柳江人头骨形态特征及柳江人演化的一些问题

为深入探讨柳江人化石形态特征的表现特点、进化程度及其与其年代数据的吻合性,本文对柳江、山顶洞、资阳、丽江等主要中国更新世晚期人类头骨化石及1 114例全新世以来不同地区现代中国人头骨进行了对比分析,结果发现:柳江人头骨绝大多数特征的出现情况位于现代中国人的变异范围,只有极个别特征与现代人不同;柳江人头骨具有的低眶等特征也可见于其他中国更新世晚期人类化石,说明柳江人化石上保留有少量常见于更新世晚期人类的原始特征,但与其他中国更新世晚期人类,尤其是山顶洞人头骨相比,柳江人显得要现代的多;柳江人与山顶洞人之间头骨形态特征的差异以体现头骨原始性及粗硕强壮程度上的差别居多,而个别特征差异或许与气候环境适应有关。我们认为:柳江人在形态进化上与现代中国人已经非常接近,他们之间的差别非常小;柳江人与山顶洞人头骨特征表现上的差异主要反映了他们之间在演化程度上的差异,同时也在一定程度上体现了各自的生存环境;现有的形态学证据不大可能为柳江人较早的时代提供支持。

Some Problems for the Late Pleistocene Human Cranium Found in Liujiang of South China Based on Morphological Analysis

The cranial and postcranial remains found in Liujiang are the most complete and well-preserved late Pleistocene human fossils ever unearthed in South China.Wu Rukang,who conducted the original study,suggested that even though the Liujiang fossils preserve some primitive,late Pleistocene features,a suite of modern Mongoloid features were also present.Wu considered the Liujiang human as protoMongoloid.However,because the exact layer that yielded the fossils is unclear and different radiometric dates exist,the age of the Liujiang fossils remains uncertain.Since the Liujiang discovery(A.D.1958)many advances have been made in paleoanthropology,with more detailed understanding of geographical and morphological variation,and the mechanisms and possible environmental influences on the evolution of our species.New hypotheses on late Pleistocene human evolution,and the formation and differentiation of modern East Asian populations have been proposed.With these new insights,the Liujiang fossils were re-examined.We proposed the following questions related to Liujiang and late Pleistocene human evolution in East Asia:(1)Does Liujiang's morphological pattern fit with its suggested minimal age of 67 Ka BP;(2)Compared with modern East Asian populations,how morphologically modern are the Liujiang fossils,and how many derived traits do the Liujiang fossils still exhibit;(3)How different morphologically are the Liujiang fossils compared to the northern Zhoukoudian("ZKD")Upper Cave specimens(i.e.,Upper Cave 102 and 103),or to the modern southern Mongoloid populations With these questions in mind,we analyzed and compared the craniae of Liujiang and ZKD Upper Cave to 1114 modern Chinese craniae of various geographic affinities.Our results show:(1)The expressions of most cranial features on Liujiang fall within the modern range of variation,but there are a few exceptions;(2)Several primitive features like lower orbit can be observed on Liujiang,indicating that it still preserves some late Pleistocene features.However,compared to the late Pleistocene specimens from ZKD Upper Cave,the Liujiang cranium is more modern;(3)The variation between Liujiang and ZKD Upper Cave are mainly in the retention of primitive and robust features on the ZKD Upper Cave craniae.We believe that a small number of these differences may be environmental adaptations,which include the deep depressed nasion on ZKD Upper Cave and the broad nasal bones on Liujiang.Based on these findings,we suggest that the cranial morphology of Liujiang is very close to those of modern Chinese and very few differences exist between them.Concomitantly,our study does not support the supposition that the Liujiang cranium is more primitive than ZKD Upper Cave and Ziyang.Since uncertainty exists of the exact provenience of the human fossils from Liujiang,and due to the similarity of the cranial morphology between Liujiang and modern Chinese,we suggest that the current morphological analysis does not support the earlier age(67 Ka BP)for the Liujiang human fossils.