Heat treated stone artifacts at Shuidonggou, Northwest China and their archaeological implications

Artifacts from the Shuidonggou (SDG) site complex in Ningxia province provide extensive information and insights regarding the activities of early modern humans in China. Based on a series of experiments and physical analyses, it appears that the stone artifacts from SDG Locality 2 and Locality 12 have undergone heat treatment that enhanced the utilization ratio and knapping properties of the lithic raw material from which they were made. In order to investigate the mechanisms involved, compression tests and XRD (X-ray Diffraction) examinations were conducted on lithic raw materials collected surround the SDG sites. The results indicate that the heated stones present lower compression strength and better ductility, and the raw material becomes more homogeneous as well. The process of crack propagation also becomes easier to control, thereby reducing knapping difficulties. The application of heat treatment technology at SDG reflects the production capacities and risk management strategies of the SDG inhabitants and provides evidence for the level of understanding associated with early modern human behavior. This discovery confirms the appearance of this technology in the East Asia around 32 ka BP (which lasts to 11 ka BP), providing new evidence for the spread and distribution of heat treatment technology.