Millet served as an important staple crop across East Asia throughout much of the Holocene, beginning roughly 11,700 years ago. A study published in PNAS (May 4) by researchers from the Chinese Academy of Sciences shows that changes in growing-season soil temperature played a major role in shaping the emergence and spread of millet farming.



Using loess deposits from the Chinese Loess Plateau, the researchers built a detailed environmental record combining radiocarbon and luminescence dating with biomarker analysis. This allowed them to reconstruct past soil temperatures and vegetation patterns, which were then compared with archaeological evidence and climate simulations.



The results indicate that warmer conditions between about 12,300 and 7,500 years ago were favorable for early millet cultivation. A subsequent cooling phase from 7,500 to 6,000 years ago likely reduced suitable growing areas, contributing to a shift in farming regions and slowing agricultural expansion. As temperatures recovered after 6,000 years ago, millet agriculture expanded more widely.



Overall, the study underscores growing-season soil temperature as a key environmental factor influencing the early development and geographic spread of millet-based agriculture in East Asia.