Four images of stalagmites with red pigment

Neanderthals painted stalagmites red

Deep in Cueva de Ardales (Cave of Ardales) in Spain, stalagmites have been painted red by artistic Neanderthals, according to a study published in PNAS.

Close-up view of the drapery hosting most of the red stains. Credit: João Zilhão.

Stalagmites, or flowstones, are long, hanging spikes made from calcite and other carbonate materials that form where water flows down cave walls and floors. The stalagmites in Cueva de Ardales, near Málaga on Spain’s south coast, are stained red in places, but it had previously been unclear whether the colouring was natural or painted.

Now, an international team of researchers, led by Africa Pitarch Martí from the University of Barcelona, Spain, has used different forms of microscopy and spectroscopy – studying how light is absorbed – to determine that the red pigment is made of ochre and not the iron-oxide-rich deposits of the cave.

This means they couldn’t have been stained naturally as the stalagmites formed, and so must have been painted.

The team found that the ochre-based pigment was applied twice – once more than 65,000 years ago and again between 45,000 and 49,000 years ago. This is when Neanderthals occupied the area, before early humans came to Europe.

The researchers suggest the pigment was brought from outside the cave, and may have been used to highlight the location of the stalagmites as an archaic form of occupational health and safety.

The two separate applications of ochre also suggest that the stalagmites were marked by different generations that returned to the cave, so may also have had symbolic value.

Researchers looking toward the massive speleothem of Cueva Ardales, with archaeological trench in the foreground. Credit: Pedro Cantalejo-Duarte.