Scientists reveal how humans populated the ancient megacontinent of Sahul

Between 75,000 and 50,000 years ago, humans began to traverse the Sahul megacontinent, a landmass that linked what are now Australia, Tasmania, New Guinea and the Aru Islands.

New research reveals more about the routes used by these early humans and the time it took them to fully explore Sahul’s extremities. It could have taken up to 10,000 years for the vast area to be completely covered by these intrepid humans, which is twice as long as previously thought.

To refine their estimates, the researchers developed a new, more sophisticated model that takes into account influences on travel such as the land’s ability to provide food, the distribution of water sources and the topography of the landscape.

Sahul's map
(Flinders University)

“The ways in which people interact with the terrain, the ecology and potentially other people change our model results, providing more realistic results,” says ecologist Corey Bradshaw of Flinders University in Australia.

“We now have a good prediction of the patterns and processes of how people settled these lands tens of thousands of years ago.”

The researchers combined data from two previously published studies, one that modeled movement patterns and population growth through a grid-based system, and another that mapped likely exploration ‘superhighways’ based on landscape features.

Sahul Maps
Routes and population spread across Sahul. (Bradshaw et al., Quaternary scientific reviews2023)

In addition to extending the prediction to the time needed to colonize the megacontinent due to constraints imposed by topography, the new model also identified a new corridor of undetected southward movement through the center of Sahul.

“A A person walking in the landscape and choosing this basic path repeatedly would likely lead to migration corridors because individuals transmit knowledge of the landscape over time to the rest of the population,” the researchers wrote in their published paper.

Migration probably started through Timor and later through western parts of New Guinea. Rapid expansion would then have taken place southwards towards the Great Australian Bight and northwards to New Guinea.

The researchers also suggest that travel to Tasmania would have been constrained by the rise and fall of sea levels in the Bass Strait – an example of how the new model influences the influence of landscape on population spread.

“Our updated modeling shows that New Guinea was populated gradually over 5,000 to 6,000 years, with an initial focus on the Central Highlands and the Arafura Sea area before reaching the Bismarck Archipelago in the east,” says Bradshaw.

“The peopling of the Far Southeast and Tasmania is predicted to have occurred between 9,000 and 10,000 years after the initial arrival on Sahul.”

The researchers think their findings could apply to other parts of the world when it comes to mapping how homo sapiens they left Africa, passed through Asia and arrived in the Americas, although the models had to be adapted to suit different regions.

These predictions could then be supported and verified using findings from archaeological excavations, which was the case in this particular study.

Whether it’s preferring a route across two mountains rather than over them or sticking close to water sources, these details can be significant when it comes to where populations spread out and how quickly.

“It also shows the power of combining computer models with archeology and anthropology to refine our understanding of humanity,” says archaeologist Stefani Crabtree of Utah State University.

The research was published in Quaternary scientific reviews.

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