When and how do harmful traditions evolve culturally and persist? These are among the most challenging questions researchers and practitioners face when addressing behaviors that are clearly cultural, but also at odds with policy objectives. We examine the cultural evolution of harmful traditions using a mix of modeling, traditional behavioral experiments, and fieldwork. Much of this work is basic research in the sense that it is not strongly tied to any specific location or cultural context. Much of the work, however, is about a specific issue in a specific place, including female genital cutting in Sudan, sex-selective abortion in Armenia, and corruption in South Africa.