I was sitting in the back row of a class on substance abuse with two jovial colleagues. The various drugs of choice were being cataloged along with their effects, symptoms, and treatments. When the presenter got to hallucinogens, he explained a history that goes way, way, back, way before LSD. He suggested some of the primitive societies' shamans, the priests and the seers who were in touch with the spirit world, were most likely using some herb to smoke their way to wherever it was they were going. He added that in the Amazon, or some other jungle, there was a frog that secreted a powerful substance. It was used as a poison on arrow heads but somehow someone found you could get a heck of a buzz if you ingested it. My guess is "shaman" means "frog-licker" in Amazonian. Another guess is that it started out as a dare from one shaman to another and shortly thereafter, all these colleagues were hooked.