Assessment of the Southern Dispersal: GIS-Based Analyses of Potential Routes at Oxygen Isotopic Stage 4

This paper explores the geographic and environmental context of the Southern Dispersal Route, which has been proposed as a migratory route for Homo sapiens from East Africa to Australasia during oxygen isotope stage (OIS) 4 (71–59 kyr). A series of assumptions and constraints garnered from modern hunter-gatherer observations are used to build a model of coastal foragers, which is then integrated with high-resolution physiographic analyses to produce a potential dispersal route along the coastline of the Indian Ocean. Paleoenvironmental conditions that may have supplied critical resources or served as obstacles to human colonization are identified and discussed in regards to human subsistence, the speed of migration, and demographic expansion. These factors suggest that rapid dispersals along coastlines and river valleys would have occurred upon the initial expansion out of Africa, but slowed as populations expanded demographically into South Asia and the Sunda Shelf. This also suggests that archaeological signatures relating to the earliest modern Homo sapiens are more likely to be recovered in South Asia.