Emerging Hot Spot Analysis Geogdetector method Global Moran’s I Neolithic China North China Famine of 1876–1879 Structural Equation Modelling Yangtze River valley Yellow River valley bronze age carbon and nitrogen stable isotope ratios climate change correlation dimension method decision tree direct and indirect effects drought heatwaves hierarchy human diet imperial China interaction effect machine learning millet cultivation multi-scale multiple time scales n/a plague precipitation precipitation prediction random forest regional interaction