Tracing the southward spread of Millets: Archaeobotanical evidence from the late Neolithic Zhaizishan site in the middle Han River valley, central China

The southward spread of millets is one of the current hotspots of Chinese archaeological research. The entry of millets into the Jianghan Plain likely followed three routes, with the Han River corridor, linking the Nanyang Basin to the Jianghan Plain, being particularly significant. However, this prevalent hypothesis still requires robust archaeobotanical evidence to support it. At the Zhaizishan site, located at the southern end of Han River corridor, flotation analysis identified rice (Oryza sativa), foxtail millet (Setaria italica) and broomcorn millet (Panicum miliaceum), along with 14 types of non-crop remains. The analysis indicated that during the Youziling culture period (5800–5300 BP), millets were already present near the Jianghan Plain but less prominent within the crop assemblage. However, its significance increased during the Qujialing culture period (5300–4500 BP), although rice continued to be dominant. During the Shijiahe culture period (4500–4200 BP), the importance of millets may have further increased. The discovery of millets at the Zhaizishan site during the Youziling culture period strongly supports the theory that the Han River corridor served as a route for the southward spread of millets, no later than 5300 years ago. In addition, by comparing crop structures at the Zhaizishan and Qujialing sites, we found that natural and cultural factors both contributed to the increasing importance of millets within the agricultural system. Additionally, the sloped terrain would have driven ancient humans to cultivate more millet. This study is of great significance for exploring the spatiotemporal processes of the southward spread of millets and the impacts of millets on the Neolithic crop structure in the middle Yangtze River region, as well as the complex relationships among the natural conditions, archaeological cultures, and prehistoric agriculture.