Ontogeny of Heel-Strike in Hominoids

该项目将研究行走和足部解剖学的一个特殊特征，这可能为人类两足动物（直立行走）的进化提供新的见解。人类和我们现存的近亲，非洲类人猿，在走路时使用一种独特的脚后跟着地模式，在脚的其余部分（脚后跟着地）之前，他们先用脚跟着地。然而，影响特殊足部姿势进化的因素和我们独特的（人类）足部模式的首次出现仍然知之甚少。人类和非洲猿类的脚跟撞击在多大程度上是相似的，它在个体一生中是如何发展的，以及不同的脚跟撞击模式如何反映在足骨的解剖结构中，这些都是未知的。这项研究追踪了非洲猿类足部姿势的发展，并提供了一个独特的机会来理解非洲猿类和人类脚跟撞击的原因，并探索古人类足部骨骼化石如何告诉我们古人类进化过程中的行走模式。该项目将支持一名早期职业女性科学家，并为研究生和本科生提供大量研究机会，特别关注女性和少数民族学生。在项目结束时，所有视频和图像数据将提供给其他科学家和教育工作者，并用于促进公共动物设施和保护区的研究和教育目标。关于脚跟撞击的信息不仅可以应用于化石记录，还可以应用于人类足部发育和损伤的研究。这个项目的目的是量化的模式脚跟打击功能形态在整个个体发育的非洲人科动物。该研究将通过实验、比较和个体发生的方法，量化使用脚跟撞击的活体灵长类动物的踏板力学和解剖学变化范围，并提出以下问题：(1)脚跟撞击的力学是否在所有情况下都是相同的？(2)体型、行为、年龄和后肢动力学如何影响跟击力学？(3)跟外和跟内解剖能否检测到跟击？为了验证关于后肢力学对足跟撞击的影响的假设，研究人员分析了婴儿和成年黑猩猩和大猩猩行走的非侵入性录像数据。为了研究在运动发展过程中足部倒立和与之相关的地面反作用力是如何变化的，我们使用安装在力平台顶部的压力垫来记录足部产生的压力中心和地面反作用力。这些数据与之前收集的野生黑猩猩的视频数据进行了比较。磁共振成像（MRI）和医学计算机断层扫描（CT）用于模拟非洲猿脚后跟垫在没有跟外侧足底突的情况下如何衰减冲击力。这些数据与圈养和野生现存类人猿和人类的跟骨小梁结构的微ct数据进行比较，然后应用于早期古人类跟骨化石（南方古猿阿法种和南方古猿sediba）。这个综合项目具有变革性，因为它研究了整个功能链：个体发育过程中的运动行为和步态力学（运动学、动力学和足底压力），现存类人猿的内部和外部跟骨结构，以及化石足骨功能形态的解释。全面了解类人猿的跟向变化及其在古人类化石中的进化，是更广泛地了解类人猿跟向进化的重要的第一步。

This project will study a particular feature of walking and foot anatomy that may provide new insight about the evolution of bipedalism (walking upright) in humans. Humans and our closest living relatives, the African great apes, use a unique foot strike pattern in which they strike the ground with the heel first, before the rest of the foot (heel strike) when walking. Yet the factors influencing the evolution of a specialized foot posture and the first appearance of our unique (human) footfall patterns are still poorly understood. It is unknown to what degree heel strike is similar across humans and African apes, how it develops throughout an individual's lifetime, and how different patterns of heel strike are reflected in the anatomy of foot bones. This study tracks the development of foot posture in African apes and provides a unique opportunity to understand why African apes and humans heel strike, and to explore how fossil hominin foot bones might tell us about walking patterns during hominin evolution. This project will support an early career female scientist and provide numerous research opportunities for graduate and undergraduate students, with a specific focus on female and minority students. At the end of the project, all video and image data will be made available to other scientists and educators, and used to promote the research and education goals of public zoological facilities and sanctuaries. Information on heel strike can be applied not only to the fossil record but also to studies of foot development and injuries in humans.The objective of this project is to quantify patterns of heel strike functional morphology throughout ontogeny in African hominoids. The study will quantify the range of variation in pedal mechanics and anatomy among living primates who use a heel strike through an experimental, comparative, ontogenetic approach, and ask: (1) are the mechanics of heel strike the same in all contexts in which it occurs?, (2) how do body size, behavior, age, and hind limb dynamics influence heel strike mechanics?, and (3) can heel strike be detected in external and internal calcaneal anatomy? To test hypotheses regarding the effect of hind limb mechanics on heel strike, kinematic data are analyzed from non-invasive video recordings of infant and adult chimpanzees and gorillas walking. To investigate how foot inversion and associated ground reaction forces that load the calcaneus change during locomotor development, the center of pressure and ground reaction forces incurred by the foot are recorded with a pressure mat mounted on top of a force platform. These data are compared with previously collected video data of wild chimpanzees. Magnetic resonance imaging (MRI) and medical computed tomography (CT) are used to model how the African ape heel pad attenuates impact forces in the absence of a calcaneal lateral plantar process. These data are compared with microCT data of calcaneal trabecular architecture in captive and wild extant apes and humans and then applied to early fossil hominin calcanei (A. afarensis, and A. sediba). This integrative project is transformative because it investigates an entire functional chain: locomotor behavior and gait mechanics (kinematics, kinetics, and plantar pressure) throughout ontogeny, internal and external calcaneal structure in extant apes, and interpretation of fossil foot bone functional morphology. A comprehensive understanding of heel strike variation in living apes and its evolution in fossil hominins is an essential first step toward a broader understanding of the evolution of heel strike in hominoids.