Australian Cranial Traits: Function, Development, and ModernHuman Origins

直立人和智人之间的关系对于理解现代人的起源至关重要。存在两种学派，一种认为智人是从东半球直立人的当地种群进化而来的，另一种认为智人起源于非洲，最终取代了当地的直立人种群。这两个学派都使用头骨字符来检验一个地理区域的连续性程度，但对这些字符的意义的解释不同。双方都认为，这种连续性的最好理由可以在澳大拉西亚找到。这项研究使用比较人体解剖学来明确测试用于连接印度尼西亚直立人和澳大利亚现代人的特征是否可能是遗传联系的良好指标。要检验的假设是：1)在现代澳大利亚人中，连接特征在功能上是否与强健的咀嚼(咀嚼)模式相关联；2)是生长的脑颅(脑)结构结果的特征对长头个体普遍存在，但不一定具有遗传价；3)头骨龙骨在结构上在不同的类群中相似。这些假设使用了15个地理上不同的现代人类样本、公制和非公制特征以及计算机断层扫描进行了验证。对这三个问题中每一个问题的回答对于评估这些连接特征是否可能反映遗传相关或其他共同的环境或发育状况至关重要。如果没有对这些特征来源的明确评估，在现代和化石样本中简单地列举特征是不能从系统发生学上解释的。

The relationship between Homo erectus and Homo sapiens is critical to understanding the origin of modern humans. Two schools of thought exist, one that sees regional evolution of Homo sapiens from local populations of H. erectus throughout the Old World, and another that sees H. sapiens originating in Africa and ultimately replacing local H. erectus populations. Both schools use cranial characters to examine the degree of continuity in a geographic region but differ on their interpretations of the significance of these characters. Both agree that the best case for such continuity can be made in Australasia. This study uses comparative human anatomy to explicitly test whether the characters used to link Indonesian H. erectus and Australian modern humans are likely to be good indicators of genetic relatedness. The hypotheses to be tested are: 1) are the linking features functionally associated with a robust masticatory (chewing) pattern in modern Australians, 2) are features of the neurocranium (braincase) structural consequences of growth universal to long-headed individuals but not necessarily of genetic valence, and 3) are cranial keels structurally similar across taxa. These hypotheses are tested using 15 geographically diverse modern human samples, metric and nonmetric traits, and Computed Tomography. Answers to each of these three questions are critical to evaluating whether the linking features are likely to reflect genetic relatedness or some other shared environmental or developmental condition. Without explicit evaluation of the sources of these features, the simple enumeration of features in modern and fossil samples is not phylogenetically interpretable.