We report archaeobotanical results from systematic flotation at what is presently the earliest Neolithic site with hard evidence for crop cultivation in the Southwestern Chinese province of Yunnan, at the site of Baiyangcun. Direct AMS dates on rice and millet seeds, included together in a Bayesian model, suggests that sedentary agricultural occupation began ca. 2650 BCE, with cultivation of already domesticated rice (Oryza sativa), broomcorn millet (Panicum miliaceum), and foxtail millet (Setaria italica). Soybean (Glycine cf. max) was also present and presumably cultivated, although it still resembles its wild progenitor in terms of seed size. Additional possible cultivars include melon (Cucumis melo) and an unknown Vigna pulse, while wild gathered resources include fruits and nuts, including hawthorn (Crateagus) and aquatic foxnut (Euryale ferox). Weed flora suggests at least some rice was cultivated in wet (flooded or irrigated fields), while dryland weeds may derive from millet fields. This subsistence system persisted throughout the site's occupation, up to ca. 2050 BCE. These data provide secure evidence for the spread of Chinese Neolithic crops to Yunnan, and provide new evidence for reconstructing possible sources of cereal agriculture in mainland Southeast Asia
