Uranium dating confirms Spanish cave art is at least 40,800 years old

Story: ~40,000 B.C.E.  |  Last updated: January 4, 0001

A smear of red ochre on a cave wall in northern Spain has rewritten the story of human creativity. When scientists measured the age of a thin crust of calcite grown over a disk of pigment at El Castillo cave in Cantabria, they confirmed it had been sitting there for at least 40,800 years — making it, at the time of the 2012 C.E. study, the oldest dated example of Spanish cave art ever confirmed by direct measurement.

Key findings

• Uranium-thorium dating: Researchers led by Alistair Pike at the University of Bristol applied the method to calcite crusts covering 50 paintings across 11 caves in Cantabria and Asturias, publishing their results in Science in 2012 C.E.
• Cave art age: The red disk at El Castillo dated to at least 40,800 years old; a hand stencil in the same cave dated to at least 37,300 years old — both figures are minimum ages, not precise dates.
• Authorship uncertainty: The 40,800-year date falls at the very edge of modern human arrival in Europe, leaving open the possibility that the artist was Homo sapiens — or, plausibly, a Neanderthal.

A dating method that changed the question

For most of the 20th century, the age of ochre-based cave paintings was essentially unknowable. Radiocarbon dating requires organic carbon, and the red and black mineral pigments used at sites like El Castillo and Altamira contain none. The art seemed fated to remain beautiful but undatable.

The solution had been growing on the rock face the entire time.

As water seeped through limestone over thousands of years, it deposited thin films of calcite directly on top of the pigment — a natural clock that started the moment the crust formed. Uranium decays into thorium at a known rate. By measuring the ratio of the two elements in those mineral layers, scientists could establish how long the calcite had been forming, and therefore how old the art beneath it had to be.

The technique doesn’t give a precise date of creation. It gives a minimum. The art is at least that old — possibly older. That distinction matters enormously, and the researchers were careful to say so.

What the caves of Cantabria actually contain

The 11 caves studied in 2012 C.E. form part of a dense cluster of Upper Paleolithic art sites along Spain’s northern coast, in a region where the Cantabrian mountains meet the Bay of Biscay. Altamira, the most celebrated, was discovered in 1868 C.E. and contains a polychrome ceiling depicting bison, horses, and deer that remains one of the most technically accomplished works of prehistoric art ever found.

The paintings were created using charcoal and ochre, sometimes diluted to produce tonal variation, sometimes blown through tubes to create stenciled hand outlines. Artists used the natural contours of the cave walls to give their subjects volume and movement. The people who made these works were not expressing primitive thought — they were solving complex visual problems with limited materials in difficult conditions, often deep in caves where they worked by lamplight.

Communities across the Franco-Cantabrian region — from what is now northern Spain into southwestern France — produced this art over a span of tens of thousands of years. It was not one moment or one culture, but a long, living tradition of image-making whose full scope we are still tracing.

The question of who made it

The 40,800-year minimum age for the El Castillo red disk landed at a scientifically uncomfortable boundary. Modern humans are thought to have arrived in Europe around 41,000 to 45,000 years ago. Neanderthals were still present in parts of the continent at that time, and would not disappear from the archaeological record for another several thousand years.

That overlap means the oldest confirmed example of Spanish cave art could have been made by a Homo sapiens — or by a Neanderthal. Subsequent research has continued to probe this question. A 2018 C.E. study published in Science used uranium-thorium dating on cave art at three sites in Spain and produced dates older than 65,000 years ago — well before modern humans arrived, which the authors argued was strong evidence of Neanderthal authorship. That conclusion remains contested. Some researchers accept it; others argue the calcite crusts may have formed before the paintings, making the dates unreliable minimums.

The debate is ongoing, and that is precisely what makes the 2012 C.E. study so significant. It didn’t just push back a date — it opened a question about the nature of symbolic thought itself.

Lasting impact

Before uranium-thorium dating was applied systematically to cave art, the conventional picture placed the flowering of human symbolic behavior — painting, sculpture, personal ornament — in Europe around 35,000 to 40,000 years ago, and often framed it as a sudden “creative explosion” unique to our species. The 2012 C.E. findings complicated that story.

If art was being made in Spain at least 40,800 years ago, and possibly far earlier, the timeline of cognitive and cultural development looks less like an explosion and more like a long, gradual unfolding — one that may have involved multiple human species. That reframing has influenced how researchers think about creativity, language, and social complexity in deep prehistory.

The method itself has proven broadly useful. Uranium-thorium dating has since been applied to cave art in Indonesia, where paintings at Sulawesi sites have returned dates older than 45,000 years, and to sites in southern Africa and elsewhere. The technique revealed that image-making was not a European invention — it was a human one, expressed independently across the world wherever the conditions allowed it to survive.

Blindspots and limits

Uranium-thorium dating of cave art produces minimum ages, not creation dates — the art could be significantly older than the calcite that covers it, and in caves where no calcite formed, the method cannot be applied at all. The authorship question for the oldest Spanish examples remains unresolved, and some scholars dispute whether the oldest uranium-thorium dates for European cave art are reliable, arguing that the calcite samples used may have been contaminated or may predate the paintings beneath them. The record is incomplete by definition: most organic materials from this period have long since decayed, and much of what was made — on perishable surfaces, in open air — is simply gone.

Read more

For more on this story, see: Cave of Altamira — Wikipedia

For more from Good News for Humankind, see:

• Rhinos return to Uganda’s Kidepo Valley after decades away
• Indigenous land rights milestone: 160 million hectares recognized at COP30
• The Good News for Humankind archive on prehistory

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