Life-size figures sketched into red rock cliffs in Canyonlands National Park were drawn a lot earlier than previously believed.
Researchers used modern luminescence dating techniques to analyze when the art went up in what is known as the "Great Gallery" in southeastern Utah's Horseshoe Canyon. They now believe the figures were created 1,000 to 2,000 years ago, instead of 2,000 to 4,000 years ago, according to the Associated Press.
The study indicates the drawings were done by humans who were transitioning to a culture of farming and moving away from hunting and gathering, said David Whitley, one of the foremost experts on rock art in North America.
Their research is important since it helps us better understand art known as Ancient Barrier Canyon-style paintings, which are usually very mysterious, added Whitley, who was not involved in the study.
Thanks to the more recent time stamp, the art was most likely created during a time of great transition, when new religions, customs, and ideologies were forming, said Steven Simms, a Utah State University anthropology professor, who worked with university geology professor Joel Pederson on the study, according to the Associated Press.
"It puts in a very momentous time," Simms said.
They published a paper of their findings in the online Early Edition of the Proceedings of the National Academy of Sciences.
Figuring out the date of rock art is very hard to do, and there has usually been very little interest from scientists in taking on the projects, said Whitely, who has studied rock art for 35 years and written 17 books, according to AP.
"We tend to think of art and science as being polar opposites. The result is that artists don't talk about science much, and scientists don't talk about art much," Whitley said. "I'm very happy they did this."
About eight years ago a man brought a piece of sandstone from the area to Pederson. The retired scientist then set out to determine if it were possible to assess the date of a drawing by looking at the composition or color of the rocks.
Pederson was determined to test the man's theory after going to see the Horseshoe Canyon figures up close, according to the Associated Press.
"I realized, we can actually figure out the date of this," Pederson said. "It was just kind of luck that a rock-art enthusiast knocked on my door."
A year later he started work on the project that would take seven years to complete, thanks to a shoestring budget.
Researchers homed in on a date estimate by studying how sunlight bleached away stored signals of radiation on the exposed rocks, Pederson said, according to AP.
The two researchers are hoping they can study other rock art to figure out more precise date estimates, adding that they believe the technique is "widely applicable."