To paint such beautiful canvases, did our ancestors knowingly deprive themselves of oxygen?

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A new published article suggests that former cave artists may have knowingly deprived themselves of oxygen deep in caves to paint their paintings in dull states.

Several thousand years ago, some of our ancestors ventured into deep, dark, winding caves to decorate the walls. Impossible however to reach the bottom of these caverns without light.

Also, Stone Age artists probably had to crawl and twist in these very narrow spaces with torches. According to a team of anthropologists, the smoke that emanated from it would then have caused the already not very high oxygen levels to drop, ultimately inducing an altered state of consciousness. And according to them, it was deliberate.

Deep in the caves

A few years ago, while I was visiting caves in France, I started to notice that most of the drawings were deep in very narrow caves.“, Explain Yafit Kedar of Tel Aviv University. “I started to wonder: why did they choose to work this way? Why not paint at the entrance to the caves to take advantage of the natural light?

In recent work, Kedar and his team modeled the effect of torches on the airflow of a cave.

In a deep cave with a single entrance, simulations show oxygen levels can drop below 18% in just fifteen minutes (compared to the usual 21%). However, in humans, oxygen deprivation can release dopamine in the brain, sometimes causing drowsiness, euphoria or hallucinations.

The additional use of fire complicates matters further. In a cave with open access to the outside world, a flame tends to create two distinct layers of air. A lower layer is then formed, made up of air from the outside, and an upper layer made up of exhaust gases (mainly CO2) emanating from the torch.

In a narrow passage, on the other hand, the top and bottom layers tend to partially blend. In addition, the oxygen atoms are lighter than those of carbon dioxide. This is why oxygen tends to float upwards, down the tunnels to the entrance. Concretely, the deeper you move through a cave system with a torch in your hand, the more oxygen you deprive yourself of.

In various simulations, when ventilation was particularly restricted, researchers found that oxygen levels could go down to 9%. Beyond that, you could pass out.

Rouffignac cave. The red dots represent the location of the drawings. Credit: Dachary

Hypoxia as the main driver of creativity

Finding yourself in such a state, bordering on bearable, could easily dissuade you from venturing into such environments. Yet the drawings are there. There is between 14,000 and 40,000 years, some of our ancestors could therefore have deliberately chosen to take refuge there. Wiping the effects of sensory deprivation combined with the lack of oxygen, they would then have allowed their creativity to be expressed.

The use of psychoactive plants to reach the same levels of consciousness will appear much later in archaeological records. Without them, our ancestors could therefore have favored hypoxia. Details of the study are published in the Journal of Archeology, Conscience and Culture.

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