can beget is very small and most of them survive.

But, moreover, in the cases of all three, vegetables, animals and men,
we find that it is the lower and more simply organized species, the
races and classes less advanced in the scale of existence, who reproduce
their several kinds with the greatest prolificness and in which
generation follows generation most rapidly on account of the brevity of
individual life.

A fern produces millions of spores, and its life is very short--while a
palm tree produces only a few dozen seeds, and lives a century.

A fish produces several thousand eggs--while the elephant or the
chimpanzee have only a few young who live many years.

Within the human species the savage races are the most prolific and
their lives are short--while the civilized races have a low birth-rate
and live longer.

From all this it follows that, even confining ourselves to the purely
biological domain, the number of victors in the struggle for existence
constantly tends to approach nearer and nearer to the number of births
with the advance or ascent in the biological scale from vegetables to
animals, from animals to men, and from the lower species or varieties to
the higher species or varieties.

The iron law of "the struggle for existence," then, constantly reduces
the number of the victims forming its hecatomb with the ascent of the
biological scale, and the rate of decrease becomes more and more rapid
as the forms of life become more complex and more perfect.