A rock shaped like an enormous python’s head, discovered in a cave in the Tsodilo hills of Botswana, puts back the date of the first known human ritual by 30,000 years, they say.

Behind the rock, which was covered in man-made indentations, was a chamber that the archaeologists believed was used by a shaman who could have spoken without being seen, giving the impression that it was the snake speaking.

“The shaman would have been able to control everything. It was perfect,” Sheila Coulson, from the University of Oslo, said.

She said that she was astonished to find the rock when she first walked into the cave this year. “You could see the mouth and eyes . . . it looked like a real python.”

Dr Coulson said that sunlight gave the indentations the appearance of scales, while at night firelight made the snake seem to move.

Buried in front of the rock were 13,000 human artefacts, including red stone spearheads that appeared to have been burnt. The researchers believe that they were an offering to the snake.

“It was a ritual destruction of artefacts,” Dr Coulson said. “There was no sign of normal habitation. No ordinary tools were found at the site.”

She said the find meant that humans were more organised and had the capacity for abstract thinking at a much earlier point in history than assumed previously.