<link rel="stylesheet" href="//fonts.googleapis.com/css?family=Roboto%3A300%2C400%2C500%2C700%7CRoboto+Slab%3A400%2C700">Neanderthals made mysterious underground structures

175,000 years ago the Neanderthals were up to something. In the dark depths of a French cave, 300 metres underground, they were re-arranging more than two tonnes of rock to make circular structures. What were they for? The exact nature of these objects remains a mystery wrapped in an enigma. But it does open the door for some fascinating implications about Neanderthal behaviour and plenty of speculation to boot.

A 3D model of the structures

A 3D model of the structures

Bruniquel Cave

In 1990 the entrance to Bruniquel Cave, France, was discovered. Or rediscovered, if you feel a particular affinity for the Neanderthals. Hearing about the famous cave art sites found nearby, people speculated that the blocked up entrance held wonders. So they dug through 30 metres of rock to find the main chamber. Prior to this, no human (or Neanderthal) had entered the cave for thousands of years. Despite this, a series of fascinating structures were found. Clearly they were ancient.

A map of the structures in the cave

A map of the structures in the cave

These were circular structures, made by stacking stalegmites on top of each other. There were 6 in total, representing more than two tonnes of rock that were moved by the inhabitants of the cave. However, two of these were particularly interesting; being much larger and enveloping many of the others. The larger of these two “main” structures was made of a whopping 1.7 tonnes of stone and 6 metres across. As if this construction alone isn’t interesting, it’s worth noting that they were found more than 300 metres from the cave entrance. No natural light got there. It all had to be lit by torches and fire (or the makers cultivated carrots well before we knew). None of these are particularly great sources of light. Estimates of stone age “torches” reveal they produced less light than a modern candle.

But whilst this fire might not have been particularly bright it does mean there was carbon found in these structures. In fact all of them – even the little ones – had some carbon in. This allowed for some radiocarbon dating; which placed the structures as having been inhabited around 50,000 years ago. This would make them just older than the arrival of modern humans in the region. Certainly close enough to not rule out that they were the manufacturers. And we do know modern humans went on to live in caves, even building structures in there.

So this isn’t a particularly exciting discovery. Unless you know anything about radiocarbon dating. 50,000 years is about the upper limit for this technique; so you should be highly skeptical of any dates around this time. So a new group of researchers decided to try an alternate method that would work better for older dates.

And they got older dates. Much older dates. Many of the structures had calcite “growing” on them. This contains certain isotopes that can be dated to figure out when the growth started (thus the structures must be older). The resulting dates placed these structures as having been built 175,000 years ago. This put them more than a hundred thousand years before modern humans arrived in Europe.

In other words, they had to be made by the Neanderthals.

Structures and speculation

So Neanderthals built a bunch of circles underground? What’s so special? Well given these structures are so mysterious it’s really hard to say. Beyond the circles themselves there’s very little evidence of human activity. No used tools or cut up bones. None of the general debris that comes from people living in a location. Without it there’s very little we can study to figure out exactly what they were doing.

However, what evidence is there does reveal some important things about the Neanderthals of Bruniquel Cave.

For starters, there’s the fact that Neanderthal structures in general are very rare. We have evidence of stone age humans building some elaborate structures (like huts made of mammoth ivory) but very little for the Neanderthals; if anything at all. Was this because Neanderthal structures were so old they had vanished, or did they just make none? This discovery shows they made at least some. This might also imply they had much more organised populations than we thought; perhaps with some degree of division. Maybe naughty Neanderthals were sent to sit in the smaller circle.

Not only is this the first reliable evidence of Neanderthal structures but the first evidence of them routinely exploiting caves. It’s something we modern humans did all the time; and we know Neanderthals did it a bit. But it was never thought they were exploiting them so thoroughly that they would start building 2 tonne structures 300 metres underground.

The structures are very far underground. Clearly the Neanderthals were up to something

The structures are very far underground. Clearly the Neanderthals were up to something

There are a few other bits of interest about these caves. Like the fact they’re the oldest evidence of fire being used this far underground. But the really interesting implications come if you start to speculate a bit. So please join me in a wonderful trip down the world of imagination.

The key point is the lack of evidence for habitation at these sites. We known Neanderthals were there and they had fires, but beyond that there’s no real evidence anyone ever lived there. As I mentioned, there’s no stone tools at the site, no food waste, no footprints (that have been reported). If not for the structures and fires there would be nothing of interest in the cave at all. In other words, they were routinely visiting these caves but not living there. Or at least, packing up all their stuff when they left. And giving their cave a really deep clean.

Either way, this sort of behaviour implies this cave was being treated unusually. It was special. So much so that – despite investing a lot of effort making structures – they didn’t seem to spend a significant amount of time in there. Certainly they didn’t live in there. Might this be because the caves were significant for another reason. This could be the first example of Neanderthal ritual and religion ever.

Perhaps this cave is a Neanderthal church, with stalagmites for pews.

How the structures look now, more than 100,000 years after they were used

How the structures look now, more than 100,000 years after they were used


Bruniquel Cave Neanderthals made circular structures underground, which they lit with fires. Beyond that we don’t know much about them because there isn’t much there. Could this be evidence they were involved in ritual?


Jaubert, J., Verheyden, S., Genty, D., Soulier, M., Cheng, H., Blamart, D., Burlet, C., Camus, H., Delaby, S., Deldicque, D. and Edwards, R.L., 2016. Early Neanderthal constructions deep in Bruniquel Cave in southwestern France. Nature,534(7605), pp.111-114.

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