Doctoral Dissertation Improvement: Environmental Effects on Human Cranial and Postcranial Sexual Dimorphism

人类体型和颅面特征的环境可塑性的知识将影响长期的人类进化研究，并可能用于测试人类性选择的行为心理学理论。 更好地了解特定性别的环境可塑性的人类二形特征将提供有关生物和文化适应，生物考古学收藏，并推断考古种群所承受的环境压力的工具。 记录人口的身体大小和颅面二型性的变化是关键的法医和生物考古背景下发展人口特异性的性别决定方法。此外，3D表面扫描技术的使用提供了新的量化和存储机会，随着软件的进步，可以进行未来的分析，促进数据共享，并在研究人员无法亲自前往收集的情况下支持协作。该项目还将支持一名女研究生的培训和专业准备。影响现代人类颅和颅后性别二型性的跨文化差异的因素还没有很好的理解。一些证据表明，女性可能会更好地缓冲对环境的压力，导致系统的减少，在身体大小的二型性在恶劣的条件下的样品。与此相反，在颅面特征，如眉脊和下巴形态的二型性已被假设为有关的配偶偏好和性选择，应该是环境中性的，甚至在恶劣的气候条件下增加。然而，量化这些离散的颅面特征已被证明是具有挑战性的，传统定性方法的主观性阻碍了性别之间或跨人群的客观统计分析。 该项目利用一种新的方法来量化颅特征形态，研究颅面特征二态性和颅后大小二态性与各种环境压力之间的关系。 将使用几何形态测量方法，使用3D激光表面扫描客观量化眉脊和下巴形态的性别二态性。这些颅面特征和身体大小的骨骼措施的性别二型性将在一系列的种族和文化多样性的人口进行评估。基因相关的，但环境不同的样本之间的具体比较将被用来试图隔离个体环境因素对颅后和颅性别二型性的影响。

Knowledge of the environmental plasticity of both body size and craniofacial traits in humans will impact long-term human evolutionary studies, and may be used to test behavioral psychology theories of human sexual selection. A better understanding of the sex-specific environmental plasticity of human dimorphic features would provide information regarding biological and cultural adaptations, bioarchaeological collections, and a tool to infer environmental stresses endured by archaeological populations. Documenting population variations in body size and craniofacial dimorphism is key to developing population-specific sex determination methods in forensic and bioarchaeological contexts. In addition, the use of 3D surface scanning technology provides new quantification and storage opportunities that allow for future analyses as software advances, facilitates data sharing, and supports collaboration in situations where researchers cannot physically travel to collections. The project will also support the training and professional preparation of a female graduate student. The factors influencing cross-cultural variation in modern human cranial and postcranial sexual dimorphism are not well understood. Some evidence suggests that females may be better buffered against environmental stressors, resulting in a systematic decrease in body size dimorphism in samples under poor conditions. In contrast, dimorphism in craniofacial traits such as brow ridge and chin morphologies has been hypothesized to be related to mate preference and sexual selection, and should be environmentally neutral or even increase under poor climatic conditions. Quantifying such discrete craniofacial traits, however, has proven challenging, and the subjectivity of traditional qualitative methods prevents objective statistical analyses between the sexes or across populations. This project utilizes a novel method of quantifying cranial trait morphologies to examine the relationship between craniofacial trait dimorphism and postcranial size dimorphism with various environmental stressors. A geometric morphometric method will be used to objectively quantify sexual dimorphism in brow ridge and chin morphologies using 3D laser surface scans. Sexual dimorphism in these craniofacial traits and skeletal measures of body size will be evaluated in an array of ethnically and culturally diverse populations. Specific comparisons between genetically related, yet environmentally disparate samples will be employed in an attempt to isolate the effects of individual environmental factors on postcranial and cranial sexual dimorphism.