Ancient humans took two routes to Australia 60,000 years ago

When and how ancient people Reaching what is now Australia and New Guinea sparked a long and heated debate. Now the results of a genetic study show that this happened at least 60,000 years ago and almost certainly occurred in two different ways.

Mainland AustraliaTasmania and New Guinea once made up the giant ancient continent of Sahul, which existed during glacial maxima when sea levels were lower. For years, archaeologists have been interested in humanity's arrival there, since even at lower sea levels it would have required a treacherous crossing of at least 100 kilometers of open ocean.

There are two main suggestions for when they reached Sahul: the first says it was at least 60,000 years ago, and the second says it was about 45,000 years ago.

As for how they did it, scientists have put forward two possible paths. The first was the southern one, which ran from what is now mainland Southeast Asia, through the Sunda region, including Malaysia, Indonesia and the island of Timor, and then by sea to Australia. The second is the northern route, which has more convincing evidence to support this – suggests that people migrated to what is now New Guinea through the Philippines and Sulawesi, where million-year-old stone tools have recently been found made by hominins.

To get to the bottom of it, Martin Richards from the University of Huddersfield in the UK and his colleagues analyzed almost 2,500 genome sequences from Indigenous Australians, Papua New Guineans and people from across the Western Pacific and Southeast Asia.

After studying the rate of DNA mutations and genetic connections between populations, the team concluded that the first settlement of Sahul People actually took both routes, although most used the northern one.

The researchers may have also asked when this happened, before bed. “We dated both settlements to about the same time—about 60,000 years ago,” says Richards. “This supports the so-called 'long chronology' of settlement, as opposed to the so-called 'short chronology', which suggests occupation from about 45,000 to 50,000 years ago.”

The study also shows that the migration was not simply one-way, based in part on the discovery of an ancient New Guinean genetic line found in a 1,700-year-old Iron Age burial site on Sulawesi. The team also found evidence that very soon after reaching Sahul, sailors and coastal residents headed to what is now the Solomon Islands.

Adam Brumm at Griffith University in Brisbane, Australia, says the growing field of paleogenetics – the study of the past using preserved genetic material – means that “history seems to change from paper to paper.”

“I think this study gives strong support to the growing idea that the northern route was key to the original settlement of Australia,” Brumm says. “This is already becoming increasingly likely based on our discoveries of very ancient rock art on Sulawesi, Wallace's largest island.”

The complex rock art here dates back to at least 51,200 years ago, Brumm said. “I strongly suspect that people were painting in the caves and shelters of Sulawesi as far back as 65,000 years ago or more.”

Peter Vet at the University of Western Australia in Perth say even the most conservative estimates at the Majedbebe site in Australia's Northern Territory now suggest signs of human activity date back more than 60,000 years ago, and the new work adds weight to the earlier arrival of people at Sahul.

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