Adaptationism is a set of methods in the evolutionary sciences for distinguishing the products of adaptation from traits that arise through other processes. It is employed in fields such as ethology and evolutionary psychology that are concerned with identifying adaptations. George Williams' Adaptation and Natural Selection was highly influential in its development, defining some of the heuristics, such as complex functional design, used to identify adaptations.
Read more about Adaptationism: Debate, Criteria of Calling Something Adaptive, Anatomical Constraints, Genetic Constraints, Adaptationist Rebuttals