Doctoral Dissertation Research: Biomechanics of Digitigrade Hand Postures in Primate Quadrupedal Locomotion

树栖性是灵长类起源和随后的辐射理论的核心组成部分，大多数现存的灵长类物种确实花了大部分时间在树上。然而，一些现存的灵长类动物主要是陆生动物，化石证据表明，陆生动物在过去可能更常见，可能在几个谱系中独立进化。事实上，有人提出，一些最早的猴子和猿类，更不用说我们人类的祖先，至少部分是陆生的。然而，尽管许多研究已经确定了与树栖习性相关的灵长类动物的行为和形态特化，但对与陆生习性相关的特征的功能形态学知之甚少。四足运动时数字化的手部姿势，虽然被认为是陆地习惯的标志，但却是其中一个鲜为人知的特征。因此，本研究的目的是通过借鉴其他哺乳动物远端不同姿势的生物力学理论，来研究灵长类动物不同手部姿势的生物力学。具体而言，本研究将量化两种密切相关的旧大陆猴子物种在四足运动期间与数字化和palmigrade手部姿势相关的运动力学。本文将介绍两方面的研究：1)实验分析灵长类动物在陆地和模拟树木上的四足运动，以定量描述和比较不同的手部姿势；2)利用计算机模拟有限元分析（FEA）探讨不同手部姿势对掌骨应变的运动学和动力学关系。这种分析将更好地理解数字化手势在功能背景下的适应价值，这些结果反过来可以应用于推导解剖学测量，以便更好地解释化石材料。因此，这一分析的结果将提高我们对形式：功能关系的认识，并有助于理解灵长类动物运动进化的过程，包括我们自己的物种。此外，对灵长类动物数字化肢体的生物力学分析可能会为理解为什么数字化肢体在脊椎动物中进化了很多次提供新的见解。这项工作的广泛影响源于多个科学学科的研究整合，包括人类学、功能形态学和生物工程。Co-PI将接受充分的训练，使用复杂的技术，包括三维运动和力板分析，骨应变和有限元分析，以解决未来作为独立研究人员与动物运动相关的各种问题。石溪大学将鼓励本科生和其他研究生参与这项研究，学习实验技术，并利用本提案获得的动物受试者探索他们自己的研究问题。所有有限元模型都将公开，以促进合作研究，并为模型的独立测试提供机会。这项研究预计将引起广泛的科学界的兴趣，包括人类学、古生物学、生物力学、骨生物学、生物医学工程、兽医学和运动医学的研究人员。

Arboreality is a central component in theories regarding the origin and subsequent radiation of the Primate Order, and most extant primate species do spend the majority of their time in the trees. However, a few living species of primates are primarily terrestrial, and fossil evidence suggests that terrestriality may have been more common in the past, possibly evolving independently in several lineages. Indeed, it has been suggested that some of the earliest monkeys and apes, not to mention the ancestors of our own species, were at least partly terrestrial. However, while many studies have identified behavioral and morphological specializations of primates associated with arboreal habits, relatively little is known about the functional morphology of features related to terrestriality. Digitigrade hand posture during quadrupedal locomotion, although considered a hallmark of terrestrial habits, is one such feature about which little is known. The goal of the present study, therefore, is to examine the biomechanics of different hand postures in primates by drawing upon biomechanical theory proposed for different postures observed in the distal extremities in other mammals. Specifically, this study will quantify the locomotor mechanics associated with digitigrade versus palmigrade hand postures in two closely related Old World monkey species during quadrupedal locomotion. Two lines of investigation will be presented: 1) experimental analysis of primate quadrupedal locomotion on both terrestrial and simulated arboreal substrates to quantitatively describe and compare different hand postures; and 2) an exploration of the association between the kinematics and kinetics of different hand postures on metacarpal bone strain using computer simulated finite element analysis (FEA). This analysis will provide a better understanding of the adaptive value of digitigrade hand postures in a functional context, and these results can in turn be applied to derive anatomical measures to be better able to interpret fossil material. Thus the results of this analysis will improve our knowledge of form:function relationships, and aid in the understanding of the course of primate locomotor evolution, including that of our own species. In addition, resolution of the biomechanics of digitigrady in primates may offer new insight into why digitigrady has evolved numerous times in vertebrates.The broader impacts of this work stem from the integration of research in multiple scientific disciplines including anthropology, functional morphology, and bioengineering. The Co-PI will be sufficiently trained using sophisticated techniques including three-dimensional motion and force plate analysis, bone strain, and finite element analysis to address a variety of questions related to animal locomotion in the future as an independent researcher. Undergraduate and other graduate students at Stony Brook University will be encouraged to participate in this research to learn experimental techniques as well as to explore their own research questions with the animal subjects acquired with this proposal. All finite element models will be made publicly available to promote collaborative research and to provide the opportunity for independent tests of the models. This research is expected to be of interest to a wide scientific community including researchers in anthropology, paleontology, biomechanics, bone biology, biomedical engineering, veterinary science, and sports medicine.