Doctoral Dissertation Improvement Grant: The Relationship Between Limb Shape and Locomotor Mechanics and Energetics

在对身体结构进化变化的分析中，一个潜在的假设是，修改的潜在优势是减少了执行特定任务所需的能量。对于体质人类学的研究人员来说，关于运动成本的激烈争论只在人类两足动物进化的研究中被考虑过。在灵长类动物更普遍的运动形式--四足行走的起源中，能量学的重要性几乎被忽视了。这项研究将考察能量学在灵长类四足动物进化中的作用。由于许多人认为四足动物是最早的灵长类动物喜欢的运动的一个方面，而且已经证明灵长类动物四足动物的运动形式在运动学和运动学上都与非灵长类哺乳动物不同，理解能量学在灵长类四足动物进化中的作用将为理解灵长类起源过程中的选择压力提供新的见解。与其他哺乳动物相比，灵长类动物的肌肉更靠近手脚，这是因为它们的四肢具有抓取力。从理论上讲，这种肢体形状应该会导致肌肉和肌腱在运动过程中消耗更多能量，从而增加运动能量成本。令人惊讶的是，研究人员发现，无论肢体形状如何，身体大小相同的动物都有相同的能量消耗。尽管文献中有很多争论，但这些结果还没有得到解释。这项研究提出，与体重相近的动物相比，四肢附近肌肉质量比例较大的动物会改变步态，以保持类似的能量消耗。肢体形状与运动的力学和能量学之间的关系将在一个纵向样本的婴儿狒狒(Papio Cynocephalus)中检验。由于婴儿的肢体形状随着年龄的增长而变化，这项研究将能够探索步态变化如何抵消远端分布的肢体质量的能量成本，从而允许动物在运动过程中做类似数量的肌肉工作。这项研究的结果将提供一个新的观点，即竞争的选择压力，如抓住四肢和减少运动成本，可能如何导致灵长类步态的某些独特方面。除了有助于我们理解灵长类运动进化，该项目还将通过在本科教育中发挥积极作用来服务于社会。两名本科生助理将接受形态测量和运动学数据收集和分析等技术方面的培训。此外，中科院还将在这项研究的基础上，为P.I.S的本科生灵长类解剖学课程开发一个运动学实验室。这个实验室将包括基于计算机的运动研究方法和数据分析教学。通过让本科生参与这个项目，以及将这个项目与课堂相结合，这项拟议中的研究将促进对用于回答灵长类进化问题的最新技术的更好理解。最后，这项研究将促进德克萨斯大学奥斯汀分校各学院之间的跨学科关系。

In the analysis of evolutionary changes in body structure, an underlying presumption is that a potential advantage of a modification is reduction in the amount of energy required to perform a particular task. For researchers in physical anthropology, energetic arguments regarding the costs of locomotion have only been considered in the study of the evolution of human bipedalism. The importance of energetics in the origins of the more generalized form of primate locomotion, quadrupedalism, has all but been ignored. This study will examine the role of energetics in the evolution of primate quadrupedalism.Since many regard quadrupedalism to have been an aspect of the locomotion favored by the earliest primates, and since it has been demonstrated that the form of quadrupedal locomotion displayed by primates differs both kinematically and kinetically from that of non-primate mammals, understanding the role energetics plays in primate quadrupedalism should provide new insights into the selection pressures acting during primate origins. Primates have muscles distributed closer to their hands and feet than other mammals due to their grasping extremities. This limb shape should theoretically cause muscles and tendons to use more energy during locomotion, thereby increasing locomotor energetic costs. Surprisingly, researchers have found that regardless of limb shape, animals of the same body size have the same energetic costs. Though there has been much debate in the literature, these results are as yet unexplained. This study proposes that animals with a greater proportion of muscle mass near their extremities will alter their gait in order to maintain similar energetic costs compared to animals of similar body mass. The relationship between limb shape and the mechanics and energetics of locomotion will be examined in a longitudinal sample of infant baboons (Papio cynocephalus). Because infants' limb shapes change with age, this study will be able explore how gait changes may offset the energetic costs of distally distributed limb mass allowing animals to do similar amounts of muscular work during locomotion. Results of this study will provide a new view of how competing selection pressures, such as grasping extremities and reduced locomotor costs, may have led to some unique aspects of primate gait.In addition to contributing to our understanding of primate locomotor evolution, this project will serve the community by taking an active role in undergraduate education. Two undergraduate assistants will be trained in techniques such as morphometric and kinematic data collection and analysis. Additionally, the CO-P.I. will be developing a kinematics laboratory based on this study for the P.I.'s undergraduate primate anatomy course. This lab will include computer-based instruction in locomotor research methodology and data analysis. By having undergraduate participation in this project, as well as integrating this project with the classroom, the proposed study promotes a greater understanding of the newest techniques used to answer questions about the evolution of primates. Finally, this study will foster inter-disciplinary relationships between colleges at The University of Texas at Austin.