Great Basin ethnography contains little information concerning rock art, suggesting that much of it is pre-Numic. The presence of historic rock art, however, should permit differences between pre-Numic and Numic populations to be identified. Anthropological theory suggests pioneer groups use ritual to socialize the landscape. Rock art may also be associated with colonizing groups to secure access to new resources. Numic populations seem to have responded to pre-Numic rock art through modification of the art. Once the landscape had been re-socialized rock art was generally avoided. This explains why rock art production became sporadic, and memory of it lost.