I’ve long been fascinated by khat, the psychoactive plant that is legal and consumed widely in Yemen and the Horn of Africa (Somalia, Ethiopia and Djibouti) but that was criminalized in recent decades in the United States, Europe and other parts of the world as Somali and other émigré communities grew. Its history and uses are somewhat analogous to coca in Latin America. Neil Carrier, a social anthropologist teaching at the University of Bristol, is one of the world’s leading experts on khat – its history, economics, markets, social roles, consumption and conflicts over its benefits, harms and “quasi-legality.”