The Descent of Man and Selection in Relation to Sex, Vol. IDarwin, Charles
Science
The Descent of Man and Selection in Relation to Sex, Vol. I
Darwin, Charles
Evolution (Biology); Human beings -- Origin; Sex differences; Sexual dimorphism (Animals); Sexual selection in animals
life, and have consequently transferred their new characters to both
sexes at a corresponding late period; and if so, such cases are not
opposed to our rule. Thus there are sub-breeds of the pigeon, described
by Neumeister,[365] both sexes of which change colour after moulting
twice or thrice, as does likewise the Almond Tumbler; nevertheless these
changes, though occurring rather late in life, are common to both sexes.
One variety of the Canary-bird, namely the London Prize, offers a nearly
analogous case.
With the breeds of the Fowl the inheritance of various characters by one
sex or by both sexes, seems generally determined by the period at which
such characters are developed. Thus in all the many breeds in which the
adult male differs greatly in colour from the female and from the adult
male parent-species, he differs from the young male, so that the newly
acquired characters must have appeared at a rather late period of life.
On the other hand with most of the breeds in which the two sexes
resemble each other, the young are coloured in nearly the same manner as
their parents, and this renders it probable that their colours first
appeared early in life. We have instances of this fact in all black and
white breeds, in which the young and old of both sexes are alike; nor
can it be maintained that there is something peculiar in a black or
white plumage, leading to its transference to both sexes; for the males
alone of many natural species are either black or white, the females
being very differently coloured. With the so-called Cuckoo sub-breeds of
the fowl, in which the feathers are transversely pencilled with dark
stripes, both sexes and the chickens are coloured in nearly the same
manner. The laced plumage of the Sebright bantam is the same in both
sexes, and in the chickens the feathers are tipped with black, which
makes a near approach to lacing. Spangled Hamburghs, however, offer a
partial exception, for the two sexes, though not quite alike, resemble
each other more closely than do the sexes of the aboriginal
parent-species, yet they acquire their characteristic plumage late in
life, for the chickens are distinctly pencilled. Turning to other
characters besides colour: the males alone of the wild parent-species
and of most domestic breeds possess a fairly well developed comb, but in
the young of the Spanish fowl it is largely developed at a very early
age, and apparently in consequence of this it is of unusual size in the
adult females. In the Game breeds pugnacity is developed at a
wonderfully early age, of which curious proofs could be given; and this
character is transmitted to both sexes, so that the hens, from their
extreme pugnacity, are now generally exhibited in separate pens. With
the Polish breeds the bony protuberance of the skull which supports the
crest is partially developed even before the chickens are hatched, and
the crest itself soon begins to grow, though at first feebly;[366] and
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