Paul Howe Shepard, Jr. was an American environmentalist and author best known for introducing the "Pleistocene paradigm" to deep ecology. His works have attempted to establish a normative framework in terms of evolutionary theory and developmental psychology. He offers a critique of sedentism/civilization and advocates modeling human lifestyles on those of nomadic prehistoric humans. He explores the connections between domestication, language, and cognition.
Based on his early study of modern ethnographic literature examining contemporary nature-based peoples, Shepard created a developmental model for understanding the role of sustained contact with nature in healthy human psychological development, positing that humans, having spent 99% of their social history in hunting and gathering environments, are therefore evolutionarily dependent on nature for proper emotional and psychological growth and development. 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.