The Holocene optimum (HO) and the response of human activity: A case study of the Huai River Basin in eastern China

There is a controversy regarding the timing of the onset of the Holocene optimum (HO) in the Huai River Basin in eastern China, reflecting the scarcity of well-dated high-resolution sedimentary records in the region. In this study we validate the time-transgressive onset of the HO in the East Asian Monsoon (EAM) region and update a regression model of the onset of the HO versus latitude. We also estimate the onset time of the HO in the Huai River Basin to 9100-8000 yr BP, which is confirmed by other well-dated geological records from within and around the basin. We also compared our age estimate with data from archaeological sites in the Huai River Basin and with the record of rice remains in eastern China. The result indicates that a dramatic increase in the number of archaeological sites and the northward expansion of rice cultivation, which eventually occupied the entire Huai River Basin, corresponds temporally to the onset of the HO. Thus our results suggest that the prosperity of prehistoric culture in the Huai River Basin was enhanced by the initiation of the HO. Our findings reveal a close relationship between the onset of the HO in the Huai River Basin and human activity, and they provide an improved understanding of the response of human activity to climate change in eastern China.