Gee, George, I don't know... I suppose from the natural patina in the carvings they've dated them...also there are other pteroglyphs in the area, and some are quite similar. There is some graffiti further up in the small gorge. If I remember correctly, there was a homestead very close to this area, and apparently there has been quite a bit of protection. This is one of the few you can drive to at Dinosaur, I think... quite a way from the digs, but inside the park boundaries...

BTW: scanned your galleries briefly... I envy your composition and quality.
Mike

How can they tell if these are real or recent? Excellent photography!