The limited variety in the subjects of rock art paintings has become increasingly evident in the many sites discovered. | The limited repertoire of subjects found in rock art has made it difficult for archaeologists to determine when each painting was created. | In the first place, there is little new archaeological information on the subject of rock art because of the limited number of recent discoveries. | Because many rock art sites cannot be dated, archaeologists have limited information about how rock art varied from period to period. |