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There is an increasing body of evidence to suggest Homo sapiens emerged from Africa episodically with at least one of these early dispersals reaching Southeast Asia and Australia; however our understanding of how, when and where this took place is still evolving. Multiple fossil sites place H. sapiens in Southeast Asia and Sunda (the Pleistocene continent now comprising the Malay Peninsula, Sumatra, Borneo, Java, and Bali) by Marine Isotope Stage 4 (MIS 4, 71–57 ka). Archaeological evidence for an MIS 4 human presence in Sahul (the Pleistocene continent now comprising Australia and New Guinea) exists at sites in a restricted geographic region in Western Arnhem Land, northern-central Australia. During the Late Pleistocene, the vast Wallacean archipelago separated Sunda and Sahul, requiring a maritime dispersal to reach Sahul from mainland Asia. There are two main migration corridors through Wallacea (termed the northern and southern routes), with computational modelling suggesting dual migration events occurred at the Bird’s Head of New Guinea (northern gateway region) and northwest Australia (southern gateway region), with genetic and disease data supporting distinct populations. In contrast to the Sunda and Sahul evidence, the earliest documentation of H. sapiens in Wallacea dates to mid-Marine Isotope Stage 3 (MIS 3, 57–29 ka), lagging behind the continents to the east and west. With over 1600 islands in the archipelago, the search for archaeological and fossil sites with an early-MIS 3 and MIS 4 record is laborious, with many regions still archaeologically unknown. To complicate matters, large portions of both Sunda and Sahul have experienced marine inundation, drowning much of the archaeological record. Additionally, excavations at many of the known archaeological sites in both Wallacea and Australia occurred some time ago, and their potential to hold evidence for early occupation may warrant reinvestigation. This thesis addresses the overarching question: “What

The peopling of Sahul (the combined continent of Australia and New Guinea) represents the earliest continental migration and settlement event of solely anatomically modern humans, but its patterns and ecological drivers remain largely conceptual in the current literature. We present an advanced stochastic-ecological model to test the relative support for scenarios describing where and when the first humans entered Sahul, and their most probable routes of early settlement. The model supports a dominant entry via the northwest Sahul Shelf first, potentially followed by a second entry through New Guinea, with initial entry most consistent with 50,000 or 75,000 years ago based on comparison with bias-corrected archaeological map layers. The model’s emergent properties predict that peopling of the entire continent occurred rapidly across all ecological environments within 156–208 human generations (4368–5599 years) and at a plausible rate of 0.71–0.92 km year . More broadly, our methods and approaches can readily inform other global migration debates, with results supporting an exit of anatomically modern humans from Africa 63,000–90,000 years ago, and the peopling of Eurasia in as little as 12,000–15,000 years via inland routes.

© 2020, Crown. India is located at a critical geographic crossroads for understanding the dispersal of Homo sapiens out of Africa and into Asia and Oceania. Here we report evidence for long-term human occupation, spanning the last ~80 thousand years, at the site of Dhaba in the Middle Son River Valley of Central India. An unchanging stone tool industry is found at Dhaba spanning the Toba eruption of ~74 ka (i.e., the Youngest Toba Tuff, YTT) bracketed between ages of 79.6 ± 3.2 and 65.2 ± 3.1 ka, with the introduction of microlithic technology ~48 ka. The lithic industry from Dhaba strongly resembles stone tool assemblages from the African Middle Stone Age (MSA) and Arabia, and the earliest artefacts from Australia, suggesting that it is likely the product of Homo sapiens as they dispersed eastward out of Africa.

The timing, context and nature of the first people to enter Sahul is still poorly understood owing to a fragmented archaeological record. However, quantifying the plausible demographic context of this founding population is essential to determine how and why the initial peopling of Sahul occurred. We developed a stochastic, age-structured model using demographic rates from hunter-gatherer societies, and relative carrying capacity hindcasted with LOVECLIM's net primary productivity for northern Sahul. We projected these populations to determine the resilience and minimum sizes required to avoid extinction. A census founding population of between 1,300 and 1,550 individuals was necessary to maintain a quasi-extinction threshold of ≲0.1. This minimum founding population could have arrived at a single point in time, or through multiple voyages of ≥130 people over ~700-900 years. This result shows that substantial population amalgamation in Sunda and Wallacea in Marine Isotope Stages 3-4 provided the conditions for the successful, large-scale and probably planned peopling of Sahul.

Colonisation of Sahul 70-60 thousand years ago (kya) represents the first great maritime migration undertaken by anatomically modern humans in one of the final phases of the Out of Africa dispersal. Visual connectivity network analyses, agent-based simulations and ocean current modelling reveal that modern humans could follow numerous northern and southern migration pathways into Sahul. Our results support a southern route out of Africa through South Asia with entry into ISEA through the Banda Arc, culminating in an early colonisation of Sahul on the northwest shelf. Our results show multiple colonisation events through other entry points were also probable, and raise interesting possibilities for complex regional migration and population histories.

The First Australians were among the world's earliest great ocean explorers, undertaking a remarkable 2,000km maritime migration through Indonesia which led to the discovery of Australia at least 65,000 years ago. But the voyaging routes taken through Indonesia's islands, and the location of first landfall in Australia, remain a much debated mystery to archaeologists. Our research, published earlier this year in Quaternary Science Reviews, highlights the most likely route by mapping islands in the region over time through changing sea levels.