Beyond the Southern Route Dispersal to Eastern Asia: Possible Inland Corridors for Modern Human Movement in the Late Pleistocene

Myat Thinn Nu Aung1*, FAN Yaobin2, and Christopher J. Bae1

Models on early human dispersals across Asia have widely emphasized the “Southern Dispersal Route” along the Indian Ocean rim. However, this study evaluates potential dispersal routes of inland ecological corridors that likely existed across Mainland Southeast Asia, including southern China during the Late Pleistocene. This work examines the paleoenvironmental and faunal records from several Late Pleistocene fossil sites in southern China to reconstruct the impact of environment during the Last Glacial Period on the ecosystem, which in turn, would have influenced the movement and behavior of modern humans in the region. As a proxy, we examine equids as the indicators of open habitats because they are typical grazers closely related to C4 grassland environments. Here, we map the spatial distribution of equid fossil sites across southern China and Mainland Southeast Asia between Marine Isotope Stages (MIS) 4 and 2 and the associated faunal assemblages, as well as available stable isotope data. We focus on two fossil cave sites in Guangxi, southern China, that have yielded Equus fossils: Nanshan Cave in Fusui and Lower Pubu Cave in Bubing, which are dated to ~30-40 ka and ~64 ka, respectively. In these sites, rainforest-adapted species declined, while Equus is present. This reflects a situation where, despite C3-based forests remaining dominant, there was an increase in C4 vegetation, collectively supporting a case for cooler and drier environments between MIS 4 and 2. This study suggests the southward expansion of a relatively open environment, which may have created corridors for larger terrestrial mammals, including humans.