The Stone Age megastructure found underwater in the Baltic Sea was not formed by nature, scientists say

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A megastructure found in the Baltic Sea may represent one of the oldest known hunting structures used in the Stone Age – and could change what is known about how hunter-gatherers lived some 11,000 years ago.

Researchers and students from the University of Kiel in Germany first encountered the surprising row of rocks located about 21 meters underwater during a marine geophysical survey along the seabed of Mecklenburg Bay, about 9.7 kilometers off the coast of Rerik, Germany.

The discovery, made in the fall of 2021 aboard the research vessel RV Alkor, revealed a wall made of 1,670 stones that stretched for more than half a mile (1 kilometer). The stones, which connected several large boulders, were almost perfectly aligned, making it seem unlikely that nature had formed the structure.

After the researchers informed the Mecklenburg-Vorpommern State Office for Culture and Monuments Conservation of their find, an investigation began to determine what the structure could be and how it ended up at the bottom of the Baltic Sea. Dive teams and an autonomous underwater vehicle were deployed to study the site.

The team determined that the wall was likely built more than 10,000 years ago by Stone Age communities to hunt reindeer.

A study describing the structure was published Monday in the journal Proceedings of the National Academy of Sciences.

“Our research indicates that a natural origin of the underwater stone wall, as well as a construction in modern times, for example in connection with the laying of submarine cables or stone harvesting, are not very likely. The methodical arrangement of the many small stones connecting the large, immovable boulders contradicts this,” says lead study author Dr. Jacob Geersen, senior scientist at the Leibniz Institute for Baltic Sea Research in Germany, said in a statement.

To turn back the time

According to the research, the wall was likely built more than 10,000 years ago along the shoreline of a lake or swamp. There were many rocks in the area at the time, left behind by glaciers that had moved across the landscape.

But studying and dating underwater structures is incredibly difficult, so the research team had to analyze how the region evolved to determine the wall’s approximate age. They collected sediment samples, created a 3D model of the wall and virtually reconstructed the landscape where it was originally built.

Sea levels rose significantly after the end of the last ice age, about 8,500 years ago, which the study authors say would have led to the wall and large parts of the landscape being flooded.

But nearly 11,000 years ago, things were different.

“At that time, the entire population in Northern Europe was probably less than 5,000 people. One of their main food sources was herds of reindeer, which migrated seasonally across the sparsely vegetated post-glacial landscape,” said co-author Dr. Marcel Bradtmöller, research assistant in prehistory and early history at the University of Rostock in Germany, said in a statement. . “The wall was probably used to guide the reindeer to a choke point between the adjacent lake shore and the wall, or even to the lake, where Stone Age hunters could more easily kill them with their weapons.”

Researchers have virtually reconstructed what the wall probably looked like during the Stone Age.  - P. Hoy, University of Rostock, model created with Agisoft Metashape by J. Auer, LAKD MV

Researchers have virtually reconstructed what the wall probably looked like during the Stone Age. – P. Hoy, University of Rostock, model created with Agisoft Metashape by J. Auer, LAKD MV

The hunter-gatherers used spears, bows and arrows to catch their prey, Bradtmöller said.

A secondary structure may have been used to create the bottleneck, but the research team has not yet found any evidence of that, Geersen said. However, it is likely that the hunters led the reindeer into the lake because the animals were slow swimmers, he said.

And the hunter-gatherer community seemed to recognize that the deer would follow the path created by the wall, the researchers said.

“It seems that the animals are attracted to such linear structures and prefer to follow the structure rather than trying to cross it, even if it is only 0.5 meters high,” says Geersen.

The discovery changes the way researchers think about highly mobile groups such as hunter-gatherers, Bradtmöller said. Building a massive permanent structure like the wall implies that these regional groups may have been more location-oriented and territorial than previously thought, he said.

Hunting locations around the world

The discovery marks the first Stone Age hunting structure in the Baltic Sea region. But other similar prehistoric hunting structures have been found elsewhere in the world, including the United States and Greenland, as well as in Saudi Arabia and Jordan, where researchers have discovered traps known as “desert kites.”

Stone walls and hunting hatches built for caribou hunting were previously found at the bottom of Lake Huron in Michigan and discovered at a depth of 100 feet. The construction and location of the Lake Huron Wall, which includes a lakeshore on one side, is most similar to that of the Baltic Sea Wall, the study authors said.

In the meantime, the scientists continue their research in the Baltic Sea using sonar and sounding equipment, and plan future dives to search for archaeological finds. Only by combining people’s expertise in areas such as marine geology, geophysics and archeology will such discoveries be possible, Geersen said.

Understanding the location of lost structures and artifacts on the seabed is critical as demand for offshore areas increases due to tourism and fishing and the construction of pipelines and wind farms, he said. And other undiscovered treasures at the bottom of the Baltic Sea could potentially shed more light on ancient hunter-gatherer societies.

“We have evidence for the existence of similar stone walls at other locations in Mecklenburg Bay. These will also be systematically investigated,” says co-author Dr. Jens Schneider von Deimling, researcher at the Marine Geophysics and Hydroacoustics group at the University of Kiel, said in a statement.

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