Agricultural intensification and its impact on environment during Neolithic Age in northern China

Abstract

The nature of an Anthropocene has been increasingly discussed and debated in the last two decades, with a focus on the arguments for or against the “Anthropocene” as a geological epoch. Some argue for an onset of Anthropocene between 1945‒1964 AD, when intensive atmospheric nuclear testing resulted in peak values of 14C that is widely recorded in tree rings and sediments, while other scholars argued its beginning may be traced back to the early Holocene. This latter argument is related to the beginnings of significant landscape modification through the development and spread of agricultural practices in old world since 10000 a BP. The Yellow River valley of northern China is the center for the domestication of millet crops (broomcorn millet and foxtail millet), however, the intensification and expansion of millet-based agriculture during the Neolithic period and its impact on the environment has not been well understood. Recent development of archaeometry methods and their application to archaeological research, such as archaeobotanical studies, and carbon and nitrogen isotope analysis of human and animal bones unearthed from Neolithic and Bronze sites in north China, has greatly deepened our understanding of the timing of millet-based agriculture and its development. In parallel, the analysis of paleoenvironment proxies including black carbon and pollen assemblages from natural sediments, has shed light on the impact of human slash-and-burn cultivation on their surrounding environments during both prehistoric and historical times. This paper reviews carbon isotope analysis of human, pig and dog bones, and radiocarbon dates from Neolithic sites, and compares them with black carbon content from palaeoenvironment records in northern China, in order to explore the temporal-spatial intensification and expansion of millet-based agriculture in the area and its possible impact on environment. It can be concluded that millet cultivation was an auxiliary subsistence strategy in northern China from 10000 to 7000 a BP with hunting-gathering the primary subsistence strategy, the earliest millet-cultivation might have emerged in eastern Inner Mongolia post 7700 a BP. Millet cultivation transited from a secondary strategy to become dominant in the Guanzhong area of north-central China during 7000‒6000 a BP, and probably facilitated the development of early Yangshao culture in the middle reaches of the Yellow River valley. Intensive millet-based agriculture emerged and widely expanded across the Yellow River valley in northern China during 6000‒4000 a BP. This promoted rapid population growth and cultural evolution in the late Neolithic period, and was key in the subsequent emergence of the ancient Chinese civilization. The temporal-spatial variation of black carbon (EC-soot) corresponds well with the intensification and expansion of millet-based agriculture during Neolithic period. The content of EC-soot increased in sediments of Daihai lake and the Horqin sandy lands in Inner Mongolia from about 7500 a BP soon after farming of millet appeared in Xinglongwa and Xinglonggou sites nearby, which evidently increased in Shaanxi Province of north central China post 6000 a BP, when intensive millet-based agriculture firstly emerged in the area. This suggests millet agriculture production activities exerted significant impact on fire frequency in northern China during the Neolithic, and thus the scale and intensity of the impact of farming increased from that period. This work provides a valuable case study for understanding the temporal and spatial development of millet agriculture, and human-environment interactions in northern China during Neolithic period from an Anthropocene perspective.