Doctoral Dissertation Improvement: Craniofacial Asymmetry, Morphological Integration, and Developmental Instability in the Human Skull

这个项目使用颅面不对称来识别人类颅骨的发育综合特征。了解颅面变异的正常范围以及变异范围的局限性，是开展涉及人类颅骨研究的必要基础。性格特征的发育整合限制了可变性，因为这些特征作为一个单一的单位一起生长、适应和进化。该项目将确定通过直接发展相互作用（发展“模块”）整合的特征，并测试它们在压力条件下是否保持整合。区分在压力下保持一致的整合模式对适应、进化变化和物种形成的研究至关重要。波动不对称研究的最新进展为识别发育综合性状提供了一种创新的新方法。波动不对称被定义为个体样本中两侧变化的随机模式。由于形态波动不对称的随机性，两个性状波动不对称的显著共变表明两个性状是发育一体化的。本项目由三个独立但相关的研究组成。首先，该方法将应用于正常成人颅骨的分析，以测试大量现有文献中关于颅骨整合的预测。其次，在生物力学约束的压力下，融合的维持将通过使用过早融合颅骨缝合线的儿童和正常对照组的数据进行测试。最后，使用两个生活在不同逆境条件下的人类考古样本的数据来测试系统压力下的整合维护。对于每次分析，Co-PI将从每个头骨上的生物学相关地标收集三维坐标。波动性不对称将使用这些坐标数据和已建立的形态计量学方法进行量化。将测试共变异的模式，以确定发育整合的特征。项目资金允许副主任参观各种收藏骨骼的博物馆。此外，还将获得足够的材料来支持本项目和进一步的相关研究，推动这位女性Co-PI的科学事业。这个项目的结果将包括关于人类头骨发育的独特信息和对压力的适应性反应的限制。

This project uses craniofacial asymmetry to identify developmentally integrated characters in the human skull. Understanding the normal range of craniofacial variation, as well as limitations on the range of variation, is a necessary foundation for research involving the human skull. Developmental integration of character traits constrains variability, because these traits grow, adapt, and evolve together as a single unit. This project will identify characters that are integrated through direct developmental interactions (developmental "modules") and test whether they remain integrated under conditions of stress. Distinguishing patterns of integration that remain consistent under stress is critical for studies of adaptation, evolutionary change and speciation.Recent advances in the study of fluctuating asymmetry offer an innovative new method for identifying developmentally integrated characters. Fluctuating asymmetry has been defined as a random pattern of between-sides variation in a sample of individuals. Because of the random nature of morphological fluctuating asymmetry, significant covariation in the fluctuating asymmetry of two characters indicates that the characters are developmentally integrated. This project consists of three separate but related studies. First, the methodology will be applied to analysis of normal adult skulls to test predictions from substantial existing literature on integration in the skull. Second, the maintenance of integration under the stress of biomechanical constraint will be tested using data from children with prematurely fused cranial sutures and a normal control group. Finally, the maintenance of integration under systemic stress is tested using data from two archaeological samples of humans that lived under conditions differing in adversity. For each analysis, the Co-PI will collect three-dimensional coordinates from biologically relevant landmarks on each skull. Fluctuating asymmetry will be quantified using these coordinate data and established morphometric methods. Patterns of covariation will be tested to identify developmentally integrated characters. Project funding permits the Co-PI to visit various museums housing skeletal collections. In addition, adequate materials will be obtained to support this project and further related research, advancing the scientific career of this female Co-PI. Results of this project will include unique information about development of the human skull and constraints on adaptive responses to stress.