Scientists reveal how humans first populated ancient megacontinent Sahul : ScienceAlert

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

New research is revealing more about the routes taken by these early people and the time it took them to fully explore the extremities of Sahul. 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 took into account travel influences such as the country’s ability to provide food, the distribution of water sources and the topography of the landscape.

Sahul card
(Flinders University)

“The way people interact with terrain, ecology and possibly other people changes our model results and provides more realistic results,” says ecologist Corey Bradshaw of Flinders University in Australia.

“We now have a good prediction of the patterns and processes by which humans first settled these lands tens of thousands of years ago.”

The researchers combined the data from two previously published studies, one that modeled patterns of population movement and population growth via a grid-based system, and one that mapped the likely “highways” of exploration based on landscape features.

Maps of Sahul
Routes and population distribution in Sahul. (Bradshaw et al., Reviews of the Quaternary Sciences2023)

The new model not only extended the prediction for the time it would take to colonize the megacontinent due to topographical constraints, but also identified an undiscovered new corridor of movement south through central Sahul.

“A Person walking on the landscape and choosing this basic path repeatedly would likely result in migratory corridors as individuals pass knowledge about the landscape to the rest of the population over time,” the researchers write in their published work.

Migration most likely began through Timor, then later through western parts of New Guinea. A rapid expansion would then have occurred southward toward the Great Australian Bight and northward into New Guinea.

The researchers also suspect travel to Tasmania would have been limited by the rise and fall in sea levels in the Bass Strait – an example of how the new model accounts for the influence of landscape on population distribution.

“Our updated modeling shows that New Guinea was gradually settled over the course of 5,000 to 6,000 years, initially concentrating on the central highlands and the Arafura Sea, before reaching the Bismarck Archipelago to the east,” says Bradshaw.

“The colonization of the extreme south-east and Tasmania is said to have occurred between 9,000 and 10,000 years after the first arrival at Sahul.”

The researchers believe their findings could be applied to other parts of the world when it comes to how to map homo sapiens from Africa via Asia to America, whereby the models had to be adapted to different regions.

These predictions could then be substantiated and verified with finds from archaeological excavations, which was the case in this particular study.

Whether it’s cutting a route through two mountains rather than over them, or staying close to water sources, these details can be important when considering where and how quickly populations are spreading.

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

The research was published in Reviews of the Quaternary Sciences.

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