The Descent of Man

ious facts and considerations, I formerly inferred
that with most animals, in which secondary
sexual characters are well developed, the
males considerably exceeded the females in
number; but this is not by any means always
true. If the males were to the females as two to
one, or as three to two, or even in a somewhat
lower ratio, the whole affair would be simple;
for the better-armed or more attractive males
would leave the largest number of offspring.
But after investigating, as far as possible, the
numerical proportion of the sexes, I do not believe
that any great inequality in number commonly
exists. In most cases sexual selection
appears to have been effective in the following
manner.
Let us take any species, a bird for instance, and
divide the females inhabiting a district into two
equal bodies, the one consisting of the more
vigorous and better-nourished individuals, and
the other of the less vigorous and healthy. The