Collaborative Research: Integrative analysis of ingestive biomechanics and dental microwear in evolutionary and ecological context

现代人牙齿小，下巴轻盈，咀嚼肌肉无力--这些解剖特征是由与饮食摄入和食物加工相关的进化过程塑造的。化石记录表明，我们的形态与我们的祖先形成了鲜明的对比，我们的祖先进化成了有又大又强壮的牙齿、巨大的下巴和强大的咀嚼肌肉。对这种变化的进化论解释包括关于饮食上的自然选择如何在人类进化过程中驱动适应的相互竞争的假设。这些假说表明，是否存在非常硬或非常硬的食物可能是影响我们祖先进化的关键因素。或者，食物的硬度或韧性可能没有用下巴和牙齿加工各种形状和大小的食物的行为(即咬、刺、压、扭、磨)那么重要。该项目将提供证据来区分这些选择性情景，从而有助于更全面地理解形成现代人体解剖学这一重要方面的进化过程。这项研究将需要专注于灵长类动物模型南美卷尾猴，它们在肌肉骨骼解剖和饮食方面表现出相关的多样性，这是检验关于食物特性(即硬度、韧性)或摄食行为如何影响摄食适应进化的假设所必需的。这项研究将观察卷尾猴在野外的觅食行为与实验室实验、使用工程方法的高级计算机建模、检查食物和其他物品对牙齿造成的微观损害(即牙齿微磨损)、测定野外食物资源的材料特性(即硬度、韧性)以及收集和分析附着在这些食物上的研磨颗粒(可能影响微磨损模式)结合在一起。总的来说，卷尾猴的这些数据将使我们能够评估我们对人类祖先的饮食行为、食物资源和生物学之间相互关系的解释所依据的假设，从而改变我们对人类进化史的理解。这项研究的更广泛的影响是相当大的。关于公众对科学的理解，这项研究提供的信息将解决一个公众非常感兴趣的话题，即我们自己的进化史。作为一个相关的好处，该项目展示了影响其他动物的生态因素如何对我们自己的物种同样相关和产生影响。在STEM培训方面，为高中生、本科生、研究生和博士后研究员提供了研究培训机会，其中许多人(根据合作机构过去的历史)预计将是年轻的女科学家。该项目还通过收集与雨林保护有关的基本生态数据来提高环境意识。在这样做的过程中，它进一步发展了与国际同行和机构的合作关系。最后，该项目向工程界展示了如何使用他们的方法来回答进化问题。

Modern humans exhibit small teeth, lightly built jaws and weak chewing muscles - anatomical features which have been shaped by evolutionary processes related to dietary intake and the processing of foods. The fossil record demonstrates that our morphology stands in contrast to that of our ancestors, who evolved to have large, strong teeth, massive jaws and powerful chewing muscles. Evolutionary explanations for this change include competing hypotheses as to how natural selection on diet drove adaptation over the course of human evolution. These hypotheses suggest that the presence or absence of either very hard or very tough foods may have been a critical factor influencing the evolution of our ancestors. Alternatively, the hardness or toughness of foods may have been less important than the behaviors (i.e., biting, puncturing, crushing, twisting, grinding) used to process foods of various shape and size with the jaws and teeth. This project will provide evidence to differentiate between these selective scenarios, thereby contributing to a fuller understanding of the evolutionary processes that have shaped this important aspect of modern human anatomy.This research will require focus on a primate model, South American capuchins, which exhibit the relevant diversity in musculoskeletal anatomy and diet requisite to testing hypotheses regarding how food properties (i.e., hardness, toughness) or feeding behaviors influence the evolution of feeding adaptations. The study integrates observations of capuchin feeding behavior in the wild with laboratory experiments, advanced computer modeling using engineering methods, examination of the microscopic damage done to teeth by food and other items (i.e., dental microwear), the determination of the material properties (i.e., hardness, toughness) of food resources in the wild, and the collection and analysis of abrasive particles adhering to those foods (that might be influencing microwear patterns). Collectively, these data in capuchins will allow us to evaluate the assumptions underlying our interpretations of the interrelationships between dietary behavior, food resources, and the biology of our human ancestors, thereby transforming our understanding of human evolutionary history.The broader impacts of this research are considerable. In relation to the public understanding of science, the research provides information that will address a topic of great public interest; namely, our own evolutionary history. As a related benefit, the project illustrates how ecological factors affecting other animals may be equally relevant and impactful for our own species. In terms of STEM training, research training opportunities are provided for high school students, undergraduates, graduate students, and postdoctoral fellows, many of whom are expected (based on past history at the collaborating institutions) to be young female scientists. The project also contributes to environmental awareness by collecting basic ecological data relevant to rainforest conservation. In the process of doing so, it further develops collaborative ties with international counterparts and institutions. Lastly, the project illustrates to the engineering community how their methods can be used to answer evolutionary questions.