南京1号与东非Bodo人类头骨化石:对"中心和边缘"假说的检测

"中心和边缘"假说认为非洲是人类演化的中心地区,东亚等地区是边缘地区。在边缘地区,人群的地区性形态特征出现较早,可上溯到直立人生活时期;在中心地区,人群的地区性形态特征出现较晚。Bodo人类头骨化石和南京1号人类头骨化石分别出自中心地区和边缘地区,二者年代都是距今60万年左右,二者都保留有面颅。因此,Bodo人类头骨化石和南京1号人类头骨化石是检测"中心和边缘"假说的最合适的材料。本文是对南京1号和Bodo头骨的面颅测量性特征作比较研究。研究结果表明:1.二者面颅测量性特征上的差别远大于这两个相应地区现代人群之间的差别,提示了人类的地区性体质形态差别早在60万年前就很明显;2.东亚的南京1号人类头骨和东非的Bodo人类头骨尽管同样古老,但各自与当地区的现代人群的面颅上的差异情况并不一致。Bodo头骨与东非现代人群显得差异较大,南京1号头骨与东亚现代人群显得较相近。这种相近,提示了在东亚这个"边缘地区",现代人群的面颅测量性特征可追溯到以南京1号头骨为代表的远古人类那里,而在"中心地区",现代人群的面颅测量性特征还很难与以Bodo为代表的远古人群相联系。本项研究结果与"中心和边缘"假说的推测相符合。

Human Cranial Fossils from Nanjing and Bodo: A Test of the "Center and Edge" Hypothesis

A significant form to the geographical distribution of human variation towards the end of the Early Pleistocene was noted by Alan Thorne and explained by his "Center and Edge" hypothesis in 1977.He recognized that populations sampled at the peripheries of the human range were more homogeneous than samples from the center,or eastern Africa.Some of the homogeneous features at the peripheries could be linked to common characteristics found in populations from the same area today.In other words,features that marked modern geographical variation have been found to appear in initial immigrants living at peripheries.The Thorne hypothesis predicts an opposite pattern of the late appearance of regional features at the center of the range and their early appearance in Homo erectus populations at geographic or ecological peripheries. Two crania Bodo and Nanjing 1 both dating approximately 0.6Ma BP are from a center and a periphery location,respectively.Both of these crania preserve comparable facial skeletons,and for these reasons,the Bodo and Nanjing 1 are ideal for testing the "Center and Edge" hypothesis. A comparison of Bodo and Nanjing 1 facial measurements indicates the following results.1)The anatomical differences between Bodo and Nanjing 1 are more marked than those between center and periphery modern populations.This result suggests that as early as 0.6Ma BP,fossil populations seemed to show more geographical variation than modern populations.2)In facial measurements,Nanjing 1 is similar to modern population of East Asia,suggesting that at the periphery,some of features that marked modern geographic variation appear in Homo erectus and were maintained for very long time periods.However,at the center region,the metric facial features of Bodo were not distinctly linked to features of modern population from the same area today.This comparison confirms the prediction of the "Center and Edge" hypothesis.