Doctoral Dissertation Research: The Biomechanics of Vertical Clinging and Grasping in Primates

博士生劳拉约翰逊（杜克大学），在丹尼尔施密特博士的监督下，将研究一组特定的灵长类动物姿势的生物力学-那些采取垂直抓住树干。这项研究的重点是与灵长类进化起源有关的一个关键的适应性转变，即复杂的树木环境的“入侵”。早期的灵长类进化出用指甲抓手和脚，而不是像其他树居物种那样保持爪子（例如，松鼠）。这种失去爪子的进化事件给生物力学提出了一个关键的悖论，即理解树栖灵长类动物如何在没有爪子的情况下保持对大型垂直树干的有效抓持。 这个问题的调查地址形态适应树栖生态位在生活和祖先的灵长类动物。灵长类动物在树上的栖息地无法利用爪子，它们必须通过使用最小化肌肉工作的姿势来抓住树木。先前对哺乳动物生物力学的研究表明，在三种情况下，涉及不同的肌肉骨骼解剖结构，基板尺寸和体重的假设变化。为了检查这些变量，在实验室环境中观察来自杜克狐猴中心的八种灵长类动物物种的样本，这些物种在解剖结构和体重上不同。个体被提示垂直依附和抓住四个增加的尺寸的基板，相对于他们的体重。地松鼠（Scurius caroliniensis）是一种有爪的非灵长类哺乳动物外类群。视频数据的收集使用八摄像头系统，以文件的姿态在三维空间中，和数据上的单肢加载模式收集利用力板插入到substrate.Results从这项研究将揭示的进化压力，导致灵长类动物失去爪子有利于指甲，适应可能与灵长类动物的身体尺寸增加，是一个必要的前兆，人类的手抓。该项目还包括本科生培训和向其他研究人员和公众（包括当地K-12学校）广泛传播数据，并将在动物园设计和灵长类动物保护中找到应用。

Doctoral student Laura Johnson (Duke University), under the supervision of Dr. Daniel Schmitt, will investigate the biomechanics of a specific set of primate postures - those adopted while vertically clinging to tree trunks. The research focuses on a key adaptive shift associated with the evolutionary origins of primates, that of the 'invasion' of the complex arboreal environment. Early primates evolved grasping hands and feet with nails, rather than keeping claws, such as found in other tree-dwelling species (e.g., squirrels). This evolutionary event of loss of claws raises a critical paradox for biomechanists, that of understanding how arboreal primates maintain an effective grip on large, vertical tree trunks without claws. The investigation of this question addresses morphological adaptation to an arboreal niche in both living and ancestral primates. Not being able to take advantage of claws in the arboreal habitat, primates must hold onto the trees by using postures that will minimize muscular work. Prior research on mammalian biomechanics suggests hypothesized variation within three contexts involving differing musculoskeletal anatomies, substrate sizes, and body weights. To examine these variables, a sample of eight primate species from the Duke Lemur Center which differ in anatomies and body weights are observed in a laboratory setting. Individuals are prompted to vertically cling and grasp to substrates of four increasing sizes, relative to their body weight. The ground squirrel, Scurius caroliniensis, is included as a clawed non-primate mammalian outgroup. Video data are collected using an eight-camera system to document postures in three dimensions, and data on single-limb loading patterns are collected utilizing force plates inserted into the substrate.Results from this study will shed light on the evolutionary pressures that led primates to lose claws in favor of nails, an adaptation that may be related to primate body size increase, and is a necessary precursor to human hand grasping. The project also incorporates undergraduate training and broad dissemination of data to other researchers and the public, including local K-12 schools, and will find application in zoo design and primate conservation.