ABSTRACT
This is a study of a rare phenomenon that provides a crucial test of theory. Preferential marriage is the familiar fact that in many societies ego, besides being forbidden to marry certain women, is expected to marry one or more of a class of women standing in certain kin relationships to him. Among the forms of preferential marriage, unilateral cross-cousin marriage exists when, as between his two female cross-cousins, ego male is expected to marry one but not the other: his mother’s brother’s daughter but not his father’s sister’s daughter or vice versa. Only a handful of societies follow such a rule: it is much less common than most of the other rules of preferential marriage. Unilateral cross-cousin marriage gets its interest from the fact that, perhaps just because it occurs only under special conditions, a study of what determines the adoption by a society of one rather than the other of its forms allows us to compare the usefulness of a final-cause theory with that of an efficient-cause theory of social behavior. We give the theories these names for want of better ones. The final-cause theory is in fact the one presented by Claude Lévi-Strauss in his book Les structures élémentaires de la parenté. 1 Whatever its title may imply, this is not a study of kinship behavior in general but of preferential marriage. The efficient-cause theory derives ultimately from A. R. Radcliffe-Brown’s classic paper, “The Mother’s Brother in South Africa.” 2
