Roy A. Rappaport (1926–1997) was an American anthropologist known for his contributions to the anthropological study of ritual and to ecological anthropology. Biography Rappaport received his Ph.D. at Columbia University and held a tenured position at the University of Michigan. One of his publications, Pigs for the Ancestors: Ritual in the Ecology of a New Guinea People (1968), is an ecological account of ritual among the Tsembaga Maring of New Guinea. This book is often considered the most influential and most cited work in ecological anthropology (see McGee and Warms 2004). In that book, and elaborated elsewhere, Rappaport coined the distinction between a people's cognized environment and their operational environment, that is, between how a people understand the effects of their actions in the world and how an anthropologist interprets the environment through measurement and observation. Work Rappaport's work demonstrates the correlation between a culture and its economy, with ritual invariably occupying a central role. His Pigs for the Ancestors: Ritual in the Ecology of a New Guinea People was published in 1968 and again in 1984. It is a classic case study of human ecology in a tribal society and the roles of culture and ritual. The research comes from his fieldwork and time spent with the Maring tribe of Papua New Guinea, who lacked hereditary chiefs or officials. Instead of treating whole cultures as separate units, Rappaport focused "on populations in the ecological sense, that is, as one of the components of a system of trophic exchanges taking place within a bounded area." (Biersack, 1999, 5). Rappaport explained his reasoning behind using populations as opposed to cultures, "Cultures and ecosystems are not directly commensurable. An ecosystem is a system of matter and energy transactions among unlike populations or organisms and between them and the non-living substances by which they are surrounded. 'Culture' is the label for the category of phenomena distinguished from others by its contingency upon symbols." (Biersack, 1999, 6). Throughout his work, he studied how an ecosystem maintains itself through a regulatory force. He aimed to show the adaptive value of different cultural forms in maintaining the pre-existing relationship of a population with their environment. In this case, it was ritual acting as the regulator, when pigs were sacrificed during times of warfare. This was done by the tribal members to acquit themselves of debts to the supernatural. Herds of pigs were maintained and fattened until