The evidence for artificial lighting in Hourglass Cave is one of the most significant aspects of the site’s archaeological record.

On cave walls in the passages leading toward the area where the bones were found, researchers documented dark smudge marks that are consistent with the soot deposited by torches — simple, ancient light sources made from organic materials that burn with enough luminosity to illuminate a cave passage but that also leave behind residues of carbon on surfaces they pass close to.

This kind of evidence — torch smudge marks on cave walls — is found in prehistoric cave sites around the world, including the famous painted caves of Europe, where the same kind of marks left by ancient lamps and torches accompany the paintings on cave walls.

The marks at Hourglass Cave were not accompanied by artwork.