achieve this. While these studies have identified many such features, significant gaps remain. First, to ensure that a structure and function are consistently linked in a specified manner, they must be evaluated in ecologically similar, yet distantly related groups. As few predictions have been tested in nonprimates, it is unclear whether patterns observed in these animals can confidently be extrapolated to their distant fossil relatives. Second, the study of jaw or dental form alone is not sufficient to discriminate among all diets. Since previous studies have considered these separately, the usefulness of evaluating both to fully characterize a species feeding habits remains largely unexplored. The goal of this research is to fill these gaps by using marsupials as a natural experiment to test the hypotheses that dental and mandibular form reflect a species' diet. Specifically, ten predictions relating tooth surface features and the internal and external proportions of the lower jaw (determined from x-ray film) to the physical properties of a species' diet will be evaluated. By testing these predictions in a group that extensively overlaps primates in most aspects of feeding ecology, this study will not only allow greater confidence in the utility of these variables for inferring diet in extinct primates, but it will also greatly expand our understanding of the ecological bases of evolution in mammals in general.