Real discoveries of underwater landscapes reflect the ongoing human interest in lost civilizations, highlighted by the legend of Plato’s Atlantis. One notable example is Sahul, a large supercontinent to the north of Australia, which was visible during the last Ice Age around 21,000 years ago. At that time, sea levels were about 120 meters (394 feet) lower due to water trapped in ice sheets and glaciers, increasing Australia’s landmass by around 20 percent. The Ice Age revealed an extra 2,000,000 square kilometers (about 772,000 square miles) of land, linking present-day Australia with New Guinea and Tasmania.
A big part of Sahul, called the Northwest Shelf, measured 400,000 square kilometers (154,000 square miles), which is more than 1.5 times the size of the United Kingdom. This area connected what is now the Kimberley region in northern Western Australia with Arnhem Land in the Northern Territory. While many archaeologists once thought these ancient landscapes were barren and little used by early Aboriginal people, new research is questioning this belief. People increasingly view this now-submerged area as crucial for comprehending Australia’s initial habitation, believed to have occurred approximately 65,000 years ago. An urgent effort is underway to uncover its hidden archaeological treasures before they vanish forever.
Revealing Lost Landscapes
As the planet entered the last Ice Age around 27,000 years ago, polar ice caps grew and sea levels fell, exposing the low-lying terrain of Sahul’s Northwest Shelf for the first time in 100,000 years. Dr. Kasih Norman, a researcher at the Max Planck Institute of Geoanthropology, led a study that combined sonar data and computer models to closely examine the Northwest Shelf. By layering past sea level estimates over high-resolution maps of the ocean floor, her team could visualize the area as it would have looked tens of thousands of years ago. The analysis showed a rich landscape with rivers, lakes, valleys, and gorges. Dr. Norman said that seeing those submerged landscapes and picturing the people who lived there during the last Ice Age sparked her imagination. The region also included a large inland sea, the Malita Sea, which covered over 18,000 square kilometers (7,000 square miles). Professor Sean Ulm, an expert in coastal and underwater archaeology from James Cook University, noted that these new findings provide essential details for understanding how these now-buried landscapes were used and valued by societies over thousands of years.
Tracing a Drowned Civilization
Norman and her team used computer models to estimate how productive these landscapes might have been and the populations they could have supported between 71,000 and 15,000 years ago. They found that, at the peak of the last Ice Age, when the Northwest Shelf was dry land, the area could support a population of over 500,000 individuals. Archaeological evidence from several islands that were once part of Sahul’s coast supports the idea that Aboriginal societies regularly visited the Northwest Shelf. Their population estimates match a recent genetic study of Indigenous people on the Tiwi Islands, located to the east of Sahul’s Northwest Shelf, which suggested a large population existed there 20,000 years ago, followed by a decline at the end of the last Ice Age. Professor Ulm stressed that understanding the lives of the people who inhabited this now-submerged area is a crucial question. He pointed out that the remarkable social, cultural, and technological diversity seen in contemporary and recent Aboriginal societies hints at a similar complexity in the past. He also explained that societies on Australia’s emerged continental shelves traveled long distances to and from the coast and kept connections with distant inland communities through trade networks. Norman and her team proposed that similarities in stone axe technology, rock art styles, and languages imply that the present-day regions of the Kimberley, Arnhem Land, and the now-flooded Northwest Shelf of Sahul formed a vast, connected cultural region during the height of the last Ice Age.
Recovering Ancient Treasures
Our limited knowledge of the culture and lifestyle of the Northwest Shelf’s inhabitants is primarily due to the fact that their ancient artifacts are now underwater. Ulm emphasized that hundreds of generations lived on lands now submerged by the sea. Fortunately, archaeologists now have better tools to locate ancient underwater sites and learn about the lives of those whose homes were lost thousands of years ago. While many submerged cultural sites worldwide were first found by accident, Ulm explained that recent years have seen more organized approaches, using various evidence to create predictive models for where sites and landscapes might still exist underwater. Ulm was part of a collaborative group that included archaeologists, rock art specialists, geomorphologists, geologists, specialized pilots, and scientific divers who worked with the Murujuga Aboriginal Corporation, representing five traditional Aboriginal groups, to investigate submerged archaeological sites off the coast of Pilbara in Western Australia.
The team used navigation charts, geological maps, and known archaeological sites on land to pinpoint possible underwater sites. They employed laser scanners and sonar to create high-resolution maps of the ocean floor to focus their search. Scientific divers then conducted underwater archaeological surveys at the best locations. This extensive effort led to the discovery in 2020 of the first submerged ancient Aboriginal archaeological sites, yielding nearly 300 stone tools for cutting and grinding that had rested on the seabed for at least 7,000 years. Unfortunately, many other artifacts face destruction due to coastal and offshore developments, including oil and gas exploration, renewable energy projects, and industrial fishing. Ulm shared that in recent years, Aboriginal and Torres Strait Islander communities have cooperated with archaeologists to lessen the impact of development on their submerged cultural heritage. Indigenous groups and archaeologists are pushing for stronger protections for these sites, as they usually fall outside the current Australian laws meant to protect more recent historical sites like shipwrecks.
Ancient Maritime Explorers
The exact timeline and ways humans first arrived in Australia are still major mysteries in anthropology, with the Northwest Shelf being a significant part of this puzzle. It’s now known that humans reached the continent at least 65,000 years ago, likely traveling from Southeast Asia to Sahul through what is now Indonesia. During this time of lower sea levels, a series of over 100 habitable islands on the Northwest Shelf connected Indonesia and Sahul. Norman suggested that this group of islands might have allowed for staged human movement from Indonesia to Australia, with people possibly using the islands as stops along the way. These islands would have been visible from higher ground on Timor and Roti, making them clear targets for early travelers. However, these journeys required a sea crossing of nearly 90 kilometers (56 miles), which was two to three times longer than trips to Timor or Roti, and would have taken several days. This strongly indicates that the first Australians were skilled seafarers, able to build maritime vessels and carefully plan and navigate multi-day journeys. Though the exact landing site is still unknown, experts suspect it is likely at least 60 meters (197 feet) underwater today. Specialists believe a founding population of over 1,000 settlers was necessary for long-term survival.
