Martin Robert M G, Hublin Jean-Jacques, Gunz Philipp, Skinner Matthew M
Department of Anthropology, University of Toronto, 19 Russell Street, Toronto M5S 2S2, Canada.
Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany.
J Hum Evol. 2017 Feb;103:20-44. doi: 10.1016/j.jhevol.2016.12.004. Epub 2017 Jan 17.
This study explores the morphological differences between the enamel-dentine junction (EDJ) of maxillary and mandibular molars of Neanderthals (n = 150) and recent modern humans (n = 106), and between an earlier Neanderthal sample (consisting of Pre-Eemian and Eemian Neanderthals dating to before 115 ka) and a later Neanderthal sample (consisting of Post-Eemian Neanderthals dating to after 115 ka). The EDJ was visualised by segmenting microtomographic scans of each molar. A geometric morphometric methodology compared the positioning of the dentine horns, the shape of the marginal ridge between the dentine horns, and the shape of the cervix. We also examined the manifestation of non-metric traits at the EDJ including the crista obliqua, cusp 5, and post-paracone tubercle. Furthermore, we report on additional morphological features including centrally placed dentine horn tips and twinned dentine horns. Our results indicate that EDJ morphology can discriminate with a high degree of reliability between Neanderthals and recent modern humans at every molar position, and discriminate between the earlier and the later Neanderthal samples at every molar position, except for the M in shape space. The cervix in isolation can also discriminate between Neanderthals and recent modern humans, except at the M in form space, and is effective at discriminating between the earlier and the later Neanderthal samples, except at the M/M in form space. In addition to demonstrating the taxonomic valence of the EDJ, our analysis reveals unique manifestations of dental traits in Neanderthals and expanded levels of trait variation that have implications for trait definitions and scoring.
本研究探讨了尼安德特人（n = 150）和现代人类（n = 106）上颌和下颌磨牙的釉牙本质界（EDJ）之间的形态差异，以及早期尼安德特人样本（由距今115 ka以前的前埃姆期和埃姆期尼安德特人组成）和晚期尼安德特人样本（由距今115 ka以后的后埃姆期尼安德特人组成）之间的形态差异。通过对每颗磨牙的显微断层扫描进行分割，使EDJ可视化。一种几何形态测量方法比较了牙本质角的位置、牙本质角之间边缘嵴的形状以及牙颈部的形状。我们还检查了EDJ处非计量性状的表现，包括斜嵴、5号牙尖和副尖后结节。此外，我们报告了其他形态特征，包括位于中央的牙本质角尖端和孪生牙本质角。我们的结果表明，EDJ形态在每个磨牙位置都能以高度可靠性区分尼安德特人和现代人类，并且在每个磨牙位置都能区分早期和晚期尼安德特人样本，但在形状空间中的M除外。单独的牙颈部在形状空间中除了M之外，也能区分尼安德特人和现代人类，并且在形状空间中除了M/M之外，能有效区分早期和晚期尼安德特人样本。除了证明EDJ的分类学价值外，我们的分析还揭示了尼安德特人牙齿性状的独特表现以及性状变异水平的扩大，这对性状定义和评分具有重要意义。
