Palaeogeography and voyage modeling indicates early human colonization of Australia was likely from Timor-Roti

Abstract

Anatomically Modern Humans (AMHs) dispersed rapidly through island southeast Asia (Sunda and Wallacea) and into Sahul (Australia, New Guinea and the Aru Islands), before 50,000 years ago. Multiple routes have been proposed for this dispersal and all involve at least one multi-day maritime voyage approaching 100km. Here we use new regional-scale bathymetry data, palaeoenvironmental reconstruction, an assessment of vertical land movements and drift modeling to assess the potential for an initial entry into northwest Australia from southern Wallacea (Timor-Roti). From ∼70,000 until ∼10,000 years ago a chain of habitable, resource-rich islands were emergent off the coast of northwest Australia (now mostly submerged). These were visible from high points close to the coast on Timor-Roti and as close as 87km. Drift models suggest the probability of accidental arrival on these islands from Timor-Roti was low at any time. However, purposeful voyages in the summer monsoon season were very likely to be successful over 4-7 days. Genomic data suggests the colonizing population size was >72-100 individuals, thereby indicating deliberate colonization. This is arguably the most dramatic early demonstration of the advanced cognitive abilities and technological capabilities of AMHs, but one that could leave little material imprint in the archaeological record beyond the evidence that colonization occurred.

A different paradigm for the initial colonisation of Sahul

“…Relying on essentially the same genetic data, Bird et al . (: 437) make this point explicitly. It is repeated by Kealy et al .…”

“…Bird et al . () are concerned mainly with routes and develop an argument that the southern route would have provided the best corridor for first colonists with “savannah‐adapted skills” as a basis for supporting initial arrival into north Australia from Timor. They work within a wider time framework for this event, between 70 and 47 ka, to cover the long and short chronologies.…”

“…() and Bird et al . () that their models result in “overwhelming support” for initial entry via the northern route, whether one considers the highest or lowest sea‐stands in the relevant period. Of minor importance here, some details of these papers will need adjustment if the sea levels during the MIS 4 glacial period argued by De Deckker et al .…”

“…Evidence from Wallacea and Sahul has slowly accumulated to judge the cognitive, technological and artistic skills of late Pleistocene AMH (see Bird et al . : 437 for a summary and references therein). The idea that both of Birdsell's routes were viable at roughly contemporaneous times seems an inevitable conclusion from the multiple papers dealing with this aspect.…”

A Holocene record of savanna vegetation dynamics in southern lowland Papua New Guinea

“…They are remnants of a once wider, now relict, Sahul geographic range, and date from the past two glacial periods (Nix and Kalma 1972;van der Kaars 1991). The presence of savanna during the last two glacial maxima is of importance to understanding the environmental contexts of human presence and colonisation; evidence of the Sunda-Sahul shelves, areas of shallow sea which may have been dry land at various times and thus providing a savanna corridor, has been used to explain the dispersal of early humans from mainland southeast Asia to Java, onward to eastern Indonesia, PNG and then to Australia (Jones 1980;Jones and Bowler 1980;Bird et al 2005Bird et al , 2016Bird et al , 2018Slik et al 2011). The southern PNG lowlands were also the setting for more recent Austronesian expansions and colonisation processes into Melanesia, notably associated with Lapita peoples of the past c. 3,300 years (for example, McNiven et al 2011McNiven et al , 2012.…”