a trait or structure which, while of no immediate
advantage to the individual, increases the probability of its
rearing a larger number of fitter offspring. Thus defence of the
young by birds may be a disadvantage to the parent, but this is more
than counterbalanced in the life of the species by the number of
young coming to maturity and inheriting the trait. Even here natural
selection favors the survival of the trait indirectly by sparing the
descendants of the individual possessing it. Natural selection may
always work on and through individuals without always working for
their sole and selfish advantage.

In human society we find the selection of families, societies,
nations, and civilizations going on, but mainly as the result of the
survival of the fittest individuals.

There may very probably be a struggle for existence between organs
or cells in the body of each individual. The amount of nutriment in
the body is a more or less fixed quantity; and if one organ seizes
more than its fair share, others may or must diminish for lack. But
the limit to this usurpation must apparently be set by the crowding
out of those individuals in which it is carried too far. Natural
selection, so to speak, leaves the individual responsible for the
distribution of the nutriment among the organs, and spares or
destroys the individual as this usurpation proves for its advantage
or disadvantage.

It makes its verdict much as the judges at a great poultry or dog
show count the series of points, giving each one of them a certain
value on a certain scale, and then award the prize to the individual
having the highest aggregate on the whole series. Any such
illustration is very liable to mislead; I wish to emphasize that
fitness to survive is determined by the aggregate of the qualities
of an individual.

But an animal having one organ of great value or capacity may thus
carry off the prize, even though its other organs deserve a much
lower mark. This is the case with man. In almost every respect,
except in brain and hand, he is surpassed by the carnivora, the cat,
for example. But muscle may be marked, in making up the aggregate,
on a scale of 500, and brain on a scale of 5,000, or perhaps of
50,000. A very slight difference in brain capacity outweighs a great
superiority in muscle in the struggle between man and the carnivora,
or between man and man.

The scale on which an organ is marked will be proportional to its
usefulness und