There is a cave in Spain with ancient red pigment on its walls that dates back to the days before modern humans are widely believed to have been in Europe.
For a long time, academics debated its origins, with some arguing that the coloring was just a natural occurrence.
But a new analysis published in the Proceedings of the National Academy of Sciences (PNAS) journal concludes that the red ochre pigment is foreign to the cave and applied intentionally. This suggests that Europe's oldest cave paintings were not drawn by modern humans, but by Neanderthals around 65,000 years ago.
It also means the cave paintings found in the Caves of Ardales in southern Spain could be the oldest in the world.
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That would make them twice as old as the famous animal cave paintings in the Chauvet-Pont d'Arc cave in France.
The Neanderthals appear to have been creating the artwork in the cave for thousands of years, according to the research.
"I believe that this art made by the Neanderthals will be in other caves, it is very clear to me because this type of non-figurative art appears in many international caves," said Pedro Cantalejo, the director of the prehistoric cave of Ardales.
"The problem is... we have always gone to the great palaeolithic arts that are the representations of animals and humans.
"And now we realize that this non-figurative art, which we have not paid attention to, may be precisely the oldest art in the world."
Cover image: A guide pointing to the red pigment on the walls of the prehistoric cave in Ardales, southern Spain. /Reuters/ Jon Nazca
Video editor Pedro Duarte.