Smith Tanya M, Olejniczak Anthony J, Reh Stefan, Reid Donald J, Hublin Jean-Jacques
Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, D-04103 Leipzig, Germany.
Am J Phys Anthropol. 2008 Jun;136(2):237-41. doi: 10.1002/ajpa.20796.
In addition to evidence for bipedality in some fossil taxa, molar enamel thickness is among the few characters distinguishing (thick-enameled) hominins from the (thin-enameled) African apes. Despite the importance of enamel thickness in taxonomic discussions and a long history of scholarship, measurements of enamel thickness are performed almost exclusively on molars, with relatively few studies examining premolars and anterior teeth. This focus on molars has limited the scope of enamel thickness studies (i.e., there exist many fossil hominin incisors, canines, and premolars). Increasing the available sample of teeth from which to compare enamel thickness measurements from the fossil record could substantially increase our understanding of this aspect of dental biology, and perhaps facilitate greater taxonomic resolution of early hominin fossils. In this study, we report absolute and relative (size-scaled) enamel thickness measurements for the complete dentition of modern humans and chimpanzees. In accord with previous studies of molars, chimpanzees show lower relative enamel thickness at each tooth position, with little overlap between the two taxa. A significant trend of increasing enamel thickness from anterior to posterior teeth is apparent in both humans and chimpanzees, indicating that inter-taxon comparisons should be limited to the same tooth position in order to compare homologous structures. As nondestructive imaging techniques become commonplace (facilitating the examination of increasing numbers of fossil specimens), studies may maximize available samples by expanding beyond molars.
除了一些化石类群中两足行走的证据外，臼齿釉质厚度是将（厚釉质的）人科动物与（薄釉质的）非洲猿类区分开来的少数特征之一。尽管釉质厚度在分类学讨论中很重要，且有悠久的学术研究历史，但釉质厚度的测量几乎只在臼齿上进行，研究前磨牙和前牙的相对较少。对臼齿的这种关注限制了釉质厚度研究的范围（即存在许多化石人科动物的门齿、犬齿和前磨牙）。增加可用于比较化石记录中釉质厚度测量值的牙齿样本，可能会大幅增进我们对牙齿生物学这一方面的理解，或许还能有助于提高早期人科动物化石的分类分辨率。在本研究中，我们报告了现代人类和黑猩猩完整牙列的绝对和相对（按大小缩放）釉质厚度测量值。与之前对臼齿的研究一致，黑猩猩在每个牙齿位置的相对釉质厚度都较低，两个类群之间几乎没有重叠。在人类和黑猩猩中，从前往后牙齿釉质厚度增加的显著趋势都很明显，这表明为了比较同源结构，类群间的比较应限于相同的牙齿位置。随着无损成像技术变得普遍（便于检查越来越多的化石标本），研究可以通过超越臼齿来扩大可用样本。
