Stone Age Wall Discovered Beneath the Baltic Sea Helped Early Hunters Trap Reindeer

Made up of some 1,600 stones, the submerged “Blinkerwall” might be Europe’s oldest known megastructure

an illustration of deer walking along a short stone wall in a flat, snowy landscape beside a lake
A reconstruction of how the newly discovered wall could have served as a hunting structure during the Stone Age, trapping deer alongside a body of water. Michal Grabowski

In 2021, scientists aboard a research vessel noticed a submerged stretch of stones off Germany’s Baltic coast. Now, after examining the site, researchers say the incidental observation could be Europe’s oldest known man-made megastructure: a wall built by Stone Age hunters to help capture prey.

The discovery, named Blinkerwall, is made up of more than 1,300 stones and roughly 300 larger boulders, and it stretches for more than half a mile along the seafloor. Resting nearly 70 feet underwater in the Bay of Mecklenburg, the wall stands, on average, about 1.5 feet tall.

Natural events, such as glacial deposits or other land movements, cannot account for this structure’s existence, researchers report in a study published Monday in Proceedings of the National Academy of Sciences. Instead, they argue, the roughly 10,000-year-old wall was a tool built by hunters to guide and trap reindeer, which tend to travel along straight elements of the landscape, such as cliffsides or streams.

“Hunters tapped into the natural behavior of the animals and created their own linear feature,” Ashley Lemke, an underwater archaeologist at the University of Wisconsin-Milwaukee who was not involved with the research, tells Science’s Andrew Curry. “It’s not an obstruction, it’s a trail. They follow it to where the hunters are waiting.”

yellow-colored maps showing the wall of stones on the seafloor in a flattened s-shape
An autonomous underwater vehicle captured the structure of the submerged wall. In the lower image, the wall's orientation changes at the site of the largest, non-moveable stone. Jacob Geersen, IOW

Though the wall is now underwater, it was likely constructed during a period between 8,500 and 14,000 years ago, when the site was on dry land. Before that window, a massive ice sheet covered the region; and after, sea levels rose and flooded everything.

When the low wall was built, it would have run adjacent to a lake, where reindeer likely congregated and were susceptible to changing their herd’s movements, the team suggests.

“When you chase the animals, they follow these structures—they don’t attempt to jump over them,” study lead author Jacob Geersen, a senior scientist at the Leibniz Institute for Baltic Sea Research, tells the Guardian’s Ian Sample. “The idea would be to create an artificial bottleneck with a second wall or with the lake shore.”

One researcher from the team, Marcel Bradtmöller, an archaeologist at the University of Rostock in Germany, hypothesizes the wall may have been built by the Kongemose culture, he tells New Scientist’s Michael Le Page. These hunter-gatherers lived in southern Scandinavia between roughly 6,000 B.C.E. and 5,200 B.C.E., used stone tools and hunted deer and boar.

A 3-D rendering of Blinkerwall, a 1.6 foot-tall wall found under the Baltic Sea
A three-dimensional model of a portion of Blinkerwall, as it currently stands underneath the Baltic Sea. The scale bar at the top right measures nearly 20 inches. P. Hoy, University of Rostock, model created using Agisoft Metashape by J. Auer, LAKD M-V

The finding suggests that early European hunter-gatherers shaped their environment more intricately than previously known. Similar constructions have been found in other areas—including the low walls of “desert kites” that trapped prey in Jordan and Saudi Arabia—but no Stone Age hunting structures had ever been identified in the Baltic Sea region before, per CNN’s Ashley Strickland. Stone walls and hunting blinds previously uncovered in Lake Huron are the most similar known structures to this new discovery.

“Such a find suggests that extensive prehistoric hunting landscapes may survive in a manner previously only seen in the Great Lakes,” Vincent Gaffney, an archaeologist at the University of Bradford, tells New Scientist. “This has very great implications for areas of the coastal shelves which were previously habitable.”

Amazingly, Blinkerwall’s discovery wouldn’t have been possible without a stroke of luck. In the fall of 2021, on an unrelated training exercise with students, Geersen was using sonar to map the seafloor a little more than six miles off the German coast. When he observed a strangely straight line of objects, which turned out to be rocks, Geersen assembled other archaeologists to take a closer look.

The researchers hope to continue exploring the site and learning about the early humans that built the structure. Scientists say a second wall might also be preserved on the sea floor, buried beneath sediment. And future excavations could reveal animal remains and other human-made artifacts, such as hunting projectiles.

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