arriage with a half-sister was
allowed by the old Hebrew law,[776] and Egyptian kings often married
their sisters.

+429+. _Theories of the origin of exogamy._ Exogamy has been referred to
a supposed scarcity of women, which forced the young men to seek wives
abroad.[777] On the assumption of early sexual promiscuity it has been
regarded as a deliberate attempt to prevent the marriage of blood
relations.[778] It has been supposed to result from the absence of
sexual attraction between persons who have been brought up
together.[779] An original human horde being assumed, it has been
suggested that the patriarch, who had possession of all the women of the
horde, would, from jealousy, drive the young men off to seek wives
elsewhere.[780] From the point of view of the totem as divine ancestor,
exogamy has been supposed to arise from religious respect for the clan
blood, which is held to share the divinity of the totem, and would be
polluted (with danger to the clan) by outside marriages.[781]

+430+. Objections may be raised to all these theories. It is doubtful
whether a scarcity of women existed in early times; and supposing that
there were not women enough in a clan for the men of the clan, this
would not stand in the way of men's taking as wives their clan
women.[782] The assumption of primitive sexual promiscuity, likewise,
cannot be said to be distinctly borne out by known facts.[783] Morgan's
theory, however, is not dependent on this assumption--it need only
suppose repugnance to the marriage of blood relations. Such repugnance
granted, the main objection to the theory rests on the difficulty of
supposing savages capable of originating so thoughtful and elastic a
scheme as the exogamous system. This is a point on which it is not
possible to speak positively. The lowest tribes have produced languages
of wonderfully intricate and delicate construction, and, supposing the
process of constructing marriage regulations to have gone on during a
very long period, modifications introduced from time to time, to meet
conditions felt to be important, might conceivably result in such
exogamous systems as are now found.

+431+. As to absence of sexual attraction between persons brought up
together,[784] this seems to be a result rather than a cause of the
prohibition of sexual relations between certain classes of persons. The
argument from habits of the lower animals is indefinite--no general
habit has been proven. In orgies in