Paleoenvironments of the late Middle Pleistocene Hualongdong, east-central China and their implications for the hominin evolution in eastern Asia

The late Middle Pleistocene (300–129 ka) was pivotal for understanding how paleoenvironmental and climatic changes shaped hominin adaptations. Hualongdong (331–275 ka) yields key human fossils, stone tools, and abundant mammalian remains, enabling detailed paleoecological analysis. Carbon isotopic data from mammalian tooth enamel indicate a C 3 vegetation-dominated forest environment at Hualongdong. The isotopic composition of a large bovid indicates, however, the co-existence of year-round C 4 grasses. Bulk and serial isotopic results reveal a mosaic of dense forests and woodlands shaped by the East Asian Summer Monsoon (EASM). Closed forests would have provided stable resources, while seasonally dynamic woodlands with localized C 4 vegetation would have supported favorable conditions for habitation and movement. Comparative analyses of Middle Pleistocene enamel stable isotopes across eastern Asia (including East and Southeast Asia) highlight distinct paleoenvironments in northern, east-central, southwestern China, as well as in Southeast Asia. Hualongdong in east-central China stands out as a mosaic of dense forests and open woodlands, distinct from the open woodlands of north China and the dense forests of southwestern China. The Hualongdong hominins exhibit a mosaic of derived and archaic traits, representing a significant morphological pattern in the late Middle Pleistocene of eastern Asia. Their successful occupation of this ecotonal landscape as revealed by our isotopic data, underscores the behavioral flexibility that characterized hominin evolution in this region. • Hualongdong (∼300 ka BP) hominins lived in a mosaic of C 3 dense forests and woodlands. • Mammalian enamel isotopes reveal diverse Middle Pleistocene Asia environments. • Comparative isotopic data highlight Hualongdong's unique mosaic environments. • Morphological mosaic shows early hominin adaptation to dense forests.