Vegetation and climatic context of rice domestication during the Paleolithic–Neolithic transition at Shangshan site in China

The middle and lower reaches of the Yangtze River in China are recognized as the core region for the origin of rice agriculture. Knowledge of the vegetation and climatic context is important for understanding the mechanisms of the origin of rice agriculture in this region. However, we lack detailed understanding of how the transition from wild to domesticated rice interacted with changes in vegetation and climate during the Paleolithic–Neolithic transition. To address this, we conducted analyzes of pollen, algae, and charcoal of a section at the Shangshan site, spanning this transitional period. We then produced quantitatively reconstructed changes in vegetation and climate using modern pollen–climate models. Our results show: 1) During the period of wild rice growth from ~100 to ~15 cal kyr BP, the regional vegetation, which alternated between north subtropical mixed forest and forest-steppe, was controlled primarily by climate. The local vegetation included hygrophilous and aquatic plants such as Gleicheniaceae, Poaceae, Cyperaceae, and Pediastrum. The mean annual precipitation (MAP) was ~1,100–1,400 mm, along with persistent subtropical components, indicating a northern subtropical–warm temperate climate that provided suitable climatic and vegetation conditions for wild rice growth. 2) During 15–13 cal kyr BP (Bølling–Allerød warm stage), broadleaved trees including evergreen Quercus and Ulmus increased slightly, accompanied by a rise in MAP to ~1,300 mm. This warm and humid climate, combined with the pressure of population growth, may have initiated wild rice management by humans. 3) During 13–11 cal kyr BP (Younger Dryas cold stage), there were decreases in broadleaved trees, including evergreen Quercus and Ulmus, decreased and MAP decreased by ~150 mm. Environmental stressors impacted but did not halt the process of wild rice domestication. 4) During 11–8 cal kyr BP, the climate warmed, MAP increased to ~1,300 mm, and broadleaved trees increased. These changes created favorable conditions for the completion of the process of rice domestication. Although anthropogenic impacts on vegetation were intensified and the charcoal concentration increased during this period, the pollen assemblages remained dominated by natural vegetation. This study provides quantitative evidence for the environmentally-driven mechanisms of rice domestication and contributes to an improved understanding of the coevolution of climate and agriculture co-evolutionary, providing data to support modern wild rice conservation strategies.