it now acquired such stability and permanence that the older and looser forms of alliance, hitherto prevalent, fell into disfavour. A natural result of the growth of private wealth and the permanence of the marital relation was the change in reckoning kinship from the maternal to the paternal line. This change was probably favoured by the prevalence of polygamy among those who were coming to be distinguished as "upper classes," since a large family of children by different mothers could be held together only by reckoning the kinship through the father. Thus, we may suppose, originated the patriarchal family. Even in its rudest form it was an immense improvement upon what had gone before, and to the stronger and higher social organization thus acquired we must largely ascribe the rise of the Aryan and Semitic peoples to the foremost rank of civilization.[68] [Footnote 68: Fenton's _Early Hebrew Life_, London, 1880, is an interesting study of the upper period of barbarism; see also Spencer, _Princip. of Sociol._, i. 724-737.] It is not intended to imply that there is no other way in which the change to the male line may have been brought about among other peoples. The explanation just given applies very well to the Aryan and Semitic peoples, but it is inapplicable to the state of things which seems to have existed in Mexico at the time of the Discovery.[69] The subject is a difficult one, and sometimes confronts us with questions much easier to ask than to answer. The change has been observed among tribes in a lower stage than that just described.[70] On the other hand, as old customs die hard, no doubt inheritance has in many places continued in the maternal line long after paternity is fully known. Symmetrical regularity in the development of human institutions has by no means been the rule, and there is often much difficulty in explaining particular cases, even when the direction of the general drift can be discerned. [Footnote 69: See below, p. 122.] [Footnote 70: As among the Hervey Islanders; Gill, _Myths and Songs of the South Pacific_, p. 36. Sir John Lubbock would account for the curious and widely spread custom of the _Couvade_ as a feature of this change. _Origin of Civilization_, pp. 14-17, 159; cf. Tylor, _Early Hist. of Mankind_, pp. 288, 297.] [Sidenote: The exogamous clan in ancient America.] In aboriginal America, as already observed, kinship through females only was the rule, and exogamy was strictly enforced,--the wife must be taken from a different clan. Indissoluble marriage, whether monogamous or polygamous, seems to have been unknown. The marriage relation was terminable at the will of either party.[71] The abiding unit upon which the social structure was founded was not the family but the exogamous clan.