A landmass that was once home to up to half a million people has been discovered off the coast of northern Australia.
The now-submerged continental shelf was a vast, habitable landscape for most of the past 65,000 years, covering about 390,000 square kilometers (about 242,300 miles)—an area larger than New Zealand.
The scientists who made the landmark discovery, led by Kasih Norman of Queensland’s Griffith University, said the “complex landscape” that existed on Australia’s northwest shelf was “unlike any landscape found on our continent today”.
And yet the people who lived there spoke similar languages and created similar styles of rock art to people living in surrounding areas, the team reported in a news release.
These regions, once connected by the shelf, still exist: West Arnhem in the north and the Kimberley in the northwest.
Norman and her colleagues explained that when the last ice age ended about 18,000 years ago, global warming caused sea levels to rise, drowning out the world’s continental belts.
This split the Sahul supercontinent into New Guinea and Australia and cut off Tasmania from the mainland.
A map showing where the continent of Sahul once stood(Kanguole via Wikipedia)
The now submerged continental shelves of Australia were considered ecologically unproductive and the original Aboriginal communities were thus largely ignored.
“But mounting archaeological evidence shows that this assumption is incorrect,” the researchers wrote.
“Many of the large islands off the Australian coast – islands that once formed part of continental shelves – show signs of occupation before sea levels rose.”
Yet until Norman and her team conducted their investigations, archaeologists were only able to speculate about the nature of these pre-Ice Age submerged landscapes and the size of their populations.
But the newly published findings have filled in many of the missing details – revealing that the Northwest Shelf was a lush realm with archipelagos, lakes, rivers and even a large inland sea.
“This area contained a mosaic of habitable freshwater and saltwater,” they said. “The most prominent of these formations was the inland sea of Malita.
This sea existed for 10,000 years (27,000 to 17,000 years ago) with an area of more than 18,000 square kilometers, according to archaeologists.
Shelf map showing various geological features(US Geological Survey.)
According to modeling done by Norman and her team, the Northwest Shelf may have supported between 50,000 and 500,000 inhabitants at various times over the past 65,000 years.
The population would have peaked at the height of the last ice age, about 20,000 years ago, when the entire shelf was dry land.
To draw their conclusions, the scientists projected past sea levels onto high-resolution maps of the ocean floor.
They found that the low sea level exposed a vast archipelago of islands on the northwest Sahul shelf, which stretches 500 kilometers towards the Indonesian island of Timor.
This archipelago appeared between 70,000 and 61,000 years ago and remained stable for about 9,000 years.
“Thanks to the rich ecosystems of these islands, people may have gradually migrated from Indonesia to Australia, using the archipelago as a springboard,” the researchers noted.
“With the descent into the last ice age, the polar ice caps grew and sea levels dropped by up to 120 meters. For the first time in 100,000 years, the shelf has been fully exposed.”
Left: Satellite image of the submerged area of the northwest shelf. Right: Map of the drowned landscape(US Geological Survey, Geoscience Australia)
At the end of this ice age, however, rising sea levels drowned the shelf and forced its inhabitants to flee as the waters encroached on the once productive landscape.
“Retreating populations would have been forced together as the available land shrank,” the experts wrote, adding that this led to “new styles of rock art” appearing in both the Kimberley and Arnhem lands.
“Sea-level rise and the drowning of the landscape is also recorded in the oral histories of First Nations people throughout the coastal fringe,” they added, noting that the histories are believed to have been passed down “over 10,000 years.” .
“This latest revelation of the intricate and complex dynamics of First Nations people responding to a rapidly changing climate adds increasing weight to calls for more Indigenous environmental management in this country and elsewhere,” they concluded in their statement.
“As we face an uncertain future together, deep indigenous knowledge and experience will be essential for successful adaptation.”
The full paper on their findings is available via Quaternary Science Review.
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