A new study seeks to explain why ancient cave painters often drew up their images in the darkest, narrowest passages of caves.
They were "motivated by an understanding of the transformative nature of an underground, oxygen-depleted space," archaeologists from Tel Aviv University say in the study, which appears in the latest issue of Time and Mind: The Journal of Archaeology, Consciousness and Culture.
In other words, the artists knew that these narrow spaces — alongside the oxygen-depleting effects of a burning torch — would deprive them of oxygen and get them high.
The study argues that this oxygen deprivation helped the artists tap into their most creative impulses and connect with the cosmos through hallucinatory imagery.
Connecting to the cosmos through torch and cave
In the study, the archaeologists describe how they "simulated the effect of torches on oxygen concentrations in structures similar to Paleolithic decorated caves and showed that the oxygen quickly decreased to levels known to induce a state of hypoxia."
Hypoxia is a potentially life-threatening state in which a region of the body, or indeed the whole body, is deprived of the necessary oxygen supply at the tissue level.
"Hypoxia increases the release of dopamine in the brain, resulting in hallucinations and out-of-body experiences," the researchers explain.
The authors of the study believe that artists from between 14,000 and 40,000 years ago lit their way through caves with fire torches knowing the effects of the fire would lead to hallucinations in the poorly ventilated spaces.
In order to test their theory, the researchers simulated the effect of fire torches on oxygen concentrations in closed spaces. They found that oxygen levels in narrow passages rapidly declined to below 18 percent, the level known to induce hypoxia in humans.
The study comes only just a few months after the discovery of what is likely the world's oldest cave painting, depicting a wild wart pig. Another recent study, from 2018, theorized that ancient humans also painted to hone their hunting techniques.
In any case, the new study draws a tantalizing link between the effects of hallucinatory experiences and the evolution of art in the early days of Homo sapiens.