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Library: Historical Documents: Charles Darwin: Descent of Man: Chapter 2


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Descent of Man [ 1871 ]

Charles Darwin [ 1809 - 1882 ]

 

Chapter II - On the Manner of Development of Man from some Lower Form




  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.* 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) 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 is has been found useful for surgical purposes to

calculate from 1040 corpses how often each course prevails.*(3) The

muscles are eminently variable: thus those of the foot were found by

Prof. Turner*(4) 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) 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) no less than twenty distinct variations

in the palmaris accessorius.



  * Investigations in the Military and Anthropological Statistics of

American Soldiers, by B. A. Gould, 1869, p. 256.

  *(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.

  *(3) Anatomy of the Arteries, by R. Quain. Preface, vol. i., 1844.

  *(4) Transactions of the Royal Society of Edinburgh, vol. xxiv., pp.

175, 189.

  *(5) Proceedings Royal Society, 1867, p. 544; also 1868, pp. 483,

524. There is a previous paper, 1866, p. 229.

  *(6) Proc. R. Irish Academy, vol. x., 1868, p. 141.



  The famous old anatomist, Wolff,* 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 the choice of typical examples of the viscera

for representation. A discussion on the beau-ideal of the liver,

lungs, kidneys, &c., as of the human face divine, sounds strange in

our ears.



  * Act. Acad. St. Petersburg, 1778, part ii., p. 217.



  The variability or diversity of the mental faculties in men of the

same race, not to mention the greater differences between the men of

distinct races, is so notorious that not a word need here be said.

So it is with the lower animals. All who have had charge of menageries

admit this fact, and we see it plainly in our dogs and other

domestic animals. Brehm especially insists that each individual monkey

of those which he kept tame in Africa had its own peculiar disposition

and temper: he mentions one baboon remarkable for its high

intelligence; and the keepers in the Zoological Gardens pointed out to

me a monkey, belonging to the New World division, equally remarkable

for intelligence. Rengger, also, insists on the diversity in the

various mental characters of the monkeys of the same species which

he kept in Paraguay; and this diversity, as he adds, is partly innate,

and partly the result of the manner in which they have been treated or

educated.*



  * Brehm, Illustriertes Thierleben, B. i., ss. 58, 87. Rengger,

Saugethiere von Paraguay, s. 57.



  I have elsewhere* so fully discussed the subject of Inheritance,

that I need here add hardly anything. A greater number of facts have

been collected with respect to the transmission of the most

trifling, as well as of the most important characters in man, than

in any of the lower animals; though the facts are copious enough

with respect to the latter. So in regard to mental qualities, their

transmission is manifest in our dogs, horses, and other domestic

animals. Besides special tastes and habits, general intelligence,

courage, bad and good temper, &c., are certainly transmitted. With man

we see similar facts in almost every family; and we now know,

through the admirable labours of Mr. Galton,*(2) that genius which

implies a wonderfully complex combination of high faculties, tends

to be inherited; and, on the other hand, it is too certain that

insanity and deteriorated mental powers likewise run in families.



  * Variation of Animals and Plants under Domestication, vol. ii.,

chap. xii.

  *(2) Hereditary Genius: an Inquiry into its Laws and Consequences,

1869.



  With respect to the causes of variability, we are in all cases

very ignorant; but we can see that in man as in the lower animals,

they stand in some relation to the conditions to which each species

has been exposed, during several generations. Domesticated animals

vary more than those in a state of nature; and this is apparently

due to the diversified and changing nature of the conditions to

which they have been subjected. In this respect the different races of

man resemble domesticated animals, and so do the individuals of the

same race, when inhabiting. a very wide area, like that of America. We

see the influence of diversified conditions in the more civilised

nations; for the members belonging to different grades of rank, and

following different occupations, present a greater range of

character than do the members of barbarous nations. But the uniformity

of savages has often been exaggerated, and in some cases can hardly be

said to exist.* It is, nevertheless, an error to speak of man, even if

we look only to the conditions to which he has been exposed, as "far

more domesticated"*(2) than any other animal. Some savage races,

such as the Australians, are not exposed to more diversified

conditions than are many species which have a wide range. In another

and much more important respect, man differs widely from any

strictly domesticated animal; for his breeding has never long been

controlled, either by methodical or unconscious selection. No race

or body of men has been so completely subjugated by other men, as that

certain individuals should be preserved, and thus unconsciously

selected, from somehow excelling in utility to their masters. Nor have

certain male and female individuals been intentionally picked out

and matched, except in the well-known case of the Prussian grenadiers;

and in this case man obeyed, as might have been expected, the law of

methodical selection; for it is asserted that many tall men were

reared in the villages inhabited by the grenadiers and their tall

wives. In Sparta, also, a form of selection was followed, for it was

enacted that all children should be examined shortly after birth;

the well-formed and vigorous being preserved, the others left to

perish.*(3)



  * Mr. Bates remarks (The Naturalist on the Amazons, 1863, vol. ii p.

159), with respect to the Indians of the same South American tribe,

"no two of them were at all similar in the shape of the head; one

man had an oval visage with fine features, and another was quite

Mongolian in breadth and prominence of cheek, spread of nostrils,

and obliquity of eyes."

  *(2) Blumenbach, Treatises on Anthropology., Eng. translat., 1865,

p. 205.

  *(3) Mitford's History of Greece, vol. i., p. 282. It appears from a

passage in Xenophon's Memorabilia, B. ii. 4 (to which my attention has

been called by the Rev. J. N. Hoare), that it was a well recognised

principle with the Greeks, that men ought to select their wives with a

view to the health and vigour of their children. The Grecian poet,

Theognis, who lived 550 B. C., clearly saw how important selection, if

carefully applied, would be for the improvement of mankind. He saw,

likewise, that wealth often checks the proper action of sexual

selection. He thus writes:



    With kine and horses, Kurnus! we proceed

    By reasonable rules, and choose a breed

    For profit and increase at any price:

    Of a sound stock, without defect or vice.

    But, in the daily matches that we make,

    The price is everything: for money's sake,

    Men marry: women are in marriage given

    The churl or ruffian, that in wealth has thriven,

    May match his offspring with the proudest race:

    Thus everything is mix'd, noble and base!

    If then in outward manner, form, and mind,

    You find us a degraded, motley kind,

    Wonder no more, my friend! the cause is plain,

    And to lament the consequence is vain.



  (The Works of J. Hookham Frere, vol. ii., 1872, p. 334.)



  If we consider all the races of man as forming a single species, his

range is enormous; but some separate races, as the Americans and

Polynesians, have very wide ranges. It is a well-known law that

widely-ranging species are much more variable than species with

restricted ranges; and the variability of man may with more truth be

compared with that of widely-ranging species, than with that of

domesticated animals.

  Not only does variability appear to be induced in man and the

lower animals by the same general causes, but in both the same parts

of the body are effected in a closely analogous manner. This has

been proved in such full detail by Godron and Quatrefages, that I need

here only refer to their works.* Monstrosities, which graduate into

slight variations, are likewise so similar in man and the lower

animals, that the same classification and the same terms can be used

for both, as has been shewn by Isidore Geoffroy St-Hilaire.*(2) In

my work on the variation of domestic animals, I have attempted to

arrange in a rude fashion the laws of variation under the following

heads:- The direct and definite action of changed conditions, as

exhibited by all or nearly all the individuals of the same species,

varying in the same manner under the same circumstances. The effects

of the long-continued use or disuse of parts. The cohesion of

homologous parts. The variability of multiple parts. Compensation of

growth; but of this law I have found no good instance in the case of

man. The effects of the mechanical pressure of one part on another; as

of the pelvis on the cranium of the infant in the womb. Arrests of

development, leading to the diminution or suppression of parts. The

reappearance of long-lost characters through reversion. And lastly,

correlated variation. All these so-called laws apply equally to man

and the lower animals; and most of them even to plants. It would be

superfluous here to discuss all of them;*(3) but several are so

important, that they must be treated at considerable length.



  * Godron, De l'Espece, 1859, tom. ii., livre 3. Quatrefages, Unite

de l'Espece Humaine, 1861. Also Lectures on Anthropology, given in the

Revue des Cours Scientifiques, 1866-1868.

  *(2) Hist. Gen. et Part. des Anomalies de l'Organisation, tom. i.,

1832.

  *(3) I have fully discussed these laws in my Variation of Animals

and Plants under Domestication, vol. ii., chaps. xxii. and xxiii. M.

J. P. Durand has lately (1868) published a valuable essay, De

l'Influence des Milieux, &c. He lays much stress, in the case of

plants, on the nature of the soil.



  The Direct and Definite Action of Changed Conditions.- This is a

most perplexing subject. It cannot be denied that changed conditions

produce some, and occasionally a considerable effect, on organisms

of all kinds; and it seems at first probable that if sufficient time

were allowed this would be the invariable result. But I have failed to

obtain clear evidence in favour of this conclusion; and valid

reasons may be urged on the other side, at least as far as the

innumerable structures are concerned, which are adapted for special

ends. There can, however, be no doubt that changed conditions induce

an almost indefinite amount of fluctuating variability, by which the

whole organisation is rendered in some degree plastic.

  In the United States, above 1,000,000 soldiers, who served in the

late war, were measured, and the States in which they were born and

reared were recorded.* From this astonishing number of observations it

is proved that local influences of some kind act directly on

stature; and we further learn that "the State where the physical

growth has in great measure taken place, and the State of birth, which

indicates the ancestry, seem to exert a marked influence on the

stature." For instance, it is established, "that residence in the

Western States, during the years of growth, tends to produce

increase of stature." On the other hand, it is certain that with

sailors, their life delays growth, as shewn "by the great difference

between the statures of soldiers and sailors at the ages of

seventeen and eighteen years." Mr. B. A. Gould endeavoured to

ascertain the nature of the influences which thus act on stature;

but he arrived only at negative results, namely that they did not

relate to climate, the elevation of the land, soil, nor even "in any

controlling degree" to the abundance or the need of the comforts of

life. This latter conclusion is directly opposed to that arrived at

by, Villerme, from the statisties of the height of the conscripts in

different parts of France. When we compare the differences in

stature between the Polynesian chiefs and the lower orders within

the same islands, or between the inhabitants of the fertile volcanic

and low barren coral islands of the same ocean,*(2) or again between

the Fuegians on the eastern and western shores of their country, where

the means of subsistence are very different, it is scarcely possible

to avoid the conclusion that better food and greater comfort do

influence stature. But the preceding statements shew how difficult

it is to arrive at any precise result. Dr. Beddoe has lately proved

that, with the inhabitants of Britain, residence in towns and

certain occupations have a deteriorating influence on height; and he

infers that the result is to a certain extent inherited, as is

likewise the case in the United States. Dr. Beddoe further believes

that wherever a "race attains its maximum of physical development,

it rises highest in energy and moral vigour."*(3)



  * Investigations in Military and Anthrop. Statistics, &c., 1869,

by B. A. Gould, pp. 93, 107, 126, 131, 134.

  *(2) For the Polynesians, see Prichard's Physical History of

Mankind, vol. v., 1847, pp. 145, 283. Also Godron, De l'Espece, tom.

ii., p. 289. There is also a remarkable difference in appearance

between the closely-allied Hindoos inhabiting the Upper Ganges and

Bengal; see Elphinstone's History of India, vol. i., p. 324.

  *(3) Memoirs, Anthropological Society, vol. iii., 1867-69, pp.

561, 565, 567.



 Whether external conditions produce any other direct effect on man is

not known. It might have been expected that differences of climate

would have had a marked influence, inasmuch as the lungs and kidneys

are brought into activity under a low temperature, and the liver and

skin under a high one.* It was formerly thought that the colour of the

skin and the character of the hair were determined by light or heat;

and although it can hardly be denied that some effect is thus

produced, almost all observers now agree that the effect has been very

small, even after exposure during many ages. But this subject will

be more properly discussed when we treat of the different races of

mankind. With our domestic animals there are grounds for believing

that cold and damp directly affect the growth of the hair; but I

have not met with any evidence on this head in the case of man.



  * Dr. Brakenridge, "Theory of Diathesis," Medical Times, June 19 and

July 17, 1869.



  Effects of the increased Use and Disuse of Parts.- It is well

known that use strengthens the muscles in the individual, and complete

disuse, or the destruction of the proper nerve, weakens them. When the

eye is destroyed, the optic nerve often becomes atrophied. When an

artery is tied, the lateral channels increase not only in diameter,

but in the thickness and strength of their coats. When one kidney

ceases to act from disease, the other increases in size, and does

double work. Bones increase not only in thickness, but in length, from

carrying a greater weight.* Different occupations, habitually

followed, lead to changed proportions in various parts of the body.

Thus it was ascertained by the United States Commission*(2) that the

legs of the sailors employed in the late war were longer by 0.217 of

an inch than those of the soldiers, though the sailors were on an

average shorter men; whilst their arms were shorter by 1.09 of an

inch, and therefore, out of proportion, shorter in relation to their

lesser height. This shortness of the arms is apparently due to their

greater use, and is an unexpected result: but sailors chiefly use

their arms in pulling, and not in supporting weights. With sailors,

the girth of the neck and the depth of the instep are greater,

whilst the circumference of the chest, waist, and hips is less, than

in soldiers.



  * I have given authorities for these several statements in my

Variation of Animals and Plants under Domestication, vol. ii., pp.

297-300. Dr. Jaeger, "Uber das Langenwachsthum der Knochen," Jenaische

Zeitschrift, B. v., Heft. i.

  *(2) Investigations, &c., by B. A. Gould, 1869, p. 288.



  Whether the several foregoing modifications would become hereditary,

if the same habits of life were followed during many generations, is

not known, but it is probable. Rengger* attributes the thin legs and

thick arms of the Payaguas Indians to successive generations having

passed nearly their whole lives in canoes, with their lower

extremities motionless. Other writers have come to a similar

conclusion in analogous cases. According to Cranz,*(2) who lived for a

long time with the Esquimaux, "The natives believe that ingenuity

and dexterity in seal-catching (their highest art and virtue) is

hereditary; there is is really something in it, for the son of a

celebrated seal-catcher will distinguish himself, though he lost his

father in childhood." But in this case it is mental aptitude, quite as

much as bodily structure, which appears to be inherited. It is

asserted that the hands of English labourers are at birth larger

than those of the gentry.*(3) From the correlation which exists, at

least in some cases,*(4) between the development of the extremities

and of the jaws, it is possible that in those classes which do not

labour much with their hands and feet, the jaws would be reduced in

size from this cause. That they are generally smaller in refined and

civilized men than in hard-working men or savages, is certain. But

with savages, as Mr. Herbert Spencer*(5) has remarked, the greater use

of the jaws in chewing coarse, uncooked food, would act in a direct

manner on the masticatory muscles, and on the bones to which they

are attached. In infants, long before birth, the skin on the soles

of the feet is thicker than on any other part of the body;*(6) and

it can hardly be doubted that this is due to the inherited effects

of pressure during a long series of generations.



  * Saugethiere von Paraguay, 1830, s. 4.

  *(2) History of Greenland, Eng. translat., 1767, vol. i., p. 230

  *(3) Intermarriage, by Alex. Walker, 1838, p. 377.

  *(4) The Variation of Animals and Plants under Domestication, vol.

i., p. 173.

  *(5) Principles of Biology, vol. i., p. 455.

  *(6) Paget, Lectures on Surgical Pathology, vol. ii, 1853, p. 209.



  It is familiar to every one that watchmakers and engravers are

liable to be short-sighted, whilst men living much out of doors, and

especially savages, are generally long-sighted.* Short-sight and

long-sight certainly tend to be inherited.*(2) The inferiority of

Europeans, in comparison with savages, in eyesight and in the other

senses, is no doubt the accumulated and transmitted effect of lessened

use during many generations; for Rengger*(3) states that he has

repeatedly observed Europeans, who had been brought up and spent their

whole lives with the wild Indians, who nevertheless did not equal them

in the sharpness of their senses. The same naturalist observes that

the cavities in the skull for the reception of the several

sense-organs are larger in the American aborigines than in

Europeans; and this probably indicates a corresponding difference in

the dimensions of the organs themselves. Blumenbach has also

remarked on the large size of the nasal cavities in the skulls of

the American aborigines, and connects this fact with their

remarkably acute power of smell. The Mongolians of the plains of

northern Asia, according to Pallas, have wonderfully perfect senses;

and Prichard believes that the great breadth of their skulls across

the zygomas follows from their highly-developed sense organs.*(4)



  * It is a singular and unexpected fact that sailors are inferior

to landsmen in their mean distance of distinct vision. Dr. B. A. Gould

(Sanitary Memoirs of the War of the Rebellion, 1869 p. 530), has

proved this to be the case; and he accounts for it by the ordinary

range of vision in sailors being "restricted to the length of the

vessel and the height of the masts."

  *(2) The Variation of Animal and Plants under Domestication, vol.

i., p. 8.

  *(3) Saugethiere von Paraguay, s. 8, 10. I have had good

opportunities for observing the extraordinary power of eyesight in the

Fuegians. See also Lawrence (Lectures on Physiology, &c., 1822, p.

404) on this same subject. M. Giraud-Teulon has recently collected

(Revue des Cours Scientifiques, 1870, p. 625) a large and valuable

body of evidence proving that the cause of short-sight, "C'est le

travail assidu, de pres."

  *(4) Prichard, Physical History of Mankind, on the authority of

Blumenbach, vol. i., 1841, p. 311; for the statement by Pallas, vol.

iv., 1844, p. 407.



  The Quechua Indians inhabit the lofty plateaux of Peru; and Alcide

d'Orbigny states* that, from continually breathing a highly rarefied

atmosphere, they have acquired chests and lungs of extraordinary

dimensions. The cells, also, of the lungs are larger and more numerous

than in Europeans. These observations have been doubted, but Mr. D.

Forbes carefully measured many Aymaras, an allied race, living at

the height of between 10,000 and 15,000 feet; and he informs me*(2)

that they differ conspicuously from the men of all other races seen by

him in the circumference and length of their bodies. In his table of

measurements, the stature of each man is taken at 1000, and the

other measurements are reduced to this standard. It is here seen

that the extended arms of the Aymaras are shorter than those of

Europeans, and much shorter than those of Negroes. The legs are

likewise shorter; and they present this remarkable peculiarity, that

in every Aymara measured, the femur is actually shorter than the

tibia. On an average, the length of the femur to that of the tibia

is as 211 to 252; whilst in two Europeans, measured at the same

time, the femora to the tibiae were as 244 to 230; and in three

Negroes as 258 to 241. The humerus is likewise shorter relatively to

the forearm. This shortening of that part of the limb which is nearest

to the body, appears to be, as suggested to me by Mr. Forbes, a case

of compensation in relation with the greatly increased length of the

trunk. The Aymaras present some other singular points of structure,

for instance, the very small projection of the heel.



  * Quoted by Prichard, Researches into the Physical History of

Mankind, vol. v., p. 463.

  *(2) Mr. Forbes' valuable paper is now published in the Journal of

the Ethnological Society of London, new series, vol. ii., 1870, p.

193.



  These men are so thoroughly acclimatised to their cold and lofty

abode, that when formerly carried down by Spaniards to the low eastern

plains, and when now tempted down by high wages to the

gold-washings, they suffer a frightful rate of mortality. Nevertheless

Mr. Forbes found a few pure families which had survived during two

generations: and he observed that they still inherited their

characteristic peculiarities. But it was manifest, even without

measurement, that these peculiarities had all decreased; and on

measurement, their bodies were found not to be so much elongated as

those of the men on the high plateau; whilst their femora had become

somewhat lengthened, as had their tibiae, although in a less degree.

The actual measurements may be seen by consulting Mr. Forbes's memoir.

From these observations, there can, I think, be no doubt that

residence during many generations at a great elevation tends, both

directly and indirectly, to induce inherited modifications in the

proportions of the body.*



  * Dr. Wilckens (Landwirthschaft. Wochenblatt, No. 10, 1869) has

lately published an interesting essay shewing how domestic animals,

which live in mountainous regions, have their frames modified.



  Although man may not have been much modified during the latter

stages of his existence through the increased or decreased use of

parts, the facts now given shew that his liability in this respect has

not been lost; and we positively know that the same law holds good

with the lower animals. Consequently we may infer that when at a

remote epoch the progenitors of man were in a transitional state,

and were changing from quadrupeds into bipeds, natural selection would

probably have been greatly aided by the inherited effects of the

increased or diminished use of the different parts of the body.



  Arrests of Development.- There is a difference between arrested

development and arrested growth, for parts in the former state

continue to grow whilst still retaining their early condition. Various

monstrosities come under this head; and some, as a cleft palate, are

known to be occasionally inherited. It will suffice for our purpose to

refer to the arrested brain-development of microcephalous idiots, as

described in Vogt's memoir.* Their skulls are smaller, and the

convolutions of the brain are less complex than in normal men. The

frontal sinus, or the projection over the eyebrows, is largely

developed, and the jaws are prognathous to an "effrayant" degree; so

that these idiots somewhat resemble the lower types of mankind.

Their intelligence, and most of their mental faculties, are

extremely feeble. They cannot acquire the power of speech, and are

wholly incapable of prolonged attention, but are much given to

imitation. They are strong and remarkably active, continually

gambolling and jumping about, and making grimaces. They often ascend

stairs on all-fours; and are curiously fond of climbing up furniture

or trees. We are thus reminded of the delight shewn by almost all boys

in climbing trees; and this again reminds us how lambs and kids,

originally alpine animals, delight to frisk on any hillock, however

small. Idiots also resemble the lower animals in some other

respects; thus several cases are recorded of their carefully

smelling every mouthful of food before eating it. One idiot is

described as often using his mouth in aid of his hands, whilst hunting

for lice. They are often filthy in their habits, and have no sense

of decency; and several cases have been published of their bodies

being remarkably hairy.*(2)



  * Memoires sur les Microcephales, 1867, pp. 50, 125, 169, 171,

184-198.

  *(2) Prof. Laycock sums up the character of brute-like idiots by

calling them theroid; Journal of Mental Science,, July, 1863. Dr.

Scott (The Deaf and Dumb, 2nd ed., 1870, p. 10) has often observed the

imbeciles smelling their food. See, on this same subject, and on the

hairiness of idiots, Dr. Maudsley, Body and Mind, 1870, pp. 46-51.

Pinel has also given a striking case of hairiness in an idiot.



  Reversion.- Many of the cases to be here given, might have been

introduced under the last heading. When a structure is arrested in its

development, but still continues growing, until it closely resembles a

corresponding structure in some lower and adult member of the same

group, it may in one sense be considered as a case of reversion. The

lower members in a group give us some idea how the common progenitor

was probably constructed; and it is hardly credible that a complex

part, arrested at an early phase of embryonic development, should go

on growing so as ultimately to perform its proper function, unless

it had acquired such power during some earlier state of existence,

when the present exceptional or arrested structure was normal. The

simple brain of a microcephalous idiot, in as far as it resembles that

of an ape' may in this sense be said to offer a case of reversion.*

There are other cases which come more strictly under our present

head of reversion. Certain structures, regularly occurring in the

lower members of the group to which man belongs, occasionally make

their appearance in him, though not found in the normal human

embryo; or, if normally present in the human embryo, they become

abnormally developed, although in a manner which is normal in the

lower members of the group. These remarks will be rendered clearer

by the following illustrations.



  * In my Variation of Animals under Domestication (vol. ii., p.

57), I attributed the not very rare cases of supernumerary mammae in

women to reversion. I was led to this as a probable conclusion, by the

additional mammae being generally placed symmetrically on the

breast; and more especially from one case, in which a single efficient

mamma occurred in the inguinal region of a woman, the daughter of

another woman with supernumerary mammae. But I now find (see, for

instance, Prof. Preyer, Der Kampf um das Dasein, 1869, s. 45) that

mammae erraticae, occur in other situations, as on the back, in the

armpit, and on the thigh; the mammae in this latter instance having

given so much milk that the child was thus nourished. The

probability that the additional mammae are due to reversion is thus

much weakened; nevertheless, it still seems to me probable, because

two pairs are often found symmetrically on the breast; and of this I

myself have received information in several cases. It is well known

that some lemurs normally have two pairs of mammae on the breast. Five

cases have been recorded of the presence of more than a pair of mammee

(of course rudimentary) in the male sex of mankind; see Journal of

Anat. and Physiology, 1872, p. 56, for a case given by Dr. Handyside

in which two brothers exhibited this peculiarity; see also a paper

by Dr. Bartels, in Reichert's and du Bois-Reymond's Archiv., 1872,

p. 304. In one of the cases alluded to by Dr. Bartels, a man bore five

mammae, one being medial and placed above the navel; Meckel von

Hemsbach thinks that this latter case is illustrated by a medial mamma

occurring in certain Cheiroptera. On the whole, we may well doubt if

additional mammae would ever have been developed in both sexes of

mankind, had not his early progenitors been provided with more than

a single pair.

  In the above work (vol. ii., p. 12), I also attributed, though

with much hesitation, the frequent cases of polydactylism in men and

various animals to reversion. I was partly led to this through Prof.

Owen's statement, that some of the Ichthyopterygia possesses more than

five digits, and therefore, as I supposed, had retained a primordial

condition; but Prof. Gegenbaur (Jenaische Zeitschrift, B. v., Heft

3, s. 341), disputes Owen's conclusion. On the other hand, according

to the opinion lately advanced by Dr. Gunther, on the paddle of

Ceratodus, which is provided with articulated bony rays on both

sides of a central chain of bones, there seems no great difficulty

in admitting that six or more digits on one side, or on both sides,

might reappear through reversion. I am informed by Dr. Zouteveen

that there is a case on record of a man having twenty-four fingers and

twenty-four toes! I was chiefly led to the conclusion that the

presence of supernumerary digits might be due to reversion from the

fact that such digits, not only are strongly inherited, but, as I then

believed, had the power of regrowth after amputation, like the

normal digits of the lower Vertebrata. But I have explained in the

second edition of my Variation under Domestication why I now place

little reliance on the recorded cases of such regrowth. Nevertheless

it deserves notice, inasmuch as arrested development and reversion are

intimately related processes; that various structures in an

embryonic or arrested condition, such as a cleft palate, bifid uterus,

&c., are frequently accompanied by polydactylism. This has been

strongly insisted on by Meckel and Isidore Geoffroy St-Hilaire. But at

present it is the safest course to give up altogether the idea that

there is any relation between the development of supernumerary

digits and reversion to some lowly organized progenitor of man.



  In various mammals the uterus graduates from a double organ with two

distinct orifices and two passages, as in the marsupials, into a

single organ, which is in no way double except from having a slight

internal fold, as in the higher apes and man. The rodents exhibit a

perfect series of gradations between these two extreme states. In

all mammals the uterus is developed from two simple primitive tubes,

the inferior portions of which form the cornua; and it is in the words

of Dr. Farre, "by the coalescence of the two cornua at their lower

extremities that the body of the uterus is formed in man; while in

those animals in which no middle portion or body exists, the cornua

remain ununited. As the development of the uterus proceeds, the two

cornua become gradually shorter, until at length they are lost, or, as

it were, absorbed into the body of the uterus." The angles of the

uterus are still produced into cornua, even in animals as high up in

the scale as the lower apes and lemurs.

  Now in women, anomalous cases are not very infrequent, in which

the mature uterus is furnished with cornua, or is partially divided

into two organs; and such cases, according to Owen, repeat "the

grade of concentrative development," attained by certain rodents. Here

perhaps we have an instance of a simple arrest of embryonic

development, with subsequent growth and perfect functional

development; for either side of the partially double uterus is capable

of performing the proper office of gestation. In other and rarer

cases, two distinct uterine cavities are formed, each having its

proper orifice and passage.* No such stage is passed through during

the ordinary development of the embryo; and it is difficult to

believe, though perhaps not impossible, that the two simple, minute,

primitive tubes should know how (if such an expression may be used) to

grow into two distinct uteri, each with a well-constructed orifice,and

passage, and each furnished with numerous muscles, nerves, glands

and vessels, if they had not formerly passed through a similar

course of development, as in the case of existing marsupials. No one

will pretend that so perfect a structure as the abnormal double uterus

in woman could be the result of mere chance. But the principle of

reversion, by which a long-lost structure is called back into

existence, might serve as the guide for its full development, even

after the lapse of an enormous interval of time.



  * See Dr. A. Farre's well-known article in the Cyclopaedia of

Anatomy and Physiology, vol. v., 1859, p. 642. Owen, Anatomy of

Vertebrates, vol. iii., 1868, p. 687. Professor Turner, in Edinburgh

Medical Journal, February, 1865.



  Professor Canestrini, after discussing the foregoing and various

analogous cases, arrives at the same conclusion as that just given. He

adduces another instance, in the case of the malar bone,* which, in

some of the Quadrumana and other mammals, normally consists of two

portions. This is its condition in the human foetus when two months

old; and through arrested development, it sometimes remains thus in

man when adult, more especially in the lower prognathous races.

Hence Canestrini concludes that some ancient progenitor of man must

have had this bone normally divided into two portions, which

afterwards became fused together. In man the frontal bone consists

of a single piece, but in the embryo, and in children, and in almost

all the lower mammals, it consists of two pieces separated by a

distinct suture. This suture occasionally persists more or less

distinctly in man after maturity; and more frequently in ancient

than in recent crania, especially, as Canestrini has observed, in

those exhumed from the Drift, and belonging to the brachycephalic

type. Here again he comes to the same conclusion as in the analogous

case of the malar bones. In this, and other instances presently to

be given, the cause of ancient races approaching the lower animals

in certain characters more frequently than do the modern races,

appears to be, that the latter stand at a somewhat greater distance in

the long line of descent from their early semi-human progenitors.



  * Annuario della Soc. dei Naturalisti, Modena, 1867, p. 83. Prof.

Canestrini gives extracts on this subject from various authorities.

Laurillard remarks, that as he has found a complete similarity in

the form, proportions, and connection of the two malar bones in

several human subjects and in certain apes, he cannot consider this

disposition of the parts as simply accidental. Another paper on this

same anomaly has been published by Dr. Saviotti in the Gazzetta

delle Cliniche, Turin, 1871, where he says that traces of the division

may be detected in about two per cent of adult skulls; he also remarks

that it more frequently occurs in prognathous skulls, not of the Aryan

race, than in others. See also G. Delorenzi on the same subject;

"Tre nuovi casi d'anomalia dell' osso malare," Torino, 1872. Also,

E. Morselli, "Sopra una rara anomalia dell' osso malare," Modena,

1872. Still more recently Gruber has written a pamphlet on the

division of this bone. I give these references because a reviewer,

without any grounds or scruples, has thrown doubts on my statements.



  Various other anomalies in man, more or less analogous to the

foregoing, have been advanced by different authors, as cases of

reversion; but these seem not a little doubtful, for we have to

descend extremely low in the mammalian series, before we find such

structures normally present.*



  * A whole series of cases is given by Isidore Geoffroy St-Hilaire,

Hist. des Anomalies, tom, iii, p. 437. A reviewer (Journal of

Anatomy and Physiology, 1871, p. 366) blames me much for not having

discussed the numerous cases, which have been recorded, of various

parts arrested in their development. He says that, according to my

theory, "every transient condition of an organ, during its

development, is not only a means to an end, but once was an end in

itself." This does not seem to me necessarily to hold good. Why should

not variations occur during an early period of development, having

no relation to reversion; yet such variations might be preserved and

accumulated, if in any way serviceable, for instance, in shortening

and simplifying the course of development? And again, why should not

injurious abnormalities, such as atrophied or hypertrophied parts,

which have no relation to a former state of existence, occur at an

early period, as well as during maturity?



  In man, the canine teeth are perfectly efficient instruments for

mastication. But their true canine character, as Owen* remarks, "is

indicated by the conical form of the crown, which terminates in an

obtuse point, is convex outward and flat or sub-concave within, at the

base of which surface there is a feeble prominence. The conical form

is best expressed in the Melanian races, especially the Australian.

The canine is more deeply implanted, and by a stronger fang than the

incisors." Nevertheless, this tooth no longer serves man as a

special weapon for tearing his enemies or prey; it may, therefore,

as far as its proper function is concerned, be considered as

rudimentary. In every large collection of human skulls some may be

found, as Haeckel*(2) observes, with the canine teeth projecting

considerably beyond the others in the same manner as in the

anthropomorphous apes, but in a less degree. In these cases, open

spaces between the teeth in the one jaw are left for the reception

of the canines of the opposite jaw. An inter-space of this kind in a

Kaffir skull, figured by Wagner, is surprisingly wide.*(3) Considering

how few are the ancient skulls which have been examined, compared to

recent skulls, it is an interesting fact that in at least three

cases the canines project largely; and in the Naulette jaw they are

spoken of as enourmous.*(4)



  * Anatomy of Vertebrates, vol. iii., 1868, p. 323.

  *(2) Generelle Morphologie, 1866, B. ii., s. clv.

  *(3) Carl Vogt's Lectures on Man, Eng. translat., 1864, p. 151.

  *(4) C. Carter Blake, on a jaw from La Naulette, Anthropological

Review, 1867, p. 295. Schaaffhausen, ibid., 1868, p. 426.



  Of the anthropomorphous apes the males alone have their canines

fully developed; but in the female gorilla, and in a less degree in

the female orang, these teeth project considerably beyond the

others; therefore the fact, of which I have been assured, that women

sometimes have considerably projecting canines, is no serious

objection to the belief that their occasional great development in man

is a case of reversion to an ape-like progenitor. He who rejects

with scorn the belief that the shape of his own canines, and their

occasional great development in other men, are due to our early

forefathers having been provided with these formidable weapons, will

probably reveal, by sneering, the line of his descent. For though he

no longer intends, nor has the power, to use these teeth as weapons,

he will unconsciously retract his "snarling muscles" (thus named by

Sir C. Bell),* so as to expose them ready for action, like a dog

prepared to fight.



  * The Anatomy of Expression, 1844, pp. 110, 131.



  Many muscles are occasionally developed in man, which are proper

to the Quadrumana or other mammals. Professor Vlacovich* examined

forty male subjects, and found a muscle, called by him the

ischio-pubic, in nineteen of them; in three others there was a

ligament which represented this muscle; and in the remaining

eighteen no trace of it. In only two out of thirty female subjects was

this muscle developed on both sides, but in three others the

rudimentary ligament was present. This muscle, therefore, appears to

be much more common in the male than in the female sex; and on the

belief in the descent of man from some lower form, the fact is

intelligible; for it has been detected in several of the lower

animals, and in all of these it serves exclusively to aid the male

in the act of reproduction.



  * Quoted by Prof. Canestrini in the Annuario, della Soc. dei

Naturalisti, 1867, p. 90.



  Mr. J. Wood, in his valuable series of papers,* has minutely

described a vast number of muscular variations in man, which

resemble normal structures in the lower animals. The muscles which

closely resemble those regularly present in our nearest allies, the

Quadrumans, are too numerous to be here even specified. In a single

male subject, having a strong bodily frame, and well-formed skull,

no less than seven muscular variations were observed, all of which

plainly represented muscles proper to various kinds of apes. This man,

for instance, had on both sides of his neck a true and powerful

"levator claviculae," such as is found in all kinds of apes, and which

is said to occur in about one out of sixty human subjects.*(2)

Again, this man had "a special abductor of the metatarsal bone of

the fifth digit, such as Professor Huxley and Mr. Flower have shewn to

exist uniformly in the higher and lower apes." I will give only two

additional cases; the acromio-basilar muscle is found in all mammals

below man, and seems to be correlated with a quadrupedal gait,*(3) and

it occurs in about one out of sixty human subjects. In the lower

extremities Mr. Bradley*(4) found an abductor ossis metatarsi quinti

in both feet of man; this muscle had not up to that time been recorded

in mankind, but is always present in the anthropomorphous apes. The

muscles of the hands and arms- parts which are so eminently

characteristic of man- are extremely liable to vary, so as to resemble

the corresponding muscles in the lower animals.*(5) Such

resemblances are either perfect or imperfect; yet in the latter case

they are manifestly of a transitional nature. Certain variations are

more common in man, and others in woman, without our being able to

assign any reason. Mr. Wood, after describing numerous variations,

makes the following pregnant remark. "Notable departures from the

ordinary type of muscular structures run in grooves or directions,

which must be taken to indicate some unknown factor, of much

importance to a comprehensive knowledge of general and scientific

anatomy."*(6)



  * These papers deserve careful study by any one who desires to learn

how frequently our muscles vary, and in varying come to resemble those

of the Quadrumana. The following references relate to the few points

touched on in my text: Proc. Royal Soc., vol. xiv., 1865, pp. 379-384;

vol. xv., 1866, pp. 241, 242; vol. xv., 1867, p. 544; vol. xvi., 1868,

p. 524. I may here add that Dr. Murie and Mr. St. George Mivart have

shewn in their Memoir on the Lemuroidea (Transactions, Zoological

Society, vol. vii., 1869, p. 96), how extraordinarily variable some of

the muscles are in these animals, the lowest members of the

primates. Gradations, also, in the muscles leading to structures found

in animals still lower in the scale, are numerous in the Lemuroidea.

  *(2) See also Prof. Macalister in Proceedings, Royal Irish

Academy, vol. x., 1868, p. 124.

  *(3) Mr. Champneys in Journal of Anatomy and Physiology, Nov., 1871,

p. 178.

  *(4) Ibid., May, 1872, p. 421.

  *(5) Prof. Macalister (ibid., p. 121) has tabulated his

observations, and finds that muscular abnormalities are most

frequent in the fore-arms, secondly, in the face, thirdly, in the

foot, &c.

  *(6) The Rev. Dr. Haughton, after giving (Proc. R. Irish Academy,

June 27, 1864, p. 715) a remarkable case of variation in the human

flexor pollicis longus, adds, "This remarkable example shows that

man may sometimes possess the arrangement of tendons of thumb and

fingers characteristic of the macaque; but whether such a case

should be regarded as a macaque passing upwards into a man, or a man

passing downwards into a macaque, or as a congenital freak of

nature, I cannot undertake to say." It is satisfactory to hear so

capable an anatomist, and so embittered an opponent of evolutionism,

admitting even the possibility of either of his first propositions.

Prof. Macalister has also described (Proceedings Royal Irish

Academy, vol. x., 1864, p. 138) variations in the flexor pollicis

longus, remarkable from their relations to the same muscle in the

Quadrumana.



  That this unknown factor is reversion to a former state of existence

may be admitted as in the highest degree probable.* It is quite

incredible that a man should through mere accident abnormally resemble

certain apes in no less than seven of his muscles, if there had been

no genetic connection between them. On the other hand, if man is

descended from some ape-like creature, no valid reason can be assigned

why certain muscles should not suddenly reappear after an interval

of many thousand generations, in the same manner as with horses,

asses, and mules, dark-coloured stripes suddenly reappear on the legs,

and shoulders, after an interval of hundreds, or more probably of

thousands of generations.



  * Since the first edition of this book appeared, Mr. Wood has

published another memoir in the Philosophical Transactions, 1870, p.

83, on the varieties of the muscles of the human neck, shoulder, and

chest. He here shows how extremely variable these muscles are, and how

often and how closely the variations resemble the normal muscles of

the lower animals. He sums up by remarking, "It will be enough for

my purpose if I have succeeded in shewing the more important forms

which, when occurring as varieties in the human subject, tend to

exhibit in a sufficiently marked manner what may be considered as

proofs and examples of the Darwinian principle of reversion, or law of

inheritance, in this department of anatomical science."



  These various cases of reversion are so closely related to those

of rudimentary organs given in the first chapter, that many of them

might have been indifferently introduced either there or here. Thus

a human uterus furnished with cornua may be said to represent, in a

rudimentary condition, the same organ in its normal state in certain

mammals. Some parts which are rudimentary in man, as the os coccyx

in both sexes, and the mammae in the male sex, are always present;

whilst others, such as the supracondyloid foramen, only occasionally

appear, and therefore might have been introduced under the head of

reversion. These several reversionary structures, as well as the

strictly rudimentary ones, reveal the descent of man from some lower

form in an unmistakable manner.



  Correlated Variation.- In man, as in the lower animals, many

structures are so intimately related, that when one part varies so

does another, without our being able, in most cases, to assign any

reason. We cannot say whether the one part governs the other, or

whether both are governed by some earlier developed part. Various

monstrosities, as I. Geoffroy repeatedly insists, are thus

intimately connected. Homologous structures are particularly liable to

change together, as we see on the opposite sides of the body, and in

the upper and lower extremities. Meckel long ago remarked, that when

the muscles of the arm depart from their proper type, they almost

always imitate those of the leg; and so, conversely, with the

muscles of the legs. The organs of sight and hearing, the teeth and

hair, the colour of the skin and of the hair, colour and constitution,

are more or less correlated.* Professor Schaaffhausen first drew

attention to the relation apparently existing between a muscular frame

and the strongly-pronounced supra-orbital ridges, which are so

characteristic of the lower races of man.



  * The authorities for these several statements are given in my

Variation of Animals and Plants under Domestication, vol. ii., pp.

320-335.



  Besides the variations which can be grouped with more or less

probability under the foregoing heads, there is a large class of

variations which may be provisionally called spontaneous, for to our

ignorance they appear to arise without any exciting cause. It can,

however, be shewn that such variations, whether consisting of slight

individual differences, or of strongly-marked and abrupt deviations of

structure, depend much more on the constitution of the organism than

on the nature of the conditions to which it has been subjected.*



  * This whole subject has been discussed in chap. xxiii., vol. ii. of

my Variation of Animals and Plants under Domestication.



  Rate of Increase.- Civilised populations have been known under

favourable conditions, as in the United States, to double their

numbers in twenty-five years; and, according to a calculation, by

Euler, this might occur in a little over twelve years.* At the

former rate, the present population of the United States (thirty

millions), would in 657 years cover the whole terraqueous globe so

thickly, that four men would have to stand on each square yard of

surface. The primary or fundamental check to the continued increase of

man is the difficulty of gaining subsistence, and of living in

comfort. We may infer that this is the case from what we see, for

instance, in the United States, where subsistence is easy, and there

is plenty of room. If such means were suddenly doubled in Great

Britain, our number would be quickly doubled. With civilised nations

this primary check acts chiefly by restraining marriages. The

greater death-rate of infants in the poorest classes is also very

important; as well as the greater mortality, from various diseases, of

the inhabitants of crowded and miserable houses, at all ages. The

effects of severe epidemics and wars are soon counterbalanced, and

more than counterbalanced, in nations placed under favourable

conditions. Emigration also comes in aid as a temporary check, but,

with the extremely poor classes, not to any great extent.



  * See the ever memorable Essay on the Principle of Population, by

the Rev. T. Malthus, vol. i. 1826. pp. 6, 517.



  There is great reason to suspect, as Malthus has remarked, that

the reproductive power is actually less in barbarous, than in

civilised races. We know nothing positively on this head, for with

savages no census has been taken; but from the concurrent testimony of

missionaries, and of others who have long resided with such people, it

appears that their families are usually small, and large ones rare.

This may be partly accounted for, as it is believed, by the women

suckling their infants during a long time; but it is highly probable

that savages, who often suffer much hardships, and who do not obtain

so much nutritious food as civilised men, would be actually less

prolific. I have shewn in a former work,* that all our domesticated

quadrupeds and birds, and all our cultivated plants, are more

fertile than the corresponding species in a state of nature. It is

no valid objection to this conclusion that animals suddenly supplied

with an excess of food, or when grown very fat; and that most plants

on sudden removal from very poor to very rich soil, are rendered

more or less sterile. We might, therefore, expect that civilised

men, who in one sense are highly domesticated, would be more

prolific than wild men. It is also probable that the increased

fertility of civilised nations would become, as with our domestic

animals, an inherited character: it is at least known that with

mankind a tendency to produce twins runs in families.*(2)



  * Variation of Animals and Plants under Domestication, vol ii.,

pp. 111-113, 163.

  *(2) Mr. Sedgwick, British and Foreign Medico-Chirurgical Review,

July, 1863, p. 170.



  Notwithstanding that savages appear to be less prolific than

civilised people, they would no doubt rapidly increase if their

numbers were not by some means rigidly kept down. The Santali, or

hill-tribes of India, have recently afforded a good illustration of

this fact; for, as shewn by Mr. Hunter,* they have increased at an

extraordinary rate since vaccination has been introduced, other

pestilences mitigated, and war sternly repressed. This increase,

however, would not have been possible had not these rude people spread

into the adjoining districts, and worked for hire. Savages almost

always marry; yet there is some prudential restraint, for they do

not commonly marry at the earliest possible age. The young men are

often required to shew that they can support a wife; and they

generally have first to earn the price with which to purchase her from

her parents. With savages the difficulty of obtaining subsistence

occasionally limits their number in a much more direct manner than

with civilised people, for all tribes periodically suffer from

severe famines. At such times savages are forced to devour much bad

food, and their health can hardly fail to be injured. Many accounts

have been published of their protruding stomachs and emaciated limbs

after and during famines. They are then, also, compelled to wander

much, and, as I was assured in Australia, their infants perish in

large numbers. As famines are periodical, depending chiefly on extreme

seasons, all tribes must fluctuate in number. They cannot steadily and

regularly increase, as there is no artificial increase in the supply

of food. Savages, when hard pressed, encroach on each other's

territories, and war is the result; but they are indeed almost

always at war with their neighbours. They are liable to many accidents

on land and water in their search for food; and in some countries they

suffer much from the larger beasts of prey. Even in India, districts

have been depopulated by the ravages of tigers.



  * The Animals of Rural Bengal, by W. W. Hunter, 1868, p. 259.



  Malthus has discussed these several checks, but he does not lay

stress enough on what is probably the most important of all, namely

infanticide, especially of female infants and the habit of procuring

abortion. These practices now prevail in many quarters of the world;

and infanticide seems formerly to have prevailed, as Mr. M'Lennan* has

shewn on a still more extensive scale. These practices appear to

have originated in savages recognising the difficulty, or rather the

impossibility of supporting all the infants that are born.

Licentiousness may also be added to the foregoing checks; but this

does not follow from failing means of subsistence; though there is

reason to believe that in some cases (as in Japan) it has been

intentionally encouraged as a means of keeping down the population.



  * Primitive Marriage, 1865.



  If we look back to an extremely remote epoch, before man had arrived

at the dignity of manhood, he would have been guided more by

instinct and less by reason than are the lowest savages at the present

time. Our early semi-human progenitors would not have practised

infanticide or polyandry; for the instincts of the lower animals are

never so perverted* as to lead them regularly to destroy their own

offspring, or to be quite devoid of jealousy. There would have been no

prudential restraint from marriage, and the sexes would have freely

united at an early age. Hence the progenitors of man would have tended

to increase rapidly; but checks of some kind, either periodical or

constant, must have kept down their numbers, even more severely than

with existing savages. What the precise nature of these checks were,

we cannot say, any more than with most other animals. We know that

horses and cattle, which are not extremely prolific animals, when

first turned loose in South America, increased at an enormous rate.

The elephant, the slowest breeder of all known animals, would in a few

thousand years stock the whole world. The increase of every species of

monkey must be checked by some means; but not, as Brehm remarks, by

the attacks of beasts of prey. No one will assume that the actual

power of reproduction in the wild horses and cattle of America, was at

first in any sensible degree increased; or that, as each district

became fully stocked, this same power was diminished. No doubt, in

this case, and in all others, many checks concur, and different checks

under different circumstances; periodical dearths, depending on

unfavourable seasons, being probably the most important of all. So

it will have been with the early progenitors of man.



  * A writer in the Spectator (March 12, 1871, p. 320) comments as

follows on this passage:- "Mr. Darwin finds himself compelled to

reintroduce a new doctrine of the fall of man. He shews that the

instincts of the higher animals are far nobler than the habits of

savage races of men, and he finds himself, therefore, compelled to

re-introduce,- in a form of the substantial orthodoxy of which he

appears to be quite unconscious,- and to introduce as a scientific

hypothesis the doctrine that man's gain of knowledge was the cause

of a temporary but long-enduring moral deterioration as indicated by

the many foul customs, especially as to marriage, of savage tribes.

What does the Jewish tradition of the moral degeneration of man

through his snatching at a knowledge forbidden him by his highest

instinct assert beyond this?"



  Natural Selection.- We have now seen that man is variable in body

and mind; and that the variations are induced, either directly or

indirectly, by the same general causes, and obey the same general

laws, as with the lower animals. Man has spread widely over the face

of the earth, and must have been exposed, during his incessant

migration,* to the most diversified conditions. The inhabitants of

Tierra del Fuego, the Cape of Good Hope, and Tasmania in the one

hemisphere, and of the arctic regions in the other, must have passed

through many climates, and changed their habits many times, before

they reached their present homes.*(2) The early progenitors of man

must also have tended, like all other animals, to have increased

beyond their means of subsistence; they must, therefore,

occasionally have been exposed to a struggle for existence, and

consequently to the rigid law of natural selection. Beneficial

variations of all kinds will thus, either occasionally or

habitually, have been preserved and injurious ones eliminated. I do

not refer to strongly-marked deviations of structure, which occur only

at long intervals of time, but to mere individual differences. We

know, for instance, that the muscles of our hands and feet, which

determine our powers of movement, are liable, like those of the

lower animals,*(3) to incessant variability. If then the progenitors

of man inhabiting any district, especially one undergoing some

change in its conditions, were divided into two equal bodies, the

one half which included all the individuals best adapted by their

powers of movement for gaining subsistence, or for defending

themselves, would on an average survive in greater numbers, and

procreate more offspring than the other and less well endowed half.



  * See some good remarks to this effect by W. Stanley Jevons, "A

Deduction from Darwin's Theory," Nature 1869, p. 231.

  *(2) Latham, Man and his Migrations, 1851, p. 135.

  *(3) Messrs. Murie and Mivart in their "Anatomy of the Lemuroidea"

(Transact. Zoolog. Soc., vol. vii., 1869, pp. 96-98) say, " some

muscles are so irregular in their distribution that they cannot be

well classed in any of the above groups." These muscles differ even on

the opposite sides of the same individual.



  Man in the rudest state in which he now exists is the most

dominant animal that has ever appeared on this earth. He has spread

more widely than any other highly organised form: and all others

have yielded before him. He manifestly owes this immense superiority

to his intellectual faculties, to his social habits, which lead him to

aid and defend his fellows, and to his corporeal structure. The

supreme importance of these characters has been proved by the final

arbitrament of the battle for life. Through his powers of intellect,

articulate language has been evolved; and on this his wonderful

advancement has mainly depended. As Mr. Chauncey Wright remarks: "A

psychological analysis of the faculty of language shews, that even the

smallest proficiency in it might require more brain power than the

greatest proficiency in any other direction."* He has invented and

is able to use various weapons, tools, traps, &c., with which he

defends himself, kills or catches prey, and otherwise obtains food. He

has made rafts or canoes for fishing or crossing over to

neighbouring fertile islands. He has discovered the art of making

fire, by which hard and stringy roots can be rendered digestible,

and poisonous roots or herbs innocuous. This discovery of fire,

probably the greatest ever made by man, excepting language, dates from

before the dawn of history. These several inventions, by which man

in the rudest state has become so pre-eminent, are the direct

results of the development of his powers of observation, memory,

curiosity, imagination, and reason. I cannot, therefore, understand

how it is that Mr. Wallace*(2) maintains, that "natural selection

could only have endowed the savage with a brain a little superior to

that of an ape."



  * "Limits of Natural Selection," North American Review, Oct.,

1870, p. 295.

  *(2) Quarterly Review, April, 1869, p. 392. This subject is more

fully discussed in Mr. Wallace's Contributions to the Theory of

Natural Selection, 1870, in which all the essays referred to in this

work are re-published. The "Essay on Man," has been ably criticised by

Prof. Claparede, one of the most distinguished zoologists in Europe,

in an article published in the Bibliotheque Universelle, June, 1870.

The remark quoted in my text will surprise every one who has read

Mr. Wallace's celebrated paper on "The Origin of Human Races Deduced

from the Theory of Natural Selection," originally published in the

Anthropological Review, May, 1864, p. clviii. I cannot here resist

quoting a most just remark by Sir J. Lubbock (Prehistoric Times, 1865,

p. 479) in reference to this paper, namely, that Mr. Wallace, "with

characteristic unselfishness, ascribes it (i. e. the idea of natural

selection) unreservedly to Mr. Darwin, although, as is well known,

he struck out the idea independently, and published it, though not

with the same elaboration, at the same time."



  Although the intellectual powers and social habits of man are of

paramount importance to him, we must not underrate the importance of

his bodily structure, to which subject the remainder of this chapter

will be devoted; the development of the intellectual and social or

moral faculties being discussed in a later chapter.

  Even to hammer with precision is no easy matter, as every one who

has tried to learn carpentry will admit. To throw a stone with as true

an aim as a Fuegian in defending himself, or in killing birds,

requires the most consummate perfection in the correlated action of

the muscles of the hand, arm, and shoulder, and, further, a fine sense

of touch. In throwing a stone or spear, and in many other actions, a

man must stand firmly on his feet; and this again demands the

perfect co-adaptation of numerous muscles. To chip a flint into the

rudest tool, or to form a barbed spear or hook from a bone, demands

the use of a perfect hand; for, as a most capable judge, Mr.

Schoolcraft,* remarks, the shaping fragments of stone into knives,

lances, or arrow-heads, shews "extraordinary ability and long

practice." This is to a great extent proved by the fact that

primeval men practised a division of labour; each man did not

manufacture his own flint tools or rude pottery, but certain

individuals appear to have devoted themselves to such work, no doubt

receiving in exchange the produce of the chase. Archaeologists are

convinced that an enormous interval of time elapsed before our

ancestors thought of grinding chipped flints into smooth tools. One

can hardly doubt, that a man-like animal who possessed a hand and

arm sufficiently perfect to throw a stone with precision, or to form a

flint into a rude tool, could, with sufficient practice, as far as

mechanical skill alone is concerned, make almost anything which a

civilised man can make. The structure of the hand in this respect

may be compared with that of the vocal organs, which in the apes are

used for uttering various signal-cries, or, as in one genus, musical

cadences; but in man the closely similar vocal organs have become

adapted through the inherited effects of use for the utterance of

articulate language.



  * Quoted by Mr. Lawson Tait in his "Law of Natural Selection,"

Dublin Quarterly Journal of Medical Science, Feb., 1869. Dr. Keller is

likewise quoted to the same effect.



  Turning now to the nearest allies of men, and therefore to the

best representatives of our early progenitors, we find that the

hands of the Quadrumana are constructed on the same general pattern as

our own, but are far less perfectly adapted for diversified uses.

Their hands do not serve for locomotion so well as the feet of a

dog; as may be seen in such monkeys as the chimpanzee and orang, which

walk on the outer margins of the palms, or on the knuckles.* Their

hands, however, are admirably adapted for climbing trees. Monkeys

seize thin branches or ropes, with the thumb on one side and the

fingers and palm on the other, in the same manner as we do. They can

thus also lift rather large objects, such as the neck of a bottle,

to their mouths. Baboons turn over stones, and scratch up roots with

their hands. They seize nuts, insects, or other small objects with the

thumb in opposition to the fingers, and no doubt they thus extract

eggs and young from the nests of birds. American monkeys beat the wild

oranges on the branches until the rind is cracked, and then tear it

off with the fingers of the two hands. In a wild state they break open

hard fruits with stones. Other monkeys open mussel-shells with the two

thumbs. With their fingers they pull out thorns and burs, and hunt for

each other's parasites. They roll down stones, or throw them at

their enemies: nevertheless, they are clumsy in these various actions,

and, as I have myself seen, are quite unable to throw a stone with

precision.



  * Owen, Anatomy of Vertebrates, vol. iii., p. 71.



  It seems to me far from true that because "objects are grasped

clumsily" by monkeys, "a much less specialised organ of prehension"

would have served them* equally well with their present hands. On

the contrary, I see no reason to doubt that more perfectly constructed

hands would have been an advantage to them, provided that they were

not thus rendered less fitted for climbing trees. We may suspect

that a hand as perfect as that of man would have been

disadvantageous for climbing; for the most arboreal monkeys in the

world, namely, Ateles in America, Colobus in Africa, and Hylobates

in Asia, are either thumbless, or their toes partially cohere, so that

their limbs are converted into mere grasping hooks.*(2)



  * Quarterly Review, April, 1869, p. 392.

  *(2) In Hylobates syndactylus, as the name expresses, two of the

toes regularly cohere; and this, as Mr. Blyth informs me, is

occasionally the case with the toes of H. agilis, lar, and

leuciscus. Colobus is strictly arboreal and extraordinarily active

(Brehm, Illustriertes Thierleben, B. i., s. 50), but whether a

better climber than the species of the allied genera, I do not know.

It deserves notice that the feet of the sloths, the most arboreal

animals in the world, are wonderfully hooklike.



  As soon as some ancient member in the great series of the primates

came to be less arboreal, owing to a change in its manner of procuring

subsistence, or to some change in the surrounding conditions, its

habitual manner of progression would have been modified: and thus it

would have been rendered more strictly quadrupedal or bipedal. Baboons

frequent hilly and rocky districts, and only from necessity climb high

trees;* and they have acquired almost the gait of a dog. Man alone has

become a biped; and we can, I think, partly see how he has come to

assume his erect attitude, which forms one of his most conspicuous

characters. Man could not have attained his present dominant

position in the world without the use of his hands, which are so

admirably adapted to act in obedience to his will. Sir C. Bell*(2)

insists that "the hand supplies all instruments, and by its

correspondence with the intellect gives him universal dominion." But

the hands and arms could hardly have become perfect enough to have

manufactured weapons, or to have hurled stones and spears with a

true aim, as long as they were habitually used for locomotion and

for supporting the whole weight of the body, or, as before remarked,

so long as they were especially fitted for climbing trees. Such

rough treatment would also have blunted the sense of touch, on which

their delicate use largely depends. From these causes alone it would

have been an advantage to man to become a biped; but for many

actions it is indispensable that the arms and whole upper part of

the body should be free; and he must for this end stand firmly on

his feet. To gain this great advantage, the feet have been rendered

flat; and the great toe has been peculiarly modified, though this

has entailed the almost complete loss of its power of prehension. It

accords with the principle of the division of physiological labour,

prevailing throughout the animal kingdom, that as the hands became

perfected for prehension, the feet should have become perfected for

support and locomotion. With some savages, however, the foot has not

altogether lost its prehensile power, as shewn by their manner of

climbing trees, and of using them in other ways.*(3)



  * Brehm, Illustriertes Thierleben, B. i., s. 80.

  *(2) "The Hand," &c., Bridgewater Treatise, 1833, p. 38.

  *(3)  Haeckel has an excellent discussion on the steps by which

man became a biped: Naturliche Schopfungsgeschicte, 1868, s. 507.

Dr. Buchner (Conferences sur la Theorie Darwinienne, 1869, p. 135) has

given good cases of the use of the foot as a prehensile organ by

man; and has also written on the manner of progression of the higher

apes, to which I allude in the following paragraph: see also Owen

(Anatomy of Vertebrates, vol. iii., p. 71) on this latter subject.



  If it be an advantage to man to stand firmly on his feet and to have

his hands and arms free, of which, from his pre-eminent success in the

battle of life, there can be no doubt, then I can see no reason why it

should not have been advantageous to the progenitors of man to have

become more and more erect or bipedal. They would thus have been

better able to defend themselves with stones or clubs, to attack their

prey, or otherwise to obtain food. The best built individuals would in

the long run have succeeded best, and have survived in larger numbers.

If the gorilla and a few allied forms had become extinct, it might

have been argued, with great force and apparent truth, that an

animal could not have been gradually converted from a quadruped into a

biped, as all the individuals in an intermediate condition would

have been miserably ill-fitted for progression. But we know (and

this is well worthy of reflection) that the anthropomorphous apes

are now actually in an intermediate condition; and no one doubts

that they are on the whole well adapted for their conditions of

life. Thus the gorilla runs with a sidelong shambling gait, but more

commonly progresses by resting on its bent hands. The long-armed

apes occasionally use their arms like crutches, swinging their

bodies forward between them, and some kinds of Hylobates, without

having been taught, can walk or run upright with tolerable

quickness; yet they move awkwardly, and much less securely than man.

We see, in short, in existing monkeys a manner of progression

intermediate between that of a quadruped and a biped; but, as an

unprejudiced judge* insists, the anthropomorphous apes approach in

structure more nearly to the bipedal than to the quadrupedal type.



  * Prof. Broca, "La Constitution des vertebres caudales"; La Revue

d'Anthropologie, 1872, p. 26, (separate copy).



  As the progenitors of man became more and more erect, with their

hands and arms more and more modified for prehension and other

purposes, with their feet and legs at the same time transformed for

firm support and progression, endless other changes of structure would

have become necessary. The pelvis would have to be broadened, the

spine peculiarly curved, and the head fixed in an altered position,

all which changes have been attained by man. Prof. Schaaffhausen*

maintains that "the powerful mastoid processes of the human skull

are the result of his erect position"; and these processes are

absent in the orang, chimpanzee, &c., and are smaller in the gorilla

than in man. Various other structures, which appear connected with

man's erect position, might here have been added. It is very difficult

to decide how far these correlated modifications are the result of

natural selection, and how far of the inherited effects of the

increased use of certain parts, or of the action of one part on

another. No doubt these means of change often co-operate: thus when

certain muscles, and the crests of bone to which they are attached,

become enlarged by habitual use, this shews that certain actions are

habitually performed and must be serviceable. Hence the individuals

which performed them best, would tend to survive in greater numbers.



  * "On the Primitive Form of the Skull," translated in

Anthropological Review, Oct., 1868, p. 428. Owen (Anatomy of

Vertebrates, vol. ii., 1866, p. 551) on the mastoid processes in the

higher apes.



  The free use of the arms and hands, partly the cause and partly

the result of man's erect position, appears to have led in an indirect

manner to other modifications of structure. The early male forefathers

of man were, as previously stated, probably furnished with great

canine teeth; but as they gradually acquired the habit of using

stones, clubs, or other weapons, for fighting with their enemies or

rivals, they would use their jaws and teeth less and less. In this

case, the jaws, together with the teeth, would become reduced in size,

as we may feel almost sure from innumerable analogous cases. In a

future chapter we shall meet with a closely parallel case, in the

reduction or complete disappearance of the canine teeth in male

ruminants, apparently in relation with the development of their horns;

and in horses, in relation to their habit of fighting with their

incisor teeth and hoofs.

  In the adult male anthropomorphous apes, as Rutimeyer,* and

others, have insisted, it is the effect on the skull of the great

development of the jaw-muscles that causes it to differ so greatly

in many respects from that of man, and has given to these animals "a

truly frightful physiognomy." Therefore, as the jaws and teeth in

man's progenitors gradually become reduced in size, the adult skull

would have come to resemble more and more that of existing man. As

we shall hereafter see, a great reduction of the canine teeth in the

males would almost certainly affect the teeth of the females through

inheritance.



  * Die Grenzen der Thierwelt, eine Betrachtung zu Darwin's Lehre,

1868, s. 51.



  As the various mental faculties gradually developed themselves the

brain would almost certainly become larger. No one, I presume,

doubts that the large proportion which the size of man's brain bears

to his body, compared to the same proportion in the gorilla or

orang, is closely connected with his higher mental powers. We meet

with closely analogous facts with insects, for in ants the cerebral

ganglia are of extraordinary dimensions, and in all the Hymenoptera

these ganglia are many times larger than in the less intelligent

orders, such as beetles.* On the other hand, no one supposes that

the intellect of any two animals or of any two men can be accurately

gauged by the cubic contents of their skulls. It is certain that there

may be extraordinary mental activity with an extremely small

absolute mass of nervous matter: thus the wonderfully diversified

instincts, mental powers, and affections of ants are notorious, yet

their cerebral ganglia are not so large as the quarter of a small

pin's head. Under this point of view, the brain of an ant is one of

the most marvellous atoms of matter in the world, perhaps more so than

the brain of a man.



  * Dujardin, Annales des Sciences Nat., 3rd series, Zoolog., tom.

xiv., 1850, p. 203. See also Mr. Lowne, Anatomy and Phys. of the Musca

vomitoria, 1870, p. 14. My son, Mr. F. Darwin, dissected for me the

cerebral ganglia of the Formica rufa.



  The belief that there exists in man some close relation between

the size of the brain and the development of the intellectual

faculties is supported by the comparison of the skulls of savage and

civilised races, of ancient and modern people, and by the analogy of

the whole vertebrate series. Dr. J. Barnard Davis has proved,* by many

careful measurements, that the mean internal capacity of the skull

in Europeans is 92.3 cubic inches; in Americans 87.5; in Asiatics

87.1; and in Australians only 81.9 cubic inches. Professor Broca*(2)

found that the nineteenth century skulls from graves in Paris were

larger than those from vaults of the twelfth century, in the

proportion of 1484 to 1426; and that the increased size, as

ascertained by measurements, was exclusively in the frontal part of

the skull- the seat of the intellectual faculties. Prichard is

persuaded that the present inhabitants of Britain have "much more

capacious braincases" than the ancient inhabitants. Nevertheless, it

must be admitted that some skulls of very high antiquity, such as

the famous one of Neanderthal, are well developed and capacious.*(3)

With respect to the lower animals, M. E. Lartet,*(4) by comparing

the crania of tertiary and recent mammals belonging to the same

groups, has come to the remarkable conclusion that the brain is

generally larger and the convolutions are more complex in the more

recent forms. On the other hand, I have shewn*(5) that the brains of

domestic rabbits are considerably reduced in bulk, in comparison

with those of the wild rabbit or hare; and this may be attributed to

their having been closely confined during many generations, so that

they have exerted their intellect, instincts, senses and voluntary

movements but little.



  * Philosophical Transactions, 1869, p. 513.

  *(2) "Les Selections," M. P. Broca, Revue d'Anthropologie,, 1873;

see also, as quoted in C. Vogt's Lectures on Man, Engl. translat.,

1864, pp. 88, 90. Prichard, Physical History of Mankind, vol. i.,

1838, p. 305.

  *(3) In the interesting article just referred to, Prof. Broca has

well remarked, that in civilised nations, the average capacity of

the skull must be lowered by the preservation of a considerable number

of individuals, weak in mind and body, who would have been promptly

eliminated in the savage state. On the other hand, with savages, the

average includes only the more capable individuals, who have been able

to survive under extremely hard conditions of life. Broca thus

explains the otherwise inexplicable fact, that the mean capacity of

the skull of the ancient troglodytes of Lozere is greater than that of

modern Frenchmen.

  *(4) Comptes-rendus des Sciences, &c., June 1, 1868.

  *(5) The Variation of Animals and Plants under Domestication, vol.

i., pp. 124-129.



  The gradually increasing weight of the brain and skull in man must

have influenced the development of the supporting spinal column,

more especially whilst he was becoming erect. As this change of

position was being brought about, the internal pressure of the brain

will also have influenced the form of the skull; for many facts shew

how easily the skull is thus effected. Ethnologists believe that it is

modified by the kind of cradle in which infants sleep. Habitual spasms

of the muscles, and a cicatrix from a severe burn, have permanently

modified the facial bones. In young persons whose heads have become

fixed either sideways or backwards, owing to disease, one of the two

eyes has changed its position, and the shape of the skull has been

altered apparently by the pressure of the brain in a new direction.* I

have shewn that with long-eared rabbits even so trifling a cause as

the lopping forward of one ear drags forward almost every bone of

the skull on that side; so that the bones on the opposite side no

longer strictly correspond. Lastly, if any animal were to increase

or diminish much in general size, without any change in its mental

powers, or if the mental powers were to be much increased or

diminished, without any great change in the size of the body, the

shape of the skull would almost certainly be altered. I infer this

from my observations on domestic rabbits, some kinds of which have

become very much larger than the wild animal, whilst others have

retained nearly the same size, but in both cases the brain has been

much reduced relatively to the size of the body. Now I was at first

much surprised on finding that in all these rabbits the skull had

become elongated or dolichocephalic; for instance, of two skulls of

nearly equal breadth, the one from a wild rabbit and the other from

a large domestic kind, the former was 3.15 and the latter 4.3 inches

in length.*(2) One of the most marked distinctions in different

races of men is that the skull in some is elongated, and in others

rounded; and here the explanation suggested by the case of the rabbits

may hold good; for Welcker finds that short "men incline more to

brachycephaly, and tall men to dolichocephaly";*(3) and tall men may

be compared with the larger and longer-bodied rabbits, all of which

have elongated skulls or are dolichocephalic.



  * Schaaffhausen gives from Blumenbach and Busch, the cases of the

spasms and cicatrix in Anthropological Review, Oct., 1868, p. 420. Dr.

Jarrold (Anthropologia, 1808, pp. 115, 116) adduces from Camper and

from his own observations, cases of the modification of the skull from

the head being fixed in an unnatural position. He believes that in

certain trades, such as that of a shoemaker, where the head is

habitually held forward, the forehead becomes more rounded and

prominent.

  *(2) Variation of Animals and Plants under Domestication, vol. i.,

p. 117, on the elongation of the skull; p. 119, on the effect of the

lopping of one ear.

  *(3) Quoted by Schaaffhausen, in Anthropological Review, Oct., 1868,

p. 419.



  From these several facts we can understand, to a certain extent, the

means by which the great size and more or less rounded form of the

skull have been acquired by man; and these are characters eminently

distinctive of him in comparison with the lower animals.

  Another most conspicuous difference between man and the lower

animals is the nakedness of his skin. Whales and porpoises

(Cetacea), dugongs (Sirenia) and the hippopotamus are naked; and

this may be advantageous to them for gliding through the water; nor

would it be injurious to them from the loss of warmth, as the species,

which inhabit the colder regions, are protected by a thick layer of

blubber, serving the same purpose as the fur of seals and otters.

Elephants and rhinoceroses are almost hairless; and as certain extinct

species, which formerly lived under an arctic climate, were covered

with long wool or hair, it would almost appear as if the existing

species of both genera had lost their hairy covering from exposure

to heat. This appears the more probable, as the elephants in India

which live on elevated and cool districts are more hairy* than those

on the lowlands. May we then infer that man became divested of hair

from having aboriginally inhabited some tropical land? That the hair

is chiefly retained in the male sex on the chest and face, and in both

sexes at the junction of all four limbs with the trunk, favours this

inference- on the assumption that the hair was lost before man

became erect; for the parts which now retain most hair would then have

been most protected from the heat of the sun. The crown of the head,

however, offers a curious exception, for at all times it must have

been one of the most exposed parts, yet it is thickly clothed with

hair. The fact, however, that the other members of the order of

primates, to which man belongs, although inhabiting various hot

regions, are well clothed with hair, generally thickest on the upper

surface,*(2) is opposed to the supposition that man became naked

through the action of the sun. Mr. Belt believes*(3) that within the

tropies it is an advantage to man to be destitute of hair, as he is

thus enabled to free himself of the multitude of ticks (acari) and

other parasites, with which he is often infested, and which

sometimes cause ulceration. But whether this evil is of sufficient

magnitude to have led to the denudation of his body through natural

selection, may be doubted, since none of the many quadrupeds

inhabiting the tropics have, as far as I know, acquired any

specialised means of relief. The view which seems to me the most

probable is that man, or rather primarily woman, became divested of

hair for ornamental purposes, as we shall see under Sexual

Selection; and, according to this belief, it is not surprising that

man should differ so greatly in hairiness from all other primates, for

characters, gained through sexual selection, often differ to an

extraordinary degree in closely related forms.



  * Owen, Anatomy of Vertebrates, vol. iii., p. 619.

  *(2) Isidore Geoffroy St-Hilaire remarks (Histoire Nat. Generale,

tom. ii., 1859, pp. 215-217) on the head of man being covered with

long hair; also on the upper surfaces of monkeys and of other

mammals being more thickly clothed than the lower surfaces. This has

likewise been observed by various authors. Prof. P. Gervais

(Histoire Nat. des Mammiferes, tom. i., 1854, p. 28), however,

states that in the gorilla the hair is thinner on the back, where it

is partly rubbed off, than on the lower surface.

  *(3) The Naturalist in Nicaragua, 1874, p. 209. As some confirmation

of Mr. Belt's view, I may quote the following passage from Sir W.

Denison (Varieties of Vice-Regal Life, vol. i., 1870, p. 440): "It

is said to be a practice with the Australians, when the vermin get

troublesome, to singe themselves."



  According to a popular impression, the absence of a tail is

eminently distinctive of man; but as those apes which come nearest

to him are destitute of this organ, its disappearance does not

relate exclusively to man. The tail often differs remarkably in length

within the same genus: thus in some species of Macacus it is longer

than the whole body, and is formed of twenty-four vertebrae; in others

it consists of a scarcely visible stump, containing only three or four

vertebrae. In some kinds of baboons there are twenty-five, whilst in

the mandrill there are ten very small stunted caudal vertebrae, or,

according to Cuvier,* sometimes only five. The tail, whether it be

long or short, almost always tapers towards the end; and this, I

presume, results from the atrophy of the terminal muscles, together

with their arteries and nerves, through disuse, leading to the atrophy

of the terminal bones. But no explanation can at present be given of

the great diversity which often occurs in its length. Here, however,

we are more specially concerned with the complete external

disappearance of the tail. Professor Broca has recently shewn*(2) that

the tail in all quadrupeds consists of two portions, generally

separated abruptly from each other; the basal portion consists of

vertebrae, more or less perfectly channelled and furnished with

apophyses like ordinary vertebrae; whereas those of the terminal

portion are not channelled, are almost smooth, and scarcely resemble

true vertebrae. A tail, though not externally visible, is really

present in man and the anthropomorphous apes, and is constructed on

exactly the same pattern in both. In the terminal portion the

vertabrae, constituting the os coccyx, are quite rudimentary, being

much reduced in size and number. In the basal portion, the vertebrae

are likewise few, are united firmly together, and are arrested in

development; but they have been rendered much broader and flatter than

the corresponding vertebrae in the tails of other animals: they

constitute what Broca calls the accessory sacral vertebrae. These

are of functional importance by supporting certain internal parts

and in other ways; and their modification is directly connected with

the erect or semi-erect attitude of man and the anthropomorphous apes.

This conclusion is the more trustworthy, as Broca formerly held a

different view, which he has now abandoned. The modification,

therefore, of the basal caudal vertebrae in man and the higher apes

may have been effected, directly or indirectly, through natural

selection.



  * Mr. St. George Mivart, Proc. Zoolog. Soc., 1865, pp. 562, 583. Dr.

J. E. Gray, Cat. Brit. Mus: " Skeletons." Owen, Anatomy of

Vertebrates, vol. ii., p. 517. Isidore Geoffroy, Hist. Nat. Gen., tom.

ii., p. 244.

  *(2) Revue d'Anthropologie, 1872; "La Constitution des vertebres

caudales."



  But what are we to say about the rudimentary and variable

vertebrae of the terminal portion of the tail, forming the os

coccyx? A notion which has often been, and will no doubt again be

ridiculed, namely, that friction has had something to do with the

disappearance of the external portion of the tail, is not so

ridiculous as it at first appears. Dr. Anderson* states that the

extremely short tail of Macacus brunneus is formed of eleven

vertebrae, including the imbedded basal ones. The extremity is

tendinous and contains no vertebrae; this is succeeded by five

rudimentary ones, so minute that together they are only one line and a

half in length, and these are permanently bent to one side in the

shape of a hook. The free part of the tail, only a little above an

inch in length, includes only four more small vertebrae. This short

tail is carried erect; but about a quarter of its total length is

doubled on to itself to the left; and this terminal part, which

includes the hook-like portion, serves "to fill up the interspace

between the upper divergent portion of the callosities"; so that the

animal sits on it, and thus renders it rough and callous. Dr. Anderson

thus sums up his observations: "These facts seem to me to have only

one explanation; this tail, from its short size, is in the monkey's

way when it sits down, and frequently becomes placed under the

animal while it is in this attitude; and from the circumstance that it

does not extend beyond the extremity of the ischial tuberosities, it

seems as if the tail originally had been bent round by the will of the

animal, into the interspace between the callosities, to escape being

pressed between them and the ground, and that in time the curvature

became permanent, fitting in of itself when the organ happens. to be

sat upon." Under these circumstances it is not surprising that the

surface of the tail should have been roughened and rendered callous,

and Dr. Murie,*(2) who carefully observed this species in the

Zoological Gardens, as well as three other closely allied forms with

slightly longer tails, says that when the animal sits down, the tail

"is necessarily thrust to one side of the buttocks; and whether long

or short its root is consequently liable to be rubbed or chafed." As

we now have evidence that mutilations occasionally produce an

inherited effect,*(3) it is not very improbable that in short-tailed

monkeys, the projecting part of the tail, being functionally

useless, should after many generations have become rudimentary and

distorted, from being continually rubbed and chafed. We see the

projecting part in this condition in the Macacus brunneus, and

absolutely aborted in the M. ecaudatus and in several of the higher

apes. Finally, then, as far as we can judge, the tail has

disappeared in man and the anthropomorphous apes, owing to the

terminal portion having been injured by friction during a long lapse

of time; the basal and embedded portion having been reduced and

modified, so as to become suitable to the erect or semi-erect

position.



  * Proceedings Zoological Society, 1872, p. 210.

  *(2) Proceedings Zoological Society, 1872, p. 786.

  *(3) I allude to Dr. Brown-Sequard's observations on the transmitted

effect of an operation causing epilepsy in guinea-pigs, and likewise

more recently on the analogous effects of cutting the sympathetic

nerve in the neck. I shall hereafter have occasion to refer to Mr.

Salvin's interesting case of the apparently inherited effects of

motmots biting off the barbs of their own tail-feathers. See also on

the general subject Variation of Animals and Plants under

Domestication, vol. ii., pp. 22-24.



  I have now endeavoured to shew that some of the most distinctive

characters of man have in all probability been acquired, either

directly, or more commonly indirectly, through natural selection. We

should bear in mind that modifications in structure or constitution

which do not serve to adapt an organism to its habits of life, to

the food which it consumes, or passively to the surrounding

conditions, cannot have been thus acquired. We must not, however, be

too confident in deciding what modifications are of service to each

being: we should remember how little we know about the use of many

parts, or what changes in the blood or tissues may serve to fit an

organism for a new climate or new kinds of food. Nor must we forget

the principle of correlation, by which, as Isidore Geoffroy has

shewn in the case of man, many strange deviations of structure are

tied together. Independently of correlation, a change in one part

often leads, through the increased or decreased use of other parts, to

other changes of a quite unexpected nature. It is also well to reflect

on such facts, as the wonderful growth of galls on plants caused by

the poison of an insect, and on the remarkable changes of colour in

the plumage of parrots when fed on certain fishes, or inoculated

with the poison of toads;* for we can thus see that the fluids of

the system, if altered for some special purpose, might induce other

changes. We should especially bear in mind that modifications acquired

and continually used during past ages for some useful purpose, would

probably become firmly fixed, and might be long inherited.



  * The Variation of Animals and Plants under Domestication, vol. ii.,

pp. 280, 282.



  Thus a large yet undefined extension may safely be given to the

direct and indirect results of natural selection; but I now admit,

after reading the essay by Nageli on plants, and the remarks by

various authors with respect to animals, more especially those

recently made by Professor Broca, that in the earlier editions of my

Origin of Species I perhaps attributed too much to the action of

natural selection or the survival of the fittest. I have altered the

fifth edition of the Origin so as to confine my remarks to adaptive

changes of structure; but I am convinced, from the light gained during

even the last few years, that very many structures which now appear to

us useless, will hereafter be proved to be useful, and will

therefore come within the range of natural selection. Nevertheless,

I did not formerly consider sufficiently the existence of

structures, which, as far as we can at present judge, are neither

beneficial nor injurious; and this I believe to be one of the greatest

oversights as yet detected in my work. I may be permitted to say, as

some excuse, that I had two distinct objects in view; firstly, to shew

that species had not been separately created, and secondly, that

natural selection had been the chief agent of change, though largely

aided by the inherited effects of habit, and slightly by the direct

action of the surrounding conditions. I was not, however, able to

annul the influence of my former belief, then almost universal, that

each species had been purposely created; and this led to my tacit

assumption that every detail of structure, excepting rudiments, was of

some special, though unrecognised, service. Any one with this

assumption in his mind would naturally extend too far the action of

natural selection, either during past or present times. Some of

those who admit the principle of evolution, but reject natural

selection, seem to forget, when criticising my book, that I had the

above two objects in view; hence if I have erred in giving to

natural selection great power, which I am very far from admitting,

or in having exaggerated its power, which is in itself probable, I

have at least, as I hope, done good service in aiding to overthrow the

dogma of separate creations.

  It is, as I can now see, probable that all organic beings, including

man, possess peculiarities of structure, which neither are now, nor

were formerly of any service to them, and which, therefore, are of

no physiological importance. We know not what produces the

numberless slight differences between the individuals of each species,

for reversion only carries the problem a few steps backwards, but each

peculiarity must have had its efficient cause. If these causes,

whatever they may be, were to act more uniformly and energetically

during a lengthened period (and against this no reason can be

assigned), the result would probably be not a mere slight individual

difference, but a well-marked and constant modification, though one of

no physiological importance. Changed structures, which are in no way

beneficial, cannot be kept uniform through natural selection, though

the injurious will be thus eliminated. Uniformity of character

would, however, naturally follow from the assumed uniformity of the

exciting causes, and likewise from the free intercrossing of many

individuals. During successive periods, the same organism might in

this manner acquire successive modifications, which would be

transmitted in a nearly uniform state as long as the exciting causes

remained the same and there was free intercrossing. With respect to

the exciting causes we can only say, as when speaking of so-called

spontaneous variations, that they relate much more closely to the

constitution of the varying organism, than to the nature of the

conditions to which it has been subjected.



  Conclusion.- In this chapter we have seen that as man at the present

day is liable, like every other animal, to multiform individual

differences or slight variations, so no doubt were the early

progenitors of man; the variations being formerly induced by the

same general causes, and governed by the same general and complex laws

as at present. As all animals tend to multiply beyond their means of

subsistence, so it must have been with the progenitors of man; and

this would inevitably lead to a struggle for existence and to

natural selection. The latter process would be greatly aided by the

inherited effects of the increased use of parts, and these two

processes would incessantly react on each other. It appears, also,

as we shall hereafter see, that various unimportant characters have

been acquired by man through sexual selection. An unexplained residuum

of change must be left to the assumed uniform action of those

unknown agencies, which occasionally induce strongly marked and abrupt

deviations of structure in our domestic productions.

  Judging from the habits of savages and of the greater number of

the Quadrumana, primeval men, and even their ape-like progenitors,

probably lived in society. With strictly social animals, natural

selection sometimes acts on the individual, through the preservation

of variations which are beneficial to the community. A community which

includes a large number of well-endowed individuals increases in

number, and is victorious over other less favoured ones; even although

each separate member gains no advantage over the others of the same

community. Associated insects have thus acquired many remarkable

structures, which are of little or no service to the individual,

such as the pollen-collecting apparatus, or the sting of the

worker-bee, or the great jaws of soldier-ants. With the higher

social animals, I am not aware that any structure has been modified

solely for the good of the community, though some are of secondary

service to it. For instance, the horns of ruminants and the great

canine teeth of baboons appear to have been acquired by the males as

weapons for sexual strife, but they are used in defence of the herd or

troop. In regard to certain mental powers the case, as we shall see in

the fifth chapter, is wholly different; for these faculties have

been chiefly, or even exclusively, gained for the benefit of the

community, and the individuals thereof have at the same time gained an

advantage indirectly.



  It has often been objected to such views as the foregoing, that

man is one of the most helpless and defenceless creatures in the

world; and that during his early and less well-developed condition, he

would have been still more helpless. The Duke of Argyll, for instance,

insists* that "the human frame has diverged from the structure of

brutes, in the direction of greater physical helplessness and

weakness. That is to say, it is a divergence which of all others it is

most impossible to ascribe to mere natural selection." He adduces

the naked and unprotected state of the body, the absence of great

teeth or claws for defence, the small strength and speed of man, and

his slight power of discovering food or of avoiding danger by smell.

To these deficiencies there might be added one still more serious,

namely, that he cannot climb quickly, and so escape from enemies.

The loss of hair would not have been a great injury to the inhabitants

of a warm country. For we know that the unclothed Fuegians can exist

under a wretched climate. When we compare the defenceless state of man

with that of apes, we must remember that the great canine teeth with

which the latter are provided, are possessed in their full development

by the males alone, and are chiefly used by them for fighting with

their rivals; yet the females, which are not thus provided, manage

to survive.



  * Primeval Man, 1869, p. 66.



  In regard to bodily size or strength, we do not know whether man

is descended from some small species, like the chimpanzee, or from one

as powerful as the gorilla; and, therefore, we cannot say whether

man has become larger and stronger, or smaller and weaker, than his

ancestors. We should, however, bear in mind that an animal

possessing great size, strength, and ferocity, and which, like the

gorilla, could defend itself from all enemies, would not perhaps

have become social: and this would most effectually have checked the

acquirement of the higher mental qualities, such as sympathy and the

love of his fellows. Hence it might have been an immense advantage

to man to have sprung from some comparatively weak creature.

  The small strength and speed of man, his want of natural weapons,

&c., are more than counterbalanced, firstly, by his intellectual

powers, through which he has formed for himself weapons, tools, &c.,

though still remaining in a barbarous state, and, secondly, by his

social qualities which lead him to give and receive aid from his

fellow-men. No country in the world abounds in a greater degree with

dangerous beasts than southern Africa; no country presents more

fearful physical hardships than the arctic regions; yet one of the

puniest of races, that of the bushmen, maintains itself in southern

Africa, as do the dwarfed Esquimaux in the arctic regions. The

ancestors of man were, no doubt, inferior in intellect, and probably

in social disposition, to the lowest existing savages; but it is quite

conceivable that they might have existed, or even flourished, if

they had advanced in intellect, whilst gradually losing their

brute-like powers such as that of climbing trees, &c. But these

ancestors would not have been exposed to any special danger, even if

far more helpless and defenceless than any existing savages, had

they inhabited some warm continent or large island, such as Australia,

New Guinea, or Borneo, which is now the home of the orang. And natural

selection arising from the competition of tribe with tribe, in some

such large area as one of these, together with the inherited effects

of habit, would, under favourable conditions, have sufficed to raise

man to his present high position in the organic scale.


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