On the former point we can afford to be brief. Apart
from the fact that modern biological opinion is by no means
agreed as to the necessarily evil results of inbreeding, there
are certain obvious difficulties in the way of Morgan's in-
terpretation. It would not be fair to object that sib exo-
gamy does not prevent the union of father and daughter in
a matrilineal, and of mother and son in a patrilineal, so-
ciety. For Morgan believes that incestuous relations be-
tween parent and child had been eliminated at an earlier
stage, and that the sib merely added to matrimonial restric-
tions by barring the union of siblings. But what Morgan
may fairly be criticized for is his failure to realize that
exogamy does much more than proscribe the marriage of
brothers and sisters: it precludes sexual relations between
certain cousins of the most remote degree of propinquity,
nay, even between wholly unrelated sib members while in
no way interfering with the relations of even first cousins
who are not of the same sib. Cross-cousin marriage is per-
fectly consistent with sib exogamy; but so are also mar-
riages between certain parallel cousins. For example, in a
tripartite matrilineal tribe two brothers of sib A may marry
women of sibs B and C, respectively, and their children
will not be prevented from marrying by the rules of the
sib. What the sib, then, really does is to bar incidentally
the union of certain close kinsfolk along with that of re-
mote and putative kindred, while permitting the marriage
of certain other close relatives.

The assumption as to the practically universal occur-
rence of the sib in primitive society requires more extended
scrutiny. I shall endeavor to establish the counter-proposi-
tion that the sib is lacking precisely among the more primi-
tive tribes and as a rule appears only when horticultural or
pastoral activities have partly or wholly superseded the
chase as the basis of economic existence. From this, I
argue, there directly follows the chronological priority of
the family. But in order to give cogency to this ar-

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