Doctoral Dissertation Improvement: Challenging Assumptions of Dental Senescence Using a Primate Framework

牙齿的严重磨损会削弱牙齿的功能特征，导致牙列丧失有效分解食物的能力（即牙齿老化）。据推测，这种功能丧失会妨碍获得食物，从而导致健康状况、生殖成功率和生存能力下降。然而，牙齿如何以及在什么时候磨损达到衰老状态尚不清楚，牙齿衰老对个人健康、营养和行为的影响程度也不清楚。自然选择应该使牙齿在磨损的情况下仍能保持咬碎食物的能力，只有在严重磨损时才停止工作。个体可以通过行为机制来补偿牙齿损伤，也可以通过性别和/或社会地位等个体特征来缓冲磨损的影响。这项研究由科罗拉多大学的博士生James Millette在Michelle Sauther博士的指导下进行，将基于地理信息系统的牙齿形态地形分析与个体行为生态学、健康和营养数据结合起来，研究马达加斯加贝扎马哈法利特别保护区环尾狐猴（Lemur catta）磨损的牙齿形态、食物处理能力和行为之间的关系。这一人群由于食用罗望子水果而表现出不同程度的牙齿磨损和频繁的牙齿脱落。这项研究将：1)确定牙齿磨损的程度与健康和营养下降有关；2)评估行为机制是否可以缓冲个人对牙齿磨损的影响；3)检查个人特征（如等级和性别）是否会影响这种模式。这也将为改进牙齿地形分析的使用提供有价值的背景信息，以评估灵长类动物化石记录中磨损的牙齿功能及其与行为和营养的关系。这项研究的开展将通过加强国际研究合作、培训马达加斯加学生、向当地社区进行教育推广以及加强对濒危栖息地的保护来加以补充。

Extensive tooth wear may ablate functional features of the teeth, resulting in the end of the dentition's capacity to effectively break down food items (i.e., dental senescence). Such a loss of function is presumed to impede access to foods, resulting in reduced health status, reproductive success, and ability to survive. Nevertheless, how and at what point of wear teeth reach a senescent state is not yet well understood, nor is the extent to which dental senescence may affect individual health, nutrition and behavior. Natural selection should produce teeth which maintain the ability to fracture foods despite wear, and which only cease to function with severe wear. Individuals may compensate for dental impairment through behavioral mechanisms, or may be buffered against the impacts of wear by individual traits such as sex and/or social rank.This study, by doctoral student James Millette (University of Colorado), under supervision of Dr. Michelle Sauther, combines Geographic Information Systems-based dental topographic analysis of tooth form with individual behavioral-ecology, health and nutritional data to examine relationships between worn tooth morphology, food processing ability and behavior for ring-tailed lemurs (Lemur catta) of the Beza Mahafaly Special Reserve, Madagascar. This population demonstrates well-documented, varying levels of tooth wear and frequent tooth loss due to tamarind fruit consumption.The research will: 1) determine what level of dental wear is associated with reduced health and nutrition, 2) assess if behavioral mechanisms can buffer individuals against the effects of dental wear, and 3) examine whether individual traits such as rank and sex may impact such patterns. It also will provide valuable contextual information towards improved use of dental topographic analysis for assessing worn tooth functionality and its relation to behavior and nutrition within the primate fossil record. The conduct of the research will be complemented by enhancing international research collaborations, training of Malagasy students and educational outreach to local communities, and enhanced conservation of endangered habitats.