Collaborative Research: Integrative Investigation of the Evolution and Biomechanics of Mandibular Form in Hominids

合作研究：原始人类下颌形态的进化和生物力学的综合研究

• 批准号: 1515165
• 负责人: Andrea Taylor
• 金额: $ 7.74万
• 依托单位: Duke University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-01 至 2017-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1515165&HistoricalAwards=false
• 关键词: Collaborative; Research; Integrative; Investigation; Evolution

Among the fundamental questions about human origins is how our hominin ancestors lived. This study uses a multidisciplinary approach (paleontology, paleoecology, comparative anatomy, experimental biology) to ask questions about how extinct populations of hominins behaved on their natural landscapes. Specifically, the investigators will analyze lower jaws (mandibles), among the most commonly represented parts of the skeleton in the early human fossil record, of modern great apes and two early species of extinct hominins (Autralopithecus), to understand how the structure of the mandible is related to changes in feeding behavior and diet. The research will provide new data about how changes in diet and feeding behavior transformed our anatomy across time, permitting more robust explanations of the processes by which we became human. Broader impacts will include undergraduate, graduate and postdoctoral training in the latest analytical techniques for fossil analyses; outreach to primary and secondary school science teachers and students using hands-on experiences and web-based content designed to enhance teaching and learning about human origins; and the production of a unique collection 3D data for modern apes and rare fossil specimens that will be available to the scientific community.Mandibles are the most common element in the hominin fossil record after teeth; they are used to diagnose species, test phylogenetic hypotheses, and infer feeding behavior and diet. However, extensive theoretical and experimental work on extant primates has not clarified which aspects of variation in mandibular form are related to variation in the positions of the tooth row, jaw muscles and jaw joint, which are related to the mandible's resistance to internal forces, and how these relate to feeding behavior and diet. Furthermore, the classical consensus on the relationship between dentognathic morphology and diet in Plio-Pleistocene hominins - adaptation to processing mechanically resistant foods - has been challenged by recent inferences from dietary isotopes, occlusal microwear, and finite element modeling, which do not converge on a shared view of early hominin diets and feeding behavior. This lack of consensus is especially glaring in light of the rich fossil record of mandibles for the Australopithecus anamensis-A. afarensis lineage (4.2-3.0 Ma), which documents clear changes in dentognathic morphology and carbon-isotope signatures over time. The primary focus of the proposed research is an integrative investigation of how spatial and mechanical determinants of mandibular form track change in diet and feeding behavior in extant hominids (great apes and humans) and early Australopithecus. The research is organized under three specific aims: 1. Quantifying and comparing the location, magnitude and nature of external and internal morphological variation in mandibles of extant (Homo, Pongo, Pan, and Gorilla) and fossil (A. anamensis, A. afarensis) hominids via computed tomography and geometric morphometrics; 2. Testing specific hypotheses about the biomechanical significance of variation in hominid mandibular morphology via finite-element models; and 3. Evaluating the extent to which spatial positioning of masticatory system components (tooth row, jaw joint, and muscle attachment points) explain variation in mandibular morphology across extant hominids and early Australopithecus. The project will provide new data on the structural and functional determinants of early hominin mandibular morphology, to help identify the factors that drove these morphological changes and allow tests of adaptive hypotheses about the early evolution of the genus.

关于人类起源的基本问题之一是我们的古人类祖先如何生活。这项研究采用多学科方法（古生物学、古生态学、比较解剖学、实验生物学）来询问已灭绝的古人类群体在自然景观中的行为方式。具体来说，研究人员将分析现代类人猿和两种早期灭绝人科动物（南方古猿）的下颌骨，这是早期人类化石记录中最常见的骨骼部分之一，以了解下颌骨的结构与摄食行为和饮食变化之间的关系。这项研究将提供有关饮食和进食行为的变化如何随着时间的推移改变我们的解剖结构的新数据，从而为我们成为人类的过程提供更强有力的解释。更广泛的影响将包括本科生、研究生和博士后有关化石分析最新分析技术的培训；利用实践经验和旨在加强人类起源教学和学习的网络内容向中小学科学教师和学生进行宣传；并为现代猿类和稀有化石标本制作独特的 3D 数据集，供科学界使用。下颌骨是古人类化石记录中仅次于牙齿的最常见元素；它们用于诊断物种、测试系统发育假设以及推断摄食行为和饮食。然而，对现存灵长类动物的大量理论和实验工作尚未阐明下颌形态变化的哪些方面与牙列、颌肌肉和颌关节位置的变化有关，这些变化与下颌骨对内力的抵抗力有关，以及这些变化与摄食行为和饮食有何关系。此外，关于上更新世古人类齿颌形态与饮食之间关系（适应加工机械抗性食物）的经典共识受到了最近来自饮食同位素、咬合微磨损和有限元模型的推论的挑战，这些推论并未就早期古人类饮食和摄食行为达成共识。鉴于南方古猿-A 下颌骨的丰富化石记录，这种共识的缺乏尤其明显。阿法种谱系（4.2-3.0 Ma），记录了牙颌形态和碳同位素特征随时间的明显变化。拟议研究的主要重点是对下颌形状的空间和机械决定因素如何跟踪现存原始人类（类人猿和人类）和早期南方古猿的饮食和摄食行为的变化进行综合研究。 该研究分为三个具体目标： 1. 通过计算机断层扫描和几何形态测量学，量化和比较现存人类（智人、庞戈、潘和大猩猩）和化石（阿纳南古猿、阿法种）下颌骨的外部和内部形态变异的位置、幅度和性质； 2. 通过有限元模型测试有关原始下颌形态变异的生物力学意义的具体假设； 3. 评估咀嚼系统组成部分（牙列、颌关节和肌肉附着点）的空间定位在多大程度上解释了现存原始人类和早期南方古猿下颌形态的变化。该项目将提供有关早期人类下颌形态的结构和功能决定因素的新数据，以帮助识别驱动这些形态变化的因素，并允许测试有关该属早期进化的适应性假设。