sex question as one merely of adaptation to extra-biological services.
In every group which has survived, some machinery--a "crust of custom,"
reinforced by more arbitrary laws or regulations--has sought to
guarantee reproduction by keeping women out of lines of endeavour which
might endanger that fundamental group necessity. Primitive societies
which got stabilized within a given territory and found their birth-rate
dangerously _high_ could always keep it down by exposing or destroying
some of the unfit children, or a certain per cent of the female
children, or both.

In primitive groups, the individual was practically _nil_. But modern
civilized society is able to survive without the rigid control of
individual activities which the old economy entailed. Man comes to
choose more and more for himself individually instead of for the group,
uniformity weakens and individualism becomes more pronounced. As
control of environment becomes more complete and easy, natural selection
grows harder to detect. We turn our interests and activities toward the
search for what we want and take survival largely for granted--something
the savage cannot do. Natural selection becomes unreal to us, because
the things we do to survive are so intricately mixed up with those we do
for other reasons. Natural selection in gregarious animals operates upon
groups rather than upon individuals. Arrangement of these groups is
often very intricate. Some have territorial boundaries and some have
not. Often they overlap, identical individuals belonging to several.
Hence it is not strange that natural selection phenomena often escape
attention.

But this must not lead us to suppose that natural selection is wholly
inoperative in civilized society. We see some nations outbreeding
others, or dominating them through superior organization. Within