naturalists who are well competent to form a sound judgment, is that man
is descended from some less highly organized form. The grounds upon
which this conclusion rests will never be shaken, for the close
similarity between man and the lower animals in embryonic development,
as well as in innumerable points of structure and constitution, both of
high and of the most trifling importance--the rudiments which he
retains, and the abnormal reversions to which he is occasionally
liable--are facts which cannot be disputed. They have long been known,
but, until recently, they told us nothing with respect to the origin of
man. Now, when viewed by the light of our knowledge of the whole organic
world, their meaning is unmistakable. The great principle of evolution
stands up clear and firm when these groups of facts are considered in
connection with others, such as the mutual affinities of the members of
the same group, their geographical distribution in past and present
times, and their geological succession. It is incredible that all these
facts should speak falsely. He who is not content to look, like a
savage, at the phenomena of Nature as disconnected, cannot any longer
believe that man is the work of a separate act of creation. He will be
forced to admit that the close resemblance of the embryo of man to that,
for instance, of a dog--the construction of his skull, limbs and whole
frame on the same plan with that of other mammals--the occasional
appearance of various structures, for instance, of several distinct
muscles, which man does not normally possess, but which are common to
the Quadrumana--and a crowd of analogous facts--all point in the
plainest manner to the conclusion that man is the co-descendant of other
mammals of a common progenitor.
We have seen that man incessantly presents individual differences in all
parts of his body and in his mental faculties. These differences or
variations seem to be induced by the same general causes, and to obey
the same laws as with the lower animals. In both cases similar laws of
inheritance prevail. Man tends to increase at a greater rate than his
means of subsistence; consequently he is occasionally subjected to a
severe struggle for existence, and natural selection will have effected
whatever lies within its scope. A succession of strongly marked
variations of a similar nature is by no means requisite; slight
fluctuating differences in the individual suffice in the work of natural
selection. We may feel assured that the inherited effects of the
long-continued use or disuse of parts will have done much in the same
direction with natural selection. Modifications formerly of importance,
though no longer of any special use, are long-inherited. When one part
is modified other parts change through the principle of correlation, of
which we have instances in many curious cases of correlated
monstrosities. Something may be attributed to the direct and definite
action of the surrounding conditions of life, such as abundant food,
heat or moisture; and, lastly, many characters of slight physiological
importance, some indeed of considerable importance, have been gained
through sexual selection.
No doubt man, as well as every other animal, presents structures, which,
as far as we can judge with our little knowledge, are not now of any
service to him, nor to have been so during any former period of his
existence, either in relation to his general conditions of life, or of
one sex to the other. Such structures cannot be accounted for by any
form of selection, or by the inherited effects of the use and disuse of
parts. We know, however, that many strange and strongly marked
peculiarities of structure occasionally appear in our domesticated
productions, and if the unknown causes which produce them were to act
more uniformly, they would probably become common to all the individuals
of the species. We may hope hereafter to understand something about the
causes of such occasional modifications, especially through the study of
monstrosities; hence, the labours of experimentalists, such as those of
M. Camille Dareste, are full of promise for the future. In general we
can only say that the cause of each slight variation and of each
monstrosity lies much more in the constitution of the organism than in
the nature of the surrounding conditions; though new and changed
conditions certainly play an important part in exciting organic changes
of many kinds.
Through the means just specified, aided perhaps by others as yet
undiscovered, man has been raised to his present state. But since he
attained to the rank of manhood, he has diverged into distinct races,
or, as they may be more fitly called, subspecies. Some of these, such as
the negro and European, are so distinct that, if specimens had been
brought to a naturalist without any further information, they would
undoubtedly have been considered by him as good and true species.
Nevertheless, all the races agree in so many unimportant details of
structure and in so many mental peculiarities, that these can be
accounted for only by inheritance from a common progenitor; and a
progenitor thus characterized would probably deserve to rank as man.
It must not be supposed that the divergence of each race from the other
races, and of all from a common stock, can be traced back to any one
pair of progenitors. On the contrary, at every stage in the process of
modification, all the individuals which were in any way best fitted for
their conditions of life, though in different degrees, would have
survived in greater numbers than the less well-fitted. The process would
have been like that followed by man, when he does not intentionally
select particular individuals, but breeds from all the superior
individuals and neglects all the inferior individuals. He thus slowly
but surely modifies his stock and unconsciously forms a new strain. So
with respect to modifications acquired independently of selection, and
due to variations arising from the nature of the organism and the
action of the surrounding conditions, or from changed habits of life, no
single pair will have been modified in a much greater degree than the
other pairs which inhabit the same country, for all will have been
continually blended through free intercrossing.
By considering the embryological structure of man--the homologies
[parallels] which he presents with the lower animals--the rudiments
which he retains--and the reversions to which he is liable, we can
partly recall in imagination the former condition of our early
progenitors; and can approximately place them in their proper place in
the zoological series. We thus learn that man is descended from a hairy,
tailed quadruped, probably arboreal in its habits [living on or among
trees] and an inhabitant of the Old World. This creature, if its whole
structure had been examined by a naturalist, would have been classed
among the Quadrumana, as surely as the still more ancient progenitor of
the Old and New World monkeys. The Quadrumana and all the higher mammals
are probably derived from an ancient marsupial animal [usually provided
with a pouch for the reception and nourishment of the young, as in the
case of the kangaroo] and this through a long line of diversified forms,
from some reptile-like or some amphibian-like creature, and this again
from some fish-like animal. In the dim obscurity of the past we can see
that the early progenitor of all the Vertebrata must have been an
aquatic animal, provided with branchiae [gills], with the two sexes
united in the same individual, and with the most important organs of the
body (such as the brain and heart) imperfectly or not at all developed.
This animal seems to have been more like the larvae of the existing
marine Ascidians than any other known form.
The greatest difficulty which presents itself when we are driven to the
above conclusion on the origin of man is the high standard of
intellectual power and of moral disposition which he has attained. But
every one who admits the principle of evolution must see that the mental
powers of the higher animals, which are the same in kind with those of
man, though so different in degree, are capable of advancement. Thus the
interval between the mental powers of one of the higher apes and of a
fish, or between those of an ant and scale-insect, is immense; yet their
development does not offer any special difficulty; for with our
domesticated animals the mental faculties are certainly variable, and
the variations are inherited. No one doubts that they are of the utmost
importance to animals in a state of nature. Therefore, the conditions
are favourable for their development through natural selection.
The same conclusion may be extended to man; the intellect must have been
all-important to him, even at a very remote period, as enabling him to
invent and use language, to make weapons, tools, traps, etc., whereby
with the aid of his social habits he long ago became the most dominant
of all living creatures.
A great stride in the development of the intellect will have followed,
as soon as the half-art and half-instinct of language came into use; for
the continued use of language will have reacted on the brain and
produced an inherited effect; and this again will have reacted on the
improvement of language. As Mr. Chauncey Wright has well remarked, the
largeness of the brain in man relatively to his body, compared with the
lower animals, may be attributed in chief part to the early use of some
simple form of language--that wonderful engine which affixes signs to
all sorts of objects and qualities, and excites trains of thought which
would never arise from the mere impression of the senses, or if they did
arise could not be followed out. The higher intellectual powers of man,
such as those of ratiocination, abstraction, self-consciousness, etc.,
will have followed from the continued improvement of other mental
faculties; but without considerable culture of the mind, both in the
race and in the individual, it is doubtful whether these high powers
would be exercised and thus fully attained.
The development of the moral qualities is a more interesting problem.
The foundation lies in the social instincts, including under this term
the family ties. These instincts are highly complex, and in the case of
the lower animals give special tendencies toward certain definite
actions; but the more important elements are love and the distinct
emotion of sympathy. Animals endowed with the social instincts take
pleasure in one another's company, warn one another of danger, defend
and aid one another in many ways. These instincts do not extend to all
the individuals of the species, but only to those of the same community.
As they are highly beneficial to the species they have in all
probability been acquired through natural selection.
A moral being is one who is capable of reflecting on his past actions
and their motives--of approving of some and disapproving of others; and
the fact that man is the one being who certainly deserves this
designation is the greatest of all distinctions between him and the
lower animals. But in the fourth chapter I have endeavoured to show that
the moral sense follows, firstly, from the enduring and ever-present
nature of the social instincts; secondly, from man's appreciation of the
approbation and disapprobation of his fellows; and, thirdly, from the
high activity of his mental faculties, with past impressions extremely
vivid; and in these latter respects he differs from the lower animals.
Owing to this condition of mind, man cannot avoid looking both backward
and forward and comparing past impressions. Hence, after some temporary
desire or passion has mastered his social instincts, he reflects and
compares the now weakened impression of such past impulses with the
ever-present social instincts; and he then feels that sense of
dissatisfaction which all unsatisfied instincts leave behind them, he
therefore resolves to act differently for the future--and this is
conscience. Any instinct permanently stronger or more enduring than
another gives rise to a feeling which we express by saying that it ought
to be obeyed. A pointer dog if able to reflect on his past conduct would
say to himself, I ought (as indeed we say of him) to have pointed at
that hare and not have yielded to the passing temptation of hunting it.
Social animals are impelled partly by a wish to aid the members of their
community in a general manner, but more commonly to perform certain
definite actions. Man is impelled by the same general wish to aid his
fellows; but has few or no special instincts. He differs also from the
lower animals in the power of expressing his desires by words, which
thus become a guide to the aid required and bestowed. The motive to give
aid is likewise much modified in man; it no longer consists solely of a
blind instinctive impulse, but is much influenced by the praise or blame
of his fellows. The appreciation and bestowal of praise and blame both
rest on sympathy; and this emotion, as we have seen, is one of the most
important elements of the social instincts. Sympathy, though gained as
an instinct, is also much strengthened by exercise or habit. As all men
desire their own happiness, praise or blame is bestowed on actions or
motives according as they lead to this end; and as happiness is an
essential part of the general good the greatest-happiness principle
indirectly serves as a nearly safe standard of right and wrong. As the
reasoning powers advance and experience is gained the remoter effects of
certain lines of conduct on the character of the individual and on the
general good are perceived; and then the self-regarding virtues come
within the scope of public opinion and receive praise and their
opposites blame. But with the less civilized nations reason often errs,
and many bad customs and base superstitions come within the same scope
and are then esteemed as high virtues and their breach as heavy crimes.
The moral faculties are generally and justly esteemed as of higher value
than the intellectual powers. But we should bear in mind that the
activity of the mind in vividly recalling past impressions is one of the
fundamental though secondary bases of conscience. This affords the
strongest argument for educating and stimulating in all possible ways
the intellectual faculties of every human being. No doubt, a man with a
torpid mind, if his social affections and sympathies are well developed,
will be led to good actions and may have a fairly sensitive conscience.
But whatever renders the imagination more vivid and strengthens the
habit of recalling and comparing past impressions will make the
conscience more sensitive, and may even somewhat compensate for weak
social affections and sympathies.
The moral nature of man has reached its present standard partly through
the advancement of his reasoning powers and consequently of a just
public opinion, but especially from his sympathies having been rendered
more tender and widely diffused through the effects of habit, example,
instruction and reflection. It is not improbable that after long
practice virtuous tendencies may be inherited. With the more civilized
races the conviction of the existence of an all-seeing Deity has had a
potent influence on the advance of morality. Ultimately man does not
accept the praise or blame of his fellows as his sole guide, though few
escape this influence, but his habitual convictions, controlled by
reason, afford him the safest rule. His conscience then becomes the
supreme judge and monitor. Nevertheless, the first foundation or origin
of the moral sense lies in the social instincts, including sympathy; and
these instincts, no doubt, were primarily gained, as in the case of the
lower animals, through natural selection.
The belief in God has often been advanced as not only the greatest but
the most complete of all the distinctions between man and the lower
animals. It is, however, impossible, as we have seen, to maintain that
this belief is innate or instinctive in man. On the other hand, a
belief in all-pervading spiritual agencies seems to be universal, and
apparently follows from a considerable advance in man's reason and from
a still greater advance in his faculties of imagination, curiosity and
wonder. I am aware that the assumed instinctive belief in God has been
used by many persons as an argument for His existence. But this is a
rash judgment, as we should thus be compelled to believe in the
existence of many cruel and malignant spirits, only a little more
powerful than man; for the belief in them is far more general than in a
beneficent Deity. The idea of a universal and beneficent Creator does
not seem to arise in the mind of man until he has been elevated by
long-continued culture.
He who believes in the advancement of man from some low organized form
will naturally ask, How does this bear on the belief in the immortality
of the soul? The barbarous races of man, as Sir J. Lubbock has shown,
possess no clear belief of this kind; but arguments derived from the
primeval beliefs of savages are, as we have just seen, of little or no
avail. Few persons feel any anxiety from the impossibility of
determining at what precise period in the development of the individual,
from the first trace of a minute germinal vesicle, man becomes an
immortal being; and there is no greater cause for anxiety because the
period in the gradually ascending organic scale cannot possibly be
determined.
I am aware that the conclusions arrived at in this work will be
denounced by some as highly irreligious; but he who denounces them is
bound to show why it is more irreligious to explain the origin of man as
a distinct species by descent from some lower form, through the laws of
variation and natural selection, than to explain the birth of the
individual through the laws of ordinary reproduction. The birth both of
the species and of the individual are equally parts of that grand
sequence of events, which our minds refuse to accept as the result of
blind chance. The understanding revolts at such a conclusion, whether or
not we are able to believe that every slight variation of structure, the
union of each pair in marriage, the dissemination of each seed, and
other such events have all been ordained for some special purpose.
Sexual selection has been treated at great length in this work; for, as
I have attempted to show, it has played an important part in the history
of the organic world. I am aware that much remains doubtful, but I have
endeavoured to give a fair view of the whole case. In the lower
divisions of the animal kingdom sexual selection seems to have done
nothing; such animals are often affixed for life to the same spot, or
have the sexes combined in the same individual, or, what is still more
important, their perceptive and intellectual faculties are not
sufficiently advanced to allow of the feelings of love and jealousy, or
of the exertion of choice. When, however, we come to the Arthropoda and
Vertebrata, even to the lowest classes in these two great sub-kingdoms,
sexual selection has effected much; and it deserves notice that we here
find the intellectual faculties developed, but in two very distinct
lines, to the highest standard, namely in the Hymenoptera [ants, bees,
etc.], among the Arthropoda [many insects, spiders, etc.], and in the
Mammalia, including man, among the Vertebrata.
In the most distinct classes of the animal kingdom--in mammals, birds,
fishes, insects and even crustaceans--the differences between the sexes
follow almost exactly the same rules. The males are almost always the
wooers; and they alone are armed with special weapons for fighting with
their rivals. They are generally stronger and larger than the females,
and are endowed with the requisite qualities of courage and pugnacity.
They are provided, either exclusively or in a much higher degree than
the females, with organs for vocal or instrumental music, and with
odoriferous glands. They are ornamented with infinitely diversified
appendages and with the most brilliant or conspicuous colors, often
arranged in elegant patterns, while the females are unadorned. When the
sexes differ in more important structures it is the male which is
provided with special sense-organs for discovering the female, with
locomotive organs for reaching her, and often with prehensile organs
for holding her. These various structures for charming or securing the
female are often developed in the male during only part of the year;
namely, the breeding season. They have in many cases been transferred in
a greater or less degree to the females; and in the latter case they
often appear in her as mere rudiments. They are lost or never gained by
the males after emasculation. Generally they are not developed in the
male during early youth, but appear a short time before the age for
reproduction. Hence, in most cases the young of both sexes resemble each
other; and the female somewhat resembles her young offspring throughout
life. In almost every great class a few anomalous cases occur, where
there has been an almost complete transposition of the characters proper
to the two sexes; the females assuming characters which properly belong
to the males. This surprisingly uniformity in the laws regulating the
differences between the sexes in so many and such widely separated
classes is intelligible if we admit the action throughout all the higher
divisions of the animal kingdom of one common cause; namely, sexual
selection.
Sexual selection depends on the success of certain individuals over
others of the same sex, in relation to the propagation of the species;
while natural selection depends on the success of both sexes, at all
ages, in relation to the general conditions of life. The sexual
struggle is of two kinds; in the one it is between the individuals of
the same sex, generally the males, in order to drive away or kill their
rivals, the females remaining passive; while in the other, the struggle
is likewise between the individuals of the same sex, in order to excite
or charm those of the opposite sex, generally the females, which no
longer remain passive, but select the more agreeable partners. This
latter kind of selection is closely analogous to that which man
unintentionally, yet effectually, brings to bear on his domesticated
productions, when he preserves during a long period the most pleasing or
useful individuals, without any wish to modify the breed.
The laws of inheritance determine whether characters gained through
sexual selection by either sex shall be transmitted to the same sex, or
to both; as well as the age at which they shall be developed. It appears
that variations arising late in life are commonly transmitted to one and
the same sex. Variability is the necessary basis for the action of
selection and is wholly independent of it. It follows from this that
variations of the same general nature have often been taken advantage of
and accumulated through sexual selection in relation to the propagation
of the species, as well as through natural selection in relation to the
general purposes of life. Hence secondary sexual characters, when
equally transmitted to both sexes, can be distinguished from ordinary
specific characters only by the light of analogy. The modifications
acquired through sexual selection are often so strongly pronounced that
the two sexes have frequently been ranked as distinct species, or even
as distinct genera. Such strongly marked differences must be in some
manner highly important; and we know that they have been acquired in
some instances at the cost not only of inconvenience, but of exposure to
actual danger.
The belief in the power of sexual selection rests chiefly on the
following considerations: The characters which we have the best reasons
for supposing to have been thus acquired are confined to one sex; and
this alone renders it probable that in most cases they are connected
with the act of reproduction. These characters in innumerable instances
are fully developed only at maturity; and often during only a part of
the year, which is always the breeding season. The males (passing over a
few exceptional cases) are the more active in courtship; they are the
best armed, and are rendered the most attractive in various ways. It is
to be especially observed that the males display their attractions with
elaborate care in the presence of the females; and that they rarely or
never display them excepting during the season of love. It is incredible
that all this should be purposeless. Lastly, we have distinct evidence
with some quadrupeds and birds that the individuals of one sex are
capable of feeling a strong antipathy or preference for certain
individuals of the other sex.