Researchers Discover the Shocking Age of the Mysterious Pecos River Rock Art

The murals were painted on limestone canyon walls, in the same style, over the span of four millennia

Researcher Carolyn Boyd examines a Pecos River style pictograph in Seminole Canyon State Park and Historic Site.
  Texas State University / Shumla Archaeological Research and Education Center

The limestone canyons along the Pecos River in southwest Texas are covered in ancient art. Painted by unidentified Indigenous peoples long ago, the Pecos River style murals stretch into northern Mexico, and they've long mystified archaeologists who have been unable to determine their age.

Now, researchers have finally dated some of the murals by analyzing the radiocarbon in paint and mineral deposits. According to their study, published in the journal Science Advances, the Pecos River valley’s inhabitants painted in the same cosmic style for millennia—from around 3700 B.C.E. until 900 C.E.

“Frankly, we were stunned to discover that the murals remained in production for over 4,000 years, and that the rule-bound painting sequence persisted throughout that period as well,” study coauthor Carolyn Boyd, an archaeologist at Texas State University, tells Live Science’s Aristos Georgiou. The canyons are like an “ancient library containing hundreds of books authored by 175 generations of painters,” she adds. “The stories they tell are still being told today.”

Researchers Tim Murphy and Diana Radillo Rolon capture microscopic images of a 10-foot feline pictograph in Panther Cave. Texas State University / Shumla Archaeological Research and Education Center

The murals were painted in pigments bound with yucca or bone marrow. Jerod Roberts / Shumla Archaeological Research and Education Center

Many of the Pecos murals, spread across countless canyon rock shelters, contain similar imagery. The researchers began their work by identifying recurring symbols, according to the study. They found that 134 of the murals include at least one of a specific group of motifs, including rabbit-eared headdresses, stylized dart tips, winged figures with antlers, power bundles and speech breath. A power bundle appears in more than 60 percent of the murals; it constitutes a plant-, animal- or human-like shape depicted at the end of two long lines extending from a figure’s hand.

“Many of the 200-plus murals in the region are huge,” Boyd tells Live Science. “Some span over 100 feet long and 20 feet tall and contain hundreds of skillfully painted images.”

Archaeologists don’t know much about who painted the Pecos murals, aside from the fact that they were nomadic hunter-gatherers. Per the study, the region boasts evidence of more than 12,500 years of hunter-gatherer occupation.

Quick fact: Scale of the Pecos River rock art

• Some of the murals measure as long as 100 feet and as tall as 20 feet. They depict human and animal figures, as well as geometric designs.

Southern Texas’ arid clime preserved the murals well but dating them still proved a difficult task. The researchers focused on 12 murals with similar imagery. Per the study, they used two independent methods of determining age. One dated the organic carbon in the paint’s binders—likely yucca plant and fatty bone marrow from deer. The other dated the carbon inside calcium oxalate accretions—mineral crusts that lie beneath and atop the paintings—to figure out the murals’ minimum and maximum ages.

“It is important to take a control sample of unpainted rock to see if there is any organic contamination in the rock surface,” study co-author Karen Steelman, science director at the Shumla Archaeological Research and Education Center, tells Artnet News. “If not (which was the case for this study), then we can be certain that the organic material that we are dating is inherent in the paint alone.”

This photomicrograph shows layers of yellow, red and black paint. Texas State University / Shumla Archaeological Research and Education Center

Anthropologists previously assumed each Pecos mural was assembled from small individual contributions over time. Actually, the radiocarbon dates of the murals’ pictographs were “clustered so closely as to be statistically indistinguishable, suggesting that they were produced during a single painting event,” Boyd tells Artnet News.

According to a statement from Texas State University, the researchers’ analyses of the 12 murals’ layers and iconography revealed that eight of them adhere to the same set of rules and established iconography—even though they were painted up to 4,000 years apart. As the researchers write in the study, this suggests “consistent messaging throughout a period marked by changes in material culture, land use and climate.”

The researchers think the Pecos River style paintings transmitted a system of “sophisticated metaphysics”—philosophy relating to concepts like being, time, space and the beginning of life. They write that the Pecos muralists’ “ancient cosmovision” likely informed the beliefs of later Mesoamerican agricultural societies, like the Olmec, Maya and Aztec.

“The murals are viewed by Indigenous people today as living, breathing, sentient ancestral deities,” Boyd tells Live Science, “who are still engaged in creation and the maintenance of the cosmos.”

The Huichol people live in western Mexico among the Sierra Madre Occidental mountains. They recognized one of the motifs in the Pecos murals: a crenellated arch below a portal through which figures pass.

“I was told by Huichol elders that it represents the sacred mountain,” Boyd tells Artnet News. “The undulations along the sides are a ladder for the sun to climb out of the world below each morning [and] to descend on its return each night.”