For a lot of the 65,000 years of Australia’s human historical past, the now-submerged northwest continental shelf linked the Kimberley and western Arnhem Land. This huge, liveable realm lined practically 390,000 sq. kilometres, an space one-and-a-half instances bigger than New Zealand is right this moment.
It was doubtless a single cultural zone, with similarities in floor stone-axe know-how, types of rock artwork, and languages discovered by archaeologists within the Kimberley and Arnhem Land.
There may be loads of archaeological proof people as soon as lived on continental cabinets – areas that at the moment are submerged – all all over the world. Such arduous proof has been retrieved from underwater websites within the North Sea, Baltic Sea and Mediterranean Sea, and alongside the coasts of North and South America, South Africa and Australia.
In a newly printed examine in Quaternary Science Critiques, we reveal particulars of the complicated panorama that existed on the Northwest Shelf of Australia. It was in contrast to any panorama discovered on our continent right this moment.
A continental cut up
Round 18,000 years in the past, the final ice age ended. Subsequent warming induced sea ranges to rise and drown enormous areas of the world’s continents. This course of cut up the supercontinent of Sahul into New Guinea and Australia, and reduce Tasmania off from the mainland.
In contrast to in the remainder of the world, the now-drowned continental cabinets of Australia had been considered environmentally unproductive and little utilized by First Nations peoples.
However mounting archaeological proof reveals this assumption is wrong. Many massive islands off Australia’s coast – islands that when fashioned a part of the continental cabinets – present indicators of occupation earlier than sea ranges rose.
Stone instruments have additionally just lately been discovered on the ocean flooring off the coast of the Pilbara area of Western Australia.
Nonetheless, archaeologists have solely been capable of speculate concerning the nature of the drowned landscapes folks roamed earlier than the tip of the final ice age, and the dimensions of their populations.
Our new analysis on the Northwest Shelf fills in a few of these particulars. This space contained archipelagos, lakes, rivers and a big inland sea.
Mapping an historic panorama
To characterise how the Northwest Shelf landscapes modified by way of the final 65,000 years of human historical past, we projected previous sea ranges onto high-resolution maps of the ocean flooring.
We discovered low sea ranges uncovered an enormous archipelago of islands on the Northwest Shelf of Sahul, extending 500km in direction of the Indonesian island of Timor. The archipelago appeared between 70,000 and 61,000 years in the past, and remained steady for round 9,000 years.
Because of the wealthy ecosystems of those islands, folks might have migrated in phases from Indonesia to Australia, utilizing the archipelago as stepping stones.
With descent into the final ice age, polar ice caps grew and sea ranges dropped by as much as 120 metres. This absolutely uncovered the shelf for the primary time in 100,000 years.
The area contained a mosaic of liveable recent and saltwater environments. Essentially the most salient of those options was the Malita inland sea.
Our projections present it existed for 10,000 years (27,000 to 17,000 years in the past), with a floor space higher than 18,000 sq. kilometres. The closest instance on the planet right this moment is the Sea of Marmara in Turkey.
We discovered the Northwest Shelf additionally contained a big lake over the past ice age, solely 30km north of the trendy day Kimberley shoreline. At its most extent it might have been half the dimensions of Kati Thandi (Lake Eyre). Many historic river channels are nonetheless seen on the ocean flooring maps. These would have flowed into Malita sea and the lake.
A thriving inhabitants
A earlier examine instructed the inhabitants of Sahul may have grown to thousands and thousands of individuals.
Our ecological modelling reveals the now-drowned Northwest Shelf may have supported between 50,000 and 500,000 folks at varied instances over the past 65,000 years. The inhabitants would have peaked on the top of the final ice age about 20,000 years in the past, when the whole shelf was dry land.
This discovering is supported by new genetic analysis indicating massive populations right now, primarily based on information from folks residing within the Tiwi Islands simply to the east of the Northwest Shelf.
On the finish of the final ice age, rising sea ranges drowned the shelf, compelling folks to fall again as waters encroached on once-productive landscapes.
Rising sea ranges and the drowning of the panorama can be recorded within the oral histories of First Nations folks from throughout the coastal margin, thought to have been handed down for over 10,000 years.
This newest revelation of the complicated and complex dynamics of First Nations folks responding to quickly altering climates lends rising weight to the decision for extra Indigenous-led environmental administration on this nation and elsewhere.
As we face an unsure future collectively, deep-time Indigenous data and expertise shall be important for profitable adaptation.
Kasih Norman, Analysis Fellow, Griffith College; Chris Clarkson, Professor in Archaeology, The College of Queensland; Corey J. A. Bradshaw, Matthew Flinders Professor of World Ecology and Fashions Theme Chief for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders College; Frédérik Saltré, Analysis Fellow in Ecology for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders College, and Tristen Anne Norrie Jones, Educational Fellow, College of Sydney