Reconstructing Palaeogeography and Inter-island Visibility in the Wallacean Archipelago During the Likely Period of Sahul Colonization, 65-45000 Years Ago

The palaeogeography of the Wallacea Archipelago is a significant factor in understanding early modern human colonization of Sahul (Australia and New Guinea), and models of colonization patterns, as well as archaeological survey and site interpretation, are all heavily dependent on the specific palaeogeographic reconstruction employed. Here we present five reconstructions for the periods 65, 60, 55, 50, and 45000 years ago, using the latest bathometric chart and a sea-level model that is adjusted to account for the average uplift rate known from Wallacea. Using this data we also reconstructed island areal extent as well as topography for each time period. These reconstructions were then used to estimate visibility for each island in the archipelago, and finally to model how intervisible each island was during the period of likely human colonization. Our models provide the first evidence for intervisibility between Timor and Australia at ca. 65-62 ka and 47-12 ka, the second of which is notable for its overlap with the oldest radiocarbon dates from Timor-Leste and Australia. Based on intervisibility alone, however, our study suggests that the northern route into Papua New Guinea was the most parsimonious route for first modern human entry into Sahul. Our study provides archaeologists with an important baseline from which to conduct physical surveys, interpret archaeological data, and theorize the colonization of Wallacea and Sahul.