DNA studies of the ancient paint binder/vehicles used in lower Pecos rock art pictographs

Radiocarbon dating has shown that Pecos River style pictographs on the walls of Seminole Canyon, Texas are about 3000 to 4200 years old. We extracted ancient DNA from two of these pictographs and subjected it to polymerase chain reaction (PCR) and phylogenetic analysis to aid in the identification of the organic binder/vehicle(s) used by the painters. Little DNA is expected to remain in a painting after several millennia; any small fraction that might survive would probably be seriously degraded. PCR has the capacity to amplify sequences from badly degraded DNA. We amplified and sequenced a 106 base-pair fragment from the highly conserved histone 4 gene and phylogenetically compared the pictograph-derived sequences to known sequences from varied vegetable and animal sources to determine the origin of the organic binder/vehicle. We used negative controls (no DNA added) and positive controls (known DNA) to assure that we were amplifying ancient DNA in the paint fragments, and not contaminating DNA from other sources. The sequences obtained revealed that the organic binder/vehicle was definitely from a mammal, probably an ungulate (hoofed animal).