广西陆那洞古人类遗址古环境背景研究

PALEOENVIRONMENT BACKGROUND RESEARCH IN LUNA CAVE, GUANGXI

期现代人起源与扩散及其环境背景变化一直是国际学术界研究热点问题之一。近年来，中国南方地区多个晚更新世早期地点发现现代人化石，为研究东亚现代人起源和演化提供了难得的依据。然而，在此框架下，现代人演化的环境背景却缺乏较为细致的研究。为此，本文综合运用了多种环境指标，如稳定同位素、孢粉、粘土矿物主量元素等，分析了广西陆那洞遗址（70~120ka B.P.）含有早期智人化石的地层，试图重建该遗址古人类生存时期的古环境。研究结果表明：该遗址所在区域的古植被类型以C3为主的森林环境；气候较为温暖湿润，未出现较为炎热或者冷的气候事件，总体上环境较为稳定。由此可以看出，较为温和和稳定的环境背景，为该遗址古人类的生存和繁衍提供了必要的生存条件，或许也为中国南方晚更新世现代人的起源、迁徙和扩散创造了良好的环境基础。

The origin and dispersal of early modern humans and the associated environment background changes have been important hot topics. In recent years, some fossils of early modern humans dated to the early Late Pleistocene have been found in South China, which provides important materials for understanding the origin and evolution of early modern humans in East Asia. However, we now still have little knowledge of the environment background of early modern humans. Luna Cave（23°36＇48＂N, 106°58＇1＂E） is located in the Karst mountains of the southeastern Bubing Basin in Guangxi Zhuang Autonomous Region, Southern China. The cave is about 30m above the valley floor and 162m above sea level. The deposits of about 0.5~2.0m in thickness are well preserved, including three different culture layers and were primarily of light brown clay containing a few limestone breccia. The Natural History Museum of Guangxi Zhuang Autonomous Region conducted the first excavation in 2004 and the second excavation in 2008. We discovered more than one hundred mammalian teeth and bones, including the two hominin teeth assigned to modern Homo sapiens that were dated between 70~120ka B.P. based on multiple MC-ICP-MS uranium-series dates of associated flowstones in clear stratigraphic context. In this paper, we used different analysis methods including enamel stable isotopes, sporopollen, and clay minerals to reconstruct the paleoenvironment of Luna Cave（70~120ka B.P.）in a multidisciplinary way. We selected nine well-preserved Cervus teeth for carbon and oxygen isotope analysis, as the Cervus teeth and human teeth were found in the same second culture layer. We used MAT 253 mass spectrometer in the State Key Laboratory of Biogeology and Environmental Geology at the China University of Geosciences（Wuhan）. The results show that the δ13C values of the Luna Cave cervid enamel are from -10.4‰ to -14.8‰ with a mean value of -13.2±1.27‰, which clearly indicate the Luna Cave was in a forest environment dominated by C3 plants. The stable isotope analysis of the enamel from Luna Cave suggests that the Luna cave dominated by C3 plants was in a region belonging to the forest but not closed forest environment, indicating the climate was relatively mild. In total, we collected eight sporopollen samples continuously from the top to the bottom from the east wall of a 1.2m deep excavation unit in Luna Cave. The sporopollen analysis was carried out in the State Key Laboratory of Earthquake Dynamics at the Institute of Geology, China Earthquake Administration. The results suggest the Luna Cave was in mild paleoenvironment without extreme hot or cold weather events. We also collected the samples for clay mineral composition and CIA index of the sediments analysis from the east wall of a 1.2m deep excavation unit in Luna Cave. The exposed stratigraphic section was carefully cleaned before sampling. The 11 samples were taken at 10cm intervals from the top to the bottom of the excavation unit. The clay mineral composition and CIA index of the sediments of the samples were analyzed using Agilent 7700e ICP-MS in the Wuhan sample Solution Analytical Technology company. The clay mineral composition and CIA index of the sediments don＇t have big changes, consistently suggesting the Luna cave was in a mild and stable paleoenvironment during the time of human living. Using multidisciplinary methods to reconstruct paleoenvironment of early modern humans enables us to get a better understanding of the paleoenvironment background of early modern humans in East Asia. Our results suggest South China had suitable climatic conditions, which probably provided a good condition for the origin and evolution of early modern humans in East Asia.