One of the most famous examples of ancient rock art in North America—the paintings of life-sized human figures on a red rock wall in Utah’s Canyonlands National Park—are possibly thousands of years younger than previously thought, according to new research.
“The most accepted hypotheses pointed to the age of these paintings as 2,000 to 4,000 years old, or perhaps even 7,000 to 8,000 years old,” Joel Pederson, a professor of geology at Utah State University, said in a news release. But, in a new study, his team determined that the figures in the 200-foot-long Great Gallery section of Horseshoe canyon were painted just 900 to 2,000 years ago.
Dating rock art is tricky because the pigments often don’t contain enough carbon to use typical dating methods. Instead, Pederson and his colleagues looked at the rock face surrounding the paintings. Grains of quartz accumulate a radioactive signature from surrounding rock when they are buried. But after sunlight hits them, the signal zeros out. Using a technique called optically-stimulated luminescence, the researchers can deduce how long quartz sediments have been exposed to light.
That analysis gave them a window of time during which Utah artists could have painted the Great Gallery. Archaeologists have a name for this kind of painting — Barrier Canyon style. (It refers to the local name for Horseshoe canyon.) The finding means that the painters lived in the area at the same time as the Fremont people, ancient Native Americans who carved petroglyphs, a completely different type of art, into other rocks in the area.
"What makes it interesting," Steven Simms, one of the study’s co-authors, told The Salt Lake Tribune, "is that period is a time of great demographic, economic and social change with the arrival of the agriculture on the Colorado Plateau, and the arrival of the bow and arrow."