The Descent of Man

NUMERICAL PROPORTION OF THE
TWO SEXES.
I have remarked that sexual selection would be
a simple affair if the males were considerably
more numerous than the females. Hence I was
led to investigate, as far as I could, the proportions
between the two sexes of as many animals
as possible; but the materials are scanty. I will
here give only a brief abstract of the results,
retaining the details for a supplementary discussion,
so as not to interfere with the course of
my argument. Domesticated animals alone afford
the means of ascertaining the proportional
numbers at birth; but no records have been
specially kept for this purpose. By indirect
means, however, I have collected a considerable
body of statistics, from which it appears
that with most of our domestic animals the
sexes are nearly equal at birth. Thus 25,560
births of race- horses have been recorded during
twenty-one years, and the male births were
to the female births as 99.7 to 100. In greyh-