The role of environmental factors in the spatiotemporal distribution of millet in Late Neolithic to Bronze Ages sites in the Tibetan plateau and surrounding regions

Abstract

The Tibetan Plateau and surrounding regions played a pivotal role in the spread of foxtail millet (Setaria italica) and broomcorn millet (Panicum miliaceum) since the late Neolithic period. However, previous research failed to analyze the spatiotemporal distribution and associated environmental factors. Herein, we collected foxtail and broomcorn millet data from 113 Late Neolithic and Bronze Age sites in the Tibetan Plateau region to reconstruct the spatiotemporal distribution, and integrated palaeoclimatic data to identify the extent of environmental factors influencing the distribution using the Maximum Entropy (MaxENT) model and Growing Degree Day (GDD) model. Our results show that the spatiotemporal distribution of millets can be classified into three routes and four stages during 6000–3500 cal yr BP. Millet agriculture thrived predominantly in areas below 2500 m asl with average summer temperature ranging from 15 to 25 °C. Temperature exerts the most significant influence on the dispersal process, followed by precipitation, distance from reliable water sources, and altitude. These findings provide important environmental insights into the spatiotemporal distribution of millets and dispersal routes surrounding the Tibetan Plateau.