Blinkerwall: This is how the Stone Age megastructure was found in the Baltic Sea

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3D model of a section of the stone wall (the scale at the bottom of the picture is 50 centimeters)

Photo: P. Hoy / University of Rostock; Model created with Agisoft Metashape: J. Auer, LAKD MV

The 55 meter long “Alkor” is one of the smaller German research ships. So far, there have been hardly any spectacular discoveries during their expeditions in the North and Baltic Seas. So no one expected a sensation when nine students from Kiel University embarked on the AL565 research trip together with three scientists in September 2021. The prospective geoscientists spent a week learning how to use measuring devices and life at sea. A routine trip, like in many years before.

But about ten kilometers from Rerik, at the so-called blinker hill, the multi-beam echo sounder showed a mysterious structure at a depth of a good 20 meters: "There was a structure stretching across the seabed for around a kilometer," says the expedition's scientific leader at the time, Jacob Geersen , who now works at the Leibniz Institute for Baltic Sea Research in Warnemünde.

A further study trip revealed that there were a total of 1,500 tennis- to football-sized boulders between a few boulders that were up to three and a half meters tall and weighed eleven tons. “Someone seems to have deliberately put it that way,” says Geersen. "We don't know of any example where a glacier arranged stones over such a length." Modern construction measures or the consequences of bottom net fishing are just as unlikely.

Instead, a research group led by Geersen is now presenting a different, fascinating interpretation of the Blinkerwall, which they named it: According to this, Stone Age people placed the boulders between naturally occurring boulders - and that must have been more than 8,500 years ago. This region has been flooded since the end of the last ice age and the associated melting of the Scandinavian glaciers.

“The currently most plausible hypothesis is that the structure is a hunting structure,” says archaeologist Marcel Bradtmöller from the University of Rostock, who is also part of the team. However, it would have been useless in the forest for hunting local game such as red deer. “Something like this only makes sense for herd animals, such as those used for reindeer hunting.” But because these animals migrated north around 10,000 years ago, the wall would have to date from at least that time.

So far only circumstantial evidence

The landscape back then was interrupted by lakes and moors. Herds of reindeer roamed the largely treeless area. Only a few people lived here, on the edge of the continent; Across Europe, their number was estimated to be only a few thousand people. They roamed the cold, desolate landscape in groups of a few dozen individuals.

They built the Blinkerwall near a lake. The georesearchers have identified the body of water using sediments. “Perhaps the animals were driven into the water and hunted from boats,” suspects archaeologist Bradtmöller. "Perhaps they were also attacked with bows and arrows or spears at a narrow point between the lake and the wall."

But why didn't the reindeer just jump over the relatively low wall to get to safety? “It wasn’t about building an enclosure,” says Bradtmöller. »Herd animals are oriented towards linear structures. A small height is enough to guide them. That’s where the attack took place.”

Experts not involved in the study are enthusiastic about the discovery at the bottom of the Baltic Sea. Vincent Gaffney from the University of Bradford is an archaeologist studying the flooded shelf areas of the North Sea. He heard about the Blinkerwall for the first time at a conference a year ago: "My jaw dropped." Although more research is still needed, he finds the interim results "remarkable."

Underrated Stone Age people

Tips of arrows or spears or even bone remains of slaughtered reindeer - such evidence is still missing even after the first research dives. The next step is therefore excavations and further sampling. Thomas Terberger from the Lower Saxony State Office for Monument Preservation and the University of Göttingen praises the work so far: "Based on the existing facts, our colleagues have derived a convincing hypothesis." The discovery contributes to a "new picture of the hunter-gatherer society." The end of the end of the Ice Age.

Terberger says that research has “long underestimated the interventions in the landscape and the cultural-technical capabilities of early human groups.” In fact, the first large stone pillar circles in the Anatolian site of Göbekli Tepe were created at that time. And in a bog in the Urals, hunters and gatherers erected a figure more than five meters high made of larch wood, the Shigir idol. In the Orient, dry stone walls were built for hunting gazelles. Such so-called desert dragons are known from Syria and Jordan or the west of Saudi Arabia. But Stone Age hunters are also said to have used walls to hunt caribou in the Lake Huron area on the border between the USA and Canada - although not for nearly as long.

However, such a megastructure was previously completely unknown in the Baltic Sea region. Because the Blinkerwall was under water the entire time, it was preserved over the millennia. The explorers are now hoping for further finds, possibly very close by. Explorer Geersen reveals: »I am optimistic that we will find more stone walls. We already have initial clues that we now need to check.”