The artists behind some prehistoric cave paintings have been hallucinating due to a shortage of oxygen, according to a new archaeological study. Tel Aviv University archaeologists Yafit Kedar, Gil Kedar, and Ran Barkai report on their findings in the Journal of Archaeology, Consciousness, and Culture. From their paper, titled "Hypoxia in Paleolithic decorated caves: the use of artificial light in deep caves reduces oxygen concentration and induces altered states of consciousness":
Many of the depictions in these caves are located in halls or narrow passages deep in the interior, navigable only with artificial light. We 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 increases the release of dopamine in the brain, resulting in hallucinations and out-of-body experiences. We discuss the significance of caves in indigenous world views and 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. The cave environment was conceived as both a liminal space and an ontological arena, allowing early humans to maintain their connectedness with the cosmos.