Doctoral Dissertation: Exploring Bison-Based Human Subsistence on the Northern Great Plains: Dental Enamel Hypoplasia, Bison Paleoecology, and the Archaeological Record

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Under the direction of Dr. David Meltzer, Ryan Byerly will investigate dental enamel hypoplasia (DEH) formation in Northern Great Plains bison from archaeological sites dating between 11,500 and 100 year ago. DEH is a deformity in tooth enamel that may reflect the seasonal condition of prehistoric bison. Understanding this would have been critical to hunters to maximize fat return. Fat is necessary in human to better digest muscle protein. Without sufficient fat rabbit starvation (eating too much lean meat) can occur. Archaeological evidence indicates that in the last 5,000 years Plains hunter-gatherers avoided rabbit starvation by hunting bison during their fattest months and intensively breaking bones for marrow to store for winter. However, it is apparent that the earliest Paleoindian bison hunters did not do this, but rather hunted episodically throughout the year and rarely broke bones for marrow. Did Paleoindians have different nutritional requirements than their descendents, or supplement their diets with nutrients other than marrow fat? Were early bison simply in better condition throughout the year than their descendants? Resolving these questions is difficult because archaeologists rely on knowledge of modern bison ecology to understand bison paleoecology. This reliance is problematic because bison have evolved significantly over the past 11,000 years in response to changing Great Plains environments. Thus, a reliable indicator of prehistoric bison health is needed to develop a stronger paleoecological record and thus also better account for the hunting and butchery behaviors of Plains hunter-gatherers. This research will evaluate DEH as such an indicator. Although it is unknown what specifically causes DEH formation in bison, it is hypothesized that seasonal diet, birthing and weaning stress, and disease are probable causes. To better understand the causes of DEH, and further appraise it as an indicator of seasonal health, this research will analyze DEH timing and explore the contribution of seasonal dietary stress to its formation through intra-tooth carbon and oxygen isotopic analysis. Since bison enamel forms at a predictable rate, measuring the location of observed DEH on tooth surfaces can provide a timeline of stress. Comparing these timelines in bison populations over the past 11,000 may help illuminate differences in birthing and weaning schedules or disease episodes. Likewise, carbon and oxygen isotope analysis of tooth enamel increments provides a rough timeline of the condition of forage and water consumed. The contribution of changing seasonal diets to DEH formation will therefore also be assessed. If successful, these data will provide critical information about prehistoric bison health and ecology that is beneficial not only to archaeologists, but also to modern bison managers and Great Plains conservation efforts. This research will serve to enhance conservation education by stressing the importance of archaeological and paleoecological work to understanding the history of bison on the Great Plains, their role as a keystone species, and ensuring their future survival.