One of the most common geometric motifs is the spiral, painted and carved throughout the world. And yet the symbolic meaning of the spiral in prehistoric art is speculative. Some argue it may have represented the sun, or the portal to a spirit world. Perhaps it represented life itself, or life beyond life – eternity. Or else, it may have had a more prosaic, functional purpose, that of a calendrical device, employed to deconstruct time into chapters, seasons and solstices.
source: ancient symbols in rock art