Food production and agricultural systems on the southwestern frontier of the Han Empire: archaeobotanical remains from the 2016 excavation of Hebosuo, Yunnan

Dian Basin in Yunnan province is an important center for both early agricultural production and centralized state formation. Settled agricultural villages are present in the province since at least the third millennium BC, and by the first millennium BC, the Dian Culture, a highly specialized bronze polity, flourished in the Dian Basin and surrounding area, until it was conquered by the Han in 109 BC. The increased deployment of flotation at recent archaeological excavations in Yunnan allowed the reconstruction of agricultural practices from the Neolithic to the early Bronze Age, documented at Baiyangcun, Haimenkou, and Xueshan among others. However, archaeobotanical evidence relating to the pivotal period right before and after the Han conquest have so far been lacking, with only limited written records about agricultural production in the Shiji by Sima Qian. Here we present for the first time direct archaeobotanical evidence relating to this transitional period as revealed by rich Han period deposits found during the 2016 excavation of Hebosuo, the largest Dian settlement investigated in Yunnan so far, dated by direct AMS on charred cereal grains and artefactual evidence as spanning from between 850 BC–220 AD. Following the Han conquest, the main components of the agricultural system did not undergo radical changes, but the weedy flora indicates a heavier reliance of wet-land rice systems, evidencing a higher level of water management or even irrigation practices, and the consequent intensification of the agricultural production. These findings on shifting agricultural regimes in Yunnan also contribute to current debates about the interplay between intensification, food risk, and ecology in times of political instability.