the leftovers, and would be poor quality. Such a division of labour
within a group would be fatally foolish and entirely uncalled for--since
there are plenty of men adapted to hunting and fighting, but entirely
unspecialized to child-bearing and nursing.

Group survival being the fundamental thing, the group is obliged to
develop a division of labour which directs the activities of the
individuals composing it to providing for its necessities, regardless
of any interference with their own desires. That is, if group survival
requires that woman use her specialization to child-bearing instead of
any adaptation she may possess in other directions, one of two things
inevitably result: (1) Either the group finds or evolves some social
control machinery which meets the necessity, or (2) it must give way to
some other group which can do so. In either case, the result is a
division of labour, which we see more clearly in primitive peoples. The
less efficient group is not necessarily exterminated, but if it loses
out in the competition until some other group is able to conquer it and
impose _its_ division of labour the result is of course the extinction
of the conquered group as an integral part of society. This is simply
natural selection working on groups. Natural selection works chiefly in
this manner on the human species, _because that species lives in
groups_. Such group control of the component individuals as has been
described has led to a division of labour between the sexes in every
primitive society. All this means is that the group adopting such a
division has greater survival value, and hence is more likely to be
represented in later ages.

It must not be supposed that such systems of control were always
logically thought out or deliberately planned. Even animals which live
in herds or colonies have divisions of labour.