ETHNOGRAPHERS distinguish several types of family. In a fratriarchate, for example, the eldest brother is the head of the family, and this authority is handed on, along with the property, from brother to brother. Evidence of this type of society has been found among the Hittites and Hurrites in Assyria and Elam. It has been claimed that there are traces of it in the Old Testament, e.g. in the institution of the levirate (which will be discussed under marriage1), in the action of Jacob's sons to avenge the rape of their sister Dinah ( Gn 34), and in the part Laban plays in the arrangement of the marriage of his sister Rebecca ( Gn 24). Though none of these examples seems conclusive, we must admit the possibility of Assyrian and Hurrite influence on the customs of Aram Naharaim; and among these two peoples the existence of a fratriarchate, in early times, is now admitted, at least as a hypothesis. We cannot, therefore, exclude the possibility of its influence on the levirate institution, and there may be traces of it in the story of Rebecca.
As a type of family, matriarchate is much more common in primitive societies. The characteristic mark of this type of society is not that the mother exercises authority (this is rare), but that a child's lineage is traced through the mother. The child belongs to the mother's family and social group, and is not considered as related to its father's connections; even rights of inheritance are fixed by maternal descent. According to the ethnographical school of Graebner and Schmidt, a matriarchate is associated with small-scale cultivation, while pastoral civilization is patriarchal.
Many authors, however, following Robertson Smith, believe that a matriarchal regime was the original form of the family among the Semites. Certain Old Testament customs and stories, they hold, indicate the presence of this regime among the Israelites. In Gn 20: 12 Abraham is excused for passing off Sarah as his sister, because she was in fact his half-sister, whom he had married. Similarly, 2 S 13: 13 gives us to understand that Amnon and Tamar could have been married, because, though both were David's children, they were born of different mothers. Marriage with one's step- sister, either on the father's or mother's side, is forbidden by the laws of____________________