When a San Shaman goes into a trance, he harnesses that power, becomes part of the world beyond, becomes invisible to the singers and dancers around him, and draws images on the rock face. Ask the San who drew the images, and they say the spirits. And the rock face is more than a surface for the paint; it is the boundary of this world and the world beyond.... part of the meaning of it all, and the rock shelter itself assumes a special status, a place of veneration.

Origins Reconsidered: In Search of What Makes Us Human (1992)