Rice cultivation and its environmental and social contexts at the Shimao site, Northwest China

The Shimao site, a large settlement that developed in the Late Longshan period (2300 − 1800 BCE), represents the northernmost recovery of rice (Oryza sativa L.) grains dating from the Late Longshan to Erlitou periods in northwest China. The presence of these rice grains has sparked debate on whether they were locally cultivated or acquired through trade. This study conducted phytolith analysis and Growing Degree Days (GDD) modeling on cultural deposits from the Huangchengtai location at the Shimao site, covering both the Shimao and Zhukaigou cultural periods. Phytolith analysis results showed a high frequency and density of rice stem and leaf phytoliths which, alongside their presence across multiple phases of occupation, supporting the possibility of local small-scale cultivation. The GDD model analysis indicates that even with a 2 °C temperature drop, the area around the Shimao site could still support the growth of japonica rice. Additionally, previous studies on charcoal and soils suggest that the climate in northern Shaanxi between 2500 and 1500 BCE was warmer and more humid than today, providing favorable conditions for rice cultivation. Evidence of social stratification, high-status artifacts, and feasting-related remains at Shimao collectively indicates that rice cultivation may have been driven by the need to display hierarchy and support ceremonial feasting. Moreover, the robust development of the Shimao site significantly enhanced its ability to procure rice resources and organize rice cultivation. This paper provides key evidence of the northernmost rice cultivation in northwest China from 2000 to 1600 BCE and offers basic information for understanding the routes and motivations behind the northward spread of rice.