Ontogeny of Heel-Strike in Hominoids

这个项目将研究步行和足部解剖学的一个特殊特征，这可能为人类两足行走(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使用一种独特的脚步撞击模式，在行走时，他们首先用脚后跟触地，然后再用脚的其余部分(脚后跟触地)。然而，影响一种特殊的脚姿进化和我们独特的(人类)足迹模式首次出现的因素仍然知之甚少。目前尚不清楚脚跟撞击在人类和非洲猿类中有多相似，在一个人的一生中是如何发展的，以及不同的鞋跟撞击模式如何在足部骨骼的解剖中反映出来。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类人猿和人类脚跟撞击的原因，并探索古人足骨化石如何告诉我们在古人类进化过程中的行走模式。该项目将支持一名职业早期的女科学家，并为研究生和本科生提供大量研究机会，重点是女性和少数族裔学生。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用于化石记录，还可以用于人类足部发育和损伤的研究。该项目的目标是量化非洲古人类个体发育过程中脚跟撞击的功能形态模式。这项研究将通过实验、比较和个体发生的方法，量化使用脚跟撞击的现存灵长类动物的踏板力学和解剖学的变异范围，并询问：(1)在所有发生鞋跟撞击的环境中，脚跟撞击的机制是相同的吗？(2)身体大小、行为、年龄和后肢动力学如何影响脚跟撞击机制？(3)脚跟撞击在跟骨外部和内部解剖中是否可以被检测到？为了验证后肢力学对脚后跟撞击的影响的假说，我们分析了幼年和成年黑猩猩以及大猩猩行走的非侵入性视频的运动学数据。为了研究足底翻转和相关的地面反作用力在运动发育过程中如何变化，用安装在测力平台顶部的压力垫记录了脚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。核磁共振成像(MRI)和医用计算机断层扫描(CT)被用来模拟非洲猿足跟垫在没有跟骨外侧足底突的情况下如何减弱冲击力。将这些数据与圈养的和野生的现存猿和人的跟骨小梁结构的显微CT数据进行比较，然后将其应用于跟骨早期化石人(阿法尔人和源人)。这个综合性的项目具有变革性，因为它研究了整个功能链：整个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)，现存猿类的内部和外部跟骨结构，以及对化石足骨功能形态的解释。全面了解现存类人猿的脚后跟撞击变异及其在化石人类中的进化，是更广泛地理解类人猿脚后跟撞击进化的必要的第一步。

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.