- (evolutionary theory) The view that many traits of organisms are evolved adaptations.
- (evolutionary theory) A set of methods for distinguishing traits resulting from adaptation from those arising through other processes.
2006, Massimo Pigliucci, Jonathan Michael Kaplan, Making Sense of Evolution: The Conceptual Foundations of Evolutionary Biology, University of Chicago Press:
- Until one is clear about just what one means by adaptationism, what evidence one needs to accuse someone of being an "adaptationist" will remain vague; this rather diminishes the force of the accusation.
- (pejorative, evolutionary theory) The belief that all traits are adaptations brought about by natural selection, when some are only functionless by-products (also called "spandrels").