make the nomenclature unworkable. For to call two boys
brothers because they have the same group of men as possible fathers is
only practicable in a society which has already evolved a system of age
grades, and has established restrictions on intercourse between
different generations, to use a somewhat indefinite term. For it is
clear that in a state of promiscuity the class of adults is continually
being recruited and that the boy passes at puberty, in so far as
restrictions in the nature of initiation ceremonies are not imposed,
from the class of sons to that of fathers. In other words, if a group
consists of M_1 M_2 M_3 M_4, and they have male children of all
ages N_1 N_2 N_3 N_4, as soon as N_1 reaches puberty he
becomes a possible father of the children O_1 O_2 O_3 O_4, who
differ in age from N_4 only by a few years at most and reckon as his
brothers. But this means that N_1 is the son of M_1, for example,
but at the same time the father of O_1, who is likewise the son of
M_1; in the same way O_1 is the brother of N_4, who is the brother
of N_1; but O_1 is not the brother of N_1. The extraordinary
complexity of the relations that would arise is at once obvious, and it
seems clear that relationship terms could never come into existence
under such circumstances unless they implied something beyond mere
relationship and denoted rights and duties[148]. But if they denoted
rights and duties, these must have preceded the relationship term, which
consequently need not be held to apply to kinship in any proper sense of
the term.

It is clear that the same difficulties apply when we try to work out the
development on the hypothesis that a group of mothers existed. We are
therefore reduced to the supposition that the term brother denoted
originally a person born within a given period of time, and that this
period was the same for whole sections of the community; in other words
that the name brother was given to all males born between, let us say,
B.C. 10,000 and B.C. 9,990. This is of course equivalent to the
establishment of age grades and is in itself not unthinkable; age grades
are of course perfectly well known among primitive peoples; but the
establishment of age grades implies a degree of social organisation;
and, what is more important, this hypothesis makes the term brother
quite meaningless as a kinship term; for at the present day a common
term of address for members of an age grade does not imply any degree of
co