necessary than the other, both being _absolutely_ necessary. But
the female specialization for furnishing the intra-maternal environment
makes her share more burdensome.

Biologically considered, not even two individuals (male and female),
together with their offspring, can be more than an arbitrary "unit" as
concerns sex, since inbreeding eventually impoverishes the stock. Hence
outcrosses are necessary. To intelligibly consider the sex problem in
the human species, then, we must always predicate a considerable _group_
of people, with such organization and division of activities as to
guarantee that all the processes necessary to survival will be carried
on. Sex is a group problem. Considering the mutual interdependence and
the diversity of activities in human society, to make the generalization
that one sex is superior to the other is on a par with saying that roots
and branches are superior to trunks and leaves. It is sheer foolishness.
Yet oceans of ink have flowed in attempts to establish one or the other
of two equally absurd propositions.

Since the specialization to furnish the intra-maternal environment for
the young makes the female part of the reproductive process essentially
and unavoidably more burdensome than the male, it results that an
economical division of the extra-reproductive activities of any group
must throw an unequal share upon the males. This specialization to carry
the young during the embryonic period is thus at the base of the
division of labour between the sexes. It is the chief factor involved in
the problems of sex, and gives rise, directly or indirectly, to most of
the others.

But the sex problem as a whole is one of adaptation as well as of
specialization. An incident of the female specialization is a type of
body on the average smaller, weaker and less well adapted to some other
activities than is the male body, even when reproduction is not
undertaken. A great complication is added by the fact that some women,
and also some men, are better adapted than others to nonreproductive
activities. This is another way of saying that the type of body
associated with either type of sex glands varies a good deal, for
reasons and in respects already pointed out.

The most important fact about this reproductive specialization is that
beyond fertilization it is _exclusive_ in the female. Since the males
cannot furnish the intra-parental environment for the young, the entire
burden must fall on