Department of Human Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
J Hum Evol. 2012 Mar;62(3):395-411. doi: 10.1016/j.jhevol.2011.12.004. Epub 2012 Feb 22.
Recent humans and their fossil relatives are classified as having thick molar enamel, one of very few dental traits that distinguish hominins from living African apes. However, little is known about enamel thickness in the earliest members of the genus Homo, and recent studies of later Homo report considerable intra- and inter-specific variation. In order to assess taxonomic, geographic, and temporal trends in enamel thickness, we applied micro-computed tomographic imaging to 150 fossil Homo teeth spanning two million years. Early Homo postcanine teeth from Africa and Asia show highly variable average and relative enamel thickness (AET and RET) values. Three molars from South Africa exceed Homo AET and RET ranges, resembling the hyper thick Paranthropus condition. Most later Homo groups (archaic European and north African Homo, and fossil and recent Homo sapiens) possess absolutely and relatively thick enamel across the entire dentition. In contrast, Neanderthals show relatively thin enamel in their incisors, canines, premolars, and molars, although incisor AET values are similar to H. sapiens. Comparisons of recent and fossil H. sapiens reveal that dental size reduction has led to a disproportionate decrease in coronal dentine compared with enamel (although both are reduced), leading to relatively thicker enamel in recent humans. General characterizations of hominins as having 'thick enamel' thus oversimplify a surprisingly variable craniodental trait with limited taxonomic utility within a genus. Moreover, estimates of dental attrition rates employed in paleodemographic reconstruction may be biased when this variation is not considered. Additional research is necessary to reconstruct hominin dietary ecology since thick enamel is not a prerequisite for hard-object feeding, and it is present in most later Homo species despite advances in technology and food processing.
最近的人类及其化石亲属被归类为具有厚的臼齿牙釉质，这是少数几种将人类与现生非洲猿区别开来的牙齿特征之一。然而，对于最早的人类属成员的牙釉质厚度知之甚少，最近对晚期人类的研究报告表明存在相当大的种内和种间变异。为了评估牙釉质厚度的分类学、地理和时间趋势，我们应用微计算机断层扫描成像技术对跨越 200 万年的 150 颗化石人类牙齿进行了研究。来自非洲和亚洲的早期人类的后臼齿显示出高度可变的平均和相对牙釉质厚度（AET 和 RET）值。南非的三颗臼齿超过了人类 AET 和 RET 范围，类似于超厚的傍人条件。大多数晚期人类群体（古老的欧洲和北非人类，以及化石和现代人类）在整个牙齿中都具有绝对和相对较厚的牙釉质。相比之下，尼安德特人在其门齿、犬齿、前臼齿和臼齿中显示出相对较薄的牙釉质，尽管门齿的 AET 值与人类相似。对现代和化石人类的比较表明，牙齿尺寸减小导致牙本质相对于牙釉质不成比例地减少（尽管两者都减少了），导致现代人类的牙釉质相对较厚。将人类概括为具有“厚牙釉质”的特征因此简化了一个具有有限分类学用途的令人惊讶的多变颅面特征。此外，在不考虑这种变异性的情况下，在古人口统计重建中使用的牙齿磨损率估计可能存在偏差。需要进行更多的研究来重建人类的饮食生态，因为厚牙釉质不是硬物体喂养的先决条件，而且尽管技术和食品加工有了进步，但它存在于大多数晚期人类物种中。
