Exogamy as such has generally been approached from a rationalistic point of view. It has been regarded as an institution voluntarily created to obviate the marriage of relatives, and is supposed to have arisen contemporaneously with another institution of like purpose, namely, tribal division. This view is championed, among other scholars, by the able American sociologist, Lewes Morgan, in his book "Ancient Society" (1870), and even by Frazer in his comprehensive work "Totemism and Exogamy" (1910), which includes in its survey all parts of the earth. Frazer says explicitly: 'In the distant past, several wise old men must have agreed to obviate the evils of endogamy, and with this end in view they instituted a system that resulted in exogamous marriage.' Thus, the determinant motive is here supposed to have been aversion to the marriage of relatives. According to Morgan's hypothesis--an extreme example of rationalistic interpretation--the aversion was due to a gradually acquired knowledge that the marriage of relatives was injurious in its effects upon offspring. The entire institution, thus, is regarded as a eugenic provision. We are to suppose that the members of these tribes not only invented this whole complicated system of tribal division, but that they foresaw its results and for this reason instituted exogamous customs. Were people who possess no names for numbers greater than four capable of such foresight, it would indeed be an unparalleled miracle. Great social transformations, of which one of the greatest is unquestionably the transition from the primitive horde to totemic tribal organization, are never effected by the ordinances of individuals, but develop of themselves through a necessity immanent in the cultural conditions. Their effects are never foreseen, but are recognized in their full import only after they have taken place. Moreover, as regards the question of the injurious effects resulting from the marriage of relatives, authorities even to-day disagree as to where the danger begins and how great it really is. That the Australians should have formed definite convictions in prehistoric times with reference to these matters, is absolutely inconceivable. At most, they might have felt a certain instinctive repugnance. Furthermore, if these institutions were established with the explicit purpose of avoiding marriage between relatives, the originators, though manifesting remarkable sagacity in their invention, made serious mistakes in their calculations. For, in the first place, the first two forms of exogamy only partially prevent a union which even endogamous custom avoids, namely, that between parents and children; in the second place, the transition from unlimited to limited exogamy with direct maternal or paternal descent does not involve an increased restriction of marriage between relations, but, as we have already seen, marks a retrogression, in the sense of a reapproach to endogamy.