Drylands, the most climate-sensitive terrestrial regions, currently support more than 38% of the world's population. Understanding long-term population responses to climate change in and around these areas provides critical insights for anticipating future societal challenges. We integrate radiocarbon-dated archaeological records, simulated climatic data, the Minimum Terrestrial Resource Model (MTRM), and pollen-based vegetation reconstructions to examine spatiotemporal variations in dryland boundary, population distribution, potential hunter-gatherer density, and plant and animal resource densities in East Asia at four key periods since the Last Glacial Maximum (LGM) (20-19 ka, 15-14 ka, 10-9 ka, and 6-5 ka). From 20-19 ka to 15-14 ka, continued warming and humidification drove a northwestward retreat of the dryland boundary, sustained steppe ecosystems, and increased wild animal food resource richness, fostering population growth and expansion. From 15-14 ka to 6-5 ka, continued climatic amelioration promoted a vegetation transition from steppe to forest in marginal areas of the dryland, decreasing wild animal resource availability and shifting population centers toward more humid regions in the southeast. This ecological transformation coincided with the emergence and intensification of agriculture. These results demonstrate a cascading mechanism in which climate change reshaped vegetation cover and food resource distribution, driving human adaptation and long-term shifts in population geography.