In the tradition of Jesuits, Anchieta was a prolific rapporteur, communicating by letters to his superiors. His reports establish him as an ethnographer, though he focused on Amerindian behavior that did not follow European norms, such as their choice of marriage partners, cannibalism, and the role of sorcerers. His detailed testimony with respect to cannibalism is often cited by anthropologists. He explained, for example, that the Amerindians "believe that true kinship comes from the side of the fathers, who are the agents, and ... that the mothers are nothing more than bags in which the children grow" and therefore treat the children of a captured female and a member of their tribe with respect but sometimes eat the children of a captured male and a female member of their own tribe. He detailed the practice of polygamy and, because it had produced dense networks of interrelations, advocated easing the church's consanguinity rules to allow all but brothers and sisters to marry.