The supposed exogamous tribes, according to the theory, enforcing the infanticide of female children, and not permitting marriage within the tribe, must have been wholly dependent upon the endogamous groups for their women. These latter groups must either have succumbed, and so have become speedily extinguished through the loss of their women (for they could not have acquired others who were not of their stock, without ceasing to be endogamous); or they must have resisted successfully, and even if the matter went no farther, the exogamous tribes must have died out or abandoned exogamy; or the endogamous tribes must have resisted and retaliated, in which case we should have this further complication that they themselves would have ceased to be endogamous, and without any reason or necessity for becoming exogamous; for with the seizure of the females of the exogamous tribes, or even, under the special circumstances, with the recovery of their own, the element of "heterogeneity" would have been introduced, and the system of endogamy would have been no longer true in theory, or possible in fact. All these results must have been immediately consequent upon the first collision, which from the very conditions of exogamy, must have occurred at the outset! Postulating exogamy, it must therefore rapidly have extirpated or absorbed every other system, and yet it could never have stood alone. Mr M'Lennan himself allows that wherever "kinship through females, the most ancient system in which the idea of blood relationship was embodied" (148) was known, there would have been a tendency among the exogamous groups to become heterogeneous, and that thus "the system of capturing wives would have been superseded."[43] In other words, exogamy would have become extinct. But if "kinship through females" was not discovered by the first children of the first mothers, how was it subsequently discovered? We are given no clue except that "the order of nature is progressive!" [43] At p. 88, Mr M'Lennan sees evidence of the "form of capture" and the fact of capture among the Jews; but he will at least allow the appeal to be made to the Scriptures, as their most authentic history. What do we find at the commencement? In the first marriage contract recorded, _i.e._ of Isaac and Rebecca? Why, the reverse of capture. Genesis xxvi. 8, "But if the woman will not follow thee thou shalt not be bound by the oath." Also v. 39, 40.