We may owe the dazzling art found deep within caves to our ancestors getting strung out on lack of oxygen, some archaeologists have proposed. The proof is elusive without a time machine, but modeling of oxygen concentrations in these spaces provides support.
For tens of thousands of years humans painted on cave walls, sometimes exquisitely. In the process, they left a legacy that has helped us understand Paleolithic ecosystems – but also left us with far more questions than answers. One question is why so much of the art was painted in deep halls that would have been very hard – and possibly dangerous – for our ancestors to enter when there was perfectly good wall space closer to the surface.
Tel-Aviv University graduate student Yafit Kedar has proposed a novel explanation: the artists needed to go deep to get high.
Sunlight never reaches the places Kedar is referring to, so the artists must have brought torches. With little airflow through the narrow openings, fire would have consumed much of the oxygen. “Hypoxia increases the release of dopamine in the brain, resulting in hallucinations and out-of-body experiences,” Kedar and co-authors note in Time and Mind.
Mind-altering drugs have contributed to much of the art we love today, even in the face of legal restrictions. Psilocybin-containing mushrooms and mescaline for religious purposes survived to modern times, but there is no evidence of their use in Paleolithic Europe. Might the first artists to leave a permanent impression have induced similar effects through the lack of oxygen?
The artists may not have understood why poorly ventilated spaces affected them as they did but the authors write: “We...contend that entering these deep, dark environments was a conscious choice, motivated by an understanding of the transformative nature of an underground, oxygen-depleted space.”
“Entering a cave while penetrating the earth might be conceived as a journey to the underworld, a potent and supernatural place, regarded also as the birthplace of everything, the locale that provides the world with the essentials for existence and well-being,” they add, noting “The rock face itself, within the cave or the rockshelter, was conceived as a membrane, a tissue connecting the here-and-now world and the underground world beyond.”
However, the paper notes that among the around 400 decorated caves in Western Europe, areas close to the entrance where most of the living occurred are usually unpainted. Meanwhile Rouffignac Cave, France has abundant art 730 meters (2,400 feet) from the entrance.
Kedar simulated conditions within these caves based on the ventilation available and light requirements. Oxygen levels usually dropped below 18 percent – the level at which the human brain first becomes affected – within 15 minutes. More extreme effects occur at around 14.5 percent oxygen concentration. How low the oxygen levels reach depends largely on entrance height; with a 1-meter passage, concentrations could get as low as 11 percent, the authors conclude.
Some of these caves, including the famous Lascaux, also have naturally produced gases that may have added to the effect.
For anyone who thinks this sounds like a cool thing to replicate, please note the symptoms of mild oxygen deprivation include poor judgment and, in the paper's words “loss of self-criticism”. It is very, very easy for those in this state to not know when to stop, leading to fatalities. It's one of the major reasons mountain climbers' locations like the slopes of Everest are strewn with bodies, revealed as the snow melts.