Human DNA survived in caves for thousands of years, new study reveals
Archaeologists discover DNA of ancient hunter-gatherers (photo: Unsplash)
Researchers from the Max Planck Institute for Evolutionary Anthropology in Germany, working with archaeologists from Spain and Portugal, have successfully extracted authentic ancient human DNA directly from cave walls for the first time, according to Nature Communications.
How DNA survived in stone for thousands of years
The First Art project was originally created to analyze pigments and determine the age of the world's oldest cave paintings.
However, scientists decided to test whether highly sensitive modern technologies could detect traces of saliva—which prehistoric people may have used to blow pigment through hollow bone tubes—or sweat left by hands touching the cave walls.
Researchers examined 24 wall panels in 11 caves and collected 54 samples of mineral deposits, bare rock, and sediment. Only five samples contained sufficient-quality genetic material, but their analysis yielded remarkable results.
Key discoveries
Pure human DNA. In Portugal's Escoural Cave, a sample taken from a pigmented calcite layer contained only human DNA, with no traces of animal genetic material.
This indicates that the DNA was deposited through direct contact with human bodily fluids.
A surprise on bare rock. Ancient DNA was also found on unpainted rock surfaces in Escoural Cave and Covarón Cave in Spain. These samples had originally been collected only as controls.
Sex and ancestry identified. DNA from Covarón Cave showed that the individuals belonged to Western European hunter-gatherer populations. Three samples were predominantly female, while one was predominantly male.
The recovered DNA is estimated to be at least 2,000 years old. However, the archaeological history of Escoural Cave suggests that some of the genetic profiles could date back 4,000 to 5,000 years.
Cave walls as living archives: Altamira setback
The new method could fundamentally change where paleogeneticists search for evidence of ancient humans. Cave walls have proven to be long-lasting archives of human presence, potentially revealing which groups ventured deep into cave systems and whether men and women used different areas of the caves.
The study also highlighted limitations of the technique. For example, a unique prehistoric airbrush made from a bird bone, discovered in the Spanish Altamira Cave and once used to spray ochre onto cave walls, yielded no ancient DNA.
Researchers believe decades of modern scientific work and repeated handling by archaeologists overwhelmed the ancient genetic traces with DNA from contemporary humans.
The team's next priority is to refine minimally invasive sampling techniques and identify caves with microclimates that best preserve ancient DNA, particularly sites where prehistoric handprints have survived.
