中国直立人牙齿特征变异及其演化意义

以往研究发现,中国直立人化石呈现较大的形态变异。对于这种变异程度及造成变异的原因,在古人类学界有不同的认识。有学者提出在直立人阶段,中国古人类已经呈现明显的区域性差异,但也有人认为这些差异似乎没有规律性。近年,本文作者采用不同方法对若干地点的中国直立人牙齿特征及其变异进行了系列研究,取得了一些新的发现和认识。本文在回顾总结这些研究的基础上,结合对其它一些地点中国直立人牙齿特征的观测对比,对中国直立人牙齿特征表现特点及变异作了进一步的分析。本研究发现,中国直立人牙齿特征具有较大的变异范围。这些变异似可分为两种主要类型,元谋、建始、郧县梅铺、和县牙齿呈现出较多的原始特点,代表一种原始类型;周口店、沂源等地点的标本特征相对进步,表现出更多的典型直立人特征。其它一些地点的直立人化石呈现出混合或中间状态。值得注意的是部分呈现出原始牙齿特征类型的中国直立人的生存年代相对较晚,其牙齿特征的原始性与生存时代不具有对应关系。作者认为中国直立人牙齿特征类型反映了更新世早期和中期不同直立人群的演化状态。原始类型牙齿特征的形成不仅与演化时序性和地理分布有关,还在一定程度上反映了一些中国直立人群的演化隔离。

Dental Morphological Variation and Evolutionary Implications of Homo erectus in China

Previous studies indicate that Chinese Homo erectus fossils have wide morphological variations, with no-agreed to cause. Some colleagues propose that hominins in China already exhibited pronounced regional morphological differences during the period of Homo erectus. However, there is other opinion arguing that there is no regular pattern for these variations. Recently, the present authors conducted research on dental morphological variations of Chinese Homo erectus using various methods. Our studies achieved some new discoveries and understanding. From this work, we propose that dental morphological variations of Chinese Homo erectus can be divided into two types. The teeth of Yuanmou, Jianshi, Yunxian Meipu, Hexian exhibit more primitive features and thus represent a primitive type. More derived features are identified in specimens from Zhoukoudian and Yiyuan showing more typical morphological patterns of Homo erectus. Some other Chinese Homo erectus teeth display mixed or intermediate variation status. It is noteworthy that the chronological ages of some Chinese Homo erectus that have primitive features are relative late and their primitive dental patterns do not fit with their expected chronological ages. The authors believe that dental morphological types of Chinese Homo erectus revealed by the present study reflect an evolutionary situation of different Chinese Homo erectus populations in Early and Middle Pleistocene. The formation of primitive dental pattern is not only related to the chronological sequence and geographical distributions of some Homo erectus groups, but also reflects isolation of some Chinese Homo erectus populations.