关于东亚早期人类生态环境的重建

在东亚早期人类生态环境重建中流行的“莫氏线”理论将东亚(包括东南亚)视为第四纪全球环境频繁、激烈和迅速变化的例外。这个主要建立在化石哺乳动物群基础上的假说存在明显的局限性,不符合近二三十年来中国黄土、西太平洋边缘海等领域研究所揭示的东亚第四纪环境变化的性质和特点。东亚早期人类生态环境重建工作的滞后不仅妨碍了考古学家对旧大陆早期人类和文化发展格局的研究,也不利于整个第四纪研究的发展。加强考古学与第四纪研究其它领域的沟通、配合和合作,是整个第四纪研究的共同任务。

ON THE RECONSTRUCTION OF PALEOECOLOGY IN EAST ASIA

Comparing with the paleoanthropology and Quaternary research, the reconstructionof paleoecology in East Asia is backward. The main reason is that the explanationof so called "Movius line" is still current.More than 50 years ago, American archaeologist H.L. Movius divided the OldWorld during the Lower Paleolithic Period into two cultural regions, the great handaxecomplex including Africa, Europe, Middle East and Peninsular India; and the greatchopper-chopping tool complex including East Asia, South Asia and northernsubeontinent India-Pakistan. Movius thought that the boundary of two regions is notonly an invisible technological barrier, but a visible ecological and geoglaphical barrier.He claimed that the climate and terrian in the forests of Asia remained stable for thepast 2 whillion years, and humans stayed backward eons in culture.During the Quaternary period, the global climatic changes frequently, violentlyand rapidly. A number of geological events took place, including the build-up of theNorth American and European ice sheets, intertropical cooling and desiccation, theexpansion of savanna at expense of tropical rainforest in Africa, the large-scalechanges in the relative levels and distribution of land and sea. However, what washappening in Asia during the same time? Is the response as "Movius line" right, ornot? Is the Pleistocene environmental reconstruction developed for Africa, Europe andNorth America do not fit well with the Asian date as some researchers claimed? TheQuaternary researches especially in the Loess Plateau of China and the China Seasduring the past two or three decades have showed us a clear response, which is incontradichon with that of Movius line.The Loess Plateau occupies about 450 000 km2 in area in the middle reaches ofthe Huanghe River. The loess deposits can be as 100m or even 200-400m thick,and recorded the complete information of the environmental changes in the last 2.5million years. Based on the concept of pedostratigraphy and the research results ofgeochemistry and geophysics, the climate of the last 2.5 million years in the LoessPlateau consisted of 37 cycles, which can be further divided into 110 sub-stages.According to the changes of magnetic capacity in the loess deposits, during the last2.5 million years there have been at least 44 climatic events similar to theinterglaciation of the Holocene. Moreover, based on the observation of pedology inloess profile, the loess-paleosol sequence records 56 events of soil-formation.Based on the research of the changes of the China Seas, the China Seas werereduced to one third of the present size due to the low sea-level during the lastglacial maximum from 20 000-15 000 aB.P. This sea level was about 120 m lowerthan at present. At the same bine, the Huanghai Sea and Bobal Sea changed into land,the East China Sea was reduced into an longitude trough, the South China Seabecame a send-enclosed sac-shaped gulf connected with the Pacific mainly throughthe Bashi Strait. Its area was about one fifth smaller than it is now. All the largerivers emptied directly into the steep continental slope then.The climatic fluctuations caused directly by the environmental changes mentionedabove can be observed from tWo major aspects. The first is the reorganization of theocean surface circulation and remarkable decrease of the sea surface temperature.During the glacial maximum, due to the Polar Front in the North Pacific shiftedsouthward, temperate waters of the North Pacific could migrate southward to reach theBashi Strait and partly enter the paleo-South China Sea; the passway of the EquatorialWarm Water to the southwestern part of South China Sea was cut off, and the albedoincreased because vast continental shelves were exposed, the sea surface temperature inthe China Seas in estimated 3.5-6℃ lower than at present. This is remarkably lowerthan that in the adjacent open oceans at the similar latitudes. The second aspect isthat both the reduction of sea area and the decline of sea surface temperature musthave caused a decrease in evaporation from the sea surfac