The Arafura Sea, on the shelf between Australia and New Guinea
Sahul shelf
A land bridge after people were already on Sahul (first underwater Aboriginal sites at least 7,000 and 8,500 years old)
The sea between Australia and New Guinea was a plain. In 2020 divers off Murujuga recorded hundreds of stone artefacts on a channel floor that has been sea for at least about 7,000 years, and one more beside a spring 14 metres down. The deep shelf, from the glacial maximum, is still almost untouched.
Why this is extraordinary
Sahul is the name for Australia, New Guinea, and the shelves between them when the sea was low enough to make one continent. The Arafura Sea, in the photograph, is the middle of that join. Even at the lowest sea, people still had to cross open water through Wallacea to arrive. The shelf made a bridge from Cape York to New Guinea. It did not make a bridge from Java. That other plain is Sundaland.
On the land that never drowned, a 2017 study at Madjedbebe, in northern Australia, reads human occupation by 65,000 years ago. That figure is argued. A mixing of sand grains can make a layer look older than the visit. The number matters here because it is the landward clock people set beside the shelf. It is not a date from the Arafura floor.
The shelf’s own archaeology is younger in the published finds, and new. In 2020 a team working with the Murujuga Aboriginal Corporation reported Australia’s first confirmed underwater Aboriginal sites, off the Dampier Archipelago in the north-west, not in the Arafura itself. At Cape Bruguieres divers recorded 269 stone artefacts down to 2.4 metres below sea level. The place cannot have stayed dry after about 7,000 calendar years ago, so the artefacts are at least that old, and they may be older. The date is the drowning, not the day a stone was struck. At Flying Foam Passage one artefact lay at a submerged freshwater spring 14 metres down. That spot was under water by about 8,500 calendar years ago. The paper’s phrase for the country still to search is about 2 million square kilometres of drowned landscape around Australia.
The catch is depth and place. These finds are in the first 14 metres. The glacial shoreline sat far deeper, on the outer shelf. A tool in ankle-deep water, left just before the tide finally covered a channel, is a real Aboriginal site on land that became sea. It is not yet the camp from the coldest centuries, when the whole Arafura was a plain. The pin is that plain. The stones we can point to are on its western edge, in water a diver can stand up in.
Why it matters
If the outer shelf holds camps from the first peopling, the earliest Australian story is mostly underwater. If the underwater artefacts are only the last centuries of a coast that was already inhabited on the hills above, they extend the map by a few metres of depth and leave the 65,000-year argument where it was, on land.
The pin is the Arafura Sea. The photograph is that sea from orbit. The rock carving is on the Burrup, above the water, beside the archipelago where the 2020 sites were found. The channel, a diver on its floor, and the stone at the spring are in the figures that follow. The wing is Drowned Lands.
Photo tour
4 photographs, unedited. On a phone, swipe the row. Choose one to look closely.
What is still unexplained
These sit beside the consensus account, with the same visual weight. None of them is marked solved.
Location and dating
- Location
- The pin is in the Arafura Sea, at about 9.2 degrees south and 136 degrees east, between Arnhem Land and New Guinea. Cape Bruguieres and Flying Foam Passage are off the Dampier Archipelago, on the north-west shelf, which is a different coast of the same drowned continent. The pin follows the land bridge. The excavated underwater sites are named in the text so they are not given a second pin.
- Period label
- Current consensus — open to revision The land bridge existed whenever the sea was low enough to expose the Arafura, including the last glacial maximum. Madjedbebe’s published occupation, on land, is by 65,000 years ago, and that age is disputed. The underwater sites are minimum ages of about 8,500 and about 7,000 calendar years ago, which is the early and middle Holocene drowning of the shallow shelf, long after the first arrival on Sahul.
- How this dating was done
- The underwater ages are sea-level ages. Once a surface is below the rising sea, people are not leaving tools on it in the air, so the drowning is a minimum age. The paper uses radiocarbon and the regional sea-level curve together. Madjedbebe’s clock is luminescence on sand grains, a light-clock that resets when grains are buried, which is why mixing of the sand is the argument against it. Neither method has yet dated a hearth on the outer Arafura floor.
- What could change it
- A date on cultural material from Flying Foam, rather than on the drowning, would say whether the stone is 8,500 years old or much older. A site below 50 metres, with artefacts in place, would reach the glacial plain. A published horizon survey is what a sky reading of these channels would need, and none is in these papers.
What is actually there
- Cape Bruguieres, 269 lithic artefacts down to 2.4 metres below sea level, at least about 7,000 calendar years old.
- Flying Foam Passage, one artefact at a freshwater spring 14 metres down, at least about 8,500 calendar years old.
- The paper names about 2 million square kilometres of drowned landscape around Australia.
- Madjedbebe, on land, is published as occupation by 65,000 years ago, and the age is disputed.
- Even at the lowest sea, Sahul was still a water crossing from Sundaland.
Open questions
| Question | Status |
|---|---|
| Are the underwater stones in the place where people left them? | Open. The 2020 paper’s case is context, condition, and the spring. A cyclone is the other reading. |
| Does the outer shelf hold the early camps? | Open. These sites are in the first 14 metres. The glacial shoreline was much deeper. |
The current narrative
Where publication stands today. It is the best-supported reading, and it is open to revision. It is not a verdict.
The current narrative — open to revision
A late shore, now a few metres down
People used the north-west coastal plain until rising seas covered the channels in the early and middle Holocene. The 269 stones and the spring find are that last dry land, dated by the drowning.
What supports this
- The artefacts lie on a Pleistocene surface below modern sea level.
- The minimum ages match when those depths were finally submerged.
- The underwater assemblage differs from the one recorded on the islands.
What pushes back
- A minimum age is not the day the stone was made.
- Storms move cobbles. The in-place reading is an argument, not a sealed hearth.
What would settle it
A direct date on worked material, or a refit of flakes that cannot have tumbled, would settle the “washed in” reading.
Emerging narratives
Other published readings. Each may be right. None is adopted here unless the evidence carries it.
An emerging narrative
The first Sahul camps are mostly underwater
The crossing and the earliest generations lived across a shelf that is now sea, so the 65,000-year land sites are the inland edge of a drowned country.
What supports this
- People were on Sahul early enough that a lower sea, and a wider shelf, was the country they entered.
- About 2 million square kilometres of that country is underwater, and two shallow sites have already produced artefacts.
What pushes back
- Madjedbebe is on land, and its age is itself disputed.
- The underwater sites date, at minimum, to the Holocene drowning, not to 65,000 years ago.
- No outer-shelf excavation is in the 2020 paper.
What would settle it
The reading becomes a site when a deep-shelf find is dated. Until then it is a map of where to look.
Should the current view be reevaluated?
Open to revision
The shallow underwater sites are a real change in what can be said about drowned Australian country. They do not yet reach the glacial Arafura, and they do not settle Madjedbebe.
What drives this
- First confirmed underwater Aboriginal sites, with counts and minimum ages.
- The outer shelf remains almost unsearched.
This is the museum’s own weighing of the evidence. It is not a visitor vote, and it is separate from the slider.
Weigh it yourself
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If the contested reading is right
What would follow if a reading that is not the consensus turned out to be true, and what could settle it. This explains the stakes. It does not adopt the reading.
The earliest Sahul occupations are largely on the drowned shelf.
The start of the Australian record would move offshore, and the land sites would be what the water left behind.
Why it is still worth a test
Take the Cape Bruguieres method below 50 metres, on the Arafura and the north-west outer shelf, with Aboriginal custodians as at Murujuga.
Sources
Image credits
- The Arafura Sea from the International Space Station, Expedition 6. The pale water is the shelf. At a lower sea this was land between Australia and New Guinea.. Earth Science and Remote Sensing Unit, Lyndon B. Johnson Space Center, Public domain. Shown unedited.
- Cape Bruguieres channel from the air, between two low shores, with a boat and two people at the surface. In the lower right a diver in a yellow hood is over the sand beside a yellow scale. This is the shallow channel where the 2020 count was made.. J. Leach, S. Wright, J. Benjamin, and M. Fowler, in Benjamin et al., PLOS ONE 2020, figure 3, CC BY 4.0. Shown unedited.
- A mottled stone among other stones on the bottom, with a yellow scale card beside it, and a diver holding a stone in open water. Below, the same stone is drawn from several sides and labeled WH-A01. The paper identifies this as the piece from the spring.. H. Yoshida, C. Wiseman, and K. Jerbić, in Benjamin et al., PLOS ONE 2020, figure 14, CC BY 4.0. Shown unedited.
- Engraved rock on the Burrup Peninsula, above the sea, in the same archipelago as the 2020 underwater sites. This panel is not one of the submerged artefacts.. Tradimus, CC0. Shown unedited.