The Descent of Man and Selection in Relation to Sex
On The Manner Of Development Of Man From Some
Variability of body and mind in man--Inheritance--Causes of variability-- Laws of
variation the same in man as in the lower animals--Direct action of the conditions of life--
Effects of the increased use and disuse of parts-- Arrested development--Reversion--
Correlated variation--Rate of increase-- Checks to increase--Natural selection--Man the
most dominant animal in the world--Importance of his corporeal structure--The causes
which have led to his becoming erect--Consequent changes of structure--Decrease in size
of the canine teeth--Increased size and altered shape of the skull--Nakedness --Absence
of a tail--Defenceless condition of man.
It is manifest that man is now subject to much variability. No two individuals of the same
race are quite alike. We may compare millions of faces, and each will be distinct. There
is an equally great amount of diversity in the proportions and dimensions of the various
parts of the body; the length of the legs being one of the most variable points. (1.
'Investigations in Military and Anthropological Statistics of American Soldiers,' by B.A.
Gould, 1869, p. 256.) Although in some quarters of the world an elongated skull, and in
other quarters a short skull prevails, yet there is great diversity of shape even within the
limits of the same race, as with the aborigines of America and South Australia--the latter
a race "probably as pure and homogeneous in blood, customs, and language as any in
existence"--and even with the inhabitants of so confined an area as the Sandwich Islands.
(2. With respect to the "Cranial forms of the American aborigines," see Dr. Aitken Meigs
in 'Proc. Acad. Nat. Sci.' Philadelphia, May 1868. On the Australians, see Huxley, in
Lyell's 'Antiquity of Man,' 1863, p. 87. On the Sandwich Islanders, Prof. J. Wyman,
'Observations on Crania,' Boston, 1868, p. 18.) An eminent dentist assures me that there
is nearly as much diversity in the teeth as in the features. The chief arteries so frequently
run in abnormal courses, that it has been found useful for surgical purposes to calculate
from 1040 corpses how often each course prevails. (3. 'Anatomy of the Arteries,' by R.
Quain. Preface, vol. i. 1844.) The muscles are eminently variable: thus those of the foot
were found by Prof. Turner (4. 'Transactions of the Royal Society of Edinburgh,' vol.
xxiv. pp. 175, 189.) not to be strictly alike in any two out of fifty bodies; and in some the
deviations were considerable. He adds, that the power of performing the appropriate
movements must have been modified in accordance with the several deviations. Mr. J.
Wood has recorded (5. 'Proceedings Royal Society,' 1867, p. 544; also 1868, pp. 483,
524. There is a previous paper, 1866, p. 229.) the occurrence of 295 muscular variations
in thirty-six subjects, and in another set of the same number no less than 558 variations,
those occurring on both sides of the body being only reckoned as one. In the last set, not
one body out of the thirty-six was "found totally wanting in departures from the standard
descriptions of the muscular system given in anatomical text books." A single body
presented the extraordinary number of twenty-five distinct abnormalities. The same
muscle sometimes varies in many ways: thus Prof. Macalister describes (6. 'Proc. R. Irish
Academy,' vol. x. 1868, p. 141.) no less than twenty distinct variations in the palmaris
The famous old anatomist, Wolff (7. 'Act. Acad. St. Petersburg,' 1778, part ii. p. 217.),
insists that the internal viscera are more variable than the external parts: Nulla particula
est quae non aliter et aliter in aliis se habeat hominibus. He has even written a treatise on