Department of Anthropology, Western Washington University, Bellingham, WA 98225;
Department of Anthropology, Universität Zürich, CH-8057 Zürich, Switzerland.
Proc Natl Acad Sci U S A. 2020 Oct 20;117(42):26183-26189. doi: 10.1073/pnas.2008037117. Epub 2020 Oct 5.
Teeth have been studied for decades and continue to reveal information relevant to human evolution. Studies have shown that many traits of the outer enamel surface evolve neutrally and can be used to infer human population structure. However, many of these traits are unavailable in archaeological and fossil individuals due to processes of wear and taphonomy. Enamel-dentine junction (EDJ) morphology, the shape of the junction between the enamel and the dentine within a tooth, captures important information about tooth development and vertebrate evolution and is informative because it is subject to less wear and thus preserves more anatomy in worn or damaged specimens, particularly in mammals with relatively thick enamel like hominids. This study looks at the molar EDJ across a large sample of human populations. We assessed EDJ morphological variation in a sample of late Holocene modern humans ( = 161) from archaeological populations using μ-CT biomedical imaging and geometric morphometric analyses. Global variation in human EDJ morphology was compared to the statistical expectations of neutral evolution and "Out of Africa" dispersal modeling of trait evolution. Significant correlations between phenetic variation and neutral genetic variation indicate that EDJ morphology has evolved neutrally in humans. While EDJ morphology reflects population history, its global distribution does not follow expectations of the Out of Africa dispersal model. This study increases our knowledge of human dental variation and contributes to our understanding of dental development more broadly, with important applications to the investigation of population history and human genetic structure.
几十年来,人们一直在研究牙齿,并不断从中发现与人类进化相关的信息。研究表明,外釉质表面的许多特征是中性进化的,可以用来推断人类的种群结构。然而,由于磨损和埋藏学的过程,许多这些特征在考古和化石个体中是不可用的。牙本质-釉质交界处(EDJ)形态,即牙齿中釉质和牙本质交界处的形状,捕捉到了关于牙齿发育和脊椎动物进化的重要信息,并且具有信息性,因为它受到的磨损较少,因此在磨损或损坏的标本中保留了更多的解剖结构,特别是在具有相对较厚釉质的哺乳动物中,如人类。本研究考察了大量人类种群的磨牙 EDJ。我们使用 μ-CT 生物医学成像和几何形态测量分析,评估了来自考古人群的晚全新世现代人类(= 161)样本中的 EDJ 形态变异。人类 EDJ 形态的全球变化与中性进化的统计预期以及特征进化的“非洲外扩散”模型进行了比较。表型变异与中性遗传变异之间的显著相关性表明,EDJ 形态在人类中是中性进化的。虽然 EDJ 形态反映了种群历史,但它的全球分布并不符合“非洲外扩散”模型的预期。本研究增加了我们对人类牙齿变异的认识,并有助于我们更广泛地理解牙齿发育,对研究人口历史和人类遗传结构具有重要应用。
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