News release

From: Frontiers

‘They weren’t burned by accident’: burned stone, child’s bones, and lost jewelry could reveal prehistoric mining camp high in the Pyrenees 

Archaeologists uncover possible evidence of ancient copper smelting spanning more than 2,000 years in a mountain cave more than 2,000 meters above sea level

In the past, scientists thought that prehistoric peoples only travelled briefly through high-altitude mountain areas, rather than staying to take advantage of their resources. But new evidence suggests that, starting about 5,500 years ago, a prehistoric community repeatedly climbed up to Cave 338, 2,235 meters above sea level in the Pyrenees, to collect and process malachite for copper — returning many times over thousands of years. Additional finds, including jewelry and remains from at least one child, suggest that much more remains to be found when excavations reopen this summer.

High in the eastern Pyrenees, archaeologists are revealing the secrets of a prehistoric cave full of hearths containing fragments of green rock that could represent early copper mining. People visited this site for well-planned, well-supplied trips spanning two thousand years, overturning previous assumptions that prehistoric peoples didn’t spend long periods at high altitude. The discovery of a child’s finger bone and baby tooth suggest that, after more excavations, we may find that it was also a burial site.

“For a long time, high-mountain environments were seen as marginal, places prehistoric communities passed through occasionally,” said Prof Carlos Tornero of the Catalan Institute of Human Paleoecology and Social Evolution, lead author of the article in Frontiers in Environmental Archaeology. “But we found a really rich archaeological sequence, including multiple combustion structures and a very large number of green mineral fragments. We can’t say exactly how long people stayed each time, but the repeated use of the space and the density of remains suggest occupations that were short to medium in duration, but happening again and again over long periods of time.”

Burning questions 

Cave 338 is found at 2,235m above sea level in the Freser Valley. The scientists excavated an area of 6m2 at its entrance, identifying four layers of occupation. The first, most recent layer was thin, showing the cave was not frequently used at that time, and contained some artefacts from historical periods. The fourth, oldest layer contains only charcoal fragments, dated at 6,000 years old.

The researchers hit the jackpot in the second and third layers of the excavation: a total of 23 hearths, containing many crushed, burned green mineral fragments. In-depth material analysis to confirm its identity is underway, but the fragments resemble malachite, which can be treated like this to produce copper. Cave 338 looks like an unexpectedly early high-altitude mining camp.

“Many of these fragments are thermally altered, while other materials in the cave are not, which clearly suggests that fire played an important role in their processing and that there was a deliberate intention behind it,” said Dr Julia Montes-Landa of the University of Granada, co-author. “In other words, they weren’t burned by accident.”

The hearths cut across each other, indicating that the visitors reused this space frequently, but are still distinct, which suggests that those visits were separated by plenty of time. Radiocarbon dating puts the hearth found in the second layer at about 3,000 years old, while the hearths in the third layer are around 5,500 to 4,000 years old.

Secrets of the mountains 

The team also found human remains in the third layer — a finger bone and a baby tooth belonging to at least one child, about 11 years old — which could mean there are burials deeper within the cave. However, there isn’t enough evidence to suggest a cause of death or determine if the two bones belonged to the same child. Jewelry found in the second layer offered more information.

“We recovered two pendants: one made from a shell and another from a brown bear tooth,” said Tornero. “They come from prehistoric contexts, most likely around the second millennium BC. The shell pendant is interesting because it has parallels in other sites in Catalonia, which suggests shared traditions or connections between different communities. The bear tooth pendant is much less common. That might point to something more specific or symbolic, possibly linked to the local environment.”

Cave 338 wasn’t a full-time home, but the people who came here found their trips valuable enough to keep returning for millennia. The researchers still have a lot of questions about those trips which they hope to answer with future research. For example, further excavation will help us understand more about how and when humans used the cave. They also want to confirm the exact identity of the green mineral and find out where it came from.

“The identification of the green mineral as malachite is still preliminary,” explained Tornero. “The research ongoing by the University of Granada and the Autonomous University of Barcelona will provide final answers shortly. Also, the excavation hasn’t yet reached the full depth of the site, so the sequence is not completely documented. This summer we will continue the archaeological work.”