Did rainforest expansion entice modern humans into Southeast Asia earlier than is suggested by the available evidence?

As the timing of modern human arrival in Southeast Asia (w48 ka e.g., NiahCave, Tabon cave, Jerimalai) is generally younger than the surrounding continents of Asia (w68 ka or 111-139 ka) and Australia (60-50 ka) it is argued that large gaps exist in the Southeast Asian evidence. These gaps relate to the subsidence, reworking and bioturbation of unconsolidated cave sediments, and a lack of suitable dating techniques applied to keysites. Clearly a new approach is vital for developing the SEA record. Palaeoenvironmental changes in this region caused by variable climatic conditions were responsible for the expansion and contraction of rain-forest environments. Open environments, in the form of savannah corri-dors, prevailed in the drier glacials, but the warm humid conditions of the interglacials brought about the expansion of rainforest corridors through SEA into Indonesia. This caused faunal turnovers, extinctions and created new faunal assemblages. The presence of rainforest diagnostic fauna such as orangutan, gibbon and sunbear in Punung, East Java suggests that this occurred as early as 128-118 ka. The link between modern humans and rainforests has been established at sites such as Niah Cave, Sarawak, where they flourished using elaborate subsistence behavior and sophisticated,habitat-tailored hunting techniques. Therefore, could these‘gaps’contain evidence of modern human arrival in SEA during early rainforest expan-sion? In this paper, we present preliminary results of a novel approach to addressing this question; 1) using breccias instead of unconsolidated sediments, which are well-preserved, rich in habitat-diagnostic fossils and represent a valuable source of palaeoenvironmental evidence; 2) applying an appropriate dating strategy–red TL, U-series, ESR/U-series combined techniques, and; 3) employing novel fossil ID procedures. This analysis demonstrates the potential of breccia deposits to provide fresh insights into the timing of human dispersal in Asia