Doctoral Dissertation Improvement: Universality and biological mechanisms of subsistence-driven masticatory reduction

University Of California-Davis, Davis CA

Investigators

Abstract

The emergence of agriculture as the predominant means by which people obtain food resources is one of the most significant economic shifts in human evolutionary history, and its biological consequences are a frequent subject in evolutionary anthropology. The history of this subsistence transition is complex, with agriculture emerging by independent invention in some parts of the world, and by the spread of cultures and/or people in others. As a result, studies that test whether the biological consequences of agriculture are better explained by unique local ecologies and histories, or instead by factors common to agricultural subsistence, wherever adopted, are of particular interest. This study by doctoral student David Katz (University of California, Davis), under the supervision of Dr. Timothy Weaver, provides a global analysis of human skull shape in order to test two hypotheses regarding the extent of agriculture's common consequences. First, the investigators test the claim that because the diets of early farmers were universally softer and more heavily processed than those of their hunter-gatherer predecessors, the shift from hunting and gathering to agriculture produced common shape changes - mostly related to reductions in size - in the chewing architecture of early agriculturalists. Second, by studying shape changes in the mandible during growth and development, the investigators test whether differences in skull shape between hunter-gatherers and agriculturalists are more likely due to natural selection or skeletal plasticity - bone's ability, particularly during development, to change shape in response to the demands of lifetime behaviors. The results of the study will directly inform public understanding of the biological consequences of the agricultural transition, and also shed light on the much longer-term relationship between technology, diet, and anatomy over the course of human evolutionary history. In addition, data from this study will be freely available on the internet for use as an educational resource.