Can this technique be used in caves outside Iberia?

In principle, yes. The calcite-based preservation mechanism is not unique to Spain and Portugal — it occurs in limestone cave systems globally. Sites in France, Australia, and Africa are theoretically amenable. The limiting factor is the low success rate: 9% of samples yielded DNA in this study, requiring extensive sampling of irreplaceable heritage sites.

What other information might future samples reveal?

With sufficient DNA, researchers can determine biological sex, genetic ancestry, and physical traits coded in ancient genomes: pigmentation genes, disease susceptibility, or genetic evidence of familial relationships. A wall touched by a group of related people could, in principle, yield a family portrait in fragments.

Cave walls have been storing human DNA for up to 16,700 years — even where there is no art

Q: Does cave wall DNA tell us who painted the art?

Not necessarily. DNA from unpigmented walls could come from anyone who passed through the cave — an artist, a child, or a hunter sheltering from rain centuries after the paintings were made. Even DNA from within painted crusts cannot establish authorship. It confirms presence, not intent.

A wall touched in the darkness of an Iberian cave 16,000 years ago may still carry the DNA of the person who touched it. Scientists have retrieved ancient human genetic material from the surfaces of 11 caves in Spain and Portugal — not only from walls bearing paintings, but from bare, unpainted rock where no art was ever found. The discovery opens a new category of paleogenetic source that no one had thought to look for.

“It is now possible for researchers to recover DNA from somebody who leaned on a wall 20,000, 30,000, or 40,000 years ago,” said Genevieve von Petzinger, a rock art specialist and National Geographic Explorer involved in the study. “Isn’t that crazy?” Until now, ancient human DNA was retrieved almost exclusively from bones and from sediment — the floors of caves, not their walls. The study, led by Alba Bossoms Mesa of the Max Planck Institute for Evolutionary Anthropology in Leipzig, and published in Nature Communications, changes where researchers know to look.

How DNA survives on rock

The mechanism is not painting. It is presence. When a prehistoric person touched a cave wall — pressing a hand to the surface, leaning against it, spitting pigment onto it while painting — minute traces of biological material transferred to the rock. Over time, a thin layer of calcium carbonate (calcite) formed naturally over the surface, sealing those traces beneath a mineral cap. The calcite acted as a preservative, slowing the degradation of DNA across thousands of years.

Bossoms Mesa’s team took 54 samples from 24 rock art panels across 11 caves, and retrieved readable ancient human DNA from 5 of those samples. The genetic material was found in two types of contexts: within colored pigment crusts on painted panels, and — crucially — from bare, unpigmented wall surfaces with no art visible at all. At Escoural Cave in Portugal, a red-painted dot covering a calcite crust yielded DNA at least 4,000 to 5,000 years old. Two unpigmented samples from Escoural’s walls gave DNA from one male and one female individual. At Covarón Cave in Spain, two more unpigmented samples yielded DNA from female individuals who lived during the Western hunter-gatherer period, between 5,200 and 16,700 years ago.

What the DNA reveals — and what it cannot

The hunter-gatherer lineages identified at Covarón push this technique’s reach back toward the end of the last Ice Age. That the samples come from unpainted surfaces means that researchers are no longer confined to studying walls with visible art: any cave wall that prehistoric people moved through, rested against, or worked beside is now a potential genetic record.

But the technique has strict limits. Of 54 samples, only 5 yielded useful DNA — a success rate of less than 10%. The process is destructive: each sample removes a small portion of the surface permanently. And while the DNA shows that someone was there, it cannot identify who they were to any named individual, or confirm whether the person whose DNA remains was the artist, an assistant, or a visitor who arrived centuries later. Several samples also showed contamination with animal DNA — from bats and rodents that have shared cave environments for millennia. “I was very skeptical,” Bossoms Mesa recalled when the first results came back. “I thought, ‘This is too good to be true.'”

The question of whether a DNA-bearing sample is prehistoric or modern contamination from researchers, tourists, or conservators is a genuine methodological challenge. The team used blank controls and handled samples under stringent conditions to distinguish ancient material — chemically degraded, with the characteristic damage patterns of aged DNA — from modern intrusions.

Why walls were never the obvious place to look

Paleogenetics has grown exponentially over the past 20 years, driven by improving techniques for extracting and sequencing degraded DNA from ancient bones. The science gave us the Denisovans, mapped Neanderthal introgression into modern humans, and traced the routes of farming populations across Europe. All of it came from hard tissue — teeth, bones — or from cave sediment.

Cave walls were overlooked for a practical reason: paint pigments were assumed to be inorganic and biologically sterile. The calcite crusts that overlie many painted surfaces were known to contain organic material useful for radiocarbon dating, but not for human DNA. The FIRST-ART team’s insight was to treat the calcite itself as a preservation medium, not merely as a dating material — and to sample not just painted surfaces but any wall that prehistoric hands might have reached.

Common questions about cave wall DNA

Can this be done in caves outside Iberia?

In principle, yes. The calcite-based preservation mechanism is not unique to Spain and Portugal — it occurs in limestone cave systems globally. Altamira (Spain), Lascaux (France), Chauvet (France), and dozens of sites across Australia and Africa are theoretically amenable. The limiting factor is the low success rate: 9% of samples yielded DNA in this study, which means extensive sampling of irreplaceable heritage sites is required.

Does this DNA tell us who painted the art?

Not necessarily. The DNA from unpigmented walls, in particular, could come from anyone who passed through the cave — an artist, a child, a hunter sheltering from rain centuries after the paintings were made. Even DNA from within a painted crust cannot establish authorship. It confirms presence, not intent.

How is ancient DNA distinguished from modern contamination?

Ancient DNA carries predictable chemical damage: cytosine-to-thymine misreadings accumulate at the ends of degraded fragments over time. Researchers look for these patterns as a signature of genuine antiquity. Fragments without those damage patterns are treated as modern contamination and excluded.

What other information might future samples yield?

With sufficient DNA, researchers can determine biological sex, genetic ancestry, and — in some cases — physical traits coded in ancient genomes: pigmentation genes, disease susceptibility markers, or genetic evidence of familial relationships between individuals at the same site. A wall touched by a group of related people could, in principle, yield a family portrait in fragments.

The FIRST-ART team has identified Altamira Cave in Spain as a priority for future sampling, given its extraordinary concentration of art and the likelihood that multiple generations of artists left traces on its surfaces across thousands of years.

Reference: Bossoms Mesa, A. et al., “Ancient human DNA from rock art and cave wall surfaces in Iberia,” Nature Communications, 2026. DOI: 10.1038/s41467-026-59948-3

Tags: archaeology, ancient DNA, Altamira Cave, cave art, Escoural Cave, hunter-gatherers