safe to say that any widespread practice of polygyny in civilized
communities would lead to a reversion to the moral standards of
barbarism in many if not in all matters. That polygyny is still a
burning question in the United States of the twentieth century is merely
good evidence that we are not very far removed yet from barbarism.

MONOGAMY, as we have already seen, has been the prevalent form of
marriage in all ages and in all countries. Wherever other forms have
existed monogamy has existed alongside of them as the dominant, even
though perhaps not the socially honored, form. All other forms of the
family must be regarded as sporadic variations, on the whole unsuited to
long survival, because essentially inconsistent with the nature of human
society. In civilized Europe monogamy has been the only form of the
family sanctioned for ages by law, custom, and religion. The leading
peoples of the world, therefore, practice monogamy, and it is safe to
say that the connection between monogamy and progressive forms of
civilization is not an accident.

What, then, are the social advantages of monogamy which favor the
development of a higher type of culture? These advantages are numerous,
but perhaps the most important of them can be grouped under six heads.

(1) The number of the two sexes, as we have already seen, is everywhere
approximately equal. This means that monogamy is in harmony with the
biological conditions that exist in the human species. The equal number
of the two sexes has probably been brought about through natural
selection. Why nature should favor this proportion of the sexes can
perhaps be in part understood when we reflect that with such proportion
there can be the largest number of family groups, and hence the best
possible conditions for the rearing of offspring.