The argument that is MOST likely to support Madhu's theory that the cave paintings might have been made by prehistoric shamans is:
Prehistoric groups may have believed that the shamans could communicate with the spirits of the animals painted in the caves.
This argument directly connects the role of shamans with the cave paintings, suggesting that the paintings could be a form of communication or a ritual related to the beliefs held by these prehistoric groups regarding their shamans and the spirits of the animals, potentially providing a spiritual context to the artwork.