In dealing with the origin of the classes it is important to bear in mind that they are undoubtedly later than the phratries.  This is clear, not only from the considerations urged on p. 71, but also from the fact that the areas covered by the same classes are in the three most important cases immensely larger than any covered by a phratriac system.  We may therefore dismiss at the outset Herr Cunow’s theory, which makes the classes the original form of organisation.

To explain the origin of the classes, as of the phratries, two kinds of theories have been put forward, which are in this case also classifiable as reformatory and developmental respectively.  The former labour under the same disadvantages, so far as they assume that particular marriages were regarded as immoral or objectionable, as do the similar hypotheses of the origin of phratries.

What is the effect of dividing a phratry into two classes?  Firstly and most obviously, to reduce by one half the number of women from whom a man may take his spouse.  Secondarily, to put in the forbidden class both his mother’s generation and his daughters’ generation.  It must however not be overlooked that it is the whole class of individuals that are thus put beyond his reach and not those only who stand to him in the relation of daughters in the European sense.  Now it is certain that the savage of the present day distinguishes blood relationship from tribal relationship; of this there are plenty of examples in Australia itself[130].  In fact the hypothesis that the introduction of class regulations was due to a desire to prevent the intermarriage of parents and children, more especially of fathers and daughters, the mothers being of course of the same phratries as their sons in the normal tribe, depends for its existence on the assumption that consanguinity was recognised.  But it is clearly a clumsy expedient to limit a man’s right of choice to the extent we have indicated solely in order to prevent him from marrying his daughter, when the simple prohibition to marry her would, so far as we can see, have been equally effective.

Dr Durkheim has suggested that phratries and classes originated together.

If we start with two exogamous local groups in which the determinant spouse removes, the result is two groups in which both phratries are found, as is evident from the following graphic representation.  The two sides represent the local grouping, the letters A and B the phratry names, and m or f male or female; the = denotes marriage, the vertical lines show the children, the brackets show that the person whose symbol is bracketed removes, and the italics that the symbol in question is that of a spouse introduced from without.