The evolutionary history and human settlement of Australia and the Pacific

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Understanding the timing and processes involved in the human settlement of Australia and the Pacific has significance for addressing some key debates relating to human origins and population expansions worldwide. Despite this, for many years, Pacific populations were seriously under-represented in genetic studies of human origins. The last 15 years, however, have seen some major genetic studies involving Australian and Pacific populations which have shed light on their origins and interactions, and the last five years have seen some major developments that are challenging long-held concepts of Pacific settlement.

Introduction

Genetic and archaeological data from the Australia-Pacific region have been important for addressing major topics in modern human evolution such as the dates and directions of the out of Africa migrations of modern humans, understanding the impact and history of integration with our hominin cousins, and theories regarding the impacts of Neolithic expansions. With recently reported dates for human occupation as early as 60,000–65,000 years before present (BP) [1], Australia represents one of the earliest locations outside of Africa to be settled by humans, while Aotearoa/New Zealand, first occupied only 730 BP, was the last major land mass to be settled [2]. The relative isolation of the region offers unique conditions that can be valuable for reconstructing migration patterns and identifying population interactions, though the extent of post-settlement interaction between geographically isolated island populations should not be underestimated. Pacific peoples were highly skilled navigators and sailors, capable of strategic and safe, two-way, long-distance, open-ocean voyaging [3].

For many years, the Australia-Pacific region was relatively underrepresented in major genetic studies and reviews. This was due to several factors, including indigenous concerns over the ethics of genetic studies [4] but also due to the isolated nature of many populations in the region, which can make it difficult and expensive to undertake fieldwork and sample collection. In recent years, however, significant inroads have been made, with frameworks for research with indigenous communities being generated by indigenous researchers [5] and education of both researchers and communities regarding rights and expectations when engaging in or participating in genetic research [6,7]. As a result, appropriate consultation and discussions regarding control of data are increasingly taking place and several genomic studies on both modern and ancient populations in the Australia-Pacific region have been published with community consent, support and engagement.

Section snippets

Hominin introgression

At some point during their migrations en route to the Australia-Pacific region, humans could have come into contact with at least three other hominin groups  Neanderthal, Denisovans and Homo floresiensis. Like all non-African populations, Pacific peoples carry evidence of introgression with Neanderthals. All indigenous populations in the Australia–Pacific region also carry Denisovan markers, with Australian Aboriginals and some populations in Near Oceania, carrying as much as 4%, the highest

Pleistocene settlement of Sahul and Near Oceania

The rapidly accumulating genetic evidence from Australia and New Guinea consistently suggests continuous occupation of Sahul, the greater Australia/New Guinea continental landmass, resulting from a single colonization event of deep time depth [9,13,14,15,16]. Archaeological evidence of human presence across the continent by 40,000 BP (Figure 1) [17] suggests that populations were low density but highly mobile. Evidence of human occupation of the Bismarck Archipelago, which was never connected

Holocene arrivals in Near and Remote Oceania

Significant changes in the landscape of the region occurred both at the beginning of the Holocene, when the rising sea levels separated New Guinea and Tasmania from the Australian continental mass, and during the mid-Holocene when major changes occurred along the north coast of New Guinea. New environments opened up for population expansion and provided new opportunities for interaction [21,22]. For example, in the Sepik-Ramu basin, which had previously been an inland sea, lowered sea levels

Neolithic, Lapita expansions

Demographic and environmental changes associated with the Neolithic revolution in Southeast Asia during the mid-Holocene resulted in the movement of people into and throughout Island Southeast Asia [26]. At this time, Neolithic peoples speaking Austronesian languages and carrying new genetic markers arrived in the Pacific and not only settled and interacted with the original, “Papuan” inhabitants, but moved out to the previously uninhabited islands of Remote Oceania (the islands to the east and

Final expansion through the Polynesian Triangle

The settlement of Central and East Polynesia was separated from the Lapita expansion by over 1500 years. This final expansion across the Pacific began only 1200–1000 years ago and ended around 750 years ago with the settlement of Rapanui/Easter Island and Aotearoa/New Zealand. It has also been suggested that Polynesians made contact with the mainland of South America at about this same point in time [41,42,43] and that return voyages introduced both South American cultivars [44,45] and genes to

Commensal plant and animal DNA as a proxy for tracing human migrations

Beginning in the late 1990s, partly in response to concerns over genetic studies of indigenous peoples in the region, it was recognized that DNA analyses of extant and ancient samples of plants and animals transported in founding canoes by the colonists who settled Remote Oceania might provide a way of tracking the movement of colonizing canoes (see [51] for a review). The genetic analyses of these `commensal’ plants and animals have and continue to provide evidence of complex histories of

Discussion and conclusion

With the rapid increase in genomic data from the region, we urge the establishment of strong, multidisciplinary relationships between geneticists and appropriate experts in the regional culture history as well as with the local indigenous communities through all phases of the research, from project design, to sample collection and finally interpretation of results. The cultural, archaeological and historical context must be considered, particularly for ancient samples and for situations where

Conflict of interest statement

Nothing declared.

References and recommended reading

Papers of particular interest, published within the period of review, have been highlighted as:

  • • of special interest

  • •• of outstanding interest

Acknowledgements

We thank Les O’Neill for contributing Figure 1, Figure 2.

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