It is to be observed that, by customary law, brothers and sisters _actual_ (and not ‘tribal’) may never intermarry.[6] In short, consanguinity is now fully understood by the natives, and too close unions are forbidden on the ground of consanguinity. It also seems that, though the blacks are all on the same level of material culture, yet reflection on marriage rules, and modification of these rules by additional restrictions and alterations, have been carried much further by some tribes than by others. I by no means deny, but rather affirm, that consanguinity is now understood, and that rules have in some tribes been consciously made, and altered, to avoid certain marriages as of ‘too near flesh.’ But I do not think that, at the beginning, the objection to consanguineous marriages, _as such_, can have been entertained, and I am not of opinion that, for the purpose of preventing such marriages, in the beginning, a horde was bisected into two phratries, and each phratry split up into totem groups. Rather, I conceive, certain primitive conditions of life led to the evolution of certain rules, independent of any theory about the noxiousness or immorality of marriages of near kin; and then reflection on those primal rules helped to beget moral ideas, and improvements on the rules themselves. In the original restrictions, morality, in our sense, was only implicitly or potentially present, though now it has risen into explicit consciousness. The tribes came to think certain marriages morally wrong, or physically noxious, _because_ they were forbidden; such unions were not, in the first instance, forbidden because they were deemed physically injurious, or morally wrong. These ideas have, by this time, been evolved; but it does not follow that they were present at the beginning.