Doctoral Dissertation Improvement: Structure, Performance and Evolution of the Primate Auditory System

听觉系统是哺乳动物中机械结构最复杂的感觉系统，由大量的骨骼、肌肉和其他软组织组成。因此，这个区域为研究不同动物群体之间的声学功能和结构差异提供了许多机会，也被用来帮助推断它们彼此之间的关系。尽管对其他哺乳动物群体（如啮齿动物）的听觉系统功能进行了大量的研究，但灵长类动物在这方面只得到了有限的关注，尽管不同灵长类动物群体内部和之间的听觉结构有很大的差异。为了帮助理解灵长类动物听觉多样性的功能和进化意义，本论文将测量十种灵长类动物和一种树鼩的一组功能相关的听觉结构。将被检查的结构包括鼓膜、中耳骨和腔以及耳蜗，并将使用最先进的技术进行分析，包括微型计算机断层扫描、印象成型、数字成像和测量。除了检查现存标本的大量比较数据集外，还将评估来自非洲的3000万年前的灵长类动物化石标本。最后，将确定体重约3.5公斤的体型相对较大的原猿（灵长类的一种“原始”种群）的听觉灵敏度。最后一步是必要的，因为只有18种灵长类动物的听力灵敏度数据可用，其中只有4种是原猴，这4种动物的体重都在2公斤或以下。这些数据将用于测试有关耳朵结构和功能的假设，并将有助于研究灵长类动物和其他密切相关群体的听力进化。反过来，这种类型的基础数据可以应用于进一步测试和推广更广泛的想法，利用声学理论对其他哺乳动物群体进行比较分析。这条研究路线可能最终被用于研究人类听力的进化及其与人类交流的独特方面的关系。该项目的一个更广泛的影响涉及到它整合了多个科学学科，将来自不同领域的研究人员、研究人员和教育工作者聚集在一起，如功能形态学、古生物学、行为生态学、解剖学、地质学和声学。这将有助于促进杜克灵长类动物研究中心、杜克医学中心听力研究实验室和德克萨斯大学奥斯汀分校计算机断层扫描设施等研究机构之间的合作关系。除了在声学和进化研究中提供启发式价值之外，从本研究中收集的信息将扩展我们对侵入性手术技术的含义的理解，这些技术需要破坏某些听觉结构以修复其他听觉结构。这项调查的多样性将允许数据和结果通过在声学、进化、行为和医学期刊上的出版物传播给广泛的专业受众。

The auditory system is the most mechanically complex sense in mammals, comprised of numerous bones, muscles, and other soft tissues. Consequently, this region provides many opportunities to study acoustical function and structural differences between various groups of animals have also been used to help infer their relationships to each other. Despite substantial investigation of the function of the auditory system in other groups of mammals (e.g., rodents), primates have received only limited attention in this regard even though considerable variation in the auditory structures both within and between different primate groups has been documented. To help understand the functional and evolutionary implications of primate auditory diversity, this dissertation will measure a set of functionally relevant auditory structures in ten species of primates and one species of tree shrew. The structures that will be examined include the eardrum, middle ear bones and cavities, and the cochlea and will be analyzed using state-of-the-art techniques including micro-computed tomography, impression molding, and digital imaging and measurement. In addition to examining a large comparative data set of extant specimens, a 30 million year old fossil primate specimen from Africa will also be evaluated. Lastly, the hearing sensitivity of a relatively large-bodied prosimian (a "primitive" group of primates), weighing approximately 3.5 kg, will be determined. This final step is necessary since hearing sensitivity data are available for only 18 species of primates and only four of these are prosimians, all four of which weigh 2 kg or less. These data will be used to test hypotheses relating ear structure and function and will be useful for studying the evolution of hearing in primates and other closely related groups. In turn, this type of fundamental data can be applied to further test and generalize broader ideas utilizing acoustic theory in comparative analyses of other mammalian groups. This line of research may eventually be used to investigate the evolution of hearing in humans and its relationship to the unique aspects of human communication.One of the broader impacts of this project relates to its integration of multiple scientific disciplines, bringing together research, researchers, and educators from various fields such as functional morphology, paleontology, behavioral ecology, anatomy, geology, and acoustics. This will help foster partnerships between research facilities such as the Duke Primate Research Center, Duke Medical Center Hearing Research Laboratories, and the Computed Tomography Facility at the University of Texas at Austin. Beyond providing heuristic value in acoustical and evolutionary studies, the information gleaned from this study will expand our understanding of the implications of invasive surgical techniques that require damaging certain auditory structures in order to repair others. The multifarious nature of this investigation will permit the data and results to reach a wide professional audience through publications in acoustical, evolutionary, behavioral, and medical journals.