(2) Similarly, the theory makes no allowance for the increased
efficiency which may come with increased population, because increase of
population makes possible better coöperation. As we have already seen,
coöperation and division of labor in a society depend upon the size of
the group to a certain extent, that is, the larger the group there is
for organization the better can be the organization and division of
labor in that group. Every increase of population, therefore, opens up
new and superior ways of applying labor; and coöperation and the
division of labor make it possible for men to do more as a group than
they could possibly accomplish working as individuals. Improved means of
coöperation, therefore, operate very much the same way in human society
in controlling nature as new inventions.

(3) The theory of Malthus makes no allowance for the general law of
animal fertility, which is that as the rate of individual evolution
increases the rate of reproduction decreases. Of course, Malthus's
theory antedates this law of animal fertility, which was first stated by
Herbert Spencer. Some scientists declare that this law does not apply
within the human species, and it must be admitted that it is not yet
certain that it does. As we have already seen, however, the lower and
less individualized classes in human society reproduce much more rapidly
than the upper or more individualized classes. Increase of food supply,
of wealth, and so on, does not necessarily mean increase of population,
and the fatal error in Malthus's theory is that he assumes that wherever
food increases population always increases also.

(4) The overpopulation which Malthus feared, so far from being an evil,
has been shown by the labors of Darwin to be the condition essential to
the working of the process of natural selection in the human species.