In the end, all the pieces of the puzzle point towards the same conclusion. A group of humans founded a village during a time when the town sat high and dry. Decades or centuries later, they realized that the changing climate threatened their way of life and they fought to keep their homes. Every single boulder in that 100+ meter wall represents a 200-1,000kg rock moved over distances of at least a mile at a time when every calorie was dearly purchased. They might have had cows. They didn’t have wheels. They did it anyway.
We know that Neolithic people deployed a variety of sophisticated strategies to manage water in various ways (the article goes into more detail on this), but the seawall found here is unique for its age. The world of that era was astonishingly empty by our standards. They could’ve gone somewhere else, right?
Maybe. But they didn’t. There’s something deeply human in that. The meters of sea-level rise they were forced to contend with would challenge the flood-managing capacity of a modern first-world nation, even in a best-case scenario. What did they have? Rocks. Imagine looking at the rising ocean when the first, last, and pretty much only tool you’ve invented for holding it back is sticking two stones next to each other and filling gaps with sand and clay.
“If they’d known what they were up against, they never would have tried,” some might say, ignoring the history of every doomed cause, last stand, and hopeless fight on Earth. Truth is, they might have tried anyway. There’s something deeply human in that, too. It’s what connects the nameless Neolithic residents of what we now call Tel Hreiz with people across the Pacific on low-lying islands, or in the Arctic, where melting permafrost is driving significant land losses and temperatures have warmed faster than anywhere else on Earth. The amount of ice melting off Greenland each year is accelerating and the island now loses 7x more ice per year than it did in the 1990s. Luckily, the rate of sea-level rise happening now is much lower than when the great ice sheets were melting off the planet, but the number of people at risk today is larger than the total number of humans alive on planet Earth in the Neolithic era.
We, of course, have far more than rocks at our disposal. But we also have far more to lose and fewer places to go.
Updated (5/12/2020): This is one of my favorite stories that I’ve ever written, though I’m not just resurfacing it for that reason. A number of readers raised additional questions of interpretation in the comments — namely, why do we think this is a wall built against sea-level rise, rather than for other purposes? There are answers to these questions, and I’d like to address them.
Humans build walls for specific purposes. To understand what those purposes are, archaeologists examine a number of site characteristics, including the layout and structure of the wall, its location relative to the town or village it guards, and what other people in the area were building at the same time. This wall would not have been built for agriculture — it’s far too close to the historical shoreline, and the area was periodically inundated even before the sea began to rise. The ground would not have been good for grazing or beast-penning for the same reasons (we don’t actually know if these people had domesticated cattle yet, so it’s not even clear they’d be building these kinds of pens yet in the first place).
The wall wasn’t a defensive structure; it would have curled around the buildings to defend from land as well if it had been. It wasn’t an agricultural terracing system, either — there’s no evidence of other terraces, and you wouldn’t build a large, complicated terrace directly over the rapidly rising ocean.
Could they have been fish traps? This was an interesting question, but the evidence suggests no. The Stilbaai Tidal Fish Traps are known examples of ancient fish traps found on the coast of West Africa. One major characteristic of these structures is that they are enclosed, made of tightly packed stones, and do not resemble the overall structure above. If the thickest part of the wall above had been hollow in the center (and larger), it might have functioned in this manner, but neither is the case.
It may help to know that we have found a great many drowned littoral villages of this sort all over the world. We have known for centuries that rivers and oceans helped nourish (literally and figuratively) early human civilizations. Drowned villages in areas corresponding to lower sea levels during the last ice age are common. There are signs in other villages nearby of various other measures humans took to combat climate change, including digging fresh wells and attempting to raise the water table to avoid brackish contamination from rising water.
We know, factually, that humans once dwelled in areas that we are now cut off from due to sea-level rise. We know that humans generally fight to remain in their homes, then and now. The surprise of discovering that humans built a seawall to fend off climate change is surprising for how early they built it, not for the fact that they tried.
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