Watch History Channel's Ancient Aliens Episode #5 The Desert Codes!!
Used globally, this Universal Language exists in all things, not restricted to just rock symbols! It can be found in ancient artifacts, tapestries, pottery and incorporated into megalithic structure designs. All incorporating the language.
My evidence points to an ancient advanced civilization sailing the great lakes of the western U.S. 12,500+ years ago! Moving goods along these corridors to the sea and the petroglyphs are the routes and harvesting sites of the goods transported.
One of the most growing arenas of evidence gathered is the geoglyph locations where man flew from high mountains over geoglyphs that were designed in great detail along the ancient lake shorelines throughout the west! These sites mark an ancient evolution of transport and technology thought very modern!