Categorization’s great debate has weighed single-system exemplar theory against the possibility of alternative processing systems. We take an evolutionary and fitness perspective toward this debate to illuminate it in a new way. There are continuities in category processes—extending across millions of years in vertebrate evolution—that have profound theoretical implications. Thus, animals are crucial behavioral ambassadors to this area. They reveal the roots of human categorization, the basic assumptions of vertebrates entering category tasks, and the surprising weakness of exemplar memory as a category-learning strategy. These results have joined neuroscience results to prompt important changes in categorization theory. Categorization’s great debate is ending. Broad-based converging evidence now makes it clear that the unitary exemplar view is insufficient. Categorization is served by multiple systems of process and representation.
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