A 500-year cycle of demographic expansion and contraction in the lower Yangtze and adjacent coastal region during the Holocene driven by East Asian summer monsoon oscillations

Centennial-scale climate–human interactions provide critical insights into societal adaptation to environmental change, yet their dynamics in East Asian coastal systems are still poorly understood. Here we analyze 1,008 radiocarbon dates from Neolithic to Bronze Age archaeological sites across the lower Yangtze River and adjacent coastal region to reconstruct 10,000 years of population dynamics using summed probability distributions. Our demographic record reveals prominent ∼500-yr cycles superimposed on long-term trends, with 14 population maxima occurring at around 9,700, 9,200, 8,600, 8,000, 7,200, 6,700, 6,300, 5,800, 5,200, 4,700, 4,300, 4,000, 3,500, and 3000 calendar years before present (cal yr BP). Time-series analysis demonstrates that these demographic cycles lag East Asian summer monsoon fluctuations by ∼60–170 yrs, indicating systematic climate-driven population responses mediated by ecological processes. Unexpectedly, weakened monsoon phases increased regional precipitation, enhanced food resource availability, and supported demographic expansion, while intensified monsoon conditions reduced precipitation and constrained population growth via food resource limitations. This climate–population coupling temporarily broke down between ∼7,800 and ∼5,500 cal yr BP, coinciding with reduced monsoon variability and enhanced societal resilience during the Kuahuqiao–Hemudu/Majiabang–Songze transitions. Our findings demonstrate a persistent centennial-scale link between monsoon variability and prehistoric demography, offering new insights into climate–societal dynamics across monsoon Asia. • Analysis of 1,008 dates reveals ∼500-yr population cycles in the lower Yangtze over the past 10 kyr. • Population lags monsoons by ∼60–170 yrs; weak monsoons drove expansion via increased precipitation. • Agriculture and social complexity decoupled population from climate between ∼7.8 and 5.5 ka BP.