The Descent of Man, and Selection in Relation to SexDarwin, Charles
History
The Descent of Man, and Selection in Relation to Sex
Darwin, Charles
Evolution (Biology); Human beings -- Origin; Sex differences; Sexual dimorphism (Animals); Sexual selection in animals
Some few persons have the power of contracting the superficial muscles
on their scalps; and these muscles are in a variable and partially
rudimentary condition. M. A. de Candolle has communicated to me a
curious instance of the long-continued persistence or inheritance of
this power, as well as of its unusual development. He knows a family,
in which one member, the present head of the family, could, when a
youth, pitch several heavy books from his head by the movement of the
scalp alone; and he won wagers by performing this feat. His father,
uncle, grandfather, and his three children possess the same power to
the same unusual degree. This family became divided eight generations
ago into two branches; so that the head of the above-mentioned branch
is cousin in the seventh degree to the head of the other branch. This
distant cousin resides in another part of France; and on being asked
whether he possessed the same faculty, immediately exhibited his power.
This case offers a good illustration how persistent may be the
transmission of an absolutely useless faculty, probably derived from
our remote semi-human progenitors; since many monkeys have, and
frequently use the power, of largely moving their scalps up and down.
(27. See my ‘Expression of the Emotions in Man and Animals,’ 1872, p.
144.)
The extrinsic muscles which serve to move the external ear, and the
intrinsic muscles which move the different parts, are in a rudimentary
condition in man, and they all belong to the system of the panniculus;
they are also variable in development, or at least in function. I have
seen one man who could draw the whole ear forwards; other men can draw
it upwards; another who could draw it backwards (28. Canestrini quotes
Hyrtl. (‘Annuario della Soc. dei Naturalisti,’ Modena, 1867, p. 97) to
the same effect.); and from what one of these persons told me, it is
probable that most of us, by often touching our ears, and thus
directing our attention towards them, could recover some power of
movement by repeated trials. The power of erecting and directing the
shell of the ears to the various points of the compass, is no doubt of
the highest service to many animals, as they thus perceive the
direction of danger; but I have never heard, on sufficient evidence, of
a man who possessed this power, the one which might be of use to him.
The whole external shell may be considered a rudiment, together with
the various folds and prominences (helix and anti-helix, tragus and
anti-tragus, etc.) which in the lower animals strengthen and support
the ear when erect, without adding much to its weight. Some authors,
however, suppose that the cartilage of the shell serves to transmit
vibrations to the acoustic nerve; but Mr. Toynbee (29. ‘The Diseases of
the Ear,’ by J. Toynbee, F.R.S., 1860, p. 12. A distinguished
physiologist, Prof. Preyer, informs me that he had lately been
experimenting on the function of the shell of the ear, and has come to
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