Doctoral Dissertation Improvement: Novel 3D analysis of hip joint mobility and the evolution of locomotor abilities in Miocene hominoids

博士候选人Ashley Hammond(密苏里大学哥伦比亚分校)在Carol Ward博士的指导下，将确定髋关节活动如何与活体类人猿(类人猿和猴子)的运动行为和解剖形式相关，以便重建具有进化关键意义的中新世时期(约2300万-500万年前)的类人猿的行为能力。树枝下悬吊行为将现代猿类与大多数猴子区分开来，而类猿运动行为的出现已成为重建类人猿进化过程的决定性问题。然而，众所周知，化石猿的行为能力很难推断，因为大多数化石猿显示出原始和现代解剖学的不同寻常的组合。悬吊行为被认为需要较高的髋关节活动度，这提供了一种基于关节功能来评估化石中悬吊能力的方法，但在仅从化石骨骼重建关节运动之前，必须表征软组织对活动范围的影响。这项研究通过测量大量活的(活体)类人猿和猴子的被动运动范围来检验这一假设，即悬挂式类人猿比非悬挂式类人猿具有更大的髋关节活动范围。然后，将从活体动物收集的测量结果与虚拟模型的运动范围进行统计比较，虚拟模型依赖骨骼解剖来限制关节运动。经过验证的关节运动模型随后被用来评估解剖变异对髋关节活动度的影响，并应用于所有可用的化石类人猿，以确定它们是否适应使用悬挂行为。这项研究建立了一种测试化石类人猿运动假说的方法，为人类起源的进化场景提供了关键数据。这里开发的形状分析技术将对所有脊椎动物形态学家有用，经过验证的虚拟模型将作为研究人员接近任何哺乳动物物种关节功能的比较模型。更广泛地说，这个项目将确定髋关节解剖形式的具体变化如何影响活动度，这可以整合到髋关节功能的临床模型中。该项目为包括少数民族在内的本科生提供培训机会，并支持由一名女科学家指导的一名女博士生的研究。

Research by doctoral candidate Ashley Hammond (University of Missouri-Columbia), under the supervision of Dr. Carol Ward, will identify how hip joint mobility relates to locomotor behavior and anatomical form in living anthropoids (apes and monkeys) in order to reconstruct behavioral capabilities in fossil apes from the evolutionarily critical Miocene time period (ca. 23-5 million years ago). Below-branch suspensory behaviors distinguish modern apes from most monkeys, and the emergence of great ape-like locomotor behaviors has become the defining issue in reconstructing how apes evolved. Behavioral capabilities are notoriously difficult to infer in fossil apes, however, because most fossil apes display unusual combinations of primitive and modern anatomies. Suspensory behaviors are hypothesized to require high hip joint mobility, providing a method for evaluating suspensory abilities in fossils based on joint function, but the influence of soft tissues on range of motion must be characterized prior to reconstructing joint movement from just fossil bones. This study tests the hypothesis that suspensory anthropoids have larger ranges of hip mobility than non-suspensory anthropoids by measuring passive range of motion on a large sample of living (in vivo) apes and monkeys. The measures collected from live animals are then statistically compared to range of motion estimates from virtual models that rely on bony anatomy to limit joint movement. The validated model of joint movement is then used to assess the influence of anatomical variation on hip joint mobility and applied to all available fossil apes in order to identify whether they were adapted for using suspensory behaviors. This study establishes a method to test locomotor hypotheses in fossil apes, providing critical data for evolutionary scenarios of human origins. The shape analysis techniques developed here will be useful for all vertebrate morphologists, and the validated virtual models will serve as a comparative model for researchers to approach joint function in any mammalian species. More broadly, this project will identify how specific variation in hip joint anatomical form affects mobility, which can be integrated into clinical models of hip function. This project provides training opportunities for undergraduate students, including minorities, and is supporting the research of a female doctoral student being mentored by a female scientist.