Eugenics
need know nothing more, and the smoke of controversy over the exact way
in which some trait or other is inherited must not be allowed for an
instant to obscure the known fact that the level can be raised.
CHAPTER VI
NATURAL SELECTION
Man has risen from the ape chiefly through the action of natural
selection. Any scheme of conscious race betterment, then, should
carefully examine nature's method, to learn to what extent it is still
acting, and to what extent it may better be supplanted or assisted by
methods of man's own invention.
Natural selection operates in two ways: (1) through a selective
death-rate and (2) through a selective birth-rate. The first of these
forms has often been considered the whole of natural selection, but
wrongly. The second steadily gains in importance as an organism rises in
the scale of evolution; until in man it is likely soon to dwarf the
lethal factor into insignificance. For it is evident that the appalling
slaughter of all but a few of the individuals born, which one usually
associates with the idea of natural selection, will take place only when
the number of individuals born is very large. As the reproductive rate
decreases, so does the death-rate, for a larger proportion of those born
are able to find food and to escape enemies.
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