PETROGLYPHS— STEWARD 419 



a few years ago, that the pictures are dinosaurs, it is sheer nonsense, 

 for the great reptiles were extinct long before man had begun to 

 evolve anywhere on the face of the earth. When, however, the 

 petroglyphs are thought to be of the giant bison, mammoth, ground 

 sloth, camel, or others of the great Pleistocene mammals which 

 are now known to have survived after man's advent to the New 

 World, the claim should be examined with care, for it is entirely 

 possible that human beings did depict these now extinct species (pi. 

 8). So far, however, none of these claims is wholly convincing, for 

 careless and unskilled drawing produced such distortions of the 

 humbler species that they might easily be mistaken for anything 

 under the sun and for many things that naver existed. It is very 

 often impossible to know whether the artist intended a now extinct 

 species, or a purely imaginary creature or whether he simply could 

 not draw any better. As well suppose that the blundering scrawls 

 of modern children are prehistoric monsters. 



TYPES OF PETROGLYPHS 



As all American petroglyphs cannot be subsumed under a single 

 description or explanation, we will now review some of the more 

 important types. Each area tends to have a distinctive style, which 

 includes both special geometric forms and conventions in handling 

 realistic subjects. 



Probably the greatest number of petroglyphs occur in the Great 

 Basin, that high, sage-covered region between the Wasatch Moun- 

 tains on the east, the Sierra Nevada Mountains on the west, the 

 Columbia Plateau on the north, and the Colorado Plateau on the 

 south. The large number of extremely hard granitic and basaltic 

 rocks were favored mediums and the semiarid climate has preserved 

 the petroglyphs extraordinarily well. If there were formerly also 

 painted pictures or if the carved designs bore paint, time has removed 

 nearly all traces of them. The complete failure of the modern 

 Shoshonean tribes of this region to understand the source of them, 

 and the geologic evidence from such sites as Grapevine Canyon and 

 the Salton Sea, mentioned above, as well as the frequent covering 

 of the figures with desert varnish, a peculiar oxidation that slowly 

 coats certain desert rocks, all point to considerable antiquity of 

 most, though not necessarily all, of these petroglyphs. 



It is as impossible to interpret as to assign authorship to these 

 petroglyphs. Although no two are alike, aU have a similarity which 

 indicates a definite purpose. Characteristically, they are geometric, 

 comprising bewildering combinations of rambling, wavy, or zigzag 

 lines, which comiect circles and are interspersed with concentric, 

 spoked, and bisected circles, "sun disks", spirals, crosses, dots, 



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