Functional Anatomy of the Knee and Development-Implications for Interpreting Early Hominin Locomotion

该项目支持一名墨西哥裔美国博士后的培训和教育，这是科学界，尤其是古人类学界代表性不足的少数群体。作为美国第一代大学毕业生，该研究员个人致力于扩大弱势群体在STEM领域的参与。该研究项目探索人类的两足行走。用两条腿走路是人类血统的一个决定性特征，然而关于人类步态的起源和进化的主要问题仍然存在。两足动物在人类谱系中进化得很早，可能早在600万年前；然而，关于最早的古人类的行走方式是否与现代人基本相同，或者不同的古人类物种在步态生物力学上是否存在差异，主要的争论一直存在。最近发现的一具异常完整的200万年前南方古猿sediba骨骼，激发了人们对人类下肢发育和功能的新探索。特别是最近对Au的解释。南方古猿的不同种类在两足行走方式上是如何变化的，Sediba的发现再次引发了争论。直接测试这些假设的唯一方法依赖于检查骨骼在生长过程中对生物力学需求敏感的方面，从而提供生长过程中步态的生物力学证据。然而，目前对步态生物力学如何影响下肢发育知之甚少。这个项目结合了实验、个体发生和比较的方法来解释和重建早期的人类两足动物。首先，在小鼠实验模型中研究了运动模式（垂直攀爬、踏板抓取树冠攀爬和轮跑）对下肢形态的影响，研究了股骨和胫骨的骨骼可塑性。在这个项目中，研究员通过华盛顿大学的少数民族学生组织（如Bouchet Society）招募少数民族学生作为助理研究员进行培训。这位研究员继续通过针对对科学感兴趣的低收入和少数民族学生的外展项目向孩子们展示她的研究。这依赖于以前实施适合年龄的活动的经验，在研究生院试点。其他提高公众对科学理解的努力包括通过史密森学会的国家自然历史博物馆的外展项目（例如，科学家在，人类起源今天（HOT）主题）吸引广泛的观众，这些项目是基于她在论文的最后一年最初为NC自然科学博物馆开发的演示文稿。该研究员继续活跃于科学领域的研究生女性，支持STEM领域的其他女科学家，并为这些女性协调外展和志愿者机会。智力上的优点：这个计划推进了我们对现代直立双足步态是如何以及何时进化的理解。目前的范式认为所有早期人类的祖先和亲属本质上是相同的，而事实上，在人类进化的早期阶段可能存在相当大的适应性多样性。因此，该项目有可能改变古人类学目前的范式，并整合实验、发展和比较数据，以实现对人类膝关节解剖功能意义的更严格理解。实验部分为解释一项全面的灵长类个体发生比较研究的结果提供了背景，该研究考察了发育轨迹是否与整个发育过程中的行为变化相关，并解决了偏离哺乳动物和灵长类动物的一般骨骺融合模式是否与特化运动相关。最后，我们将早期直立人和其他早期人类物种的下肢化石纳入研究，根据上述实验和个体发生的结果，检验和提出关于发育形态的功能意义的假设。

This project supports the training and education of a Mexican American Postdoctoral Fellow, an under-represented minority in science and especially paleoanthropology. As a Chicana and first generation college graduate, the Fellow is personally committed to broadening participation of under-represented individuals in STEM fields. The research project explores bipedalism in humans. Walking on two legs is a defining feature of the human lineage, and yet major questions remain about the origin and evolution of human gait. Bipedalism evolved early in the human lineage, possibly as early as six million years ago; however, major debate has persisted over whether the earliest hominins walked essentially like modern humans do today, or whether various hominin species differ in their gait biomechanics. The recent discovery of an unusually complete, 2 million year old skeleton belonging to Australopithecus sediba has inspired new inquiry into the development and function of the hominin lower limb. In particular, recent interpretations of Au. sediba have refueled the debate as to how different species of australopiths may have varied in their form of bipedalism. The only way to directly test those hypotheses relies on examining aspects of the skeleton are sensitive to biomechanical demands during growth, and thus provide evidence of the biomechanics of gait during growth. However, little is currently known about how gait biomechanics influences the development of the lower limb. This project combines experimental, ontogenetic, and comparative approaches to interpret and reconstruct early hominin bipedalism. First, the effect of locomotor regimes (vertical climbing, pedal grasping canopy climbing, and wheel-running) on lower limb morphology are studied in a mouse experimental model, addressing skeletal plasticity of the femur and tibia. In running this project, the Fellow recruits minority students to be trained as assistant researchers through minority student organizations at GWU such as the Bouchet Society. The Fellow continues to present her research to children through outreach programs targeting low-income and minority students interested in science. This relies on previous experiences implementing age-appropriate activities, piloted during graduate school. Other efforts to improve public understanding of science include engaging broad audiences through the Smithsonian Institution's National Museum of Natural History's outreach programs (e.g., Scientist Is In, Human Origins Today (HOT) Topics), based on presentations originally developed for the NC Museum of Natural Sciences during the final year of her dissertation. The Fellow continues to be active in Graduate Women in Science, supporting other female scientists across STEM fields as well as coordinating outreach and volunteer opportunities for these women.Intellectual Merit: The proposed project advances our understanding of how and when our modern style of upright, bipedal gait evolved. The current paradigm views all early human ancestors and relatives as essentially the same, when in fact there may be considerable adaptive diversity in the early phase of human evolution. This project therefore has the potential to transform the current paradigm in paleoanthropology, and integrates experimental, developmental, and comparative data to achieve a more rigorous understanding of the functional significance of knee anatomy in humans. The experimental component provides the context for interpreting the results of a comprehensive ontogenetic primate comparative study, which examines whether developmental trajectories are correlated with behavioral changes throughout development, and addresses whether deviations from the general mammalian and primate pattern of epiphyseal fusion are correlated with specialized locomotion. Finally, lower limb fossils belonging to early Homo erectus and other early hominin species are included to test and advance hypotheses about the functional significance of developing morphology in light of the aforementioned experimental and ontogenetic results.