Doctoral Dissertation: A Three-Dimensional Analysis of Age-Related Change in the Adult Craniofacial Skeleton

大多数骨骼研究都假设人类头骨在20岁之后不会改变形状或大小。 事实上，大多数研究都是在这样的假设下进行的，即年龄在成人颅骨变异中几乎没有作用，任何年龄的成人都可以平等地用于人类颅骨形态的研究。 与这种假设相反，许多科学家发现成年人的头骨在性成熟后很长一段时间内发生了显着变化。 这给数百项临床、古人类学和法医学研究带来了潜在的问题，这些研究在选择人类比较样本时没有考虑与年龄相关的头骨形态变化。一个来自医学领域的假设例子最清楚地证明了这一点，尽管这本身并不是医学研究。 一些临床研究比较了正常和异常成人颅骨的形状，以更好地了解影响颅骨发育的遗传疾病的性质。如果成人颅骨随年龄而变化，则将60岁的正常和异常样本进行比较。奥尔兹人的头骨形状和大小可能存在很大差异。 使用正常和异常20年的样本进行相同的比较。另一方面，奥尔兹可能表现出很少或没有差异。 根据比较样本的年龄组成，医生可能会避免治疗实际上是病理性的颅骨区域，或者试图纠正一个人的颅骨，只是看起来不正常。 研究人员从来没有想过要比较年龄不匹配的青少年，但这是成年人的常见做法。如果存在成人颅骨变化，任何不考虑样本年龄变化的颅骨研究都不能确定其结果的有效性或无偏倚性。 拟议的研究将严格测试成人颅骨稳定性的假设，使用三维方法。 多个已知年龄和性别的骨骼样本，牙齿脱落的不同阶段，并从不同的地理区域将进行检查，在头骨中与年龄相关的变化的系统模式。 将从颅骨和下颌骨上的115个标志收集三维坐标数据。 将使用欧氏距离矩阵分析对这些数据进行分析。 使用这种方法的试点研究支持存在系统的变化，在成人头骨和文件的性别差异，在以前的研究中没有检测到这种变化的模式。 这些试点数据表明，迫切需要考虑成人年龄相关的变化，在分析人类头骨的形式，以及所提出的研究在重组和重新解释以前的作品中的重要作用。

Most skeletal research assumes that the human skull does not change in shape or size after age 20. Indeed, most studies work under the assumption that aging plays little or no role in adult cranial variation, and adults of any age can be used equally in a study of human cranial form. Contrary to this assumption, many scientists have found significant change in the adult skull long after sexual maturation. This poses potential problemsfor hundreds of clinical, paleoanthropological, and forensic studies that donot consider age-related variability in skull form in their choice of humancomparative samples. A hypothetical example from the medical realm demonstrates this most clearly, though this is not itself medical research. Some clinical studies compare the shape of normal and abnormal adult skulls to better understand the nature of genetic diseases affecting skull development. If the adult skull changes with age, a comparison between a normal and abnormal sample of 60 yr. olds might display extensive differences in skull shape and size. The same comparison using samples of normal and abnormal 20 yr. olds, on the other hand, might show few or no differences. Depending on the age-composition of comparative samples, doctors may refrain from treating skull regions that are actually pathological, or alternatively, attempt to correct an individual's skull that only appears to be abnormal. Researchers would never think of comparing non-age-matched juveniles, yet this is common practice with adults. If adult cranial change exists, any study of the skull that does not consider variation due to age in their samples cannot be sure of the validity or unbiased character of their results. The proposed study will rigorously test assumptions of adult cranial stability using three-dimensional methods. Multiple skeletal samples of known age and sex, differing stages of tooth-loss, and from different geographic regions will be examined for systematic patterns of age-related change in the skull. Three-dimensional coordinate data will be collected from 115 landmarks on the skull and mandible. These data will be analyzed using Euclidean Distance Matrix Analysis. A pilot study using this method supports the presence of systematic change in the adult skull and documents sex differences in the patterns of this change that were not detected in previous studies. These pilot data demonstrate the critical need to consider adult age-related change in analyses of human skull form, and the essential role the proposed study has in the restructuring and reinterpretation of previous works.