Human cultural life is replete with examples of adaptations to the social, physical, and biological environments that have been built gradually, cumulatively, by hidden-hand mechanisms. The impressive technologies, natural history databases, and exchange networks of traditional peoples have been built in this way. But the ethnological record is also replete with evidence of maladaptive beliefs and practices, and of failures to adapt to changing circumstances. This paper is about such failures. In what ways is cultural evolution constrained, and what explains (...) those constraints? In what ways are those constraints similar to those that affect gene-based evolution; in what ways are they different? In this paper I argue that there are some similar mechanisms of constraint ; there are some differences ; but the major difference results from a division of labor between inheritance systems; the problem of fast change has been offloaded from the genetic to the cultural system. (shrink)