Doctoral Dissertation Research: Evolutionary biomechanics of the human hyolingual apparatus

人类舌头和舌骨在语言进化中的作用已被广泛研究。一些研究人员假设，我们独特的舌头和舌骨形态也使我们更容易窒息。本研究使用先进的成像技术和计算模型来测试人类舌舌形态对吞咽是否有益或有害。虽然本研究的重点是在进化背景下的吞咽功能，但本研究的发现也将促进我们对正常吞咽机制的理解，因此可能具有临床应用价值。本项目生成的计算模型软件将在完成后免费提供。该项目不仅为科学领域的女性提供指导研究，而且为研究生物力学的女性提供指导研究，这是一个女性代表性不足的领域。此外，该项目还将支持芝加哥大学的本科生研究和多样化学生群体的培训。人类的短脸、低舌、舌骨和喉头被认为是为了适应说话而不适应吞咽。最近的研究对这两种说法都提出了质疑，促使人们进一步探索其他假说，以解释人类独特的舌器的起源。这个项目测试了唇舌生物力学约束形态学的假设，特别是当脸变短时，低舌器是维持吞咽性能所必需的。x射线运动形态学重建（XROMM）、扩散碘基对比增强CT （diceCT）和肌电图（EMG）将用于在灵长类动物模型系统中获得骨、舌头和肌肉生物力学的高时空分辨率体内测量，包括舌肌长度、速度和活动。这些数据将用于验证对吞咽生物力学和性能的影响的计算模型，以及舌舌位置和颅面形态的变化。约束假设的证伪将为人类声道形态是语言表现自然选择的结果这一假设提供间接支持。该项目将为未来的研究提供信息，以了解现存和灭绝类群中舌舌器的功能需求如何影响周围结构的形态，例如下颌联合。

The human tongue and hyoid bone have been extensively studied for their role in the evolution of speech. Some researchers hypothesize that our unique tongue and hyoid morphology also makes us more prone to choking. This research uses advanced imaging techniques and computational modeling to test whether human hyolingual morphology is beneficial or detrimental for swallowing. While this research focuses on swallowing function in an evolutionary context, the findings of this research will also advance our understanding of normal swallowing mechanisms and therefore may have clinical applications. The software for the computational model generated by this project will be made freely available upon completion. This project provides mentored research not only to a woman in science but specifically one studying biomechanics, a field in which women are underrepresented. Furthermore, the project will support undergraduate research and training for a diverse group of students at the University of Chicago.The short faces and low tongue, hyoid, and larynx of humans have been argued to be adapted for speech and maladapted for swallowing. Recent studies cast doubt on both of these claims, prompting further exploration of alternative hypotheses to explain the origin of the uniquely human hyolingual apparatus. This project tests the hypothesis that hyolingual biomechanics constrain morphology, specifically that a low hyolingual apparatus is necessary to maintain swallowing performance as the face becomes shorter. X-ray Reconstruction of Moving Morphology (XROMM), diffusible iodine-based contrast-enhanced CT (diceCT), and electromyography (EMG) will be used to obtain high spatiotemporal resolution in vivo measurements of bone, tongue, and muscle biomechanics, including hyolingual muscle length, velocity, and activity in a primate model system. These data will then be used to validate a computational model of the impacts on swallowing biomechanics and performance of variation in hyolingual position, and craniofacial morphology. Falsification of the constraint hypothesis would provide indirect support for the hypothesis that the morphology of the human vocal tract is the result of natural selection for speech performance. This project will inform future research on how the functional requirements of the hyolingual apparatus may have influenced the morphology of surrounding structures, e.g., the mandibular symphysis, in both extant and extinct taxa.