McClenon argues that hominins developed more complex rituals that produced therapeutic altered states of consciousness. He claims, citing Winkelman, that shamanic healing "was present in all regions of the world at some time in their hunting and gathering past." According to McClenon, those who were most suggestible in our evolutionary past would have benefited most from shamanic healing ceremonies, resulting in lower morbidity and mortality rates. Accepting the efficacy of shamanistic healing would have been particularly valuable to birthing mothers, and thus would have directly contributed to reproductive success. McClenon concludes that suggestibility and susceptibility to hypnosis confer adaptive advantages on those who possess these traits. [Citations omitted; bolded emphasis mine.]
In fact, childbirth customs, medicine, magic, magic to sustain life, magic to increase life, false beliefs, belief in supernatural/religion, mood- or consciousness-altering techniques and/or substances, and healing the sick (or attempting to) are each found in every human society ever studied.
The effect of this kind of social hypnosis is so strong, its incidents so immediately felt, that it was studied in an earlier era of science as "animal magnetism."