First Stages
Early hominids were omnivores that relied substantially on forest floor foods, including mushrooms. The presence of mycophagy and self-medication among both primates and Paleolithic humans) suggests hominins also incorporated fungi with bioactive properties in their diet. It is likely that psychedelic mushrooms from the genus Psilocybe were ingested by our ancestors since the Pliocene (beginning 5.3 million years ago [mya]), when semi-arboreal hominids intensified foraging activity on the ground. Exposures to psychedelic fungi by australopithecines and early Homo during the Pleistocene (beginning 2.5 mya) are implied by their presence in African grasslands; Stoned Ape Theory is a hypothesis of one of America's most influential psychonauts, Terence McKenna.
This theory was outlined in McKenna’s 1992 book “Food of The Gods.” In its pages, it states that one of our earliest ancestors, Homo Erectus, began to eat Psilocybe cubensis as part of its diet. The theory is based on the alleged effects of psychedelic mushrooms, cited in studies from the 1960s and 1970s by the likes of Roland L. Fischer. According to the Stoned Ape Theory, this simple act could have profoundly changed the brain of our ancestors. McKenna claims that low doses of psilocybin improve visual acuity, especially edge detection. Basically, the new addition of psilocybin to the diet of pack-hunting primates allowed them to be more discerning, skilled, and communicative hunters.