The purpose of this paper is to disconfirm Piaget's theory of an invariant sequence of intellectual maturation for all youths in all cultures. The author's view is that the kinds and sequences of human development vary greatly, depending on the cultural milieu. The author derives 36 propositions from Piaget's theory, dismisses 5 of them as definitional and therefore not subject to testing, then uses evidence taken from 173 reports on 49 cultures to disconfirm the remaining 31 propositions in whole or in part. For example, Piaget claims that preconceptual categorizing arises between the ages of 21 and 48 months. The author cites counter examples, such as the Hottentot child that is taught by its mother to identify and gather edible roots, wild honey, lizards, and mice as soon as it can stand. Another proposition, stating that intellect peaks in logic and mathematics, is criticized as European-centered and in conflict with the higher regard in which tradition and experience are held in many cultures. The author's own theory of cultural materialism, which stresses the importance of various cultural influences rather than a genetically-determined sequence of intellectual development, is not elaborated here. The author notes that Piaget recognizes the existence of culture, but characterizes Piaget as using the concept of culture as a mere dumping ground for contrary evidence. (IM)