Michael Harner was born in 1929 and trained as an anthropologist at the University of California, Berkeley, conducting doctoral fieldwork among the Conibo people of the Peruvian Amazon and, more extensively, the Shuar, historically called the Jivaro, known in anthropological literature for their practice of shrinking the heads of enemies, a people among whom Harner lived and studied their shamanic tradition directly across repeated visits from the late 1950s onward. During this fieldwork he participated personally in ayahuasca ceremonies and other shamanic practices rather than observing only from the outside, an immersive method that shaped both his anthropological writing and, eventually, a very different second career.
By the 1970s Harner had concluded that the shamanic techniques he had studied across the Americas and, in his broader comparative reading, across shamanic cultures worldwide, shared a recognizable technical core, above all sustained rhythmic percussion used to induce a trance state in which the practitioner experiences a journey to non-ordinary reality to retrieve information or healing power, that could be taught and practiced independent of any single culture's specific cosmology or religious framework. He called this distilled technique core shamanism and set out its practice in his 1980 book The Way of the Shaman, a text that became the most widely read introduction to shamanic practice for a general Western readership and remains in print more than four decades later.