CHAPTER VII.

ON THE RACES OF MAN.

The nature and value of specific characters--Application to the

races of man--Arguments in favour of, and opposed to, ranking

the so-called races of man as distinct

species--Sub-species--Monogenists and polygenists--Convergence

of character--Numerous points of resemblance in body and mind

between the most distinct races of man--The state of man when

he first spread over the earth--Each race not descended from a

single pair--The extinction of races--The formation of

races--The effects of crossing--Slight influence of the direct

action of the conditions of life--Slight or no influence of

natural selection--Sexual selection.

It is not my intention here to describe the several so-called races of

men; but to inquire what is the value of the differences between them

under a classificatory point of view, and how they have originated. In

determining whether two or more allied forms ought to be ranked as

species or varieties, naturalists are practically guided by the

following considerations; namely, the amount of difference between them,

and whether such differences relate to few or many points of structure,

and whether they are of physiological importance; but more especially

whether they are constant. Constancy of character is what is chiefly

valued and sought for by naturalists. Whenever it can be shewn, or

rendered probable, that the forms in question have remained distinct for

a long period, this becomes an argument of much weight in favour of

treating them as species. Even a slight degree of sterility between any

two forms when first crossed, or in their offspring, is generally

considered as a decisive test of their specific distinctness; and their

continued persistence without blending within the same area, is usually

accepted as sufficient evidence, either of some degree of mutual

sterility, or in the case of animals of some repugnance to mutual

pairing.

Independently of blending from intercrossing, the complete absence, in a

well-investigated region, of varieties linking together any two

closely-allied forms, is probably the most important of all the

criterions of their specific distinctness; and this is a somewhat

different consideration from mere constancy of character, for two forms

may be highly variable and yet not yield intermediate varieties.

Geographical distribution is often unconsciously and sometimes

consciously brought into play; so that forms living in two widely

separated areas, in which most of the other inhabitants are specifically

distinct, are themselves usually looked at as distinct; but in truth

this affords no aid in distinguishing geographical races from so-called

good or true species.

Now let us apply these generally-admitted principles to the races of

man, viewing him in the same spirit as a naturalist would any other

animal. In regard to the amount of difference between the races, we must

make some allowance for our nice powers of discrimination gained by the

long habit of observing ourselves. In India, as Elphinstone

remarks,[282] although a newly-arrived European cannot at first

distinguish the various native races, yet they soon appear to him

extremely dissimilar; and the Hindoo cannot at first perceive any

difference between the several European nations. Even the most distinct

races of man, with the exception of certain negro tribes, are much more

like each other in form than would at first be supposed. This is well

shewn by the French photographs in the Collection Anthropologique du

Museum of the men belonging to various races, the greater number of

which, as many persons to whom I have shown them have remarked, might

pass for Europeans. Nevertheless, these men if seen alive would

undoubtedly appear very distinct, so that we are clearly much influenced

in our judgment by the mere colour of the skin and hair, by slight

differences in the features, and by expression.

There is, however, no doubt that the various races, when carefully

compared and measured, differ much from each other,--as in the texture

of the hair, the relative proportions of all parts of the body,[283] the

capacity of the lungs, the form and capacity of the skull, and even in

the convolutions of the brain.[284] But it would be an endless task to

specify the numerous points of structural difference. The races differ

also in constitution, in acclimatisation, and in liability to certain

diseases. Their mental characteristics are likewise very distinct;

chiefly as it would appear in their emotional, but partly in their

intellectual, faculties. Every one who has had the opportunity of

comparison, must have been struck with the contrast between the

taciturn, even morose, aborigines of S. America and the light-hearted,

talkative negroes. There is a nearly similar contrast between the Malays

and the Papuans,[285] who live under the same physical conditions, and

are separated from each other only by a narrow space of sea.

We will first consider the arguments which may be advanced in favour of

classing the races of man as distinct species, and then those on the

other side. If a naturalist, who had never before seen such beings, were

to compare a Negro, Hottentot, Australian, or Mongolian, he would at

once perceive that they differed in a multitude of characters, some of

slight and some of considerable importance. On inquiry he would find

that they were adapted to live under widely different climates, and that

they differed somewhat in bodily constitution and mental disposition. If

he were then told that hundreds of similar specimens could be brought

from the same countries, he would assuredly declare that they were as

good species as many to which he had been in the habit of affixing

specific names. This conclusion would be greatly strengthened as soon as

he had ascertained that these forms had all retained the same character

for many centuries; and that negroes, apparently identical with existing

negroes, had lived at least 4000 years ago.[286] He would also hear from

an excellent observer, Dr. Lund,[287] that the human skulls found in

the caves of Brazil, entombed with many extinct mammals, belonged to the

same type as that now prevailing throughout the American Continent.

Our naturalist would then perhaps turn to geographical distribution, and

he would probably declare that forms differing not only in appearance,

but fitted for the hottest and dampest or driest countries, as well as

for the arctic regions, must be distinct species. He might appeal to the

fact that no one species in the group next to man, namely the

Quadrumana, can resist a low temperature or any considerable change of

climate; and that those species which come nearest to man have never

been reared to maturity, even under the temperate climate of Europe. He

would be deeply impressed with the fact, first noticed by Agassiz,[288]

that the different races of man are distributed over the world in the

same zoological provinces, as those inhabited by undoubtedly distinct

species and genera of mammals. This is manifestly the case with the

Australian, Mongolian, and Negro races of man; in a less well-marked

manner with the Hottentots; but plainly with the Papuans and Malays, who

are separated, as Mr. Wallace has shewn, by nearly the same line which

divides the great Malayan and Australian zoological provinces. The

aborigines of America range throughout the Continent; and this at first

appears opposed to the above rule, for most of the productions of the

Southern and Northern halves differ widely; yet some few living forms,

as the opossum, range from the one into the other, as did formerly some

of the gigantic Edentata. The Esquimaux, like other Arctic animals,

extend round the whole polar regions. It should be observed that the

mammalian forms which inhabit the several zoological provinces, do not

differ from each other in the same degree; so that it can hardly be

considered as an anomaly that the Negro differs more, and the American

much less, from the other races of man than do the mammals of the same

continents from those of the other provinces. Man, it may be added, does

not appear to have aboriginally inhabited any oceanic island; and in

this respect he resembles the other members of his class.

In determining whether the varieties of the same kind of domestic animal

should be ranked as specifically distinct, that is, whether any of them

are descended from distinct wild species, every naturalist would lay

much stress on the fact, if established, of their external parasites

being specifically distinct. All the more stress would be laid on this

fact, as it would be an exceptional one, for I am informed by Mr. Denny

that the most different kinds of dogs, fowls, and pigeons, in England,

are infested by the same species of Pediculi or lice. Now Mr. A. Murray

has carefully examined the Pediculi collected in different countries

from the different races of man;[289] and he finds that they differ, not

only in colour, but in the structure of their claws and limbs. In every

case in which numerous specimens were obtained the differences were

constant. The surgeon of a whaling ship in the Pacific assured me that

when the Pediculi, with which some Sandwich Islanders on board swarmed,

strayed on to the bodies of the English sailors, they died in the course

of three or four days. These Pediculi were darker coloured and appeared

different from those proper to the natives of Chiloe in South America,

of which he gave me specimens. These, again, appeared larger and much

softer than European lice. Mr. Murray procured four kinds from Africa,

namely from the Negroes of the Eastern and Western coasts, from the

Hottentots and Caffres; two kinds from the natives of Australia; two

from North, and two from South America. In these latter cases it may be

presumed that the Pediculi came from natives inhabiting different

districts. With insects slight structural differences, if constant, are

generally esteemed of specific value: and the fact of the races of man

being infested by parasites, which appear to be specifically distinct,

might fairly be urged as an argument that the races themselves ought to

be classed as distinct species.

Our supposed naturalist having proceeded thus far in his investigation,

would next inquire whether the races of men, when crossed, were in any

degree sterile. He might consult the work[290] of a cautious and

philosophical observer, Professor Broca; and in this he would find good,

evidence that some races were quite fertile together; but evidence of an

opposite nature in regard to other races. Thus it has been asserted that

the native women of Australia and Tasmania rarely produce children to

European men; the evidence, however, on this head has now been shewn to

be almost valueless. The half-castes are killed by the pure blacks; and

an account has lately been published of eleven half-caste youths

murdered and burnt at the same time, whose remains were found by the

police.[291] Again, it has often been said that when mulattoes

intermarry they produce few children; on the other hand, Dr. Bachman of

Charlestown[292] positively asserts that he has known mulatto families

which have intermarried for several generations, and have continued on

an average as fertile as either pure whites or pure blacks. Inquiries

formerly made by Sir C. Lyell on this subject led him, as he informs me,

to the same conclusion. In the United States the census for the year

1854 included, according to Dr. Bachman, 405,751 mulattoes; and this

number, considering all the circumstances of the case, seems small; but

it may partly be accounted for by the degraded and anomalous position of

the class, and by the profligacy of the women. A certain amount of

absorption of mulattoes into negroes must always be in progress; and

this would lead to an apparent diminution of the former. The inferior

vitality of mulattoes is spoken of in a trustworthy work[293] as a

well-known phenomenon; but this is a different consideration from their

lessened fertility; and can hardly be advanced as a proof of the

specific distinctness of the parent races. No doubt both animal and

vegetable hybrids, when produced from extremely distinct species, are

liable to premature death; but the parents of mulattoes cannot be put

under the category of extremely distinct species. The common Mule, so

notorious for long life and vigour, and yet so sterile, shews how little

necessary connection there is in hybrids between lessened fertility and

vitality: other analogous cases could be added.

Even if it should hereafter be proved that all the races of men were

perfectly fertile together, he who was inclined from other reasons to

rank them as distinct species, might with justice argue that fertility

and sterility are not safe criterions of specific distinctness. We know

that these qualities are easily affected by changed conditions of life

or by close inter-breeding, and that they are governed by highly complex

laws, for instance that of the unequal fertility of reciprocal crosses

between the same two species. With forms which must be ranked as

undoubted species, a perfect series exists from those which are

absolutely sterile when crossed, to those which are almost or quite

fertile. The degrees of sterility do not coincide strictly with the

degrees of difference in external structure or habits of life. Man in

many respects may be compared with those animals which have long been

domesticated, and a large body of evidence can be advanced in favour of

the Pallasian doctrine[294] that domestication tends to eliminate the

sterility which is so general a result of the crossing of species in a

state of nature. From these several considerations, it may be justly

urged that the perfect fertility of the intercrossed races of man, if

established, would not absolutely preclude us from ranking them as

distinct species.

Independently of fertility, the character of the offspring from a cross

has sometimes been thought to afford evidence whether the parent-forms

ought to be ranked as species or varieties; but after carefully studying

the evidence, I have come to the conclusion that no general rules of

this kind can be trusted. Thus with mankind the offspring of distinct

races resemble in all respects the offspring of true species and of

varieties. This is shewn, for instance, by the manner in which the

characters of both parents are blended, and by one form absorbing

another through repeated crosses. In this latter case the progeny both

of crossed species and varieties retain for a long period a tendency to

revert to their ancestors, especially to that one which is prepotent in

transmission. When any character has suddenly appeared in a race or

species as the result of a single act of variation, as is general with

monstrosities,[295] and this race is crossed with another not thus

characterised, the characters in question do not commonly appear in a

blended condition in the young, but are transmitted to them either

perfectly developed or not at all. As with the crossed races of man

cases of this kind rarely or never occur, this may be used as an

argument against the view suggested by some ethnologists, namely that

certain characters, for instance the blackness of the negro, first

appeared as a sudden variation or sport. Had this occurred, it is

probable that mulattoes would often have been born, either completely

black or completely white.

We have now seen that a naturalist might feel himself fully justified in

ranking the races of man as distinct species; for he has found that they

are distinguished by many differences in structure and constitution,

some being of importance. These differences have, also, remained nearly

constant for very long periods of time. He will have been in some degree

influenced by the enormous range of man, which is a great anomaly in the

class of mammals, if mankind be viewed as a single species. He will have

been struck with the distribution of the several so-called races, in

accordance with that of other undoubtedly distinct species of mammals.

Finally he might urge that the mutual fertility of all the races has not

as yet been fully proved; and even if proved would not be an absolute

proof of their specific identity.

On the other side of the question, if our supposed naturalist were to

enquire whether the forms of man kept distinct like ordinary species,

when mingled together in large numbers in the same country, he would

immediately discover that this was by no means the case. In Brazil he

would behold an immense mongrel population of Negroes and Portuguese; in

Chiloe and other parts of South America, he would behold the whole

population consisting of Indians and Spaniards blended in various

degrees.[296] In many parts of the same continent he would meet with the

most complex crosses between Negroes, Indians, and Europeans; and such

triple crosses afford the severest test, judging from the vegetable

kingdom, of the mutual fertility of the parent-forms. In one island of

the Pacific he would find a small population of mingled Polynesian and

English blood; and in the Viti Archipelago a population of Polynesians

and Negritos crossed in all degrees. Many analogous cases could be

added, for instance, in South Africa. Hence the races of man are not

sufficiently distinct to co-exist without fusion; and this it is, which

in all ordinary cases affords the usual test of specific distinctness.

Our naturalist would likewise be much disturbed as soon as he perceived

that the distinctive characters of every race of man were highly

variable. This strikes every one when he first beholds the negro-slaves

in Brazil, who have been imported from all parts of Africa. The same

remark holds good with the Polynesians, and with many other races. It

may be doubted whether any character can be named which is distinctive

of a race and is constant. Savages, even within the limits of the same

tribe, are not nearly so uniform in character, as has often been said.

Hottentot women offer certain peculiarities, more strongly marked than

those occurring in any other race, but these are known not to be of

constant occurrence. In the several American tribes, colour and

hairyness differ considerably; as does colour to a certain degree, and

the shape of the features greatly, in the Negroes of Africa. The shape

of the skull varies much in some races;[297] and so it is with every

other character. Now all naturalists have learnt by dearly-bought

experience, how rash it is to attempt to define species by the aid of

inconstant characters.

But the most weighty of all the arguments against treating the races of

man as distinct species, is that they graduate into each other,

independently in many cases, as far as we can judge, of their having

intercrossed. Man has been studied more carefully than any other organic

being, and yet there is the greatest possible diversity amongst capable

judges whether he should be classed as a single species or race, or as

two (Virey), as three (Jacquinot), as four (Kant), five (Blumenbach),

six (Buffon), seven (Hunter), eight (Agassiz), eleven (Pickering),

fifteen (Bory St. Vincent), sixteen (Desmoulins), twenty-two (Morton),

sixty (Crawfurd), or as sixty-three, according to Burke.[298] This

diversity of judgment does not prove that the races ought not to be

ranked as species, but it shews that they graduate into each other, and

that it is hardly possible to discover clear distinctive characters

between them.

Every naturalist who has had the misfortune to undertake the

description of a group of highly varying organisms, has encountered

cases (I speak after experience) precisely like that of man; and if of a

cautious disposition, he will end by uniting all the forms which

graduate into each other as a single species; for he will say to himself

that he has no right to give names to objects which he cannot define.

Cases of this kind occur in the Order which includes man, namely in

certain genera of monkeys; whilst in other genera, as in Cercopithecus,

most of the species can be determined with certainty. In the American

genus Cebus, the various forms are ranked by some naturalists as

species, by others as mere geographical races. Now if numerous specimens

of Cebus were collected from all parts of South America, and those forms

which at present appear to be specifically distinct, were found to

graduate into each other by close steps, they would be ranked by most

naturalists as mere varieties or races; and thus the greater number of

naturalists have acted with respect to the races of man. Nevertheless it

must be confessed that there are forms, at least in the vegetable

kingdom,[299] which we cannot avoid naming as species, but which are

connected together, independently of intercrossing, by numberless

gradations.

Some naturalists have lately employed the term "sub-species" to

designate forms which possess many of the characteristics of true

species, but which hardly deserve so high a rank. Now if we reflect on

the weighty arguments, above given, for raising the races of man to the

dignity of species, and the insuperable difficulties on the other side

in defining them, the term "sub-species" might here be used with much

propriety. But from long habit the term "race" will perhaps always be

employed. The choice of terms is only so far important as it is highly

desirable to use, as far as that may be possible, the same terms for the

same degrees of difference. Unfortunately this is rarely possible; for

within the same family the larger genera generally include

closely-allied forms, which can be distinguished only with much

difficulty, whilst the smaller genera include forms that are perfectly

distinct; yet all must equally be ranked as species. So again the

species within the same large genus by no means resemble each other to

the same degree: on the contrary, in most cases some of them can be

arranged in little groups round other species, like satellites round

planets.[300]

The question whether mankind consists of one or several species has of

late years been much agitated by anthropologists, who are divided into

two schools of monogenists and polygenists. Those who do not admit the

principle of evolution, must look at species either as separate

creations or as in some manner distinct entities; and they must decide

what forms to rank as species by the analogy of other organic beings

which are commonly thus received. But it is a hopeless endeavour to

decide this point on sound grounds, until some definition of the term

"species" is generally accepted; and the definition must not include an

element which cannot possibly be ascertained, such as an act of

creation. We might as well attempt without any definition to decide

whether a certain number of houses should be called a village, or town,

or city. We have a practical illustration of the difficulty in the

never-ending doubts whether many closely-allied mammals, birds,

insects, and plants, which represent each other in North America and

Europe, should be ranked species or geographical races; and so it is

with the productions of many islands situated at some little distance

from the nearest continent.

Those naturalists, on the other hand, who admit the principle of

evolution, and this is now admitted by the greater number of rising men,

will feel no doubt that all the races of man are descended from a single

primitive stock; whether or not they think fit to designate them as

distinct species, for the sake of expressing their amount of

difference.[301] With our domestic animals the question whether the

various races have arisen from one or more species is different.

Although all such races, as well as all the natural species within the

same genus, have undoubtedly sprung from the same primitive stock, yet

it is a fit subject for discussion, whether, for instance, all the

domestic races of the dog have acquired their present differences since

some one species was first domesticated and bred by man; or whether they

owe some of their characters to inheritance from distinct species, which

had already been modified in a state of nature. With mankind no such

question can arise, for he cannot be said to have been domesticated at

any particular period.

When the races of man diverged at an extremely remote epoch from their

common progenitor, they will have differed but little from each other,

and been few in number; consequently they will then, as far as their

distinguishing characters are concerned, have had less claim to rank as

distinct species, than the existing so-called races. Nevertheless such

early races would perhaps have been ranked by some naturalists as

distinct species, so arbitrary is the term, if their differences,

although extremely slight, had been more constant than at present, and

had not graduated into each other.

It is, however, possible, though far from probable, that the early

progenitors of man might at first have diverged much in character, until

they became more unlike each other than are any existing races; but that

subsequently, as suggested by Vogt,[302] they converged in character.

When man selects for the same object the offspring of two distinct

species, he sometimes induces, as far as general appearance is

concerned, a considerable amount of convergence. This is the case, as

shewn by Von Nathusius,[303] with the improved breeds of pigs, which are

descended from two distinct species; and in a less well-marked manner

with the improved breeds of cattle. A great anatomist, Gratiolet,

maintains that the anthropomorphous apes do not form a natural

sub-group; but that the orang is a highly developed gibbon or

semnopithecus; the chimpanzee a highly developed macacus; and the

gorilla a highly developed mandrill. If this conclusion, which rests

almost exclusively on brain-characters, be admitted, we should have a

case of convergence at least in external characters, for the

anthropomorphous apes are certainly more like each other in many points

than they are to other apes. All analogical resemblances, as of a whale

to a fish, may indeed be said to be cases of convergence; but this term

has never been applied to superficial and adaptive resemblances. It

would be extremely rash in most cases to attribute to convergence close

similarity in many points of structure in beings which had once been

widely different. The form of a crystal is determined solely by the

molecular forces, and it is not surprising that dissimilar substances

should sometimes assume the same form; but with organic beings we should

bear in mind that the form of each depends on an infinitude of complex

relations, namely on the variations which have arisen, these being due

to causes far too intricate to be followed out,--on the nature of the

variations which have been preserved, and this depends on the

surrounding physical conditions, and in a still higher degree on the

surrounding organisms with which each has come into competition,--and

lastly, on inheritance (in itself a fluctuating element) from

innumerable progenitors, all of which have had their forms determined

through equally complex relations. It appears utterly incredible that

two organisms, if differing in a marked manner, should ever afterwards

converge so closely as to lead to a near approach to identity throughout

their whole organisation. In the case of the convergent pigs above

referred to, evidence of their descent from two primitive stocks is

still plainly retained, according to Von Nathusius, in certain bones of

their skulls. If the races of man were descended, as supposed by some

naturalists, from two or more distinct species, which had differed as

much, or nearly as much, from each other, as the orang differs from the

gorilla, it can hardly be doubted that marked differences in the

structure of certain bones would still have been discoverable in man as

he now exists.

Although the existing races of man differ in many respects, as in

colour, hair, shape of skull, proportions of the body, &c., yet if their

whole organisation be taken into consideration they are found to

resemble each other closely in a multitude of points. Many of these

points are of so unimportant or of so singular a nature, that it is

extremely improbable that they should have been independently acquired

by aboriginally distinct species or races. The same remark holds good

with equal or greater force with respect to the numerous points of

mental similarity between the most distinct races of man. The American

aborigines, Negroes and Europeans differ as much from each other in mind

as any three races that can be named; yet I was incessantly struck,

whilst living with the Fuegians on board the "Beagle," with the many

little traits of character, shewing how similar their minds were to

ours; and so it was with a full-blooded negro with whom I happened once

to be intimate.

He who will carefully read Mr. Tylor's and Sir J. Lubbock's interesting

works[304] can hardly fail to be deeply impressed with the close

similarity between the men of all races in tastes, dispositions and

habits. This is shewn by the pleasure which they all take in dancing,

rude music, acting, painting, tattooing, and otherwise decorating

themselves,--in their mutual comprehension of gesture-language--and, as

I shall be able to shew in a future essay, by the same expression in

their features, and by the same inarticulate cries, when they are

excited by various emotions. This similarity, or rather identity, is

striking, when contrasted with the different expressions which may be

observed in distinct species of monkeys. There is good evidence that the

art of shooting with bows and arrows has not been handed down from any

common progenitor of mankind, yet the stone arrow-heads, brought from

the most distant parts of the world and manufactured at the most remote

periods, are, as Nilsson has shewn,[305] almost identical; and this fact

can only be accounted for by the various races having similar inventive

or mental powers. The same observation has been made by

archaeologists[306] with respect to certain widely-prevalent ornaments,

such as zigzags, &c.; and with respect to various simple beliefs and

customs, such as the burying of the dead under megalithic structures. I

remember observing in South America,[307] that there, as in so many

other parts of the world, man has generally chosen the summits of lofty

hills, on which to throw up piles of stones, either for the sake of

recording some remarkable event, or for burying his dead.

Now when naturalists observe a close agreement in numerous small details

of habits, tastes and dispositions between two or more domestic races,

or between nearly-allied natural forms, they use this fact as an

argument that all are descended from a common progenitor who was thus

endowed; and consequently that all should be classed under the same

species. The same argument may be applied with much force to the races

of man.

As it is improbable that the numerous and unimportant points of

resemblance between the several races of man in bodily structure and

mental faculties (I do not here refer to similar customs) should all

have been independently acquired, they must have been inherited from

progenitors who were thus characterised. We thus gain some insight into

the early state of man, before he had spread step by step over the face

of the earth. The spreading of man to regions widely separated by the

sea, no doubt, preceded any considerable amount of divergence of

character in the several races; for otherwise we should sometimes meet

with the same race in distinct continents; and this is never the case.

Sir J. Lubbock, after comparing the arts now practised by savages in all

parts of the world, specifies those which man could not have known, when

he first wandered from his original birthplace; for if once learnt they

would never have been forgotten.[308] He thus shews that "the spear,

which is but a development of the knife-point, and the club, which is

but a long hammer, are the only things left." He admits, however, that

the art of making fire probably had already been discovered, for it is

common to all the races now existing, and was known to the ancient

cave-inhabitants of Europe. Perhaps the art of making rude canoes or

rafts was likewise known; but as man existed at a remote epoch, when the

land in many places stood at a very different level, he would have been

able, without the aid of canoes, to have spread widely. Sir J. Lubbock

further remarks how improbable it is that our earliest ancestors could

have "counted as high as ten, considering that so many races now in

existence cannot get beyond four." Nevertheless, at this early period,

the intellectual and social faculties of man could hardly have been

inferior in any extreme degree to those now possessed by the lowest

savages; otherwise primeval man could not have been so eminently

successful in the struggle for life, as proved by his early and wide

diffusion.

From the fundamental differences between certain languages, some

philologists have inferred that when man first became widely diffused he

was not a speaking animal; but it may be suspected that languages, far

less perfect than any now spoken, aided by gestures, might have been

used, and yet have left no traces on subsequent and more

highly-developed tongues. Without the use of some language, however

imperfect, it appears doubtful whether man's intellect could have risen

to the standard implied by his dominant position at an early period.

Whether primeval man, when he possessed very few arts of the rudest

kind, and when his power of language was extremely imperfect, would have

deserved to be called man, must depend on the definition which we

employ. In a series of forms graduating insensibly from some ape-like

creature to man as he now exists, it would be impossible to fix on any

definite point when the term "man" ought to be used. But this is a

matter of very little importance. So again it is almost a matter of

indifference whether the so-called races of man are thus designated, or

are ranked as species or sub-species; but the latter term appears the

most appropriate. Finally, we may conclude that when the principles of

evolution are generally accepted, as they surely will be before long,

the dispute between the monogenists and the polygenists will die a

silent and unobserved death.

One other question ought not to be passed over without notice, namely,

whether, as is sometimes assumed, each sub-species or race of man has

sprung from a single pair of progenitors. With our domestic animals a

new race can readily be formed from a single pair possessing some new

character, or even from a single individual thus characterised, by

carefully matching the varying offspring; but most of our races have

been formed, not intentionally from a selected pair, but unconsciously

by the preservation of many individuals which have varied, however

slightly, in some useful or desired manner. If in one country stronger

and heavier horses, and in another country lighter and fleeter horses,

were habitually preferred, we may feel sure that two distinct sub-breeds

would, in the course of time, be produced, without any particular pairs

or individuals having been separated and bred from in either country.

Many races have been thus formed, and their manner of formation is

closely analogous with that of natural species. We know, also, that the

horses which have been brought to the Falkland Islands have become,

during successive generations, smaller and weaker, whilst those which

have run wild on the Pampas have acquired larger and coarser heads; and

such changes are manifestly due, not to any one pair, but to all the

individuals having been subjected to the same conditions, aided,

perhaps, by the principle of reversion. The new sub-breeds in none of

these cases are descended from any single pair, but from many

individuals which have varied in different degrees, but in the same

general manner; and we may conclude that the races of man have been

similarly produced, the modifications being either the direct result of

exposure to different conditions, or the indirect result of some form of

selection. But to this latter subject we shall presently return.

_On the Extinction of the Races of Man._--The partial and complete

extinction of many races and sub-races of man are historically known

events. Humboldt saw in South America a parrot which was the sole living

creature that could speak the language of a lost tribe. Ancient

monuments and stone implements found in all parts of the world, of which

no tradition is preserved by the present inhabitants, indicate much

extinction. Some small and broken tribes, remnants of former races,

still survive in isolated and generally mountainous districts. In Europe

the ancient races were all, according to Schaaffhausen,[309] "lower in

the scale than the rudest living savages;" they must therefore have

differed, to a certain extent, from any existing race. The remains

described by Professor Broca[310] from Les Eyzies, though they

unfortunately appear to have belonged to a single family, indicate a

race with a most singular combination of low or simious and high

characteristics, and is "entirely different from any other race, ancient

or modern, that we have ever heard of." It differed, therefore, from the

quaternary race of the caverns of Belgium.

Unfavourable physical conditions appear to have had but little effect in

the extinction of races.[311] Man has long lived in the extreme regions

of the North, with no wood wherewith to make his canoes or other

implements, and with blubber alone for burning and giving him warmth,

but more especially for melting the snow. In the Southern extremity of

America the Fuegians survive without the protection of clothes, or of

any building worthy to be called a hovel. In South Africa the aborigines

wander over the most arid plains, where dangerous beasts abound. Man can

withstand the deadly influence of the Terai at the foot of the Himalaya,

and the pestilential shores of tropical Africa.

Extinction follows chiefly from the competition of tribe with tribe,

and race with race. Various checks are always in action, as specified in

a former chapter, which serve to keep down the numbers of each savage

tribe,--such as periodical famines, the wandering of the parents and the

consequent deaths of infants, prolonged suckling, the stealing of women,

wars, accidents, sickness, licentiousness, especially infanticide, and,

perhaps, lessened fertility from less nutritious food, and many

hardships. If from any cause any one of these checks is lessened, even

in a slight degree, the tribe thus favoured will tend to increase; and

when one of two adjoining tribes becomes more numerous and powerful than

the other, the contest is soon settled by war, slaughter, cannibalism,

slavery, and absorption. Even when a weaker tribe is not thus abruptly

swept away, if it once begins to decrease, it generally goes on

decreasing until it is extinct.[312]

When civilised nations come into contact with barbarians the struggle is

short, except where a deadly climate gives its aid to the native race.

Of the causes which lead to the victory of civilised nations, some are

plain and some very obscure. We can see that the cultivation of the land

will be fatal in many ways to savages, for they cannot, or will not,

change their habits. New diseases and vices are highly destructive; and

it appears that in every nation a new disease causes much death, until

those who are most susceptible to its destructive influence are

gradually weeded out;[313] and so it may be with the evil effects from

spirituous liquors, as well as with the unconquerably strong taste for

them shewn by so many savages. It further appears, mysterious as is the

fact, that the first meeting of distinct and separated people generates

disease.[314] Mr. Sproat, who in Vancouver Island closely attended to

the subject of extinction, believes that changed habits of life, which

always follow from the advent of Europeans, induces much ill-health. He

lays, also, great stress on so trifling a cause as that the natives

become "bewildered and dull by the new life around them; they lose the

motives for exertion, and get no new ones in their place."[315]

The grade of civilisation seems a most important element in the success

of nations which come in competition. A few centuries ago Europe feared

the inroads of Eastern barbarians; now, any such fear would be

ridiculous. It is a more curious fact, that savages did not formerly

waste away, as Mr. Bagehot has remarked, before the classical nations,

as they now do before modern civilised nations; had they done so, the

old moralists would have mused over the event; but there is no lament in

any writer of that period over the perishing barbarians.[316]

Although the gradual decrease and final extinction of the races of man

is an obscure problem, we can see that it depends on many causes,

differing in different places and at different times. It is the same

difficult problem as that presented by the extinction of one of the

higher animals--of the fossil horse, for instance, which disappeared

from South America, soon afterwards to be replaced, within the same

districts, by countless troops of the Spanish horse. The New Zealander

seems conscious of this parallelism, for he compares his future fate

with that of the native rat almost exterminated by the European rat. The

difficulty, though great to our imagination, and really great if we wish

to ascertain the precise causes, ought not to be so to our reason, as

long as we keep steadily in mind that the increase of each species and

each race is constantly hindered by various checks; so that if any new

check, or cause of destruction, even a slight one, be superadded, the

race will surely decrease in number; and as it has everywhere been

observed that savages are much opposed to any change of habits, by which

means injurious checks could be counterbalanced, decreasing numbers will

sooner or later lead to extinction; the end, in most cases, being

promptly determined by the inroads of increasing and conquering tribes.

_On the Formation of the Races of Man._--It may be premised that when we

find the same race, though broken up into distinct tribes, ranging over

a great area, as over America, we may attribute their general

resemblance to descent from a common stock. In some cases the crossing

of races already, distinct has led to the formation of new races. The

singular fact that Europeans and Hindoos, who belong to the same Aryan

stock and speak a language fundamentally the same, differ widely in

appearance, whilst Europeans differ but little from Jews, who belong to

the Semitic stock and speak quite another language, has been accounted

for by Broca[317] through the Aryan branches having been largely crossed

during their wide diffusion by various indigenous tribes. When two races

in close contact cross, the first result is a heterogeneous mixture:

thus Mr. Hunter, in describing the Santali or hill-tribes of India, says

that hundreds of imperceptible gradations may be traced "from the black,

squat tribes of the mountains to the tall olive-coloured Brahman, with

his intellectual brow, calm eyes, and high but narrow head;" so that it

is necessary in courts of justice to ask the witnesses whether they are

Santalis or Hindoos.[318] Whether a heterogeneous people, such as the

inhabitants of some of the Polynesian islands, formed by the crossing of

two distinct races, with few or no pure members left, would ever become

homogeneous, is not known from direct evidence. But as with our

domesticated animals, a crossed breed can certainly, in the course of a

few generations, be fixed and made uniform by careful selection,[319] we

may infer that the free and prolonged intercrossing during many

generations of a heterogeneous mixture would supply the place of

selection, and overcome any tendency to reversion, so that a crossed

race would ultimately become homogeneous, though it might not partake in

an equal degree of the characters of the two parent-races.

Of all the differences between the races of man, the colour of the skin

is the most conspicuous and one of the best marked. Differences of this

kind, it was formerly thought, could be accounted for by long exposure

under different climates; but Pallas first shewed that this view is not

tenable, and he has been followed by almost all anthropologists.[320]

The view has been rejected chiefly because the distribution of the

variously coloured races, most of whom must have long inhabited their

present homes, does not coincide with corresponding differences of

climate. Weight must also be given to such cases as that of the Dutch

families, who, as we hear on excellent authority,[321] have not

undergone the least change of colour, after residing for three centuries

in South Africa. The uniform appearance in various parts of the world of

gypsies and Jews, though the uniformity of the latter has been somewhat

exaggerated,[322] is likewise an argument on the same side. A very damp

or a very dry atmosphere has been supposed to be more influential in

modifying the colour of the skin than mere heat; but as D'Orbigny in

South America, and Livingstone in Africa, arrived at diametrically

opposite conclusions with respect to dampness and dryness, any

conclusion on this head must be considered as very doubtful.[323]

Various facts, which I have elsewhere given, prove that the colour of

the skin and hair is sometimes correlated in a surprising manner with a

complete immunity from the action of certain vegetable poisons and from

the attacks of certain parasites. Hence it occurred to me, that negroes

and other dark races might have acquired their dark tints by the darker

individuals escaping during a long series of generations from the deadly

influence of the miasmas of their native countries.

I afterwards found that the same idea had long ago occurred to Dr.

Wells.[324] That negroes, and even mulattoes, are almost completely

exempt from the yellow-fever, which is so destructive in tropical

America, has long been known.[325] They likewise escape to a large

extent the fatal intermittent fevers that prevail along, at least, 2600

miles of the shores of Africa, and which annually cause one-fifth of the

white settlers to die, and another fifth to return home invalided.[326]

This immunity in the negro seems to be partly inherent, depending on

some unknown peculiarity of constitution, and partly the result of

acclimatisation. Pouchet[327] states that the negro regiments, borrowed

from the Viceroy of Egypt for the Mexican war, which had been recruited

near the Soudan, escaped the yellow-fever almost equally well with the

negroes originally brought from various parts of Africa, and accustomed

to the climate of the West Indies. That acclimatisation plays a part is

shewn by the many cases in which negroes, after having resided for some

time in a colder climate, have become to a certain extent liable to

tropical fevers.[328] The nature of the climate under which the white

races have long resided, likewise has some influence on them; for during

the fearful epidemic of yellow-fever in Demerara during 1837, Dr. Blair

found that the death-rate of the immigrants was proportional to the

latitude of the country whence they had come. With the negro the

immunity, as far as it is the result of acclimatisation, implies

exposure during a prodigious length of time; for the aborigines of

tropical America, who have resided there from time immemorial, are not

exempt from yellow-fever; and the Rev. B. Tristram states, that there

are districts in Northern Africa which the native inhabitants are

compelled annually to leave, though the negroes can remain with safety.

That the immunity of the negro is in any degree correlated with the

colour of his skin is a mere conjecture: it may be correlated with some

difference in his blood, nervous system, or other tissues. Nevertheless,

from the facts above alluded to, and from some connection apparently

existing between complexion and a tendency to consumption, the

conjecture seemed to me not improbable. Consequently I endeavoured, with

but little success,[329] to ascertain how far it held good. The late

Dr. Daniell, who had long lived on the West Coast of Africa, told me

that he did not believe in any such relation. He was himself unusually

fair, and had withstood the climate in a wonderful manner. When he first

arrived as a boy on the coast, an old and experienced negro chief

predicted from his appearance that this would prove the case. Dr.

Nicholson, of Antigua, after having attended to this subject, wrote to

me that he did not think that dark-coloured Europeans escaped the

yellow-fever better than those that were light-coloured. Mr. J. M.

Harris altogether denies[330] that Europeans with dark hair withstand a

hot climate better than other men; on the contrary, experience has

taught him in making a selection of men for service on the coast of

Africa, to choose those with red hair. As far, therefore, as these

slight indications serve, there seems no foundation for the hypothesis,

which has been accepted by several writers, that the colour of the black

races may have resulted from darker and darker individuals having

survived in greater numbers, during their exposure to the

fever-generating miasmas of their native countries.

Although with our present knowledge we cannot account for the

strongly-marked differences in colour between the races of man, either

through correlation with constitutional peculiarities, or through the

direct action of climate; yet we must not quite ignore the latter

agency, for there is good reason to believe that some inherited effect

is thus produced.[331]

We have seen in our third chapter that the conditions of life, such as

abundant food and general comfort, affect in a direct manner the

development of the bodily frame, the effects being transmitted. Through

the combined influences of climate and changed habits of life, European

settlers, in the United States undergo, as is generally admitted, a

slight but extraordinarily rapid change of appearance. There is, also, a

considerable body of evidence shewing that in the Southern States the

house-slaves of the third generation present a markedly different

appearance from the field-slaves.[332]

If, however, we look to the races of man, as distributed over the world,

we must infer that their characteristic differences cannot be accounted

for by the direct action of different conditions of life, even after

exposure to them for an enormous period of time. The Esquimaux live

exclusively on animal food; they are clothed in thick fur, and are

exposed to intense cold and to prolonged darkness; yet they do not

differ in any extreme degree from the inhabitants of Southern China, who

live entirely on vegetable food and are exposed almost naked to a hot,

glaring climate. The unclothed Fuegians live on the marine productions

of their inhospitable shores; the Botocudos of Brazil wander about the

hot forests of the interior and live chiefly on vegetable productions;

yet these tribes resemble each other so closely that the Fuegians on

board the "Beagle" were mistaken by some Brazilians for Botocudos. The

Botocudos again, as well as the other inhabitants of tropical America,

are wholly different from the Negroes who inhabit the opposite shores of

the Atlantic, are exposed to a nearly similar climate, and follow nearly

the same habits of life.

Nor can the differences between the races of man be accounted for,

except to a quite insignificant degree, by the inherited effects of the

increased or decreased use of parts. Men who habitually live in canoes,

may have their legs somewhat stunted; those who inhabit lofty regions

have their chests enlarged; and those who constantly use certain

sense-organs have the cavities in which they are lodged somewhat

increased in size, and their features consequently a little modified.

With civilised nations, the reduced size of the jaws from lessened use,

the habitual play of different muscles serving to express different

emotions, and the increased size of the brain from greater intellectual

activity, have together produced a considerable effect on their general

appearance in comparison with savages.[333] It is also possible that

increased bodily stature, with no corresponding increase in the size of

the brain, may have given to some races (judging from the previously

adduced cases of the rabbits) an elongated skull of the dolichocephalic

type.

Lastly, the little-understood principle of correlation will almost

certainly have come into action, as in the case of great muscular

development and strongly projecting supra-orbital ridges. It is not

improbable that the texture of the hair, which differs much in the

different races, may stand in some kind of correlation with the

structure of the skin; for the colour of the hair and skin are certainly

correlated, as is its colour and texture with the Mandans.[334] The

colour of the skin and the odour emitted by it are likewise in some

manner connected. With the breeds of sheep the number of hairs within a

given space and the number of the excretory pores stand in some relation

to each other.[335] If we may judge from the analogy of our domesticated

animals, many modifications of structure in man probably come under this

principle of correlated growth.

We have now seen that the characteristic differences between the races

of man cannot be accounted for in a satisfactory manner by the direct

action of the conditions of life, nor by the effects of the continued

use of parts, nor through the principle of correlation. We are therefore

led to inquire whether slight individual differences, to which man is

eminently liable, may not have been preserved and augmented during a

long series of generations through natural selection. But here we are at

once met by the objection that beneficial variations alone can be thus

preserved; and as far as we are enabled to judge (although always liable

to error on this head) not one of the external differences between the

races of man are of any direct or special service to him. The

intellectual and moral or social faculties must of course be excepted

from this remark; but differences in these faculties can have had little

or no influence on external characters. The variability of all the

characteristic differences between the races, before referred to,

likewise indicates that these differences cannot be of much importance;

for, had they been important, they would long ago have been either fixed

and preserved, or eliminated. In this respect man resembles those forms,

called by naturalists protean or polymorphic, which have remained

extremely variable, owing, as it seems, to their variations being of an

indifferent nature, and consequently to their having escaped the action

of natural selection.

We have thus far been baffled in all our attempts to account for the

differences between the races of man; but there remains one important

agency, namely Sexual Selection, which appears to have acted as

powerfully on man, as on many other animals. I do not intend to assert

that sexual selection will account for all the differences between the

races. An unexplained residuum is left, about which we can in our

ignorance only say, that as individuals are continually born with, for

instance, heads a little rounder or narrower, and with noses a little

longer or shorter, such slight differences might become fixed and

uniform, if the unknown agencies which induced them were to act in a

more constant manner, aided by long-continued intercrossing. Such

modifications come under the provisional class, alluded to in our fourth

chapter, which for the want of a better term have been called

spontaneous variations. Nor do I pretend that the effects of sexual

selection can be indicated with scientific precision; but it can be

shewn that it would be an inexplicable fact if man had not been modified

by this agency, which has acted so powerfully on innumerable animals,

both high and low in the scale. It can further be shewn that the

differences between the races of man, as in colour, hairyness, form of

features, &c., are of the nature which it might have been expected would

have been acted on by sexual selection. But in order to treat this

subject in a fitting manner, I have found it necessary to pass the whole

animal kingdom in review; I have therefore devoted to it the Second Part

of this work. At the close I shall return to man, and, after attempting

to shew how far he has been modified through sexual selection, will give

a brief summary of the chapters in this First Part.

PART II.--SEXUAL SELECTION.

CHAPTER VIII.

PRINCIPLES OF SEXUAL SELECTION.

Secondary sexual characters--Sexual selection--Manner of

action--Excess of males--Polygamy--The male alone generally

modified through sexual selection--Eagerness of the

male--Variability of the male--Choice exerted by the

female--Sexual compared with natural selection--Inheritance, at

corresponding periods of life, at corresponding seasons of the

year, and as limited by sex--Relations between the several

forms of inheritance--Causes why one sex and the young are not

modified through sexual selection--Supplement on the

proportional numbers of the two sexes throughout the animal

kingdom--On the limitation of the numbers of the two sexes

through natural selection.

With animals which have their sexes separated, the males necessarily

differ from the females in their organs of reproduction; and these

afford the primary sexual characters. But the sexes often differ in what

Hunter has called secondary sexual characters, which are not directly

connected with the act of reproduction; for instance, in the male

possessing certain organs of sense or locomotion, of which the female is

quite destitute, or in having them more highly-developed, in order that

he may readily find or reach her; or again, in the male having special

organs of prehension so as to hold her securely. These latter organs of

infinitely diversified kinds graduate into, and in some cases can hardly

be distinguished from, those which are commonly ranked as primary, such

as the complex appendages at the apex of the abdomen in male insects.

Unless indeed we confine the term "primary" to the reproductive glands,

it is scarcely possible to decide, as far as the organs of prehension

are concerned, which ought to be called primary and which secondary.

The female often differs from the male in having organs for the

nourishment or protection of her young, as the mammary glands of

mammals, and the abdominal sacks of the marsupials. The male, also, in

some few cases differs from the female in possessing analogous organs,

as the receptacles for the ova possessed by the males of certain fishes,

and those temporarily developed in certain male frogs. Female bees have

a special apparatus for collecting and carrying pollen, and their

ovipositor is modified into a sting for the defence of their larvae and

the community. In the females of many insects the ovipositor is modified

in the most complex manner for the safe placing of the eggs. Numerous

similar cases could be given, but they do not here concern us. There

are, however, other sexual differences quite disconnected with the

primary organs with which we are more especially concerned--such as the

greater size, strength, and pugnacity of the male, his weapons of

offence or means of defence against rivals, his gaudy colouring and

various ornaments, his power of song, and other such characters.

Besides the foregoing primary and secondary sexual differences, the male

and female sometimes differ in structures connected with different

habits of life, and not at all, or only indirectly, related to the

reproductive functions. Thus the females of certain flies (Culicidae and

Tabanidae) are blood-suckers, whilst the males live on flowers and have

their mouths destitute of mandibles.[336] The males alone of certain

moths and of some crustaceans (_e.g._ Tanais) have imperfect, closed

mouths, and cannot feed. The Complemental males of certain cirripedes

live like epiphytic plants either on the female or hermaphrodite form,

and are destitute of a mouth and prehensile limbs. In these cases it is

the male which has been modified and has lost certain important organs,

which the other members of the same group possess. In other cases it is

the female which has lost such parts; for instance, the female glow-worm

is destitute of wings, as are many female moths, some of which never

leave their cocoons. Many female parasitic crustaceans have lost their

natatory legs. In some weevil-beetles (Curculionidae) there is a great

difference between the male and female in the length of the rostrum or

snout;[337] but the meaning of this and of many analogous differences,

is not at all understood. Differences of structure between the two sexes

in relation to different habits of life are generally confined to the

lower animals; but with some few birds the beak of the male differs from

that of the female. No doubt in most, but apparently not in all these

cases, the differences are indirectly connected with the propagation of

the species: thus a female which has to nourish a multitude of ova will

require more food than the male, and consequently will require special

means for procuring it. A male animal which lived for a very short time

might without detriment lose through disuse its organs for procuring

food; but he would retain his locomotive organs in a perfect state, so

that he might reach the female. The female, on the other hand, might

safely lose her organs for flying, swimming, or walking, if she

gradually acquired habits which rendered such powers useless.

We are, however, here concerned only with that kind of selection, which

I have called sexual selection. This depends on the advantage which

certain individuals have over other individuals of the same sex and

species, in exclusive relation to reproduction. When the two sexes

differ in structure in relation to different habits of life, as in the

cases above mentioned, they have no doubt been modified through natural

selection, accompanied by inheritance limited to one and the same sex.

So again the primary sexual organs, and those for nourishing or

protecting the young, come under this same head; for those individuals

which generated or nourished their offspring best, would leave, _caeteris

paribus_, the greatest number to inherit their superiority; whilst those

which generated or nourished their offspring badly, would leave but few

to inherit their weaker powers. As the male has to search for the

female, he requires for this purpose organs of sense and locomotion, but

if these organs are necessary for the other purposes of life, as is

generally the case, they will have been developed through natural

selection. When the male has found the female he sometimes absolutely

requires prehensile organs to hold her; thus Dr. Wallace informs me that

the males of certain moths cannot unite with the females if their tarsi

or feet are broken. The males of many oceanic crustaceans have their

legs and antennae modified in an extraordinary manner for the prehension

of the female; hence we may suspect that owing to these animals being

washed about by the waves of the open sea, they absolutely require these

organs in order to propagate their kind, and if so their development

will have been the result of ordinary or natural selection.

When the two sexes follow exactly the same habits of life, and the male

has more highly developed sense or locomotive organs than the female, it

may be that these in their perfected state are indispensable to the male

for finding the female; but in the vast majority of cases, they serve

only to give one male an advantage over another, for the less

well-endowed males, if time were allowed them, would succeed in pairing

with the females; and they would in all other respects, judging from the

structure of the female, be equally well adapted for their ordinary

habits of life. In such cases sexual selection must have come into

action, for the males have acquired their present structure, not from

being better fitted to survive in the struggle for existence, but from

having gained an advantage over other males, and from having transmitted

this advantage to their male offspring alone. It was the importance of

this distinction which led me to designate this form of selection as

sexual selection. So again, if the chief service rendered to the male by

his prehensile organs is to prevent the escape of the female before the

arrival of other males, or when assaulted by them, these organs will

have been perfected through sexual selection, that is by the advantage

acquired by certain males over their rivals. But in most cases it is

scarcely possible to distinguish between the effects of natural and

sexual selection. Whole chapters could easily be filled with details on

the differences between the sexes in their sensory, locomotive, and

prehensile organs. As, however, these structures are not more

interesting than others adapted for the ordinary purposes of life, I

shall almost pass them over, giving only a few instances under each

class.

There are many other structures and instincts which must have been

developed through sexual selection--such as the weapons of offence and

the means of defence possessed by the males for fighting with and

driving away their rivals--their courage and pugnacity--their ornaments

of many kinds--their organs for producing vocal or instrumental

music--and their glands for emitting odours; most of these latter

structures serving only to allure or excite the female. That these

characters are the result of sexual and not of ordinary selection is

clear, as unarmed, unornamented, or unattractive males would succeed

equally well in the battle for life and in leaving a numerous progeny,

if better endowed males were not present. We may infer that this would

be the case, for the females, which are unarmed and unornamented, are

able to survive and procreate their kind. Secondary sexual characters of

the kind just referred to, will be fully discussed in the following

chapters, as they are in many respects interesting, but more especially

as they depend on the will, choice, and rivalry of the individuals of

either sex. When we behold two males fighting for the possession of the

female, or several male birds displaying their gorgeous plumage, and

performing the strangest antics before an assembled body of females, we

cannot doubt that, though led by instinct, they know what they are

about, and consciously exert their mental and bodily powers.

In the same manner as man can improve the breed of his game-cocks by the

selection of those birds which are victorious in the cockpit, so it

appears that the strongest and most vigorous males, or those provided

with the best weapons, have prevailed under nature, and have led to the

improvement of the natural breed or species. Through repeated deadly

contests, a slight degree of variability, if it led to some advantage,

however slight, would suffice for the work of sexual selection; and it

is certain that secondary sexual characters are eminently variable. In

the same manner as man can give beauty, according to his standard of

taste, to his male poultry--can give to the Sebright bantam a new and

elegant plumage, an erect and peculiar carriage--so it appears that in a

state of nature female birds, by having long selected the more

attractive males, have added to their beauty. No doubt this implies

powers of discrimination and taste on the part of the female which will

at first appear extremely improbable; but I hope hereafter to shew that

this is not the case.

From our ignorance on several points, the precise manner in which sexual

selection acts is to a certain extent uncertain. Nevertheless if those

naturalists who already believe in the mutability of species, will read

the following chapters, they will, I think, agree with me that sexual

selection has played an important part in the history of the organic

world. It is certain that with almost all animals there is a struggle

between the males for the possession of the female. This fact is so

notorious that it would be superfluous to give instances. Hence the

females, supposing that their mental capacity sufficed for the exertion

of a choice, could select one out of several males. But in numerous

cases it appears as if it had been specially arranged that there should

be a struggle between many males. Thus with migratory birds, the males

generally arrive before the females at their place of breeding, so that

many males are ready to contend for each female. The bird-catchers

assert that this is invariably the case with the nightingale and

blackcap, as I am informed by Mr. Jenner Weir, who confirms the

statement with respect to the latter species.

Mr. Swaysland of Brighton, who has been in the habit, during the last

forty years, of catching our migratory birds on their first arrival,

writes to me that he has never known the females of any species to

arrive before their males. During one spring he shot thirty-nine males

of Ray's wagtail (_Budytes Raii_) before he saw a single female. Mr.

Gould has ascertained by dissection, as he informs me, that male snipes

arrive in this country before the females. In the case of fish, at the

period when the salmon ascend our rivers, the males in large numbers are

ready to breed before the females. So it apparently is with frogs and

toads. Throughout the great class of insects the males almost always

emerge from the pupal state before the other sex, so that they generally

swarm for a time before any females can be seen.[338] The cause of this

difference between the males and females in their periods of arrival and

maturity is sufficiently obvious. Those males which annually first

migrated into any country, or which in the spring were first ready to

breed, or were the most eager, would leave the largest number of

offspring; and these would tend to inherit similar instincts and

constitutions. On the whole there can be no doubt that with almost all

animals, in which the sexes are separate, there is a constantly

recurrent struggle between the males for the possession of the females.

Our difficulty in regard to sexual selection lies in understanding how

it is that the males which conquer other males, or those which prove the

most attractive to the females, leave a greater number of offspring to

inherit their superiority than the beaten and less attractive males.

Unless this result followed, the characters which gave to certain males

an advantage over others, could not be perfected and augmented through

sexual selection. When the sexes exist in exactly equal numbers, the

worst-endowed males will ultimately find females (excepting where

polygamy prevails), and leave as many offspring, equally well fitted for

their general habits of life, as the best-endowed males. From various

facts and considerations, I formerly inferred that with most animals, in

which secondary sexual characters were well developed, the males

considerably exceeded the females in number; and this does hold good in

some few cases. If the males were to the females as two to one, or as

three to two, or even in a somewhat lower ratio, the whole affair would

be simple; for the better-armed or more attractive males would leave the

largest number of offspring. But after investigating, as far as

possible, the numerical proportions of the sexes, I do not believe that

any great inequality in number commonly exists. In most cases sexual

selection appears to have been effective in the following manner.

Let us take any species, a bird for instance, and divide the females

inhabiting a district into two equal bodies: the one consisting of the

more vigorous and better-nourished individuals, and the other of the

less vigorous and healthy. The former, there can be little doubt, would

be ready to breed in the spring before the others; and this is the

opinion of Mr. Jenner Weir, who has during many years carefully attended

to the habits of birds. There can also be no doubt that the most

vigorous, healthy, and best-nourished females would on an average

succeed in rearing the largest number of offspring. The males, as we

have seen, are generally ready to breed before the females; of the males

the strongest, and with some species the best armed, drive away the

weaker males; and the former would then unite with the more vigorous and

best-nourished females, as these are the first to breed. Such vigorous

pairs would surely rear a larger number of offspring than the retarded

females, which would be compelled, supposing the sexes to be numerically

equal, to unite with the conquered and less powerful males; and this is

all that is wanted to add, in the course of successive generations, to

the size, strength and courage of the males, or to improve their

weapons.

But in a multitude of cases the males which conquer other males, do not

obtain possession of the females, independently of choice on the part of

the latter. The courtship of animals is by no means so simple and short

an affair as might be thought. The females are most excited by, or

prefer pairing with, the more ornamented males, or those which are the

best songsters, or play the best antics; but it is obviously probable,

as has been actually observed in some cases, that they would at the same

time prefer the more vigorous and lively males.[339] Thus the more

vigorous females, which are the first to breed, will have the choice of

many males; and though they may not always select the strongest or best

armed, they will select those which are vigorous and well armed, and in

other respects the most attractive. Such early pairs would have the same

advantage in rearing offspring on the female side as above explained,

and nearly the same advantage on the male side. And this apparently has

sufficed during a long course of generations to add not only to the

strength and fighting-powers of the males, but likewise to their

various ornaments or other attractions.

In the converse and much rarer case of the males selecting particular

females, it is plain that those which were the most vigorous and had

conquered others, would have the freest choice; and it is almost certain

that they would select vigorous as well as attractive females. Such

pairs would have an advantage in rearing offspring, more especially if

the male had the power to defend the female during the pairing-season,

as occurs with some of the higher animals, or aided in providing for the

young. The same principles would apply if both sexes mutually preferred

and selected certain individuals of the opposite sex; supposing that

they selected not only the more attractive, but likewise the more

vigorous individuals.

_Numerical Proportion of the Two Sexes._--I have remarked that sexual

selection would be a simple affair if the males considerably exceeded in

number the females. Hence I was led to investigate, as far as I could,

the proportions between the two sexes of as many animals as possible;

but the materials are scanty. I will here give only a brief abstract of

the results, retaining the details for a supplementary discussion, so as

not to interfere with the course of my argument. Domesticated animals

alone afford the opportunity of ascertaining the proportional numbers at

birth; but no records have been specially kept for this purpose. By

indirect means, however, I have collected a considerable body of

statistical data, from which it appears that with most of our domestic

animals the sexes are nearly equal at birth. Thus with race-horses,

25,560 births have been recorded during twenty-one years, and the male

births have been to the female births as 99.7 to 100. With greyhounds

the inequality is greater than with any other animal, for during twelve

years, out of 6878 births, the male births have been as 110.1 to 100

female births. It is, however, in some degree doubtful whether it is

safe to infer that the same proportional numbers would hold good under

natural conditions as under domestication; for slight and unknown

differences in the conditions affect to a certain extent the proportion

of the sexes. Thus with mankind, the male births in England are as

104.5, in Russia as 108.9, and with the Jews of Livornia as 120 _to_ 100

females. The proportion is also mysteriously affected by the

circumstance of the births being legitimate or illegitimate.

For our present purpose we are concerned with the proportion of the

sexes, not at birth, but at maturity, and this adds another element of

doubt; for it is a well ascertained fact that with man a considerably

larger proportion of males than of females die before or during birth,

and during the first few years of infancy. So it almost certainly is

with male lambs, and so it may be with the males of other animals. The

males of some animals kill each other by fighting; or they drive each

other about until they become greatly emaciated. They must, also, whilst

wandering about in eager search for the females, be often exposed to

various dangers. With many kinds of fish the males are much smaller than

the females, and they are believed often to be devoured by the latter or

by other fishes. With some birds the females appear to die in larger

proportion than the males: they are also liable to be destroyed on their

nests, or whilst in charge of their young. With insects the female larvae

are often larger than those of the males, and would consequently be more

likely to be devoured: in some cases the mature females are less active

and less rapid in their movements than the males, and would not be so

well able to escape from danger. Hence, with animals in a state of

nature, in order to judge of the proportions of the sexes at maturity,

we must rely on mere estimation; and this, except perhaps when the

inequality is strongly marked, is but little trustworthy. Nevertheless,

as far as a judgment can be formed, we may conclude from the facts given

in the supplement, that the males of some few mammals, of many birds, of

some fish and insects, considerably exceed in number the females.

The proportion between the sexes fluctuates slightly during successive

years: thus with race-horses, for every 100 females born, the males

varied from 107.1 in one year to 92.6 in another year, and with

greyhounds from 116.3 to 95.3. But had larger numbers been tabulated

throughout a more extensive area than England, these fluctuations would

probably have disappeared; and such as they are, they would hardly

suffice to lead under a state of nature to the effective action of

sexual selection. Nevertheless with some few wild animals, the

proportions seem, as shewn in the supplement, to fluctuate either during

different seasons or in different localities in a sufficient degree to

lead to such action. For it should be observed that any advantage gained

during certain years or in certain localities by those males which were

able to conquer other males, or were the most attractive to the females,

would probably be transmitted to the offspring and would not

subsequently be eliminated. During the succeeding seasons, when from the

equality of the sexes every male was everywhere able to procure a

female, the stronger or more attractive males previously produced would

still have at least as good a chance of leaving offspring as the less

strong or less attractive.

_Polygamy._--The practice of polygamy leads to the same results as

would follow from an actual inequality in the number of the sexes; for

if each male secures two or more females, many males will not be able to

pair; and the latter assuredly will be the weaker or less attractive

individuals. Many mammals and some few birds are polygamous, but with

animals belonging to the lower classes I have found no evidence of this

habit. The intellectual powers of such animals are, perhaps, not

sufficient to lead them to collect and guard a harem of females. That

some relation exists between polygamy and the development of secondary

sexual characters, appears nearly certain; and this supports the view

that a numerical preponderance of males would be eminently favourable to

the action of sexual selection. Nevertheless many animals, especially

birds, which are strictly monogamous, display strongly-marked secondary

sexual characters; whilst some few animals, which are polygamous, are

not thus characterised.

We will first briefly run through the class of mammals, and then turn to

birds. The gorilla seems to be a polygamist, and the male differs

considerably from the female; so it is with some baboons which live in

herds containing twice as many adult females as males. In South America

the _Mycetes caraya_ presents well-marked sexual differences in colour,

beard, and vocal organs, and the male generally lives with two or three

wives: the male of the _Cebus capucinus_ differs somewhat from the

female, and appears to be polygamous.[340] Little is known on this head

with respect to most other monkeys, but some species are strictly

monogamous. The ruminants are eminently polygamous, and they more

frequently present sexual differences than almost any other group of

mammals, especially in their weapons, but likewise in other characters.

Most deer, cattle, and sheep are polygamous; as are most antelopes,

though some of the latter are monogamous. Sir Andrew Smith, in speaking

of the antelopes of South Africa, says that in herds of about a dozen

there was rarely more than one mature male. The Asiatic _Antilope saiga_

appears to be the most inordinate polygamist in the world; for

Pallas[341] states that the male drives away all rivals, and collects a

herd of about a hundred, consisting of females and kids: the female is

hornless and has softer hair, but does not otherwise differ much from

the male. The horse is polygamous, but, except in his greater size and

in the proportions of his body, differs but little from the mare. The

wild boar, in his great tusks and some other characters, presents

well-marked sexual characters; in Europe and in India he leads a

solitary life, except during the breeding-season; but at this season he

consorts in India with several females, as Sir W. Elliot, who has had

large experience in observing this animal, believes: whether this holds

good in Europe is doubtful, but is supported by some statements. The

adult male Indian elephant, like the boar, passes much of his time in

solitude; but when associating with others, "it is rare to find," as Dr.

Campbell states, "more than one male with a whole herd of females." The

larger males expel or kill the smaller and weaker ones. The male differs

from the female by his immense tusks and greater size, strength, and

endurance; so great is the difference in these latter respects, that

the males when caught are valued at twenty per cent. above the

females.[342] With other pachydermatous animals the sexes differ very

little or not at all, and they are not, as far as known, polygamists.

Hardly a single species amongst the Cheiroptera and Edentata, or in the

great Orders of the Rodents and Insectivora, presents well-developed

secondary sexual differences; and I can find no account of any species

being polygamous, excepting, perhaps, the common rat, the males of

which, as some rat-catchers affirm, live with several females.

The lion in South Africa, as I hear from Sir Andrew Smith, sometimes

lives with a single female, but generally with more than one, and, in

one case, was found with as many as five females, so that he is

polygamous. He is, as far as I can discover, the sole polygamist in the

whole group of the terrestrial Carnivora, and he alone presents

well-marked sexual characters. If, however, we turn to the marine

Carnivora, the case is widely different; for many species of seals

offer, as we shall hereafter see, extraordinary sexual differences, and

they are eminently polygamous. Thus the male sea-elephant of the

Southern Ocean, always possesses, according to Peron, several females,

and the sea-lion of Forster is said to be surrounded by from twenty to

thirty females. In the North, the male sea-bear of Steller is

accompanied by even a greater number of females.

With respect to birds, many species, the sexes of which differ greatly

from each other, are certainly monogamous. In Great Britain we see

well-marked sexual differences in, for instance, the wild-duck which

pairs with a single female, with the common blackbird, and with the

bullfinch which is said to pair for life. So it is, as I am informed by

Mr. Wallace, with the Chatterers or Cotingidae of South America, and

numerous other birds. In several groups I have not been able to discover

whether the species are polygamous or monogamous. Lesson says that birds

of paradise, so remarkable for their sexual differences, are polygamous,

but Mr. Wallace doubts whether he had sufficient evidence. Mr. Salvin

informs me that he has been led to believe that humming-birds are

polygamous. The male widow-bird; remarkable for his caudal plumes,

certainly seems to be a polygamist.[343] I have been assured by Mr.

Jenner Weir and by others, that three starlings not rarely frequent the

same nest; but whether this is a case of polygamy or polyandry has not

been ascertained.

The Gallinaceae present almost as strongly marked sexual differences as

birds of paradise or humming-birds, and many of the species are, as is

well known, polygamous; others being strictly monogamous. What a

contrast is presented between the sexes by the polygamous peacock or

pheasant, and the monogamous guinea-fowl or partridge! Many similar

cases could be given, as in the grouse tribe, in which the males of the

polygamous capercailzie and black-cock differ greatly from the females;

whilst the sexes of the monogamous red grouse and ptarmigan differ very

little. Amongst the Cursores, no great number of species offer

strongly-marked sexual differences, except the bustards, and the great

bustard (_Otis tarda_), is said to be polygamous. With the Grallatores,

extremely few species differ sexually, but the ruff (_Machetes pugnax_)

affords a strong exception, and this species is believed by Montagu to

be a polygamist. Hence it appears that with birds there often exists a

close relation between polygamy and the development of strongly-marked

sexual differences. On asking Mr. Bartlett, at the Zoological Gardens,

who has had such large experience with birds, whether the male tragopan

(one of the Gallinaceae) was polygamous, I was struck by his answering,

"I do not know, but should think so from his splendid colours."

It deserves notice that the instinct of pairing with a single female is

easily lost under domestication. The wild-duck is strictly monogamous,

the domestic-duck highly polygamous. The Rev. W. D. Fox informs me that

with some half-tamed wild-ducks, kept on a large pond in his

neighbourhood, so many mallards were shot by the gamekeeper that only

one was left for every seven or eight females; yet unusually large

broods were reared. The guinea-fowl is strictly monogamous; but Mr. Fox

finds that his birds succeed best when he keeps one cock to two or three

hens.[344] Canary-birds pair in a state of nature, but the breeders in

England successfully put one male to four or five females; nevertheless

the first female, as Mr. Fox has been assured, is alone treated as the

wife, she and her young ones being fed by him; the others are treated as

concubines. I have noticed these cases, as it renders it in some degree

probable that monogamous species, in a state of nature, might readily

become either temporarily or permanently polygamous.

With respect to reptiles and fishes, too little is known of their habits

to enable us to speak of their marriage arrangements. The stickle-back

Gasterosteus, however, is said to be a polygamist;[345] and the male

during the breeding-season differs conspicuously from the female.

To sum up on the means through which, as far as we can judge, sexual

selection has led to the development of secondary sexual characters. It

has been shewn that the largest number of vigorous offspring will be

reared from the pairing of the strongest and best-armed males, which

have conquered other males, with the most vigorous and best-nourished

females, which are the first to breed in the spring. Such females, if

they select the more attractive, and at the same time vigorous, males,

will rear a larger number of offspring than the retarded females, which

must pair with the less vigorous and less attractive males. So it will

be if the more vigorous males select the more attractive and at the same

time healthy and vigorous females; and this will especially hold good if

the male defends the female, and aids in providing food for the young.

The advantage thus gained by the more vigorous pairs in rearing a larger

number of offspring has apparently sufficed to render sexual selection

efficient. But a large preponderance in number of the males over the

females would be still more efficient; whether the preponderance was

only occasional and local, or permanent; whether it occurred at birth,

or subsequently from the greater destruction of the females; or whether

it indirectly followed from the practice of polygamy.

_The Male generally more modified than the Female._--Throughout the

animal kingdom, when the sexes differ from each other in external

appearance, it is the male which, with rare exceptions, has been chiefly

modified; for the female still remains more like the young of her own

species, and more like the other members of the same group. The cause of

this seems to lie in the males of almost all animals having stronger

passions than the females. Hence it is the males that fight together and

sedulously display their charms before the females; and those which are

victorious transmit their superiority to their male offspring. Why the

males do not transmit their characters to both sexes will hereafter be

considered. That the males of all mammals eagerly pursue the females is

notorious to every one. So it is with birds; but many male birds do not

so much pursue the female, as display their plumage, perform strange

antics, and pour forth their song, in her presence. With the few fish

which have been observed, the male seems much more eager than the

female; and so it is with alligators, and apparently with Batrachians.

Throughout the enormous class of insects, as Kirby remarks,[346] "the

law is, that the male shall seek the female." With spiders and

crustaceans, as I hear from two great authorities, Mr. Blackwall and Mr.

C. Spence Bate, the males are more active and more erratic in their

habits than the females. With insects and crustaceans, when the organs

of sense or locomotion are present in the one sex and absent in the

other, or when, as is frequently the case, they are more highly

developed in the one than the other, it is almost invariably the male,

as far as I can discover, which retains such organs, or has them most

developed; and this shews that the male is the more active member in the

courtship of the sexes.[347]

The female, on the other hand, with the rarest exception, is less eager

than the male. As the illustrious Hunter[348] long ago observed, she

generally "requires to be courted;" she is coy, and may often be seen

endeavouring for a long time to escape from the male. Every one who has

attended to the habits of animals will be able to call to mind instances

of this kind. Judging from various facts, hereafter to be given, and

from the results which may fairly be attributed to sexual selection, the

female, though comparatively passive, generally exerts some choice and

accepts one male in preference to others. Or she may accept, as

appearances would sometimes lead us to believe, not the male which is

the most attractive to her, but the one which is the least distasteful.

The exertion of some choice on the part of the female seems almost as

general a law as the eagerness of the male.

We are naturally led to enquire why the male in so many and such widely

distinct classes has been rendered more eager than the female, so that

he searches for her and plays the more active part in courtship. It

would be no advantage and some loss of power if both sexes were mutually

to search for each other; but why should the male almost always be the

seeker? With plants, the ovules after fertilisation have to be nourished

for a time; hence the pollen is necessarily brought to the female

organs--being placed on the stigma, through the agency of insects or of

the wind, or by the spontaneous movements of the stamens; and with the

Algae, &c., by the locomotive power of the antherozooids. With

lowly-organised animals permanently affixed to the same spot and having

their sexes separate, the male element is invariably brought to the

female; and we can see the reason; for the ova, even if detached before

being fertilised and not requiring subsequent nourishment or protection,

would be, from their larger relative size, less easily transported than

the male element. Hence plants[349] and many of the lower animals are,

in this respect, analogous. In the case of animals not affixed to the

same spot, but enclosed within a shell with no power of protruding any

part of their bodies, and in the case of animals having little power of

locomotion, the males must trust the fertilising element to the risk of

at least a short transit through the waters of the sea. It would,

therefore, be a great advantage to such animals, as their organisation

became perfected, if the males when ready to emit the fertilising

element, were to acquire the habit of approaching the female as closely

as possible. The males of various lowly-organised animals having thus

aboriginally acquired the habit of approaching and seeking the females,

the same habit would naturally be transmitted to their more highly

developed male descendants; and in order that they should become

efficient seekers, they would have to be endowed with strong passions.

The acquirement of such passions would naturally follow from the more

eager males leaving a larger number of offspring than the less eager.

The great eagerness of the male has thus indirectly led to the much

more frequent development of secondary sexual characters in the male

than in the female. But the development of such characters will have

been much aided, if the conclusion at which I arrived after studying

domesticated animals, can be trusted, namely, that the male is more

liable to vary than the female. I am aware how difficult it is to verify

a conclusion of this kind. Some slight evidence, however, can be gained

by comparing the two sexes in mankind, as man has been more carefully

observed than any other animal. During the Novara Expedition[350] a vast

number of measurements of various parts of the body in different races

were made, and the men were found in almost every case to present a

greater range of variation than the women; but I shall have to recur to

this subject in a future chapter. Mr. J. Wood,[351] who has carefully

attended to the variation of the muscles in man, puts in italics the

conclusion that "the greatest number of abnormalities in each subject is

found in the males." He had previously remarked that "altogether in 102

subjects the varieties of redundancy were found to be half as many again

as in females, contrasting widely with the greater frequency of

deficiency in females before described." Professor Macalister like wise

remarks[352] that variations in the muscles "are probably more common in

males than females." Certain muscles which are not normally present in

mankind are also more frequently developed in the male than in the

female sex, although exceptions to this rule are said to occur. Dr.

Burt Wilder[353] has tabulated the cases of 152 individuals with

supernumerary digits, of which 86 were males, and 39, or less than half,

females; the remaining 27 being of unknown sex. It should not, however,

be overlooked that women would more frequently endeavour to conceal a

deformity of this kind than men. Whether the large proportional number

of deaths of the male offspring of man and apparently of sheep, compared

with the female offspring, before, during, and shortly after birth (see

supplement), has any relation to a stronger tendency in the organs of

the male to vary and thus to become abnormal in structure or function, I

will not pretend to conjecture.

In various classes of animals a few exceptional cases occur, in which

the female instead of the male has acquired well pronounced secondary

sexual characters, such as brighter colours, greater size, strength, or

pugnacity. With birds, as we shall hereafter see, there has sometimes

been a complete transposition of the ordinary characters proper to each

sex; the females having become the more eager in courtship, the males

remaining comparatively passive, but apparently selecting, as we may

infer from the results, the more attractive females. Certain female

birds have thus been rendered more highly coloured or otherwise

ornamented, as well as more powerful and pugnacious than the males,

these characters being transmitted to the female offspring alone.

It may be suggested that in some cases a double process of selection has

been carried on; the males having selected the more attractive females,

and the latter the more attractive males. This process however, though

it might lead to the modification of both sexes, would not make the one

sex different from the other, unless indeed their taste for the

beautiful differed; but this is a supposition too improbable in the case

of any animal, excepting man, to be worth considering. There are,

however, many animals, in which the sexes resemble each other, both

being furnished with the same ornaments, which analogy would lead us to

attribute to the agency of sexual selection. In such cases it may be

suggested with more plausibility, that there has been a double or mutual

process of sexual selection; the more vigorous and precocious females

having selected the more attractive and vigorous males, the latter

having rejected all except the more attractive females. But from what we

know of the habits of animals, this view is hardly probable, the male

being generally eager to pair with any female. It is more probable that

the ornaments common to both sexes were acquired by one sex, generally

the male, and then transmitted to the offspring of both sexes. If,

indeed, during a lengthened period the males of any species were greatly

to exceed the females in number, and then during another lengthened

period under different conditions the reverse were to occur, a double,

but not simultaneous, process of sexual selection might easily be

carried on, by which the two sexes might be rendered widely different.

We shall hereafter see that many animals exist, of which neither sex is

brilliantly coloured or provided with special ornaments, and yet the

members of both sexes or of one alone have probably been modified

through sexual selection. The absence of bright tints or other ornaments

may be the result of variations of the right kind never having occurred,

or of the animals themselves preferring simple colours, such as plain

black or white. Obscure colours have often been acquired through natural

selection for the sake of protection, and the acquirement through

sexual selection of conspicuous colours, may have been checked from the

danger thus incurred. But in other cases the males have probably

struggled together during long ages, through brute force, or by the

display of their charms, or by both means combined, and yet no effect

will have been produced unless a larger number of offspring were left by

the more successful males to inherit their superiority, than by the less

successful males; and this, as previously shewn, depends on various

complex contingencies.

Sexual selection acts in a less rigorous manner than natural selection.

The latter produces its effects by the life or death at all ages of the

more or less successful individuals. Death, indeed, not rarely ensues

from the conflicts of rival males. But generally the less successful

male merely fails to obtain a female, or obtains later in the season a

retarded and less vigorous female, or, if polygamous, obtains fewer

females; so that they leave fewer, or less vigorous, or no offspring. In

regard to structures acquired through ordinary or natural selection,

there is in most cases, as long as the conditions of life remain the

same, a limit to the amount of advantageous modification in relation to

certain special ends; but in regard to structures adapted to make one

male victorious over another, either in fighting or in charming the

female, there is no definite limit to the amount of advantageous

modification; so that as long as the proper variations arise the work of

sexual selection will go on. This circumstance may partly account for

the frequent and extraordinary amount of variability presented by

secondary sexual characters. Nevertheless, natural selection will

determine that characters of this kind shall not be acquired by the

victorious males, which would be injurious to them in any high degree,

either by expending too much of their vital powers, or by exposing them

to any great danger. The development, however, of certain structures--of

the horns, for instance, in certain stags--has been carried to a

wonderful extreme; and in some instances to an extreme which, as far as

the general conditions of life are concerned, must be slightly injurious

to the male. From this fact we learn that the advantages which favoured

males have derived from conquering other males in battle or courtship,

and thus leaving a numerous progeny, have been in the long run greater

than those derived from rather more perfect adaptation to the external

conditions of life. We shall further see, and this could never have been

anticipated, that the power to charm the female has been in some few

instances more important than the power to conquer other males in

battle.

LAWS OF INHERITANCE.

In order to understand how sexual selection has acted, and in the course

of ages has produced conspicuous results with many animals of many

classes, it is necessary to bear in mind the laws of inheritance, as far

as they are known. Two distinct elements are included under the term

"inheritance," namely the transmission and the development of

characters; but as these generally go together, the distinction is often

overlooked. We see this distinction in those characters which are

transmitted through the early years of life, but are developed only at

maturity or during old age. We see the same distinction more clearly

with secondary sexual characters, for these are transmitted through both

sexes, though developed in one alone. That they are present in both

sexes, is manifest when two species, having strongly-marked sexual

characters, are crossed, for each transmits the characters proper to

its own male and female sex to the hybrid offspring of both sexes. The

same fact is likewise manifest, when characters proper to the male are

occasionally developed in the female when she grows old or becomes

diseased; and so conversely with the male. Again, characters

occasionally appear, as if transferred from the male to the female, as

when, in certain breeds of the fowl, spurs regularly appear in the young

and healthy females; but in truth they are simply developed in the

female; for in every breed each detail in the structure of the spur is

transmitted through the female to her male offspring. In all cases of

reversion, characters are transmitted through two, three, or many

generations, and are then under certain unknown favourable conditions

developed. This important distinction between transmission and

development will be easiest kept in mind by the aid of the hypothesis of

pangenesis, whether or not it be accepted as true. According to this

hypothesis, every unit or cell of the body throws off gemmules or

undeveloped atoms, which are transmitted to the offspring of both sexes,

and are multiplied by self-division. They may remain undeveloped during

the early years of life or during successive generations; their

development into units or cells, like those from which they were

derived, depending on their affinity for, and union with, other units or

cells previously developed in the due order of growth.

_Inheritance at Corresponding Periods of Life._--This tendency is well

established. If a new character appears in an animal whilst young,

whether it endures throughout life or lasts only for a time, it will

reappear, as a general rule, at the same age and in the same manner in

the offspring. If, on the other hand, a new character appears at

maturity, or even during old age, it tends to reappear in the offspring

at the same advanced age. When deviations from this rule occur, the

transmitted characters much oftener appear before than after the

corresponding age. As I have discussed this subject at sufficient length

in another work,[354] I will here merely give two or three instances,

for the sake of recalling the subject to the reader's mind. In several

breeds of the Fowl, the chickens whilst covered with down, in their

first true plumage, and in their adult plumage, differ greatly from each

other, as well as from their common parent-form, the _Gallus bankiva_;

and these characters are faithfully transmitted by each breed to their

offspring at the corresponding period of life. For instance, the

chickens of spangled Hamburghs, whilst covered with down, have a few

dark spots on the head and rump, but are not longitudinally striped, as

in many other breeds; in their first true plumage, "they are beautifully

pencilled," that is each feather is transversely marked by numerous dark

bars; but in their second plumage the feathers all become spangled or

tipped with a dark round spot.[355] Hence in this breed variations have

occurred and have been transmitted at three distinct periods of life.

The Pigeon offers a more remarkable case, because the aboriginal

parent-species does not undergo with advancing age any change of

plumage, excepting that at maturity the breast becomes more iridescent;

yet there are breeds which do not acquire their characteristic colours

until they have moulted two, three, or four times; and these

modifications of plumage are regularly transmitted.

_Inheritance at Corresponding Seasons of the Year._--With animals in a

state of nature innumerable instances occur of characters periodically

appearing at different seasons. We see this with the horns of the stag,

and with the fur of arctic animals which becomes thick and white during

the winter. Numerous birds acquire bright colours and other decorations

during the breeding-season alone. I can throw but little light on this

form of inheritance from facts observed under domestication. Pallas

states,[356] that in Siberia domestic cattle and horses periodically

become lighter-coloured during the winter; and I have observed a similar

marked change of colour in certain ponies in England. Although I do not

know that this tendency to assume a differently coloured coat during

different seasons of the year is transmitted, yet it probably is so, as

all shades of colour are strongly inherited by the horse. Nor is this

form of inheritance, as limited by season, more remarkable than

inheritance as limited by age or sex.

_Inheritance as Limited by Sex._--The equal transmission of characters

to both, sexes is the commonest form of inheritance, at least with those

animals which do not present strongly-marked sexual differences, and

indeed with many of these. But characters are not rarely transferred

exclusively to that sex, in which they first appeared. Ample evidence on

this head has been advanced in my work on Variation under

Domestication; but a few instances may here be given. There are breeds

of the sheep and goat, in which the horns of the male differ greatly in

shape from those of the female; and these differences, acquired under

domestication, are regularly transmitted to the same sex. With

tortoise-shell cats the females alone, as a general rule, are thus

coloured, the males being rusty-red. With most breeds of the fowl, the

characters proper to each sex are transmitted to the same sex alone. So

general is this form of transmission that it is an anomaly when we see

in certain breeds variations transmitted equally to both sexes. There

are also certain sub-breeds of the fowl in which the males can hardly be

distinguished from each other, whilst the females differ considerably in

colour. With the pigeon the sexes of the parent-species do not differ in

any external character; nevertheless in certain domesticated breeds the

male is differently coloured from the female.[357] The wattle in the

English Carrier pigeon and the crop in the Pouter are more highly

developed in the male than in the female; and although these characters

have been gained through long-continued selection by man, the difference

between the two sexes is wholly due to the form of inheritance which has

prevailed; for it has arisen, not from, but rather in opposition to, the

wishes of the breeder.

Most of our domestic races have been formed by the accumulation of many

slight variations; and as some of the successive steps have been

transmitted to one sex alone, and some to both sexes, we find in the

different breeds of the same species all gradations between great sexual

dissimilarity and complete similarity. Instances have already been

given with the breeds of the fowl and pigeon; and under nature analogous

cases are of frequent occurrence. With animals under domestication, but

whether under nature I will not venture to say, one sex may lose

characters proper to it, and may thus come to resemble to a certain

extent the opposite sex; for instance, the males of some breeds of the

fowl have lost their masculine plumes and hackles. On the other hand the

differences between the sexes may be increased under domestication, as

with merino sheep, in which the ewes have lost their horns. Again,

characters proper to one sex may suddenly appear in the other sex; as

with those sub-breeds of the fowl in which the hens whilst young acquire

spurs; or, as in certain Polish sub-breeds, in which the females, as

there is reason to believe, originally acquired a crest, and

subsequently transferred it to the males. All these cases are

intelligible on the hypothesis of pangenesis; for they depend on the

gemmules of certain units of the body, although present in both sexes,

becoming through the influence of domestication dormant in the one sex;

or if naturally dormant, becoming developed.

There is one difficult question which it will be convenient to defer to

a future chapter; namely, whether a character at first developed in both

sexes, can be rendered through selection limited in its development to

one sex alone. If, for instance, a breeder observed that some of his

pigeons (in which species characters are usually transferred in an equal

degree to both sexes) varied into pale blue; could he by long-continued

selection make a breed, in which the males alone should be of this tint,

whilst the females remained unchanged? I will here only say, that this,

though perhaps not impossible, would be extremely difficult; for the

natural result of breeding from the pale-blue males would be to change

his whole stock, including both sexes, into this tint. If, however,

variations of the desired tint appeared, which were from the first

limited in their development to the male sex, there would not be the

least difficulty in making a breed characterised by the two sexes being

of a different colour, as indeed has been effected with a Belgian breed,

in which the males alone are streaked with black. In a similar manner,

if any variation appeared in a female pigeon, which was from the first

sexually limited in its development, it would be easy to make a breed

with the females alone thus characterised; but if the variation was not

thus originally limited, the process would be extremely difficult,

perhaps impossible.

_On the Relation between the period of Development of a Character and

its transmission to one sex or to both sexes._--Why certain characters

should be inherited by both sexes, and other characters by one sex

alone, namely by that sex in which the character first appeared, is in

most cases quite unknown. We cannot even conjecture why with certain

sub-breeds of the pigeon, black striae, though transmitted through the

female, should be developed in the male alone, whilst every other

character is equally transferred to both sexes. Why, again, with cats,

the tortoise-shell colour should, with rare exceptions, be developed in

the female alone. The very same characters, such as deficient or

supernumerary digits, colour-blindness, &c., may with mankind be

inherited by the males alone of one family, and in another family by the

females alone, though in both cases transmitted through the opposite as

well as the same sex.[358] Although we are thus ignorant, two rules

often hold good, namely that variations which, first appear in either

sex at a late period of life, tend to be developed in the same sex

alone; whilst variations which first appear early in life in either sex

tend to be developed in both sexes. I am, however, far from supposing

that this is the sole determining cause. As I have not elsewhere

discussed this subject, and as it has an important bearing on sexual

selection, I must here enter into lengthy and somewhat intricate

details.

It is in itself probable that any character appearing at an early age

would tend to be inherited equally by both sexes, for the sexes do not

differ much in constitution, before the power of reproduction is gained.

On the other hand, after this power has been gained and the sexes have

come to differ in constitution, the gemmules (if I may again use the

language of pangenesis) which are cast off from each varying part in the

one sex would be much more likely to possess the proper affinities for

uniting with the tissues of the same sex, and thus becoming developed,

than with those of the opposite sex.

I was first led to infer that a relation of this kind exists, from the

fact that whenever and in whatever manner the adult male has come to

differ from the adult female, he differs in the same manner from the

young of both sexes. The generality of this fact is quite remarkable: it

holds good with almost all mammals, birds, amphibians, and fishes; also

with many crustaceans, spiders and some few insects, namely certain

orthoptera and libellulae. In all these cases the variations, through the

accumulation of which the male acquired his proper masculine characters,

must have occurred at a somewhat late period of life; otherwise the

young males would have been similarly characterised; and conformably

with our rule, they are transmitted to and developed in the adult males

alone. When, on the other hand, the adult male closely resembles the

young of both sexes (these, with rare exceptions, being alike), he

generally resembles the adult female; and in most of these cases the

variations through which the young and old acquired their present

characters, probably occurred in conformity with our rule during youth.

But there is here room for doubt, as characters are sometimes

transferred to the offspring at an earlier age than that at which they

first appeared in the parents, so that the parents may have varied when

adult, and have transferred their characters to their offspring whilst

young. There are, moreover, many animals, in which the two sexes closely

resemble each other, and yet both differ from their young; and here the

characters of the adults must have been acquired late in life;

nevertheless, these characters in apparent contradiction to our rule,

are transferred to both sexes. We must not, however, overlook the

possibility or even probability of successive variations of the same

nature sometimes occurring, under exposure to similar conditions,

simultaneously in both sexes at a rather late period of life; and in

this case the variations would be transferred to the offspring of both

sexes at a corresponding late age; and there would be no real

contradiction to our rule of the variations which occur late in life

being transferred exclusively to the sex in which they first appeared.

This latter rule seems to hold true more generally than the second rule,

namely, that variations which occur in either sex early in life tend to

be transferred to both sexes. As it was obviously impossible even to

estimate in how large a number of cases throughout the animal kingdom

these two propositions hold good, it occurred to me to investigate some

striking or crucial instances, and to rely on the result.

An excellent case for investigation is afforded by the Deer Family. In

all the species, excepting one, the horns are developed in the male

alone, though certainly transmitted through the female, and capable of

occasional abnormal development in her. In the reindeer, on the other

hand, the female is provided with horns; so that in this species, the

horns ought, according to our rule, to appear early in life, long before

the two sexes had arrived at maturity and had come to differ much in

constitution. In all the other species of deer the horns ought to appear

later in life, leading to their development in that sex alone, in which

they first appeared in the progenitor of the whole Family. Now in seven

species, belonging to distinct sections of the family and inhabiting

different regions, in which the stags alone bear horns, I find that the

horns first appear at periods varying from nine months after birth in

the roebuck to ten or twelve or even more months in the stags of the six

other larger species.[359] But with the reindeer the case is widely

different, for as I hear from Prof. Nilsson, who kindly made special

enquiries for me in Lapland, the horns appear in the young animals

within four or five weeks after birth, and at the same time in both

sexes. So that here we have a structure, developed at a most unusually

early age in one species of the family, and common to both sexes in this

one species.

In several kinds of antelopes the males alone are provided with horns,

whilst in the greater number both sexes have horns. With respect to the

period of development, Mr. Blyth informs me that there lived at one time

in the Zoological Gardens a young koodoo (_Ant. strepsiceros_), in which

species the males alone are horned, and the young of a closely-allied

species, viz. the eland (_Ant. oreas_), in which both sexes are horned.

Now in strict conformity with our rule, in the young male koodoo,

although arrived at the age of ten months, the horns were remarkably

small considering the size ultimately attained by them: whilst in the

young male eland, although only three months old, the horns were already

very much larger than in the koodoo. It is also worth notice that in the

prong-horned antelope,[360] in which species the horns, though present

in both sexes, are almost rudimentary in the female, they do not appear

until about five or six months after birth. With sheep, goats, and

cattle, in which the horns are well developed in both sexes, though not

quite equal in size, they can be felt, or even seen, at birth or soon

afterwards.[361] Our rule, however, fails in regard to some breeds of

sheep, for instance merinos, in which the rams alone are horned; for I

cannot find on enquiry,[362] that the horns are developed later in life

in this breed than in ordinary sheep in which both sexes are horned. But

with domesticated sheep the presence or absence of horns is not a firmly

fixed character; a certain proportion of the merino ewes bearing small

horns, and some of the rams being hornless; whilst with ordinary sheep

hornless ewes are occasionally produced.

In most of the species of the splendid family of the Pheasants, the

males differ conspicuously from the females, and they acquire their

ornaments at a rather late period of life. The eared pheasant

(_Crossoptilon auritum_), however, offers a remarkable exception, for

both sexes possess the fine caudal plumes, the large ear-tufts and the

crimson velvet about the head; and I find on enquiry in the Zoological

Gardens that all these characters, in accordance with our rule, appear

very early in life. The adult male can, however, be distinguished from

the adult female by one character, namely by the presence of spurs; and

conformably with our rule, these do not begin to be developed, as I am

assured by Mr. Bartlett, before the age of six months, and even at this

age, can hardly be distinguished in the two sexes.[363] The male and

female Peacock differ conspicuously from each other in almost every

part of their plumage, except in the elegant head-crest, which is common

to both sexes; and this is developed very early in life, long before the

other ornaments which are confined to the male. The wild-duck offers an

analogous case, for the beautiful green speculum on the wings is common

to both sexes, though duller and somewhat smaller in the female, and it

is developed early in life, whilst the curled tail-feathers and other

ornaments peculiar to the male are developed later.[364] Between such

extreme cases of close sexual resemblance and wide dissimilarity, as

those of the Crossoptilon and peacock, many intermediate ones could be

given, in which the characters follow in their order of development our

two rules.

As most insects emerge from their pupal state in a mature condition, it

is doubtful whether the period of development determines the

transference of their characters to one or both sexes. But we do not

know that the coloured scales, for instance, in two species of

butterflies, in one of which the sexes differ in colour, whilst in the

other they are alike, are developed at the same relative age in the

cocoon. Nor do we know whether all the scales are simultaneously

developed on the wings of the same species of butterfly, in which

certain coloured marks are confined to one sex, whilst other marks are

common to both sexes. A difference of this kind in the period of

development is not so improbable as it may at first appear; for with the

Orthoptera, which assume their adult state, not by a single

metamorphosis, but by a succession of moults, the young males of some

species at first resemble the females, and acquire their distinctive

masculine characters only during a later moult. Strictly analogous cases

occur during the successive moults of certain male crustaceans.

We have as yet only considered the transference of characters,

relatively to their period of development, with species in a natural

state; we will now turn to domesticated animals; first touching on

monstrosities and diseases. The presence of supernumerary digits, and

the absence of certain phalanges, must be determined at an early

embryonic period--the tendency to profuse bleeding is at least

congenital, as is probably colour-blindness--yet these peculiarities,

and other similar ones, are often limited in their transmission to one

sex; so that the rule that characters which are developed at an early

period tend to be transmitted to both sexes, here wholly fails. But this

rule, as before remarked, does not appear to be nearly so generally true

as the converse proposition, namely, that characters which appear late

in life in one sex are transmitted exclusively to the same sex. From the

fact of the above abnormal peculiarities becoming attached to one sex,

long before the sexual functions are active, we may infer that there

must be a difference of some kind between the sexes at an extremely

early age. With respect to sexually-limited diseases, we know too little

of the period at which they originate, to draw any fair conclusion.

Gout, however, seems to fall under our rule; for it is generally caused

by intemperance after early youth, and is transmitted from the father to

his sons in a much more marked manner than to his daughters.

In the various domestic breeds of sheep, goats, and cattle, the males

differ from their respective females in the shape or development of

their horns, forehead, mane, dewlap, tail, and hump on the shoulders;

and these peculiarities, in accordance with our rule, are not fully

developed until rather late in life. With dogs, the sexes do not differ,

except that in certain breeds, especially in the Scotch deer-hound, the

male is much larger and heavier than the female; and as we shall see in

a future chapter, the male goes on increasing in size to an unusually

late period of life, which will account, according to our rule, for his

increased size being transmitted to his male offspring alone. On the

other hand, the tortoise-shell colour of the hair, which is confined to

female cats, is quite distinct at birth, and this case violates our

rule. There is a breed of pigeons in which the males alone are streaked

with black, and the streaks can be detected even in the nestlings; but

they become more conspicuous at each successive moult, so that this case

partly opposes and partly supports the rule. With the English Carrier

and Pouter pigeon the full development of the wattle and the crop occurs

rather late in life, and these characters, conformably with our rule,

are transmitted in full perfection to the males alone. The following

cases perhaps come within the class previously alluded to, in which the

two sexes have varied in the same manner at a rather late period of

life, and have consequently transferred their new characters to both

sexes at a corresponding late period; and if so, such cases are not

opposed to our rule. Thus there are sub-breeds of the pigeon, described

by Neumeister,[365] both sexes of which change colour after moulting

twice or thrice, as does likewise the Almond Tumbler; nevertheless these

changes, though occurring rather late in life, are common to both sexes.

One variety of the Canary-bird, namely the London Prize, offers a nearly

analogous case.

With the breeds of the Fowl the inheritance of various characters by one

sex or by both sexes, seems generally determined by the period at which

such characters are developed. Thus in all the many breeds in which the

adult male differs greatly in colour from the female and from the adult

male parent-species, he differs from the young male, so that the newly

acquired characters must have appeared at a rather late period of life.

On the other hand with most of the breeds in which the two sexes

resemble each other, the young are coloured in nearly the same manner as

their parents, and this renders it probable that their colours first

appeared early in life. We have instances of this fact in all black and

white breeds, in which the young and old of both sexes are alike; nor

can it be maintained that there is something peculiar in a black or

white plumage, leading to its transference to both sexes; for the males

alone of many natural species are either black or white, the females

being very differently coloured. With the so-called Cuckoo sub-breeds of

the fowl, in which the feathers are transversely pencilled with dark

stripes, both sexes and the chickens are coloured in nearly the same

manner. The laced plumage of the Sebright bantam is the same in both

sexes, and in the chickens the feathers are tipped with black, which

makes a near approach to lacing. Spangled Hamburghs, however, offer a

partial exception, for the two sexes, though not quite alike, resemble

each other more closely than do the sexes of the aboriginal

parent-species, yet they acquire their characteristic plumage late in

life, for the chickens are distinctly pencilled. Turning to other

characters besides colour: the males alone of the wild parent-species

and of most domestic breeds possess a fairly well developed comb, but in

the young of the Spanish fowl it is largely developed at a very early

age, and apparently in consequence of this it is of unusual size in the

adult females. In the Game breeds pugnacity is developed at a

wonderfully early age, of which curious proofs could be given; and this

character is transmitted to both sexes, so that the hens, from their

extreme pugnacity, are now generally exhibited in separate pens. With

the Polish breeds the bony protuberance of the skull which supports the

crest is partially developed even before the chickens are hatched, and

the crest itself soon begins to grow, though at first feebly;[366] and

in this breed a great bony protuberance and an immense crest

characterise the adults of both sexes.

Finally, from what we have now seen of the relation which exists in many

natural species and domesticated races, between the period of the

development of their characters and the manner of their

transmission--for example the striking fact of the early growth of the

horns in the reindeer, in which both sexes have horns, in comparison

with their much later growth in the other species in which the male

alone bears horns--we may conclude that one cause, though not the sole

cause, of characters being exclusively inherited by one sex, is their

development at a late age. And secondly, that one, though apparently a

less efficient, cause of characters being inherited by both sexes is

their development at an early age, whilst the sexes differ but little in

constitution. It appears, however, that some difference must exist

between the sexes even during an early embryonic period, for characters

developed at this age not rarely become attached to one sex.

_Summary and concluding remarks._--From the foregoing discussion on the

various laws of inheritance, we learn that characters often or even

generally tend to become developed in the same sex, at the same age, and

periodically at the same season of the year, in which they first

appeared in the parents. But these laws, from unknown causes, are very

liable to change. Hence the successive steps in the modification of a

species might readily be transmitted in different ways; some of the

steps being transmitted to one sex, and some to both; some to the

offspring at one age, and some at all ages. Not only are the laws of

inheritance extremely complex, but so are the causes which induce and

govern variability. The variations thus caused are preserved and

accumulated by sexual selection, which is in itself an extremely complex

affair, depending, as it does, on ardour in love, courage, and the

rivalry of the males, and on the powers of perception, taste, and will

of the female. Sexual selection will also be dominated by natural

selection for the general welfare of the species. Hence the manner in

which the individuals of either sex or of both sexes are affected

through sexual selection cannot fail to be complex in the highest

degree.

When variations occur late in life in one sex, and are transmitted to

the same sex at the same age, the other sex and the young are

necessarily left unmodified. When they occur late in life, but are

transmitted to both sexes at the same age, the young alone are left

unmodified. Variations, however, may occur at any period of life in one

sex or in both, and be transmitted to both sexes at all ages, and then

all the individuals of the species will be similarly modified. In the

following chapters it will be seen that all these cases frequently occur

under nature.

Sexual selection can never act on any animal whilst young, before the

age for reproduction has arrived. From the great eagerness of the male

it has generally acted on this sex and not on the females. The males

have thus become provided with weapons for fighting with their rivals,

or with organs for discovering and securely holding the female, or for

exciting and charming her. When the sexes differ in these respects, it

is also, as we have seen, an extremely general law that the adult male

differs more or less from the young male; and we may conclude from this

fact that the successive variations, by which the adult male became

modified, cannot have occurred much before the age for reproduction. How

then are we to account for this general and remarkable coincidence

between the period of variability and that of sexual selection,--

principles which are quite independent of each other? I

think we can see the cause: it is not that the males have never varied

at an early age, but that such variations have commonly been lost,

whilst those occurring at a later age have been preserved.

All animals produce more offspring than can survive to maturity; and we

have every reason to believe that death falls heavily on the weak and

inexperienced young. If then a certain proportion of the offspring were

to vary at birth or soon afterwards, in some manner which at this age

was of no service to them, the chance of the preservation of such

variations would be small. We have good evidence under domestication how

soon variations of all kinds are lost, if not selected. But variations

which occurred at or near maturity, and which were of immediate service

to either sex, would probably be preserved; as would similar variations

occurring at an earlier period in any individuals which happened to

survive. As this principle has an important bearing on sexual selection,

it may be advisable to give an imaginary illustration. We will take a

pair of animals, neither very fertile nor the reverse, and assume that

after arriving at maturity they live on an average for five years,

producing each year five young. They would thus produce 25 offspring;

and it would not, I think, be an unfair estimate to assume that 18 or 20

out of the 25 would perish before maturity, whilst still young and

inexperienced; the remaining seven or five sufficing to keep up the

stock of mature individuals. If so, we can see that variations which

occurred during youth, for instance in brightness, and which were not of

the least service to the young, would run a good chance of being utterly

lost. Whilst similar variations, which occurring at or near maturity in

the comparatively few individuals surviving to this age, and which

immediately gave an advantage to certain males, by rendering them more

attractive to the females, would be likely to be preserved. No doubt

some of the variations in brightness which occurred at an earlier age

would by chance be preserved, and eventually give to the male the same

advantage as those which appeared later; and this will account for the

young males commonly partaking to a certain extent (as may be observed

with many birds) of the bright colours of their adult male parents. If

only a few of the successive variations in brightness were to occur at a

late age, the adult male would be only a little brighter than the young

male; and such cases are common.

In this illustration I have assumed that the young varied in a manner

which was of no service to them; but many characters proper to the adult

male would be actually injurious to the young,--as bright colours from

making them conspicuous, or horns of large size from expending much

vital force. Such variations in the young would promptly be eliminated

through natural selection. With the adult and experienced males, on the

other hand, the advantage thus derived in their rivalry with other males

would often more than counterbalance exposure to some degree of danger.

Thus we can understand how it is that variations which must originally

have appeared rather late in life have alone or in chief part been

preserved for the development of secondary sexual characters; and the

remarkable coincidence between the periods of variability and of sexual

selection is intelligible.

As variations which give to the male an advantage in lighting with other

males, or in finding, securing, or charming the female, would be of no

use to the female, they will not have been preserved in this sex either

during youth or maturity. Consequently such variations would be

extremely liable to be lost; and the female, as far as these characters

are concerned, would be left unmodified, excepting in so far as she may

have received them by transference from the male. No doubt if the female

varied and transferred serviceable characters to her male offspring,

these would be favoured through sexual selection; and then both sexes

would thus far be modified in the same manner. But I shall hereafter

have to recur to these more intricate contingencies.