nection as blood
connection is understood in that group at the time. Other prohibitions
may be expedient, or may seem required by propriety (e.g. the marriage
of a man with his father's widow), but they do not come under incest.

Restrictions on marriage by kinship, as the people in question construed
kinship, go back to the most primitive society. Some very primitive
people have intricate restrictions, and they maintain them by the
severest social sanctions.

+509. Incest notion produced from the folkways.+ It is evident that
primitive people must have received a suggestion or impression of some
important interest at stake in this matter. They adopted taboos and
established folkways to protect interests. In time these taboos and
folkways won very great force and high religious sanction; also a sense
of abomination was produced which seemed to be a "natural" feeling.
There certainly is no natural feeling. The abomination is conventional
and traditional. The Pharaohs, Ptolemies, and Incas, also the
Zoroastrians, are sufficient to show that there is no reason for the
abomination in any absolute or universal facts. The sanctions by which
savage people sustained the taboo were the strongest possible,--exile
and death. Here we have, therefore, a social limitation of the greatest
force, sanctioned by religion and group consent and growing into an
abomination which has come down to us and which we all feel, but which
is a product of the most primitive folkways; and yet we do not know the
motive for it in the minds of primitive men. In the matter of
cannibalism we saw (Chapter VIII) that with advancing civilization a
taboo has been set up against a food custom which appears to have been
universal amongst primitive men; that is, we have reversed and hold in
abomination what they did. In regard to incest we have accepted and
fully ratified their taboo.

+510. Notion that inbreeding is harmful.+ This taboo and the reasons for
it are a complete enigma unless the primitive people had observed the
evils of close inbreeding. Inbreeding maintains the excellence of a
breed at the expense of its vigor. Outbreeding (unless too far out)
develops vigor at the expense of the characteristic traits. It is very
probable, but not absolutely certain, that inbreeding is harmful. Any
marriage between persons who have the same faults of inheritance causes
the offspring to accumulate faults and to degenerate. Close kinship
creates a probable dange