关键词: 近现代人;牙齿;齿质;形态测量;三维

Abstract: The enamel-dentine junction (EDJ) is the developmental precursor of morphology on the outer enamel surface (OES). The EDJ morphology is more closely related to the genetic basis than the OES. This study employs micro-CT (micro-computed tomography) to complete scan of 100 isolated upper premolars (50 P3s and 50 P4s) of recent modern human with an agricultural background collected from central China. These specimens belonged to four periods of history, i.e. the Neolithic Age, the Eastern Zhou Dynasty, the Qin/Han Dynasties-Song/Yuan Dynasties, and the Ming/Qing Dynasties. After reconstructing the EDJ surfaces, 2 landmarks were defined on the dental horn (of buccal and lingual cusps) and 28 semi-landmarks along the occlusal border for each specimen. We then performed 3D geometric morphometric analyses to quantify the EDJ shapes. The result indicates that the lingual region exhibits a slightly higher degree of variability than that buccal region. Within the population, the main variation is expressed in following ways: 1) the depth of occlusal basin increase with the buccal and lingual cusps moving towards each other; 2) the relative dentine horn height of buccal and lingual cusps varies; 3) the mesiodistal dimension of the lingual cusps varies; 4) the degree of symmetry in the occlusal shape increase or reduce when the mesial ridge of buccal cusp shifted outwards or inwards; and 5) the MD/BL value of the whole occlusal area varies. To further explore the component of those variations abovementioned, we carried out analyses of sexual dimorphism and temporal micro-evolution. Comparison of mean shape shows that male specimens are inclined to have a relatively wider lingual region and a lower mesial ridge of buccal cusp. Nevertheless, both principal component analysis and Permutation test don’t present a significant sexual dimorphism in the EDJ shape explored here. Likewise, specimens from four periods of history are not differentiated from each other. It suggests that the pattern of variation present in the Chinese recent modern human could be at least traced back to the early Holocene. The future analysis of geometric morphometrics on the EDJ surface will continue to explore the difference between specimens of different physical sex, territories, and evolutional stage through expanding the sample size of dental materials.

Key words: Contemporary modern human; Teeth; Dentine; Morphometrics; 3D