The Spatial-Temporal Simulation of Mankind’s Expansion on the Tibetan Plateau During Last Deglaciation-Middle Holocene

Abstract

Attributed by vast territory, extremely harsh physical environment, and comparatively integrated geographical unit, the Qinghai-Tibet Plateau has become a valuable site to investigate adaptation regime of prehistoric human to extreme environment. Which is currently focused on single dependent site in most studies, where a integrated research that coves complete scope the plateau is needed. to better understand expansion logic of prehistoric human moving towards the Plateau. This paper build a comprehensive index to indicate the characteristics of natural environment by using GIS software, which is composited with elevation, vegetable type, level of river system, and accumulated temperature of 0 °C etc., combined with the archaeological ages of 69 gathered microlithic sites, followed by environmental adaptation and spreading hypothesis, namely the doctrine of the time of human expansion was broadly consistent in the regions where the natural environments were similar. We simulated the spatial and temporal process of prehistoric human’s migration and expansion on the plateau during Last Deglaciation- Middle Holocene. The results of our study indicated that during the Last Glacial Maximum(24–16 ka B.P., LGM), human activities were very weak, which is mostly likely distributed in the Huang River Valley area of northeastern margin of Tibet Plateau and Yarlung Zangbo River valley of southern Tibet, where elevation was 1,640 m on average; During 15–13 ka B.P., the microlithic hunter-gatherer activities became strong, which had expanded to Qinghai Lake-Gonghe basin of the northeast of Tibet Plateau, and Hengduan Mountains valleys in the east, where elevation was 2,800 m on average. The area of activity region accounted for 5.5% in the Tibet Plateau. Also, during the periods of 13–11 ka B.P., prehistoric human expanded towards higher zones along the valleys of Yellow River, Ya-lung River, Yangtze River and Yarlung Zangbo River, where elevation was 3,658 m on average, the increased expansion area accounted for 11.4% in the Tibet Plateau. The expansion was relatively obvious; During 11–9 ka B.P., with the rapid improvement of environmental conditions, hunter-gatherers expanded to the principal part of the Tibet Plateau. The elevation of expansion area was 3,971 m on average. The increased expansion area accounted for 11.5% in the Tibet Plateau. During 9–7 ka B.P., the human expansion speed was the fastest. During the periods, the expansion area was wide, and the area was maximum in the period. Human activities rapidly expanded to the hinterland of the Tibet Plateau, including the northern Tibet Plateau, the source regions of the Yangtze and Yellow Rivers and Kunlun Mountains. Many regions among them were depopulated zones nowadays. But the locations where some microlithic sites were found, The increased expansion area accounted for 52.2%, in the Tibet Plateau during 9–7 ka B.P. The elevation of expansion area was 4,700 m on average during the periods. And the expansion and occupation of prehistoric human towards the Tibet Plateau was basically completed by then. But regions (accounting for 19% of the plateau) with extreme environmental conditions, such as cold mountain area, desert plateau in Northern Tibet, salt desert in Qaidam Basin had not been occupied. Migration and expansion of prehistoric human towards Tibet Plateau in prehistoric period occurred multiple times. The human expansion during 15–7 ka B.P. was oriented by hunter-gatherers, which happened from the west to the east, from low to high, from the margin to the principal part of Tibet Plateau. The environmental evolution acted as important driver of hunter-gatherers expansion towards the Tibet Plateau during the Last Deglaciation- Middle Holocene. Yellow River and Yangtze River valleys were important passages of prehistoric human expansion towards the Tibet Plateau.