The Descent of Man

tail- feathers of the female are somewhat shorter
than those of the male, it might be argued
that their full development had been prevented
through natural selection. But if the development
of the tail of the peahen had been checked
only when it became inconveniently or dangerously
great, she would have retained a much
longer tail than she actually possesses; for her
tail is not nearly so long, relatively to the size of
her body, as that of many female pheasants, nor
longer than that of the female turkey. It must
also be borne in mind that, in accordance with
this view, as soon as the tail of the peahen became
dangerously long, and its development
was consequently checked, she would have
continually reacted on her male progeny, and
thus have prevented the peacock from acquiring
his present magnificent train. We may therefore
infer that the length of the tail in the peacock
and its shortness in the peahen are the
result of the requisite variations in the male