 Drawing from ideas of neoteny, Shepard postulated that many humans in post-agricultural society are often not fully mature, but are trapped in infantilism or an adolescent state.He died of lung cancer on July 21, 1996 in Salt Lake City.Some of his most influential books are "The Tender Carnivore and the Sacred Game", "Nature and Madness", "Coming Home to the Pleistocene", "Where we Belong", and "the Others".