Petroglyphs, I think they are called. They are pretty common in Northern New Mexico as well. If you go hiking in the Carson or Santa Fe National Forests or out in the Ghost Ranch area, you see them all over the place. We came upon this one spot where some band had hollowed out what amounted to four or five little bunk beds in the soft tufa rock, I would imagine it was a military outpost of some sort in service to the large city at Bandolier. The petroglyphs were everywhere. I would liken them more to Egyptian hieroglyphs. I still like the theory that the cradle of civilization was not Africa, but the Borneo Islands. It spread from there to Egypt(then to Europe), China and the Americas, by people who became more advanced out of necessity. The need to depend on the sea and learn boat building and tool use seems to me a better theoritical basis for why these people were the forerunners of the advanced civilizations of the earth. It might also explain the DNA evidence presented on the PBS thing as well. I believe a book you mentioned, "Guns, Germs and Steel", makes this case as well.