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Hereditary Genius
353
agencies has been strongly and banefully exerted in the precisely
opposite direction.
An estimate of the effect of the average age of marriage on the
growth of any section of a nation, is therefore the first subject that
requires investigation. Everybody is prepared to admit that it is an
element, sure to produce some sensible effect, but few will anticipate
its real magnitude, or will be disposed to believe that its results have
so vast and irresistible an influence on the natural ability of a race, as
I shall be able to demonstrate.
The average age of marriage affects population in a threefold
manner. Firstly, those who marry when young, have the larger
families; secondly, they produce more generations within a given
period, and therefore the growth of a prolific race, progressing as it
does, “geometrically,” would be vastly increased at the end of a long
period, by a habit of early marriages; and, thirdly, more generations
are alive at the same time, among those races who marry when they
are young.
In explanation of the aggregate effect of these three influences, it
will be best to take two examples that are widely but not extremely
separated. Suppose two men, M and N, about 22 years old, each of
them having therefore the expectation of living to the age of 55, or 33
years longer; and suppose that M marries at once, and that his
descendants, when they arrive at the same age, do the same; but that
N delays until he has laid by money, and does not marry before he is
33 years old, that is to say, 11 years later than M, and his
descendants also follow his example. Let us further make the two
very moderate suppositions, that the early marriages of race M result
in an increase of l.5 in the next generation, and also in the production
of 3.75 generations in a century, while the late marriages of race N
result in an increase of only 1.25 in the next generation and in 2.5
generations in one century.
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