 Folke Henschen, a Swedish doctor and historian, asserts that Soviet excavations of the banks of the Dnieper River in the 1970s show the existence of trepanation in Mesolithic times dated to approximately 12000 BCE.The remains suggest a belief that trepanning could cure epileptic seizures, migraines, and certain mental disorders.There is significant evidence of healing of the bones of the skull in prehistoric skeletons, suggesting that many of those that proceeded with the surgery survived their operation.