What Are The Thorns In Your Crown?

Petroglyphs in the Valley of Fire

Within the canyons of the Valley of Fire. 

These were my main reason for visiting the Valley of Fire Henry,

I wanted to see the petroglyphs.

I had read in Guns, Germs, and Steel about the lack of a written language in native US cultures...but couldn't these and other imagery (e.g. hide painting) be indicative of a written language?

I need to write to Jared Diamond and find out.

xoxo a.d.