How did Homo erectus reach Java? Least-cost pathway models and a consideration of possible Sumatran routes

The earliest Homo erectus remains in Southeast Asia are in opposite reaches of this geographical region. H. erectus material from Gongwangling, China, and Mojokerto, Java, represent some of the earliest body fossils recovered for this species, but very few H. erectus records exist from between these regions. We examine possible routes that H. erectus could have taken on their journey southward, using a least-cost pathway analysis. Our models suggest that the easiest pathway ran through the centre of Sundaland, an area now almost entirely submerged. During periods of higher sea-levels, however, the pathway moved west and could coincide with emergent areas on or just off the east coast of Sumatra. Geological conditions on the east coast of Sumatra, while of the right age to contain early hominin remains, are not conducive to the preservation of fossil material or the retention of suitable quarries for stone artefact production. The Riau archipelago also lies on probable migration routes; however, geological outcrops of the right age will probably be difficult to find there.