Expansion of grassland/open woodland across the East China Sea shelf since MIS 4 facilitated the early human dispersal

During the last glacial period, there has been controversy over whether the exposed area of the East China Sea (ECS) continental shelf was a vast expanse of grassland or a dense forest. So far, direct paleovegetation and paleoenvironmental evidence over the stages from MIS 4 to MIS 2 on this shelf has been scarce. Moreover, the exposed continental shelf since ca. 60 ka has been hypothesized as a potential migratory corridor for Homo sapiens entering East Asia during the Late Pleistocene. This makes the study of the paleovegetation in the exposed continental shelf areas even more important. The present study is based on a high-resolution, well-dated palynological and sedimentological dataset obtained from core TBF-1, collected from the outer ECS continental shelf, spanning the past 71,000 years. Our results demonstrate a distinct vegetational response to global sea-level fluctuations and concomitant monsoon variability. During the lowstand intervals of MIS 4 and MIS 2 (including the Last Glacial Maximum), the exposed ECS shelf was dominated by a cool, dry temperate grassland biome, characterized by high abundance of herbs such as Artemisia , Poaceae, and Chenopodiaceae, alongside substantial wetland communities indicated by Cyperaceae and Typha . In contrast, the milder conditions of MIS 3 supported a heterogeneous open-forest landscape comprising temperate deciduous broadleaved forests, such as Quercus , Fagus , and Juglans , interspersed with persistent grasslands. These extensive grasslands and associated wetlands formed a vast coastal plain that connected mainland China to the Korean Peninsula and the Japanese archipelago, providing critical resources such as freshwater, game, and traversable terrain for early human foragers. Collectively, these findings provide the first direct paleoecological evidence that the exposed ECS shelf constituted a favorable and viable ecosystem during the last glacial period, thereby substantiating the hypothesis that it served as a crucial conduit facilitating the initial dispersal of early modern humans into East Asia. • First direct pollen evidence from the exposed East China Sea shelf since MIS 4. • Glacial lowstands supported a vast temperate grassland , not forest, on the shelf. • This grassland-wetland mosaic formed a continuous, facilitative corridor from China to Japan. • Vegetation dynamics were tightly linked to global sea-level and monsoon changes. • Provides paleoecological validation for the shelf as a route for early human dispersal.