In our own species, the selective process is marked by all the features
common to selection throughout the whole animal kingdom; but it is also,
as might be expected, far more specialised, far more individualised, far
more cognisant of personal traits and minor peculiarities. It is
furthermore exerted to a far greater extent upon mental and moral as
well as physical peculiarities in the individual.

We cannot fall in love with everybody alike. Some of us fall in love
with one person, some with another. This instinctive and deep-seated
differential feeling we may regard as the outcome of complementary
features, mental, moral, or physical, in the two persons concerned; and
experience shows us that, in nine cases out of ten, it is a reciprocal
affection, that is to say, in other words, an affection roused in unison
by varying qualities in the respective individuals.

Of its eminently conservative and even upward tendency very little doubt
can be reasonably entertained. We _do_ fall in love, taking us in the
lump, with the young, the beautiful, the strong, and the healthy; we do
_not_ fall in love, taking us in the lump, with the aged, the ugly, the
feeble, and the sickly. The prohibition of the Church is scarcely needed
to prevent a man from marrying his grandmother. Moralists have always
borne a special grudge to pretty faces; but, as Mr. Herbert Spencer
admirably put it (long before the appearance of Darwin's selective
theory), 'the saying that beauty is but skin-deep is itself but a
skin-deep saying.' In reality, beauty is one of the very best guides we
can possibly have to the desirability, so far as race-preservation is
concerned, of any man or any woman as a partner in marriage. A fine
form, a good figure, a beautiful bust, a round arm and neck, a fresh
complexion, a lovely face, are all outward and visible signs of the