About 30,000 years ago, global sea levels abruptly fell by about 40 meters (130 feet) as the most recent Ice Age cycle reached its peak. From that point, the waters continued to recede more slowly for thousands of years. By about 16,000 years ago, the mean sea level was about 130 meters below the present. And then, as the ice sheets and glaciers retreated, sea level began to rise anew.
And as the waters rose, they drowned human communities along the world’s coasts until the sea level stabilized roughly where it is today, between 7,000 to 6,000 years ago.
No, there is no credible evidence whatsoever of submerged super-civilizations, but there is a lot of evidence for prehistoric coastal communities lost to the waves. Now an international team of archaeologists has made the first confirmed discovery of ancient Australian aboriginal sites drowned by the rising waters.
One is at Cape Bruguieres, in shallow water 2.4 meters below today’s sea level. That one is at least 7,000 years old – that being the time the site was submerged. The second is called the Flying Foam Passage and could be at least 8,500 years old, though the team qualifies that these estimates are minimums. Both sites could be far older, the researchers reported in PLOS One on Wednesday.
“At one point there would have been dry land stretching out 160 kilometers from the current shoreline,” says Chelsea Wiseman from Flinders University, who has been working on the Deep History of Sea Country (DHSC) project as part of Ph.D. research. In other words, the new discovery is likely just the beginning for the study of lost aboriginal sites.
Put otherwise: A good 2 million square kilometers of Australian continental shelf is now underwater, but had once plausibly thronged with prehistoric peoples. It’s just that until now, little effort had been made to find evidence of them in the Aussie waters.
Come the interglacial
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By the time the last Ice Age peaked and the interglacial warming period began – with intense glacial melting (“deglaciation) starting around 16,500 years ago – humans had long since conquered southeast Asia and Australia, and the Americas too. The dating of arrival remains controversial, but it seems Australia was occupied at least 40,000 years ago (dates as old as 65,000 years ago have been postulated, but proof is lacking). The Americas were apparently accessed over 23,000 years ago in multiple waves; again, the evidence is scanty and controversial.
What isn’t controversial is that people everywhere clustered (if not exclusively) on the coasts, and as the interglacial melt began and waters rose, they lost their homes.
Just this year, archaeologists reported finding a seawall dating to about 7,000 years ago to protect coastal villages from the rising waters of the Mediterranean. It didn’t work. All of Doggerland, a lush Neolithic land between the British Isles and Scandinavia, was lost to the rising North Sea, though its final doom was also caused by a mega-tsunami following the collapse of a section of Finland’s continental shelf – an event called the Storegga Slide. Apropos, Neolithic villages off the Finnish coast have also been found underwater – in this case because the rising seas caused a rise in groundwater too. In England, archaeologists even found the remains of Neolithic villages in the English Channel, just off the Isle of Wight.
The aboriginal population of Paleolithic Australia would likely have liked the sea view and sea food as well, box jellyfish notwithstanding. And now two ancient sites with assemblies of hundreds of stone tools have been found off the Pilbara coast in Western Australia, through archaeological and geophysical surveys in the Dampier Archipelago.
The work was done by archaeologists from Flinders University, the University of Western Australia, James Cook University, ARA – Airborne Research Australia, and the University of York (England), in partnership with the Murujuga Aboriginal Corporation.
“Australia is a massive continent, but few people realize that more than 30 percent of its land mass was drowned by sea-level rise after the last ice age,” says Associate Professor Jonathan Benjamin of Flinders.
The Flying Foam Passage includes a freshwater spring now 14 meters below sea level. This site is estimated to be at least 8,500 years old.
To be clear about the dating of the two submerged sites, it’s based on when they would have been inundated by the rising sea. The character of the stone tools found there suit discoveries on land from about the same time, the team explains.
The environment of the now-submerged paleo-coast would have been warm and swampy, rich in freshwater springs and streams, and featuring mangroves.
On-land archaeological sites in the region are predominantly open-air, including engraved rock art panels and possibly the foundations of stone housing, steles (standing stones of possible ritual significance) and shell middens (i.e., discarded shells from meals) that formed mounds as much as 5 meters thick. Most of those date to the Holocene – the last 11,000 years – but some of the rock art depicts extinct animals, demonstrating occupation extending back into the Pleistocene, the team explains.
And why hadn’t offshore hunter-gatherer sites from Australian prehistory been found to date? As said, there hadn’t been an orderly survey until now. But the team also stresses the “unobtrusive or ephemeral nature of hunter-gatherer material culture” – a good point.
While it has become clear that hunter-gatherers in Eurasia did lug pottery about, in contrast to earlier thinking that they would prefer to roam unburdened – it is hard to nail down the lifestyle of nomads who died thousands of years ago. Let alone if their hunting and foraging ground is now under meters of seawater and coral.
Scientists had noticed stone artifact sites and quarries, and stone-walled fish traps, in intertidal zones. But they generally seem to have been extensions of activities on the shorelines as we know them today, not Neolithic remnants when the shores were a good 160 kilometers out to sea compared with their position today.