This 7000-year-old wall was the earliest known defense against rising seas. It failed

About 7000 years ago, seas were rising all over the world. Ice age glaciers were melting, and the ocean crept up shorelines and toward people’s homes on every inhabited continent. Now, archaeologists have discovered the earliest known defense against those rising seas: a 7000-year-old sea wall built to protect a farming village from worsening storm surges and encroaching saltwater from the Mediterranean Sea. Ultimately, however, the wall failed. It now lies drowned off the coast of Israel, along with the rest of the village it was meant to protect.

“All the different kinds of responses we see toward sea level rise 7000, 8000, 9000 years ago—we’re still seeing all those same responses today,” says Amy Gusick, an archaeologist at the Natural History Museum in Los Angles, California, who studies this period around California’s Channel Islands. They, too, are stopgaps, she notes. “It’s a lesson for us.”

Many drowned ancient villages lie off the northern coast of Israel, which was dotted with farming settlements at the time, says Ehud Galili, an archaeologist at the University of Haifa in Israel. Often they are blanketed by about 1 meter of sand, which helps preserve the ruins but also hides them, until a storm briefly sweeps them clean. “If you are in the right place at the right time, you can see the exposed features,” which look like dark patches in the water, Galili says.

He and his team first discovered the sea wall in 2012, in a submerged settlement called Tel Hreiz that extends as far as 90 meters offshore in up to 4 meters of water. After a winter storm, they raced out with scuba gear to document as much of the village and wall as they could in the 2 days the area was free of sand. A storm in 2015 gave them another chance. They found the ruins of houses built of stone and wood, bones from domestic animals including cattle and dogs, hundreds of olive pits from olive oil production, flint tools, a hearth, and even two human burials. Radiocarbon dates from wood and bone date the village to about 7000 years ago.

The sea wall ran along an ancient beach between the village and the ocean, the team reports today in PLOS ONE . It was about 100 meters long and made of large boulders, some weighing up to 1000 kilograms, which the villagers likely moved from river mouths up to 4 kilometers away. At some point over the 200 or 300 years the village existed, Galili explains, “People noticed that the catastrophic winter storms became more and more frequent.” Much like modern sea walls, the ancient one would have protected the settlement from such storms. “This is the earliest evidence of humans protecting the coast in order to adapt to sea level rise,” he says.

At the time, sea level near Tel Hreiz was rising about 4 or 5 millimeters a year. “It’s not a tsunami,” Galili says. But the seas had been rising in fits and starts for millennia. “The people in [Tel Hreiz] would have known that this has happened before,” says Jim Leary, an archaeologist at the University of York in the United Kingdom who has studied Doggerland, the now submerged land under the North Sea. “And presumably at some point they would have also understood that they were going to have to get out of that place.”

That’s what eventually happened. As the sea kept creeping up the beach, the wall wouldn’t have been able to hold back creeping sand dunes, saltwater seeping into wells, or flooding over the barrier. “They tried to adapt. But in the end, they didn’t have enough resources to stop the sea,” Galili says.