Felicitas Becker (PhD, Cambridge) is Assistant Professor of African History at Simon Fraser University, Vancouver. She has written Becoming Muslim in Mainland Tanzania, 1890-2000 (OUP, 2008), and articles in the Journal of African History, Journal of Global History and African Affairs a.o. Currently, she is researching the history of writing in the Swahili and Portuguese languages in Africa, and the role of audiotapes among Islamists in East Africa.Wenzel Geissler is a social anthropologist at the London School of Hygiene and the Institute of Social Anthropology in Oslo. He has published on health and body in Africa and on kinship, memory and change in Kenya. Presently he conducts ethnographic fieldwork on medical research in Kenya, and works with the London-based Research Group for the Anthropology of African Biosciences. With Ruth Prince he wrote The land is dying - contingency, creativity and conflict in western Kenya (Berghahn).