For the first time, Australian Aboriginal tools have been found in previously inhabited areas now swallowed by the sea. The artifacts date back at least 7,000 years, but may be far older, and reveal intriguing differences between the tools used at the time and those found on land.
At the peak of the last Ice Age glaciers locked up so much water Australia was 30 percent larger. Now-submerged locations close to the ancient coastline would have been among the most attractive places to live.
Despite finding objects in what are now inter-tidal zones (but would have been dry land when made) and at the bottom of lakes, archaeologists had found no signs of ancient human habitation off the current coast until now. A team led by Dr Jonathan Benjamin of Flinders University has changed that, finding hundreds of stone tools off Western Australia's Burrup Peninsula.
"Today we announce the discovery of two underwater archaeological sites that were once on dry land. This is an exciting step for Australian archaeology as we integrate maritime and Indigenous archaeology and draw connections between land and sea," Benjamin said in a statement.
Benjamin told IFLScience there have been unsuccessful attempts to find such sites, adding, “What we do is very hard, it takes lots of skill and some luck.” Finding a stone tool on a rocky/sand sea bed partially obscured by seaweed requires a diver looking in the right place and an excellent capacity to spot what they seek.
In PLOS ONE, Benjamin and co-authors describe many steps to identify locations that were both likely to have been heavily used by Indigenous Australians when seas were lower, and where tools might still be visible.
At one site, Cape Bruguieres Channel, Benjamin's PhD students were successful almost immediately, and over many dives found 269 artifacts, including grinding stones. A few of these items would be exposed at extremely low tide, but most lay in waters so deep the site has not been habitable for 7,000 years putting a minimum on the age of items found there. The team hopes eventually to establish the items' true age, but have not been able to do so.
Cape Bruguieres provided a rich haul, but towards the end of the expedition they also investigated Flying Foam Passage, near the site of one of Australia's worst massacres. The contours of the sea bottom are shaped in ways that indicate they were formed by a freshwater spring, which would have been very attractive to people in the low rainfall conditions. Unfortunately finding objects 14 meters (46 feet) below sea level, where the spring now lies is much harder than the 2.4-meter (8 feet) maximum depth at Cape Bruguieres.
However, on the last dive of the expedition's last day, the team struck gold, finding a flaked stone that dates back at least 8,500 years.
The recovered tools are on average substantially larger and heavier than those found on the peninsula itself. The authors express confidence this is not just because they missed the smaller finds, nor that currents swept smaller items away. Benjamin told IFLScience it is common to see trends in tool size over time, but the reasons remain unknown.
The team had the enthusiastic support of the Peninsula’s traditional owners who provided advice on the areas their ancestors would have preferred. Peter Jeffries of the Murujaga Aboriginal Corporation, an author on the paper, said in a statement, "Further exploration could unearth similar cultural relics and help us better understand the life of the people who were so connected to these areas of land which are now underwater."
"Managing, investigating and understanding the archaeology of the Australian continental shelf in partnership with Aboriginal and Torres Strait Islander traditional owners and custodians is one of the last frontiers in Australian archaeology," said Benjamin. "Our results represent the first step in a journey of discovery to explore the potential of archaeology on the continental shelves which can fill a major gap in the human history of the continent"
Rio Tinto's destruction of exceptional cave shelters to expand a coal mine revealed the vulnerability of Western Australia's archaeological sites. Like the astonishing rock art on the peninsular itself, the offshore waters are threatened by pipelines from the proposed Scarborough offshore gas platforms. Benjamin told IFLScience, “There is a need for archaeologists to work with both traditional owners and industry... to mitigate damage to cultural heritage.”
The sites have been placed on the WA Aboriginal Heritage List and are waiting to hear if they qualify for Australia's Underwater Cultural Heritage Act. If so, this will afford automatic protection to all Aboriginal underwater sites that may come after.