Doctoral Dissertation Research: Molar Topographic Shape as a System for Inferring Paleoecology and Developmental Patterning in Ceropithecoid Evolution

Primates use their molar teeth to break down food as a first step to its digestion and the acquisition of its nutrients. As might be expected, molar shapes are observed to be tightly linked to the types of foods a species consumes. Additionally, it has been found that the shapes of molar teeth are produced in embryo by an elegant patterning mechanism whereby first molar development has a cascade effect over later-developing teeth. Because teeth are durable and dominate most fossil assemblages, molars are an excellent model system by which to elucidate the biology of extinct animals. This project, conducted by doctoral student Julia Winchester (SUNY Stony Brook University) under the guidance of Dr. Frederick Grine, examines molar shape in living and extinct old world monkeys in order to better understand their evolutionary dietary adaptations, and the embryological developmental patterning of these species. Old world monkeys exhibit what is referred to as a bilophodont form of molar cusp organization, and questions persist regarding the type of dietary items that might provided the selective force for the evolution of bilophodonty. Is it an adaptation to diets that consisted largely of leaves or durable nuts, seeds, and/or fruits? In addition, very little is known regarding early dental development, even of living old world monkeys. This research will use technologies such as X-ray microtomography to create virtual models of molars of living and fossil primates, and cutting-edge analytical techniques from computer science will quantify whole tooth molar shape. For living species with known diets, comparative datasets will be built and used to infer dietary evolutionary transitions in extinct species. Relative shape and form across intra-individual molar teeth in species will be compared with experimental studies of rodents in order to make the first conclusions regarding dental developmental patterning in monkeys. Through these methods, the use of molar teeth as a key to unlock questions regarding dietary adaptations and embryological development in living and fossil primates will be developed, supporting understanding of the ways in which embryological dental development may be related to adaptive function, and how evolutionary adaptation is constrained by available developmental mechanisms. In its broader impacts, this project will (1) broaden participation of under-represented groups by training a graduate woman in science, (2) enhance the infrastructure for research via free software development and participation in open, online-accessible databases of dental shape data, and (3) support scientific dissemination through public outreach to enhance scientific understanding.