Paddy fields are central to the origin and spread of rice agriculture and their development ultimately underpinned the formation of complex societies in Asia. Here, the authors report on the stratigraphy, radiocarbon dating and archaeobotanical record from Shiao, including one of the earliest and largest paddy fields yet identified (c. 6700 cal BP). As at nearby sites, paddy fields were successively overlaid with peat and marine sediments as sea level vacillated. With each iteration, the fields evolved from strip-like to ‘hash’-shaped configurations, representing growing labour input and, crucially, a corresponding increase in sustainable population size.