Variation in human hair morphology within and among human populations

人类头皮的头发在形状和颜色上有很大的不同，在人类内部和人群之间。这项研究将分析最近收集的代表广泛人群的头发样本，从而对人类头皮头发特征的可变性进行前所未有的微观研究，并为未来将头发的形状和颜色与其潜在的遗传学联系起来的研究奠定基础。该项目将通过提供头发变异的额外测量方法来推进科学发展，造福社会，这些方法可用于法医环境，以解决祖先和个人身份的问题，并通过提供关于进化力量如何影响我们物种的头发形态的新信息。研究人员将应用光学显微镜、透射电子显微镜（TEM）和三维扫描电子显微镜（3D SEM）等最新技术来定义和测量头发外部形态和内部结构的尺寸。特别注意将集中在鉴定卷曲模式、横截面尺寸、角质层厚度和毛干内部和沿毛干长度的皮质结构方向的变化模式。观察到的变化模式的性质和意义将使用适当的统计方法进行严格检验。由于头发样本与基因型DNA样本相关，因此未来的研究将有可能将单核苷酸多态性（snp）与形态变异联系起来。这些研究有望揭示人类头发形态多样性的范围，阐明头发形态趋同进化的实例，并为进一步探索自然选择、基因流和遗传漂变在人类头皮头发形态进化中的相对作用提供具体途径。通过详细了解毛发的形态特征，研究人员将能够为基因发现和法医工作规划有效和集中的表型程序。本项目由美国国家司法研究所和美国国家科学基金会生物人类学项目联合资助。

Human scalp hair varies considerably in form and color, within and among human populations. This study will analyze recently collected hair samples representing a wide range of human populations, enabling an unprecedented microscopic investigation of variability in human scalp hair features and laying the groundwork for future research that links hair form and color with their underlying genetics. The project will advance science and benefit society by providing additional measures of hair variation that can be used in forensic contexts to address questions of ancestry and personal identification, and by providing new information on how the forces of evolution have influenced hair morphology in our species. The investigators will apply recent technological advances in optical microscopy, transmission electron microscopy (TEM), and three dimensional scanning electron microscopy (3D SEM) to define and measure the dimensions of external hair forms and internal structures. Specific attention will be focused on identification of patterns of variation in curl patterns, cross sectional dimensions, cuticle thickness, and orientation of cortical structures within and along the length of the hair shaft. The nature and significance of the observed patterns of variation will be rigorously tested using appropriate statistical methods. Because the hair samples are associated with genotyped DNA samples, future studies correlating single nucleotide polymorphisms (SNPs) and morphological variation will be possible. These investigations are expected to shed light on the range of diversity in human hair forms, illuminate instances of convergent evolution in hair form, and suggest specific avenues for further exploration of the relative roles of natural selection, gene flow, and genetic drift in the evolution of human scalp hair form. By understanding the morphological hair features in detail the investigators will be able to plan efficient and focused phenotyping programs for both gene discovery and forensic efforts.This project is jointly supported by the National Institute of Justice and the Biological Anthropology Program at NSF.