A landmass was discovered off the coast of northern Australia that was once home to up to half a million people.
For most of the past 65,000 years, the continental shelf that is now submerged was an extensive, habitable landscape covering about 390,000 square kilometers – an area larger than New Zealand.
The scientists who made the groundbreaking discovery, led by Kasih Norman of Griffith University in Queensland, said the “complex landscape” that existed on Australia’s northwest shelf was “unlike any landscape found on our continent today.”
Yet the people who lived there spoke similar languages and created similar types of rock paintings as people in surrounding areas, the team said in a press release.
These regions, once connected by the shelf, still exist today: western Arnhem Land in the north and Kimberley in the northwest.
Norman and her colleagues explained that global warming following the end of the last ice age about 18,000 years ago led to a rise in sea levels that flooded large parts of the continents.
This divided the supercontinent Sahul into New Guinea and Australia and cut Tasmania off from the mainland.
A map showing where the continent of Sahul once lay(Kanguole via Wikipedia)
Australia’s now submerged continental shelves were considered ecologically unproductive and were therefore largely ignored by the original indigenous communities.
“But increasing archaeological evidence shows that this assumption is false,” the researchers wrote.
“Many large islands off the coast of Australia – islands that were once part of the continental shelves – show signs of settlement before sea levels rose.”
Before Norman and her team conducted their research, however, archaeologists could only speculate about the nature of these pre-Ice Age sunken landscapes and the size of their populations.
But the newly published findings provide many missing details – they reveal that the Northwest Shelf was a lush realm with island groups, lakes, rivers and even a large inland sea.
“The region contained a mosaic of habitable freshwater and saltwater environments,” they said. “The most striking of these features was the Malita Inland Sea.”
This sea existed for 10,000 years (27,000 to 17,000 years ago) and, according to archaeologists, had a surface area of more than 18,000 square kilometers.
A map of the shelf with various geological features(US Geological Survey.)
According to model calculations by Norman and her team, the Northwest Shelf could have been home to between 50,000 and 500,000 inhabitants at various times over the last 65,000 years.
The population probably reached its peak at the height of the last ice age around 20,000 years ago, when the entire shelf consisted of dry land.
To draw their conclusions, the researchers projected past sea levels onto high-resolution maps of the ocean floor.
They found that low sea levels on the northwest shelf of the Sahul Massif exposed an extensive archipelago of islands extending 500 kilometers toward the Indonesian island of Timor.
This archipelago was formed between 70,000 and 61,000 years ago and remained stable for about 9,000 years.
“Thanks to the diverse ecosystems of these islands, people may have gradually migrated from Indonesia to Australia, using the archipelago as a stepping stone,” the scientists found.
“With the beginning of the last ice age, the polar caps grew and sea levels fell by up to 120 meters. This completely exposed the shelf for the first time in 100,000 years.”
Left: A satellite image of the submerged northwest shelf region. Right: A map of the submerged landscape(US Geological Survey, Geosciences Australia)
But at the end of this ice age, rising sea levels flooded the shelf and forced residents to flee as water invaded the once fertile landscapes.
“The retreating populations would have been forced to congregate as the available land area shrank,” the experts wrote, noting that this led to the emergence of “new rock art styles” in both the Kimberley and Arnhem Land.
“Rising sea levels and flooding of the landscape are also documented in the oral traditions of First Nations peoples across the coastal region,” they added, noting that these stories have probably been passed down for “over 10,000 years.”
“These recent insights into the complex and complicated dynamics of First Nations responses to rapid climate change add growing weight to calls for more Indigenous-led environmental management in this country and elsewhere,” they concluded their statement.
“As we face an uncertain future together, the centuries-old knowledge and experience of indigenous peoples are critical to successful adaptation.”
The full publication of their results can be found at Quaternary Science Reviews.
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