A discovery inside a California cave suggests people were combining hallucinogenic drugs and art nearly 500 years ago

• On the ceiling of a California cave, a red pinwheel-shaped drawing likely depicts a psychoactive plant called datura.
• Researchers recently found chewed-up lumps of datura stuffed in the cave’s ceiling.
• The finding is the first clear evidence that hallucinogens were used at a rock art site. It suggests that humans may have painted cave art to enhance hallucinations.
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For decades, researchers have thought that hallucinogenic substances likely played a role in rock art, inspiring many of the vivid drawings that adorn cliffs and caves across all six habitable continents.

But according to a new study, it could go the other way around: Paintings in caves could have acted as visual aids for drug-induced hallucinations.

The study, published in the journal Proceedings of the National Academy of Sciences this week, describes a cave in Southern California, between Santa Barbara and Bakersfield. It’s within the historic territory of the indigenous Chumash people and is known as the “Pinwheel Cave” because of the pinwheel-shaped painting on its ceiling. The painting resembles the datura plant, which delivers intense psychoactive effects when ingested. 

David Robinson, the study’s lead researcher, has been investigating the cave since 2007. He and a team of archaeologists have over the years discovered and analyzed chewed wads, or “quids,” of datura that were stuffed into cracks in the ceiling of the cave up to 490 years ago. Their analysis also showed that humans occupied the cave from about 1530 to 1890, and “in all probability” chewed the datura during that period.

Combined, this set of discoveries makes the Pinwheel Cave the first known site that links evidence of hallucinogen use to cave paintings.

Which came first: the rock art or the hallucinogens?

Indigenous Californians used datura for centuries. People once processed the plant into a drink called toloache for coming-of-age ceremonies, and the Chumash consumed it before "vision quests" in which individuals sought interaction with spirits. In the group's mythology, the plant is personified as a supernatural grandmother named Momoy.

The paintings in the Pinwheel Cave seem to depict datura and its primary pollinator, the hawk moth, in its larval stage. The researchers think the Chumash people painted the images while sober and intended them to serve either as "visual catalysts for communal experiences" or simply as signposts to indicate where to take datura. 

The new analysis also contradicts what Robinson calls "the myth of the lone shaman": the idea that a single individual would go into a cave and do hallucinogens on their own. Both the density of the quids, as well as the presence of many tools in the cave, suggest that many Chumash people used the space.

"This is a community site," Robinson, who is a reader in archaeology at the University of Central Lancashire in England, told Live Science.

What's more, the fact that these images evoke the plant and its pollinator, the researchers wrote, contradicts the idea that humans took hallucinogens partly for artistic inspiration. The drawing does not seem to be a reflection of divine or spiritual inspiration from the hallucinogenic effects of the plant.

In that sense, the cave painting "calls into question assumptions that rock art imagery directly reflects private images seen in trance," the researchers wrote. 

A ritual discouraged as the result of US government policy

Datura's likely role in communal rituals makes sense given its importance to the Chumash people, according to Devlin Gandy, a co-author of the study.

"Datura is far more than a hallucinogen," Gandy told National Geographic. "It is a sacred being which is part of prayers, utilized for cleansing, as well as healing."

The US government suppressed tribal rituals like datura ceremonies in the 20th century via forced cultural assimilation policies and the displacement of native people from traditional lands. President Jimmy Carter finally passed the American Indian Religious Freedom Act in 1978, which protected religious freedom for indigenous tribes. But modern-day Chumash people no longer ingest the plant.

Sandra Hernandez, a spokesperson for the Tejon Tribe, which has Chumash people enrolled, told National Geographic she finds her ancestors' relationship to datura inspiring.

"I find myself at times with a lack of words to define the feeling of how great it is to know how smart our ancestors were," she said. "I can never get around that. We knew things because we communed with creators and we communed with nature."