We got very excited, then we got something completely different
In the limestone passages of Spain and Portugal, scientists have recovered something the caves kept secret for millennia: the genetic traces of people who moved through them between five thousand and twelve thousand years ago. By sampling pigment and bare rock across eleven sites, researchers have opened a new kind of conversation with the deep human past — one that may eventually reveal not only who made the world's oldest art, but whether we made it alone. The discovery was partly accidental, born from a student's persistence and a single positive result that changed the direction of an entire expedition. What the caves have preserved, it turns out, is not just image but identity.
- For months, every sample came back negative — then a single pigment result changed everything, sending the team back into the caves with a new strategy.
- Paradoxically, the richest DNA did not come from the paintings themselves but from the bare rock walls nearby, suggesting the caves absorbed the living presence of people who simply passed through.
- Five usable samples linked to western hunter-gatherers of the Mesolithic period — people who touched, sneezed, or bled on stone that sealed itself shut thousands of years ago.
- Fragments from two caves already hint at gender patterns, with some chambers yielding predominantly female DNA, quietly reshaping assumptions about who inhabited these underground spaces.
- The deeper urgency now is whether refined techniques can detect Neanderthal or Denisovan DNA on cave walls — a question that could rewrite the story of symbolic thought itself.
In caves across Spain and Portugal, scientists have recovered the genetic fingerprints of people who walked those passages thousands of years ago. By analyzing pigment samples and rock surfaces from eleven sites, researchers detected ancient human DNA — opening a new window into who created some of humanity's oldest art.
The breakthrough came almost by accident. Alba Bossoms Mesa, a PhD student at the Max Planck Institute for Evolutionary Anthropology, was part of a team dating cave paintings and analyzing their chemistry. DNA extraction was an afterthought. For months, every sample came back negative. Then a single pigment result changed everything, and the team returned with renewed purpose — this time collecting from bare rock walls as well as the paintings themselves. That decision proved crucial.
The richest DNA did not come from the pigments at all, but from the unpainted walls. Five samples yielded usable ancient human material, though whether it came from artists or passing visitors remains unknown. Touch, saliva, blood — the caves preserved these traces for millennia without revealing their origin. Comparison with precisely dated ancient bones placed the DNA among western hunter-gatherers who inhabited Iberia between five thousand and twelve thousand years ago.
The samples offered more than ancestry. Fragments from Escoural Cave in Portugal revealed biological sex — one predominantly male, one predominantly female — while another cave yielded two predominantly female samples, hinting at patterns of movement and use that remain only partially visible.
What makes the work significant is not what it answers but what it now makes possible to ask. Researchers hold complete genomes for Neanderthals and Denisovans. If techniques can be refined, they could test whether DNA from these extinct species appears on cave walls — potentially settling the long debate over whether modern humans created prehistoric art alone. They could map gender patterns across chambers and reconstruct the social life of these underground spaces in ways that seemed impossible just months ago. The DNA on these walls, invisible to the eye, may yet tell us something fundamental about what it means to be human.
In caves scattered across Spain and Portugal, scientists have recovered something no one expected to find: the genetic fingerprints of people who walked those passages thousands of years ago. By analyzing pigment samples and rock surfaces from eleven sites, researchers detected ancient human DNA—a discovery that opens an entirely new window into who created some of humanity's oldest art and how they moved through these underground spaces.
The breakthrough came almost by accident. Alba Bossoms Mesa, a PhD student at the Max Planck Institute for Evolutionary Anthropology, was part of a team tasked with dating cave paintings and analyzing their chemical composition. DNA extraction was an afterthought, a bonus if it happened to work. For months, nothing did. Sample after sample came back negative. Then, just before one of the final expeditions, a single pigment sample yielded positive results. The team returned to the caves with renewed purpose, this time collecting not just from the paintings themselves but from the bare rock walls nearby—a control that would prove crucial.
What they found was unexpected. The richest DNA samples did not come from the pigments at all, but from the unpainted cave walls. Five samples in total yielded usable ancient human DNA, though the researchers cannot say with certainty whether these traces came from the artists themselves or from other people who passed through the caves. The DNA could have been deposited through touch, through saliva from a sneeze, or through blood. A person reclining while painting might have left their mark on the wall. A visitor slipping on stone could have done the same. The caves kept these genetic echoes for millennia without revealing their source.
Dating the DNA proved tricky. The samples lacked sufficient mitochondrial DNA—the biological clock scientists typically use to age genetic material. But other evidence pointed in a consistent direction. For some caves, geological records showed that all entrances had been sealed by rockfalls at least four thousand years ago, establishing an upper bound. More tellingly, when researchers compared one sample to known DNA from precisely dated ancient bones, they found a genetic match with western hunter-gatherers who inhabited Iberia between five thousand and twelve thousand years ago. These were people of the Mesolithic, living in a landscape very different from the one we know today.
The team could extract more than just ancestry from the samples. Two DNA fragments from Escoural Cave in Portugal revealed biological sex: one predominantly male, one predominantly female. In another cave, both samples appeared predominantly female. These small details hint at patterns of movement and use within the caves, though the picture remains fragmentary.
What makes this work genuinely significant is not what it answers but what it makes possible to ask. For decades, archaeologists have debated whether cave art was the exclusive creation of modern humans or whether other human species—Neanderthals, Denisovans—also contributed to it. We have complete genomes for both. If techniques can be refined, researchers could theoretically test whether DNA from these extinct species appears on ancient cave walls. They could map gender patterns across different chambers, track which areas saw the most human activity, and reconstruct the social life of caves in ways that seemed impossible just months ago.
Bossoms Mesa speaks of this potential with genuine wonder. Imagine being able to ask whether women and men used different parts of the caves. Imagine settling the question of whether Neanderthals ventured as deep into these passages as modern humans did, whether they too left their mark on stone. These are not idle questions. They touch on fundamental aspects of what it means to be human—our capacity for symbolic expression, our relationship to darkness and stone, our place in a world we shared with other intelligent species. The DNA on these cave walls, invisible to the eye, may yet tell us.
Citas Notables
What happened was a very happy but also weird surprise. We didn't get any more positives from pigments, but we got positives from the controls—from the cave walls without painting.— Alba Bossoms Mesa, Max Planck Institute for Evolutionary Anthropology
Imagine that we improve the techniques and we can then start to ask more about how humans were interacting with the caves. To be able to say if we were the only ones making art or if Neanderthals were also able to, that's my dream.— Alba Bossoms Mesa
La Conversación del Hearth Otra perspectiva de la historia
So they found DNA on cave walls, not in the paintings themselves. That seems backwards. Why would the paintings be less useful?
Because pigment is inert—it's mineral and binder, applied to stone. The DNA that matters is what people left behind when they touched the wall, breathed on it, bled on it. The pigment itself doesn't preserve human genetic material well. The bare rock, paradoxically, was a better keeper of secrets.
But then how do they know this DNA is actually from the people who made the art? It could be anyone who wandered through.
That's the honest answer: they don't know for certain. It could be the artist. It could be someone who came centuries later. What they do know is the age of the DNA—it matches people who lived five to twelve thousand years ago. And they know it's human, not contamination from animals or water flow. Beyond that, they're working with fragments.
The real story here seems to be about Neanderthals. Whether they made art.
Yes. That's the dream, as Bossoms Mesa says. We have Neanderthal genomes. If we can extract DNA from cave walls and improve the technique, we could theoretically find out if Neanderthals left their genetic mark on art sites. It would answer one of the deepest questions in human prehistory.
And if they did? If Neanderthals made art?
Then we'd have to rewrite what we think about consciousness, creativity, symbolic thought. We'd have to admit that what we thought was uniquely ours was shared with another kind of human. That changes everything.
But this is still very early.
Very early. Five samples. Mostly questions. But that's how revolutions start—with one unexpected positive result, then the decision to go back and look harder.