Stone age people may have deliberately ventured into oxygen-depleted caves to paint while having out-of-body experiences and hallucinations, according to a new study.
By analyzing cave paintings from the Upper Paleolithic period, some 40,000 to 14,000 years ago, researchers at Tel Aviv University discovered that many were located in narrow corridors or passages deep within navigable cave systems with only artificial light.
The study focuses on decorated caves in Europe, primarily Spain and France, and offers an explanation of why cave painters would choose to decorate areas deep within cave systems.
“It seems that the Upper Paleolithic people hardly used the interior of the deep caves for daily household activities. Such activities were carried out mainly in open-air places, rocky shelters or cave entrances,” the study reads. But why would people go through the trouble of walking through narrow cave passages to make art?
To answer this question, a group of researchers at Tel Aviv University focused on a characteristic of such deep, narrow caves, especially those that require artificial light to navigate: low levels of oxygen. The researchers ran computer simulations of model caves with different passageway lengths that lead to slightly larger “hall” areas where paintings may be found and analyzed the changes in oxygen concentrations if a person was to stand in the different parts of the cave burning a torch. Fire, such as that from torches, is one of several factors that depletes oxygen inside caves.
They found that oxygen concentration depended on the height of the passageways, with the shorter passageways having less oxygen. In most of the simulations, oxygen concentrations dropped from the natural atmosphere level of 21% to 18% after being inside the caves for only about 15 minutes.
Such low levels of oxygen can induce hypoxia in the body, a condition that can cause headache, shortness of breath, confusion and restlessness; but hypoxia also increases the hormone dopamine in the brain, which can sometimes lead to hallucinations and out-of-body experiences, according to the study. For caves with low ceilings or small halls, the oxygen concentration dipped as low as 11%, which would cause the more severe symptoms of hypoxia.
The researchers hypothesize that ancient people crawled into these deep, dark spaces to induce altered states of consciousness. According to Ran Barkai, co-author and professor of prehistoric archaeology, “painting in these conditions was a conscious choice designed to help them interact with the cosmos.”
“It was used to connect with things,” added Barkai. “We don’t call it rock art. It is not a museum.” Cave painters thought of the rock face as a membrane connecting their world to the underworld, which they believed to be a place of abundance, Barkai explained.
The cave paintings depict animals such as mammoths, bison, and ibex, and their purpose has long been debated by experts. The researchers argued that the caves played an important role in the belief systems of the Upper Paleolithic period and that the paintings were part of this relationship.
“It was not the decoration that made the caves significant, but quite the opposite: the importance of the chosen caves was the reason for their decoration,” the study reads.
Barkai also suggested that the cave paintings could have been used as part of a kind of rite of passage, given the evidence that children were present. Additional research will examine why the children were brought into these deep cave areas, as well as investigate whether the people were able to develop resistance to low oxygen levels.
The findings were published on March 31 in “Time and Mind: The Journal of Archaeology, Consciousness and Culture”