Cyclic climate impacts on human activity in northern Central China recorded by varve evidence from the western Loess Plateau

Disentangling the relationship between climate change and human activities is a major challenge in paleoenvironmental research. Here, we report a decadal-resolution sedimentological record from an annually laminated archive from the western Loess Plateau spanning the Middle-Late Holocene, along with a database of archaeological radiocarbon dates in northern central China. Our results reveal the occurrence of 400-600-yr cyclic variations in the climate over the last 6200 years, which correlate well with the periodicities of solar activity and the East Asian summer monsoon. This mode of climate change is associated temporally and regionally with specific prehistoric human activities. More favorable warm-humid environmental conditions may have simultaneously facilitated cultural prosperity and population growth, while less favorable cold-dry periods may have led to cultural alterations and population decline. In addition, we determine that there is a closely coupled relationship between the fluctuations in geopolitical and socioeconomic variables and the cyclicity of the environmental changes in imperial China. That is, the warm-humid cycles are characterized by the northward expansion of agriculturalist empires, a decrease in the number of battles, bumper grain harvests, and economic development, while the cold-dry cycles are characterized by the southward expansion of pastoralist empires, an increase in the number of battles, famines, and economic recession. Further analysis of our study will increase the understanding of human dispersal, cultural exchanges, and climate-human interactions within and beyond northern China.