The propriety of setting out with the foregoing purely natural-history
view will be evident upon learning that among low savages the relations
of the sexes are substantially like those common among inferior
creatures. The effect of promiscuity, however, being to hinder social
evolution, wherever it was accompanied by unions having some duration,
the product of such unions were likely to be superior to others, and
from this primitive stage domestic evolution takes place in several
directions by increase of coherence and definiteness.
From promiscuity we pass to that form of polyandry in which the
unrelated husbands have but one wife; thence to the form in which the
husbands are related; and finally to the form in which they are brothers
only, as in the fraternal polyandry of the ancient Britons. It is almost
needless to point out that, as in passing from promiscuity to polyandry
the domestic relations become more coherent and definite, so do they in
passing from the lower forms of polyandry to the higher. That polygyny
is better than polyandry may be concluded from its effects. It conduces
in a higher degree to social self-preservation than the inferioi types
of marital relations by making possible more rapid replacement of men
lost in war, and so increases the chance of social survival. By
establishment of descent in the male line it conduces to political
stability; and, by making possible a developed form of ancestor-worship,
it consolidates society.