现代中国人群形成与分化的形态证据--亚洲与非洲现代人群上颌第一臼齿齿尖相对面积的对比分析

Morphological Evidence of the Formation and Diversification of Modern Chinese: the Comparative Analysis of M^1 Relative Cuspal Areas of Recent Asian and African Populations

现代人群形成与分化造成的具有地域差别的人群标志性体质特征是研究人群之间关系的重要信息。作为臼齿形态测量的组成部分,上颌第一臼齿齿尖相对面积在人类演化以及现代人群关系上的研究价值已经引起了人类学界的关注。然而,迄今对上颌第一臼齿齿尖相对面积在世界各地的现代人群之间是否具有地域性差异还不是很清楚。本文对代表亚洲和非洲现代人群的208枚上颌第一臼齿齿尖相对面积的研究发现,上颌第一臼齿四个主要齿尖相对面积在亚洲和非洲现代人群之间都存在明显差异。亚洲现代人上颌第一臼齿近中齿尖(原尖和前尖)相对面积较大,而远中齿尖(后尖和次尖)相对面积较小。非洲现代人上颌第一臼齿各齿尖相对面积均较亚洲人群具有更大的变异,尤其在原尖和次尖相对面积上。采用判别分析可以将69.2%的标本正确地判别归入其原来所属的组群。通过与化石人类相关数据的对比发现,非洲现代人比亚洲现代人在原尖和次尖相对面积以及前尖/后尖相对面积比例上更加接近于人类演化的早期形式。现有的证据显示,亚洲和非洲现代人群在齿尖相对面积的分化至少可以追溯到全新世早期,更加精确的分化时间需要结合更新世晚期甚至中期化石人类数据去获得。本研究揭示出的非洲现代人上颌第一臼齿齿尖相对面积的高异质性(heterogeneity)和相对原始性在现代人形成与分化方面的作用尚需进一步的研究。

The processes of formation and diversification of modem human populations resulted in a series of physical characteristics in different geographic regions. These characteristics were consequently important in tracing population affinity. As an essential part of molar morphometrics, the relative cuspal area has gained intense interest due to its value in studies of both human evolution and population affinity. However, it was not clear whether the regional variation of M1 relative cuspal areas exists among different populations. Based on measurements and comparisons of relative cuspal areas of 208 Mls, the present study revealed that recent Asian and African populations were significant different from each other in relative sizes of all four cusps. Specifically, Asians had a relatively large protocone and paracone, and a relatively small metacone and hypocone. Ranges of variations of all four cusps were larger in African specimens than in Asian ones, especially the relative protocone and hypocone sizes. Discriminant analysis could correctly discriminate 69.2% of the specimens into their original groups. After comparisons with corresponding data of fossil hominins, recent Africans were found to be more close to early forms of human evolution in relative cuspal areas of protocone and hypocone, as well as in the proportion of paracone/metacone. Diversification of recent Asian and African populations in the M1 relative cuspal areas can be traced back at least to the early Holocene, and the acquiring of a more precise diversification time required involvement of hominins of Late and even Middle Pleistocene. The high degree of heterogeneity and relative primitiveness of recent African specimens revealed by the present study need to be ascertained through further studies.