Researchers have recovered ancient human mitochondrial DNA directly from cave walls for the first time, opening new avenues to study prehistoric human presence without disturbing archaeological deposits. The discovery was announced alongside a separate breakthrough utilizing UV fluorescence to map invisible calcite varnishes and torch marks on ancient artworks in Chauvet Cave.
Prehistoric visitors left genetic traces on cave surfaces that have survived for millennia, according to a study published in Nature Communications. The interdisciplinary First Art project, which involves institutions across Spain, Portugal, the UK, China, and Germany, carried out the work in collaboration with the Max Planck Institute for Evolutionary Anthropology.
Researchers examined 24 rock art panels across 11 caves, testing pigmented and unpigmented wall fragments, sediments, bones, and a rare prehistoric bird bone airbrush used to apply red ochre. Out of 54 samples collected, exactly five yielded authentic ancient human mitochondrial DNA. One came from a calcite crust with pigment underneath it on Panel 11 in Escoural Cave, Portugal. Two more came from unpigmented walls in a deeper gallery of the same cave, and two from unpigmented surfaces beside rock art in Covarón Cave in northern Spain.
Escoural Cave and Covarón Cave Genetic Results
The unpigmented areas where four of the positive samples turned up had initially been treated as negative controls, making the genetic recovery unexpected. Three of the positive samples contained both human and animal DNA, indicating an indirect transfer route via sediments or water movement. However, two of the samples contained no detectable animal mitochondrial DNA, pointing to direct human deposition through saliva or other bodily fluids.
Researchers extracted DNA from a Neanderthal bone fragment found in Russia's Denisova Cave, and the genome is shedding light on how small and isolated their groups were.(Image credit: Diyendo Massilani.)https://t.co/bEI5K4nSnh#fossils #paleontology pic.twitter.com/CqwQBiiXX1
Among the five positive samples overall, the study notes that recovering that evidence remains difficult, and none of the cave artists have been identified.
We were surprised to see that ancient DNA can be recovered not only from pigmented samples, but also from cave walls that show no visible evidence of past human activity. We can now ask new questions: Who touched this wall? Was it a man or a woman? Which population did they belong to? How far did ancient humans venture into deep cave systems?
Matthias Meyer, Max Planck Institute for Evolutionary Anthropology
The study offers clues to prehistoric visitors’ sex and ancestry, providing a method to investigate underground chamber usage without disturbing sensitive archaeological deposits. Despite these breakthroughs, recovery remains difficult. An examination of the prehistoric bird bone airbrush from the Cave of Altamira yielded no ancient human DNA.
The preservation of human DNA on cave walls is highly variable. But when it does survive, it tells a powerful story. And while these first results are promising, I think our priority now should be to refine the methods and to understand under what conditions we can expect a higher success rate.
Alba Bossoms Mesa, Max Planck Institute for Evolutionary Anthropology
Ultraviolet Fluorescence Spectroscopy at Chauvet Cave
While paleogeneticists sampled walls in Spain and Portugal, another research team deployed optical technology inside France’s Chauvet Cave to study artwork created roughly 37,000 years ago. Because the cave floor holds fragile animal tracks and human footprints, visitors must stay on protective walkways, keeping investigators between 1 and 6 meters away from the decorated panels. Scientists from Sorbonne Université and the French National Center for Scientific Research addressed this distance by constructing a portable spectroscopy instrument built around a 3-meter fiber-optic bundle on a carbon-fiber pole, powered by a 365-nanometer UV LED and a battery pack.
Shining ultraviolet light onto the walls allowed the team to analyze faint fluorescence from mineral deposits and charcoal drawings in the humid, 13-degree-Celsius cave air. The bedrock limestone and the calcite deposits covering it share a near-identical chemical makeup, but organic impurities make their fluorescent spectral signatures distinct. The analysis revealed that water carrying minerals had coated limestone surfaces with thin calcite layers that glowed blue under blacklight, acting as a natural varnish over the prehistoric imagery.
Our methodology is much like forensic investigation: We examine every piece of evidence to decode the techniques of prehistoric artists and understand how the paintings have been preserved over time.
Philippe Walter, lead author on the study
Researchers also discovered an unexpected orange glow beneath certain charcoal marks and around torch smears. Laboratory tests confirmed that heated limestone and heated calcite produce a similar orange signal, demonstrating that prehistoric artists drew specific lines using hot or burning charcoal that physically altered the rock underneath. The findings showcase the careful interaction between humans and geology that protected the Paleolithic masterpieces for millennia.
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