Ancient cave paintings may be holding onto something besides pigment. Scientists have recovered human DNA from them for the first time, raising the prospect that caves could serve as “genetic archives” of the people who made the art.

The research looked at caves in Spain and Portugal, and the findings were recently published in Nature Communications. The team says the method could be used in caves elsewhere, too.

“The samples with better DNA, which allowed us to look into their genetic ancestry, these could be up to 16,000 years old,” says geneticist Alba Bossoms Mesa, a doctoral student at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

Researchers took pigment samples from ancient cave paintings and from nearby unpainted rock surfaces inside 11 caves. Bossoms Mesa, the study’s first author, said they collected the material in ways that preserved the art.

In some cases, scientists took tiny surface samples from areas that had already been damaged. In others, including Spain’s Altamira Cave, they collected water that naturally flows over some of the ancient paintings.

The team recovered ancient human DNA from samples in five of the 11 caves. In most cases, it was mixed with ancient animal DNA, often from bats and rodents.

The researchers believe that mixture likely shows sediments from the cave floor were naturally transferred to the walls.

In Portugal’s Escoural Cave, though, the team found isolated human DNA that they believe came from the original artists, possibly from touch, from resting against the wall, or from saliva or sweat during painting.

At Spain’s Covarón Cave, most samples contained mixed animal and human DNA, but they also held much more ancient DNA than samples from the other caves. That allowed the team to trace the genetic ancestry of people who had once lived there.

Their analysis suggests the cave paintings at Covarón were probably made by hunter-gatherers who lived in Western and Central Europe between 16,700 and 5,200 years ago. The findings could help date the paintings to the Upper Palaeolithic period, which spanned from 50,000 to 12,000 years ago.

Unmixed human DNA from that period was found only on unpainted cave walls, so the researchers say it is unclear if those people were the artists.

Adam Brumm, an archaeologist at Australia’s Griffith University who was not involved in the study, said the results were promising.

“Several years ago we tried to extract ancient DNA from dated Late Pleistocene hand stencils in Sulawesi and Borneo,” he says. “We had no success, so I’m glad to see the promising results obtained by this team.”

Brumm was one of the scientists who found the earliest-known cave art on Sulawesi, which is thought to be more than 67,800 years old.

“The demonstration that human DNA can persist on cave walls for thousands of years is encouraging,” he says. If successful, extracting ancient human DNA from rock art “will be a game changer that will revolutionise our understanding of early human culture.”

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