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

现代人类的牙齿较小，下颚结构较轻，咀嚼肌肉较弱，这些解剖学特征是与饮食摄入和食物加工相关的进化过程形成的。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，我们的祖先进化出了大而强壮的牙齿、巨大的下颚和有力的咀嚼肌肉。对这种变化的进化论解释包括关于饮食的自然选择如何在人类进化过程中推动适应的相互竞争的假设。这些假设表明，非常坚硬或非常坚硬的食物的存在与否可能是影响我们祖先进化的关键因素。另外，食物的硬度或韧性可能不如用颌和牙齿处理各种形状和大小的食物时的行为（即咬、刺、压、扭、磨）重要。该项目将为区分这些选择性情景提供证据，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。这项研究将需要关注灵长类动物模型，南美卷尾猴，它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。该研究将野外卷尾猴进食行为的观察与实验室实验、使用工程方法的先进计算机建模、食物和其他物品对牙齿造成的微观损伤（即牙齿微磨损）的检查、野外食物资源的材料特性（即硬度、韧性）的测定以及粘附在这些食物上的研磨颗粒（可能影响微磨损模式）的收集和分析结合起来。总的来说，这些卷尾猴的数据将使我们能够评估我们对饮食行为、食物资源和人类祖先生物学之间相互关系的解释的假设，从而改变我们对人类进化史的理解。这项研究的广泛影响是相当大的。就公众对科学的理解而言，该研究提供的信息将涉及公众感兴趣的话题；也就是我们自己的进化史。作为一个相关的好处，该项目说明了影响其他动物的生态因素对我们自己的物种可能同样相关和影响。在STEM培训方面，为高中生、本科生、研究生和博士后提供研究培训机会，其中许多人（根据合作机构的过去历史）有望成为年轻的女性科学家。该项目还通过收集与雨林保护有关的基本生态数据，提高人们的环保意识。在此过程中，它进一步发展了与国际同行和机构的合作关系。最后，该项目向工程界说明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.