CHAPTER IV.

ON THE MANNER OF DEVELOPMENT OF MAN FROM SOME LOWER FORM.

Variability of body and mind in man--Inheritance--Causes of

variability--Laws of variation the same in man as in the lower

animals--Direct action of the conditions of life--Effects of

the increased use and disuse of parts--Arrested

development--Reversion--Correlated variation--Rate of

increase--Checks to increase--Natural selection--Man the most

dominant animal in the world--Importance of his corporeal

structure--The causes which have led to his becoming

erect--Consequent changes of structure--Decrease in size of the

canine teeth--Increased size and altered shape of the

skull--Nakedness--Absence of a tail--Defenceless condition of

man.

We have seen in the first chapter that the homological structure of man,

his embryological development and the rudiments which he still retains,

all declare in the plainest manner that he is descended from some lower

form. The possession of exalted mental powers is no insuperable

objection to this conclusion. In order that an ape-like creature should

have been transformed into man, it is necessary that this early form, as

well as many successive links, should all have varied in mind and body.

It is impossible to obtain direct evidence on this head; but if it can

be shewn that man now varies--that his variations are induced by the

same general causes, and obey the same general laws, as in the case of

the lower animals--there can be little doubt that the preceding

intermediate links varied in a like manner. The variations at each

successive stage of descent must, also, have been in some manner

accumulated and fixed.

The facts and conclusions to be given in this chapter relate almost

exclusively to the probable means by which the transformation of man has

been effected, as far as his bodily structure is concerned. The

following chapter will be devoted to the development of his intellectual

and moral faculties. But the present discussion likewise bears on the

origin of the different races or species of mankind, whichever term may

be preferred.

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.[140]

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.[141] An eminent dentist assures me that there is nearly as much

diversity in the teeth, as in the features. The chief arteries so

frequently run in abnormal courses, that it has been found useful for

surgical purposes to calculate from 12,000 corpses how often each

course prevails.[142] The muscles are eminently variable: thus those of

the foot were found by Prof. Turner[143] not to be strictly alike in any

two out of fifty bodies; and in some the deviations were considerable.

Prof. Turner adds that the power of performing the appropriate movements

must have been modified in accordance with the several deviations. Mr.

J. Wood has recorded[144] the occurrence of 295 muscular variations in

thirty-six subjects, and in another set of the same number no less than

558 variations, reckoning both sides of the body 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[145] no less than

twenty distinct variations in the _palmaris accessorius_.

The famous old anatomist, Wolff,[146] 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.

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, as has been illustrated by a few examples in

the last chapter. 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

under confinement 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.[147]

I have elsewhere[148] 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[149]

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 the

same families.

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 with 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 their conditions. The different races

of man resemble in this respect 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, the members of which belong to different grades of

rank and follow different occupations, presenting a greater range of

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

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

to exist.[150] It is nevertheless an error to speak of man, even if we

look only to the conditions to which he has been subjected, as "far more

domesticated"[151] than any other animal. Some savage races, such as

the Australians, are not exposed to more diversified conditions than are

many species which have very wide ranges. In another and much more

important respect, man differs widely from any strictly domesticated

animal; for his breeding has not been controlled, either through

methodical or unconscious selection. No race or body of men has been so

completely subjugated by other men, that certain individuals have been

preserved and thus unconsciously selected, from being in some way more

useful 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

with their tall wives.

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 characters are

affected 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.[152] 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 may be seen

in Isidore Geoffroy St.-Hilaire's great work.[153] This is a necessary

consequence of the same laws of change prevailing throughout the animal

kingdom. 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 shewn 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 instances 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;[154] but several are so important for us, that they must be

treated at considerable length.

_The direct and definite action of changed conditions._--This is a most

perplexing subject. It cannot be denied that changed conditions produce

some effect, 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

recorded.[155] 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 manner of life delays

growth, as shewn "by the great difference between the statures of

soldiers and sailors at the ages of 17 and 18 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 need of the comforts of life.

This latter conclusion is directly opposed to that arrived at by

Villerme from the statistics 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,[156] 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."[157]

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, as the lungs and kidneys are brought into

fuller activity under a low temperature, and the liver and skin under a

high one.[158] 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.

_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 acting

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.[159] Different occupations habitually followed lead to changed

proportions in various parts of the body. Thus it was clearly

ascertained by the United States Commission[160] 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. The girth of the neck and the depth of the instep

are greater, whilst the circumference of the chest, waist, and hips is

less in sailors than in soldiers.

Whether the several foregoing modifications would become hereditary, if

the same habits of life were followed during many generations, is not

known, but is probable. Rengger[161] 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 other

analogous cases. According to Cranz,[162] 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

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.[163] From the

correlation which exists, at least in some cases,[164] 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 civilised men than in hard-working men or

savages, is certain. But with savages, as Mr. Herbert Spencer[165] 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;[166] and it can hardly be doubted that this is due to the

inherited effects of pressure during a long series of generations.

It is familiar to every one that watchmakers and engravers are liable to

become short-sighted, whilst sailors and especially savages are

generally long-sighted. Short-sight and long-sight certainly tend to be

inherited.[167] 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[168] 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 no doubt 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.[169]

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

d'Orbigny states[170] 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 ten and fifteen thousand feet; and he informs me[171]

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 fore-arm. 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.

These men are so thoroughly acclimatised to their cold and lofty abode,

that when formerly carried down by the 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 but in a less

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

memoir. From these valuable 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.[172]

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._--Arrested development differs from arrested

growth, as parts in the former state continue to grow whilst still

retaining their early condition. Various monstrosities come under this

head, and some are known to be occasionally inherited, as a

cleft-palate. It will suffice for our purpose to refer to the arrested

brain-development of microcephalous idiots, as described in Vogt's great

memoir.[173] 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 gamboling 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.

_Reversion._--Many of the cases to be here given might have been

introduced under the last heading. Whenever 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, we may in one sense consider it as a case of reversion. The lower

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

group was probably constructed; and it is hardly credible that a part

arrested at an early phase of embryonic development should be enabled to

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

it had acquired this power of continued growth 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 heading 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 present in the normal human embryo, they become developed in an

abnormal manner, though this manner of development is proper to the

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

by the following illustrations.

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, showing no signs of doubleness except 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 so high in the scale as in the lower apes, and their

allies the 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.[174] 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 could 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 long-lost dormant structures are

called back into existence, might serve as the guide for the full

development of the organ, even after the lapse of an enormous interval

of time.

Professor Canestrini,[175] after discussing the foregoing and various

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

adduces, as another instance, the malar bone, which, in some of the

Quadrumana and other mammals, normally consists of two portions. This is

its condition in the two-months-old human foetus; and thus it

sometimes remains, through arrested development, in man when adult, more

especially in the lower prognathous races. Hence Canestrini concludes

that some ancient progenitor of man must have possessed this bone

normally divided into two portions, which subsequently 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.

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

foregoing, have been advanced by different authors[176] 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.[177]

In man the canine teeth are perfectly efficient instruments for

mastication. But their true canine character, as Owen[178] 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[179]

observes, with the canine teeth projecting considerably beyond the

others in the same manner, but in a less degree, as in the

anthropomorphous apes. In these cases, open spaces between the teeth in

the one jaw are left for the reception of the canines belonging to the

opposite jaw. An interspace of this kind in a Kaffir skull, figured by

Wagner, is surprisingly wide.[180] Considering how few ancient skulls

have been examined in comparison with 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 enormous.[181]

The males alone of the anthropomorphous apes 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 that women sometimes have, as I have been assured, 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 progenitors 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)[182] so as to expose them ready for

action, like a dog prepared to fight.

Many muscles are occasionally developed in man, which are proper to the

Quadrumana or other mammals. Professor Vlacovich[183] examined forty

male subjects, and found a muscle, called by him the ischiopubic, in

nineteen of them; in three others there was a ligament which represented

this muscle; and in the remaining eighteen no trace of it. Out of thirty

female subjects this muscle was developed on both sides in only two, 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 principle of the descent of man from some lower form,

its presence can be understood; 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.

Mr. J. Wood, in his valuable series of papers,[184] has minutely

described a vast number of muscular variations in man, which resemble

normal structures in the lower animals. Looking only to the muscles

which closely resemble those regularly present in our nearest allies,

the Quadrumana, they 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.[185] 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." The hands and arms of man are

eminently characteristic structures, but their muscles are extremely

liable to vary, so as to resemble the corresponding muscles in the lower

animals.[186] Such resemblances are either complete and perfect or

imperfect, yet in this latter case 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

cases, makes the following pregnant remark: "Notable departures from the

ordinary type of the 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."[187]

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, in no less

than seven of his muscles, certain apes, 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 thousands, of generations.

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 in either chapter. 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 rudimental in man, as the os coccyx in both sexes and

the mammae in the male sex, are always present; whilst others, such as

the supra-condyloid foramen, only occasionally appear, and therefore

might have been introduced under the head of reversion. These several

reversionary, as well as the strictly rudimentary, structures reveal the

descent of man from some lower form in an unmistakeable 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 hair, colour and

constitution, are more or less correlated.[188] Professor Schaaffhausen

first drew attention to the relation apparently existing between a

muscular frame and strongly-pronounced supra-orbital ridges, which are

so characteristic of the lower races of man.

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 they

appear, owing to our ignorance, 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.[189]

_Rate of Increase._--Civilised populations have been known under

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

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

might occur in a little over twelve years.[190] At the former rate the

present population of the United States, namely, 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 the above 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 at all

ages, and from various diseases, of the inhabitants of crowded and

miserable houses. 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 not to any great extent with the extremely poor classes.

There is 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 for a prolonged period; but it is highly probable that

savages, who often suffer much hardship, and who do not obtain so much

nutritious food as civilised men, would be actually less prolific. I

have shewn in a former work,[191] 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 rendered very fat, and that most plants when suddenly removed

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.[192]

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 they have

increased, as shewn by Mr. Hunter,[193] 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 show 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 about,

and their infants, as I was assured in Australia, 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 hardly 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 must suffer much from

the larger beasts of prey. Even in India, districts have been

depopulated by the ravages of tigers.

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[194] 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.

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 savages at the present time. Our early

semi-human progenitors would not have practised infanticide, for the

instincts of the lower animals are never so perverted as to lead them

regularly to destroy their own offspring. 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 may have

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

horses and cattle, which are not highly prolific animals, when first

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

slowest breeder of all known animals, namely the elephant, 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.

_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 migrations,[195]

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.[196] 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,[197] to

incessant variability. If then the ape-like progenitors of man which

inhabited 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 number and procreate more offspring than the other

and less well endowed half.

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

animal that has ever appeared on the 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, 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. 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 on which to fish

or cross 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 last discovery,

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

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

the rudest state has become so preeminent, are the direct result of the

development of his powers of observation, memory, curiosity,

imagination, and reason. I cannot, therefore, understand how it is that

Mr. Wallace[198] maintains, that "natural selection could only have

endowed the savage with a brain a little superior to that of an ape."

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 will be discussed in the following 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 can 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, not to mention 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 coadaptation 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,[199] remarks, the shaping

fragments of stone into knives, lances, or arrow-heads, shews

"extraordinary ability and long practice." We have evidence of this in

primeval men having 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. 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, it can hardly be

doubted, with sufficient practice make almost anything, as far as

mechanical skill alone is concerned, 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 species, musical cadences; but in man

closely similar vocal organs have become adapted through the inherited

effects of use for the utterance of articulate language.

Turning now to the nearest allies of man, and therefore to the best

representatives of our early progenitors, we find that the hands in the

Quadrumana are constructed on the same general pattern as in us, but are

far less perfectly adapted for diversified uses. Their hands do not

serve so well as the feet of a dog for locomotion; as may be seen in

those monkeys which walk on the outer margins of the palms, or on the

backs of their bent fingers, as in the chimpanzee and orang.[200] 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 side, in the same manner as we do. They can thus also

carry 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 the

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. Other monkeys open mussel-shells with the two

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

each other's parasites. In a state of nature they break open hard fruits

with the aid of stones. They roll down stones or throw them at their

enemies; nevertheless, they perform these various actions clumsily, and

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

precision.

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[201] as well as their present hands. On the contrary, I see

no reason to doubt that a more perfectly constructed hand would have

been an advantage to them, provided, and it is important to note this,

that their hands had not thus been rendered less well adapted for

climbing trees. We may suspect that a perfect hand would have been

disadvantageous for climbing; as the most arboreal monkeys in the world,

namely Ateles in America and Hylobates in Asia, either have their thumbs

much reduced in size and even rudimentary, or their fingers

partially coherent, so that their hands are converted into mere

grasping-hooks.[202]

As soon as some ancient member in the great series of the Primates came,

owing to a change in its manner of procuring subsistence, or to a change

in the conditions of its native country, to live somewhat less on trees

and more on the ground, its manner of progression would have been

modified; and in this case it would have had to become either more

strictly quadrupedal or bipedal. Baboons frequent hilly and rocky

districts, and only from necessity climb up high trees;[203] 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 the most conspicuous differences between

him and his nearest allies. 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. As Sir C. Bell[204]

insists "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 long as they were especially well adapted, as previously

remarked, 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 have

become a biped; but for many actions it is almost necessary that both

arms and the 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 peculiarly modified,

though this has entailed the loss of the power of prehension. It accords

with the principle of the division of physiological labour, which

prevails 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.[205]

If it be an advantage to man to have his hands and arms free and to

stand firmly on his feet, of which there can be no doubt from his

preeminent success in the battle of life, 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 have defended themselves with stones or clubs, or to have

attacked their prey, or otherwise obtained food. The best constructed

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 several kinds of apes are now actually

in this 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, with existing monkeys various gradations

between a form of progression strictly like that of a quadruped and that

of a biped or man.

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 modified for firm support and

progression, endless other changes of structure would have been

necessary. The pelvis would have had to be made broader, the spine

peculiarly curved and the head fixed in an altered position, and all

these changes have been attained by man. Prof. Schaaffhausen[206]

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 might here have been specified, which appear

connected with man's erect position. It is very difficult to decide how

far all 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 act and react on each other: thus when certain muscles,

and the crests of bone to which they are attached, become enlarged by

habitual use, this shews that certain fictions are habitually performed

and must be serviceable. Hence the individuals which performed them

best, would tend to survive in greater numbers.

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 progenitors

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, they would have used

their jaws and teeth less and less. In this case, the jaws, together

with the teeth, would have become reduced in size, as we may feel 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 with their habit

of fighting with their incisor teeth and hoofs.

In the adult male anthropomorphous apes, as Ruetimeyer,[207] and others

have insisted, it is precisely the effect which the jaw-muscles by their

great development have produced on the skull, that causes it to differ

so greatly in many respects from that of man, and has given to it "a

truly frightful physiognomy." Therefore as the jaws and teeth in the

progenitors of man gradually become reduced in size, the adult skull

would have presented nearly the same characters which it offers in the

young of the anthropomorphous apes, and would thus have come to resemble

more nearly that of existing man. A great reduction of the canine teeth

in the males would almost certainly, as we shall hereafter see, have

affected through inheritance the teeth of the females.

As the various mental faculties were gradually developed, the brain

would almost certainly have become larger. No one, I presume, doubts

that the large size of the brain in man, relatively to his body, in

comparison with that of the gorilla or orang, is closely connected with

his higher mental powers. We meet with closely analogous facts with

insects, in which the cerebral ganglia are of extraordinary dimensions

in ants; these ganglia in all the Hymenoptera being many times larger

than in the less intelligent orders, such as beetles.[208] 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

generally known, yet their cerebral ganglia are not so large as the

quarter of a small pin's head. Under this latter point of view, the

brain of an ant is one of the most marvellous atoms of matter in the

world, perhaps more marvellous than the brain of man.

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[209] 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 inches. Professor Broca[210] found that skulls

from graves in Paris of the nineteenth century, were larger than those

from vaults of the twelfth century, in the proportion of 1484 to 1426;

and Prichard is persuaded that the present inhabitants of Britain have

"much more capacious brain-cases" 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. With respect to the lower animals, M. E. Lartet,[211] 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 more complex in the more recent

form. On the other hand I have shewn[212] 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 but

little their intellect, instincts, senses, and voluntary movements.

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 affected. 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 from disease have become

fixed either sideways or backwards, one of the eyes has changed its

position, and the bones of the skull have been modified; and this

apparently results from the brain pressing in a new direction.[213] I

have shewn that with long-eared rabbits, even so trifling a cause as the

lopping forward of one ear drags forward on that side almost every bone

of the skull; so that the bones on the opposite sides 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 by 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 only 3.15 and the latter 4.3 inches

in length.[214] One of the most marked distinctions in different races

of man is that the skull in some is elongated, and in others rounded;

and here the explanation suggested by the case of the rabbits may

partially hold good; for Welcker finds that short "men incline more to

brachycephaly, and tall men to dolichocephaly;"[215] and tall men may be

compared with the larger and longer-bodied rabbits, all of which have

elongated skulls, or are dolichocephalic.

From these several facts we can to a certain extent understand the means

through which the great size and more or less rounded form of the skull

has 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 dolphins (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[216] than those on the lowlands. May we then infer that man became

divested of hair from having aboriginally inhabited some tropical land?

The fact of the hair being 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, assuming 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.

In this respect man agrees with the great majority of quadrupeds, which

generally have their upper and exposed surfaces more thickly clothed

than the lower surface. Nevertheless, the fact 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,[217] is strongly opposed to the supposition that man became

naked through the action of the sun. I am inclined to believe, as we

shall see under sexual selection, that man, or rather primarily woman,

became divested of hair for ornamental purposes; and according to this

belief it is not surprising that man should differ so greatly in

hairiness from all his lower brethren, for characters gained through

sexual selection often differ in closely-related forms to an

extraordinary degree.

According to a popular impression, the absence of a tail is eminently

distinctive of man; but as those apes which come nearest to man are

destitute of this organ, its disappearance does not especially concern

us. Nevertheless it may be well to own that no explanation, as far as I

am aware, has ever been given of the loss of the tail by certain apes

and man. Its loss, however, is not surprising, for it sometimes differs

remarkably in length in species of the same genera: thus in some species

of Macacus the tail is longer than the whole body, consisting 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,[218] sometimes only five. This

great diversity in the structure and length of the tail in animals

belonging to the same genera, and following nearly the same habits of

life, renders it probable that the tail is not of much importance to

them; and if so, we might have expected that it would sometimes have

become more or less rudimentary, in accordance with what we incessantly

see with other structures. The tail almost always tapers towards the end

whether it be long or short; and this, I presume, results from the

atrophy, through disuse, of the terminal muscles together with their

arteries and nerves, leading to the atrophy of the terminal bones. With

respect to the os coccyx, which in man and the higher apes manifestly

consists of the few basal and tapering segments of an ordinary tail, I

have heard it asked how could these have become completely embedded

within the body; but there is no difficulty in this respect, for in many

monkeys the basal segments of the true tail are thus embedded. For

instance, Mr. Murie informs me that in the skeleton of a not full-grown

_Macacus inornatus_, he counted nine or ten caudal vertebrae, which

altogether were only 1.8 inch in length. Of these the three basal ones

appeared to have been embedded; the remainder forming the free part of

the tail, which was only one inch in length, and half an inch in

diameter. Here, then, the three embedded caudal vertebrae plainly

correspond with the four coalesced vertebrae of the human os coccyx.

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 are of no service to an organism in adapting it 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 some new kind of food. Nor must we forget the principle

of correlation, by which, as Isidore Geoffroy has shewn in the case of

man, many fit-range 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;[219] for we can thus see that the fluids of the system, if

altered for some special purpose, might induce other strange 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.

Thus a very 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 Naegeli 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 probably 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. I had not

formerly sufficiently considered the existence of many structures which

appear to be, as far as we can judge, 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.

Nevertheless I was not able to annul the influence of my former belief,

then widely prevalent, that each species had been purposely created; and

this led to my tacitly assuming 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 the

action of natural selection, either during past or present times, too

far. 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 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.

That all organic beings, including man, present many modifications of

structure which are of no service to them at present, nor have been

formerly, is, as I can now see, probable. 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 own efficient cause. If these causes,

whatever they may be, were to act more uniformly and energetically

during a lengthened period (and no reason can be assigned why this

should not sometimes occur), the result would probably be not mere

slight individual differences, but well-marked, constant modifications.

Modifications which are in no way beneficial cannot have been kept

uniform through natural selection, though any which were injurious would

have been 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. The same

organism might acquire in this manner during successive periods

successive modifications, and these 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 then as now induced by the same general

causes, and governed by the same general and complex laws. As all

animals tend to multiply beyond their means of subsistence, so it must

have been with the progenitors of man; and this will inevitably have led

to a struggle for existence and to natural selection. This latter

process will have been greatly aided by the inherited effects of the

increased use of parts; these two processes incessantly reacting 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, perhaps a large one, 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 the ape-like progenitors of man,

probably lived in society. With strictly social animals, natural

selection sometimes acts indirectly on the individual, through the

preservation of variations which are beneficial only to the community. A

community including a large number of well-endowed individuals increases

in number and is victorious over other and less well-endowed

communities; although each separate member may gain no advantage over

the other members of the same community. With associated insects many

remarkable structures, which are of little or no service to the

individual or its own offspring, such as the pollen-collecting

apparatus, or the sting of the worker-bee, or the great jaws of

soldier-ants, have been thus acquired. 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

faculties the case, as we shall see in the following chapter, is wholly

different; for these faculties have been chiefly, or even exclusively,

gained for the benefit of the community; the individuals composing the

community being at the same time indirectly benefited.

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[220]

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 little

strength of man, his small speed in running, and his slight power of

smell, by which to discover food or to avoid danger. To these

deficiencies there might have been added the still more serious loss of

the power of quickly climbing trees, so as to escape from enemies.

Seeing that the unclothed Fuegians can exist under their wretched

climate, the loss of hair would not have been a great injury to primeval

man, if he inhabited a warm country. When we compare defenceless man

with the apes, many of which are provided with formidable canine teeth,

we must remember that these in their fully-developed condition are

possessed by the males alone, being chiefly used by them for fighting

with their rivals; yet the females which are not thus provided, are able

to survive.

In regard to bodily size or strength, we do not know whether man is

descended from some comparatively 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, in

comparison with his progenitors. 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 probably,

though not necessarily, have failed to become social; and this would

most effectually have checked the acquirement by man of his higher

mental qualities, such as sympathy and the love of his fellow-creatures.

Hence it might have been an immense advantage to man to have sprung

from some comparatively weak creature.

The slight corporeal strength of man, his little speed, his want of

natural weapons, &c., are more than counterbalanced, firstly by his

intellectual powers, through which he has, whilst still remaining in a

barbarous state, formed for himself weapons, tools, &c., and secondly by

his social qualities which lead him to give aid to his fellow-men and to

receive it in return. 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 races, namely, the Bushmen, maintain themselves in Southern

Africa, as do the dwarfed Esquimaux in the Arctic regions. The early

progenitors 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, whilst

they gradually lost their brute-like powers, such as climbing trees,

&c., they at the same time advanced in intellect. But granting that the

progenitors of man were far more helpless and defenceless than any

existing savages, if they had inhabited some warm continent or large

island, such as Australia or New Guinea, or Borneo (the latter island

being now tenanted by the orang), they would not have been exposed to

any special danger. In an area as large as one of these islands, the

competition between tribe and tribe would have been sufficient, under

favourable conditions, to have raised man, through the survival of the

fittest, combined with the inherited effects of habit, to his present

high position in the organic scale.