Since its discovery, cave art has provoked great curiosity about why it appeared when and where it did, how it was made, and what it meant to the communities that created it. David Lewis-Williams proposes that the explanation for this lies in the evolution of the human mind. Cro-Magnons, unlike the Neanderthals, possessed a more advanced neurological makeup that enabled them to experience shamanistic trances and vivid mental imagery. It became important for people to "fix," or paint, these images on cave walls, which they perceived as the membrane between their world and the spirit world from...