In the study of kinship, the alliance theory is also known as the general theory of exchange. This theory states that in kinship systems, inheritance and the continuation of the vertical line (descent) are of less significance than the horizontal connections (alliances) and relationships of exchange and reciprocity between members of two different groups that is introduced through marriages. This theory attempts to illuminate how inter-individual relationships are woven together to form society as a whole.
The main exponent and originator of this theory is French structuralist Claude Lévi-Strauss and therefore it is also known as the structural way of studying kinship ties. He introduced it for the first time in his monumental work entitled “Les Structures élémentaires de la parenté” (1949) i.e. Elementary structures of Kinship. Rodney Needham and Louis Dumont also contributed to the analytical assessment.
Lévi-Strauss studied and observed the connections formed between consanguinity and affinity in his investigation of Non-European societies. Consanguinity and Affinity are both opposite and complementary to each other, hence rules of preferential marriage and marriage prohibitions are an incorporated part of this theory. In Strauss's view, it is marriage ties that create interdependence between families and lineages.
Alliance theory is based on incest taboo; the prohibition of which is observed universally, a fundamental aspect of human social life. That is, a man is not allowed to make a woman of his immediate kin his wife. According to Strauss, this prohibition is beyond any sociological explanation and clearly shows that the difference between consanguinity and affinity is the basis of kinship system.
He stated that incest taboo is seen as a negative prescription and the only cause for man to move out of his own kinship group, thus leading to positive marriage rules. Hence the main notion of his theory comes to - a reciprocal exchange which creates affinity.
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