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

对人类体型和头面部特征的环境可塑性的了解将影响人类长期的进化研究，并可能被用来检验人类性别选择的行为心理学理论。更好地了解人类两面性特征的性别环境可塑性将提供有关生物和文化适应、生物考古收藏的信息，并提供一种工具来推断考古人口承受的环境压力。在法医和生物考古学的背景下，记录种群大小和头面部二型性的变化是开发针对种群的性别确定方法的关键。此外，3D表面扫描技术的使用提供了新的量化和存储机会，允许随着软件的进步进行未来的分析，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合作。该项目还将支持一名女研究生的培训和专业准备。影响现代人类颅骨和颅后性别二型性的跨文化变异的因素还不是很清楚。一些证据表明，女性可能对环境压力有更好的缓冲能力，导致在恶劣条件下样本的体型二型性系统性地减少。相比之下，眉脊和下巴形态等头面部特征的二形性被假设与配偶偏好和性选择有关，在恶劣的气候条件下应该是环境中立的，甚至增加。然而，量化这种离散的头面部特征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。本研究利用一种新的量化颅面特征形态的方法来研究不同环境应激源下颅面特征二态与颅后大小二态之间的关系。一种几何形态测量方法将被用来通过3D激光表面扫描客观地量化眉脊和下巴形态中的性别二型性。这些头面部特征和骨骼尺寸的性别二形性将在一系列不同种族和文化的人群中进行评估。在遗传相关但环境不同的样本之间的具体比较将被用来试图分离个体环境因素对颅后和颅骨性别二型性的影响。

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.