SPECIES.
We have now arrived at the limits of the task which we proposed to
attempt, and we hope, after what has gone before, that we shall be able
to arrive at some scientific conclusion.
After having endeavoured to establish in the introduction the route
we had to follow in anthropological studies, we gave an account of
the system of purely philosophic researches, putting every foreign
or prejudicial idea on one side, and, resting on facts and on
mathematical reasoning, we have endeavoured to apply these principles.
We endeavoured at first to prove that man was not a being as foreign
and superior to the rest of animal nature, as certain naturalists have
thought, taking themselves, the first from among men, as the point of
comparison. We have considered the inferior races, and we have shown
that between these and the first animals the distance was neither
absolute nor well-defined; that man came into the zoological series,
and that he only forms definitively a separate _family_. Changing our
direction, we abandoned this acquired knowledge, and we passed on to
the study of varieties among men; we found them profound, indeed, and
of every description.
Then came the study of the influences to which man may be subjected.
We saw that hybridity did not play any serious part in this, since it
could only weaken pre-existing differences. On the other hand, we have
acknowledged that _in the limits of time accessible to our knowledge_,
nothing justified the hypothesis, that climate had such an extensive
influence in changing man so as to make the differences which we may
observe between ancestors and descendants such as would suffice, in
any other zoological group, to characterise distinct species.
In regarding man as a separate kingdom, we are, by this fact, exempted
from applying the same rules as in zoology; but, by proving that he
comes into the zoological series, we have implicitly proved that he
must be submitted to the same laws. Science cannot have two different
modes of proceeding: it must follow the same paths in the same subjects
in order to arrive at comparable results. It is the only truly
philosophic road: nature is _one_, and the work of the modern sciences
is precisely to tend towards unity. The most diverse phenomena in the
hands of analysts compare and assimilate themselves to the rays of
a spirit of synthesis; magnetism, electricity, light, heat, motion,
everything is mingled and linked together so well, that we know not how
to make a distinction any more.
The pure and simple adoption of the law of organic unity brings us to
the following proposition:--
PROPOSITION.--_Either we must admit different species in the genus
Homo, or we must entirely reform zoological classification._
This last hypothesis will mean, then, that the works of Linnæus,
Cuvier, De Blainville, and the two Geoffroys, will be of no value, and
that we must commence anew the great work of classification upon the
same basis which we wish to adopt in anthropology. Of the two terms of
the preceding proposition, the second merits particular consideration.
Zoological classification has been created and established by the
greatest thinkers of which humanity can boast; even more, independent
by its nature from all religious influence, it has been freely done,
and without prejudice, as every scientific question ought to be, by
means of facts and reasoning. It has not always been so with the works
of those who desire that man should be an exception to universal
nature, and beyond the limits of the animal kingdom. Zoological
classification need not be reformed,--it is that of the genus _Homo_.
We touch now on the much discussed and controverted question of
species, and at the same time on the question of the origin of man. We
do not believe, as many eminent men have done, that this origin must
eternally be concealed, that man will never be permitted to tear the
veil from this statue of Isis. Let it suffice us to say that we are
about to enter on slippery ground, where we shall only find as few
resting places as the stones of a ford half destroyed by a torrent.
And since we shall only find here and there the fragile aid of one
hypothesis against so many others, in order to assist the consequents
of our reasonings, is it a reason for drawing back? We do not think so.
Every period of a science has its own tendency; at given moments the
efforts of all tend involuntarily towards one sole end,--one question
absorbs all, and all partial solutions tend to the same general
solution. At the present day, the great question in natural history
is that of species; inquiries are ardently pursued, and materials
are produced from every side,--opinions are mooted, and objections
raised. We have only to call attention on this point to the works of
Isidore Geoffroy, Morton, Nott, Godron, Broca,[285] Darwin, Fée, etc.
The question of spontaneous generation is but a phase of the same
discussion, an episode in the work of the birth of time.
Some people have made a sort of bugbear out of this word _spontaneous
generation_, or rather, _spontaneous genesis_.[286] And yet, here
is one of these truths to which, we think, we shall be led by the
observation of facts and by reasoning. The great harm of examining
into the question is to be strangely mistaken as to its bearing, and
inclined to restrict its limits. It has, in fact, been said, that
every day genital organs are discovered in beings whom it was thought
were reproduced spontaneously. This is a specious argument to which
Plutarch has long ago done justice. A person, whom he brings forward in
one of his books, asks, “Which had the first existence, the egg or the
hen?” and concludes that “it was evidently the hen.” Even in treating
lightly on this subject,--in making it a familiar conversation, the
Greek physician was, however, not mistaken about the importance of
the matter. “So that,” answers one of the guests, “with this little
question of the egg and the hen, we raise, as with a lever, the great
and dark question of the generation of the world.”[287]
That the animals which we know all reproduce by eggs, is possible,
although it has not been proved, but this is not an important point;
we want to know if all the animals which we are able to observe do not
remount necessarily, in a more or less direct manner, and at a more or
less distant period, to a spontaneous beginning.[288] The difficulty is
everywhere the same,--everywhere we arrive at that immense obscurity
which envelopes the origin of life on the surface of our planet; but it
is essential in every case not to give to the phenomenon of spontaneous
beginning any other signification than it ought to have. We must not
believe, for instance, that matter is formed by the agglomeration of
parts which do not yet live in a perfect being, having already all its
organs distributed and proportionate, uniting in one living whole. This
would be to cast ourselves on the field of an absolutely improbable
hypothesis. Histology teaches us that each animal, its instincts and
intellect included, is at a given moment merely a mass of amorphous
matter, which, at a later period, will form itself, or in the midst of
which will be _spontaneously_ developed an anatomical element, that
is to say, an organised body. To admit spontaneous genesis, then, is
simply to admit the formation of organic amorphous primitive matter
apart from an already living body, at the cost of and in the heart
of which can be born the initial anatomical element of one of these
animals, very properly called _protozoa_. We can even ask, whether
this latent primary life, this atomic life, has not always been the
ruling life on our planet.[289] And since, when account is taken of
everything, we are almost entirely ignorant of the conditions necessary
to the fecundity of any primitive embryo, excepting certain physical
conditions of temperature, liquidity, etc.; and as, on the other hand,
nothing authorises us to believe that the laws existing at the origin
of life on our planet have since been abrogated, we see that, if we
must necessarily conclude a spontaneous primitive genesis, there is
nothing irrational in admitting, until we know farther on the subject,
the persistence of the phenomenon.
Let us return to the subject of species, which, however, we did not
quite leave in speaking on the subject of spontaneous generation.
Isidore Geoffroy wishes to advance slowly in this matter, and only when
facts become patent to all. But he himself has more than once shown, by
a noble example, the benefits which science obtains by casting itself
beyond the limits of fact, provided that care is taken at first not to
give more than a simple hypothetical value to that which we may desire
to bring forward. In the question which occupies our attention, we must
embrace at one glance the whole animal kingdom since its commencement,
in order to deduce the truth of facts which have been observed; only
then these relations, for which science so ardently seeks, would appear
in their proper light. On account of this impossibility, we must
hope for some more enlightenment, chiefly from geology, and perhaps
from experiments. “How many facts would be necessary,” said Buffon,
“in order to pronounce authoritatively, or even to conjecture? How
many experiments are to be tried in order to discover these facts,
to acknowledge them, or even to anticipate them by well-founded
conjectures?”
Two opinions on the origin of species deserve to be noticed,--those
of Cuvier and Lamarck. This last held Buffon’s opinions at the end of
his career, and it ought to find in Étienne Geoffroy a defender even
more powerful in our eyes than Isidore Geoffroy himself; and especially
Darwin, to whom belongs the merit, however, of having propagated, in
his popular work, the ideas of Lamarck.
Cuvier’s theory seems to be still the dominant one; it is surrounded by
that scholastic _prestige_ which is explained by the word _classical_;
it is only fit for universities. Cuvier proclaimed the _immutability of
species_, and wished that at every revolution of the globe (the word
alone then made his fortune), a new _fauna_ might come ready made from
the hands of God, to animate the burning or icy lands of the old world.
But Cuvier, in proclaiming organic immutability, excepted mankind. We
must be allowed to doubt whether it was done with good faith. “Cuvier,
full of good taste regarding political propriety,” said a son of the
republic, his former master, now his adversary,--“Cuvier, filling his
mind with wise mental reservations concerning the future of society,
declared that it was not fitting that new discoveries, just dug from
the heart of the earth, should attack and oppose with hostile malignity
the venerated and ancient revelations of our holy books.”[290] This
remark, in which Étienne Geoffroy has concealed his anger and contempt
under a guise of perfect urbanity, will remain to the end, we are
convinced, as the judgment of posterity upon the naturalist statesman,
and upon that which they call in France at the present day _official
science_. Species was, then, a definite entity in Cuvier’s opinion,
and if he had been consistent, he would doubtless have become the
promoter of the idea which has been taken up by Agassiz,--that there
were several centres of creation on the surface of our planet after the
_last_ flood; in each of these centres would appear a special fauna,
and also one of the species constituting the genus _homo_.
These different species of men and these different fauna would since
have continued to occupy the same geographical areas with merely some
alteration. An absolute value is given to species in Cuvier’s theory,
as well as in that of Agassiz; it is unchangeable; it may disappear,
but cannot be modified, so that “each of them,” as Buffon said at the
commencement of his career, when he held the same views, “remains
always separated from the others by an interval which nature cannot
overstep.”[291]
Such has been, for a long time, the theory of the origin of species
which we have held, and which we maintained in the first edition
of this book. In fact, the solution which we now offer differs
considerably from that which we then gave. But there is evolution
rather than contradiction in going from one to the other. The
differences which separate mankind are not lessened, and have not
diminished in value in our eyes: we merely explain these differences in
another way. It cannot be called contradiction, or even inconsistency,
to change one’s manner of viewing things with the times; to regard
things otherwise which, as we said before, have no absolute basis; or
to change in five years one’s opinion concerning the origin of the
living beings on the surface of the globe.
In Buffon’s last opinion[292] species was not that definite entity in
which Cuvier believed, commencing at a given geological moment, in
order to terminate at another. Buffon says, in his latest works, that
the idea of species can only be seized upon by man at “this or that
instant of his age,”[293] and that it is merely the expression of the
ambient medium. Let this remain as before, it will not change; but when
the conditions of the medium become modified, _species_ will change. We
thus arrive at this definition:--
DEFINITION.--“_Species is a collection or group of individuals
characterised by a similarity of distinctive points; the transmission
of which is accomplished naturally, regularly, and indefinitely, in a
given order of things._”[294]
It is, in more scientific terms, the definition by Lamarck, “a
collection of similar individuals which generation perpetuates in
the same state, so that the circumstances of their situation do not
sufficiently alter so as to make their habits, their character, or
their form vary.”[295] Lamarck, to whom Isidore Geoffroy has rendered
greater justice than any one else before or after him,[296] admitted
the _unlimited variableness of species_. He admitted that we all
descend, just as we are, from an anatomical element, developed in a
determinate sense, and that we may have been worms, insects,[297]
birds, and mammals before becoming men, running through all the phases
through which animal organisation has passed during our uterine life.
We see that Lamarck approached frankly and resolutely the problem of
the origin of humanity.
In taking but superficially certain exaggerations into which Lamarck
fell, at a time less rich in facts than our own, it is not difficult
to give a certain grotesque turn to his ideas, and to laugh at them as
being unnatural; but we must not thus judge the work of a man’s whole
life, and we must appreciate Lamarck by the basis of his doctrine more
than by the examples he has given us: “a profound philosopher,” said
Étienne Geoffroy,[298] “able in laying down principles, less able in
the choice of his proofs.”
We must judge Lamarck as Isidore Geoffroy has done in his _Histoire
Naturelle Générale_, where we find a complete and impartial
chronological statement concerning the grave question of species.[299]
“Circumstances have an influence upon form and organisation,” such is
the fundamental principle of Lamarck’s doctrine;[300] he says the same
elsewhere:[301] “Circumstances determine positively what each body
may be;” and he concludes, “among living bodies, nature only shows
individuals who succeed one another. Species, amongst themselves, are
only _relative_, and are only temporarily so.”[302]
If from these general considerations we enter in detail into Lamarck’s
theory, we find room for the objections with which the opponents
of the system of variety are engrossed, with which they have made
those weapons of ridicule which act so well on minds which are not
forewarned, and who are ignorant of this master’s _whole system_ of
ideas. The grandeur of Lamarck’s views, the majestic simplicity of
his theory, ought to be sufficient to shield him from such attacks.
He saw at the beginning organic matter grouping itself under simple
forms. These first outlines, altered by time and circumstances, have
successively given birth to radiated creatures, to the inferior
molluscs, the articulate animals, then the lowest fishes, then man.
Here is a mistake, in our opinion; if there exists (until we know more)
an immense and impassable difference somewhere in the animal kingdom,
it is between the vertebrate and the invertebrate animals. Whilst the
first show an admirable unity of organic composition, the second do
not seem to have any at all, so that they do not admit of serial or
linear classification. Each of the groups which they form is united
by some particularity to all the other groups, and naturalists have
even been able to differ about what must be considered as the highest
round in the animal ladder. The organism of the invertebrata possesses
a flexibility and immense variety, which is almost a characteristic
special to these beings in which the nervous system ceases to present
the profound unity which we see in the vertebrata; whilst the entire
group has only a negative characteristic, _the want of vertebræ_, which
is sufficient alone to show how unnatural it is. As for the rest, the
vertebrate animal, even at the first moment of his embryo life, is
absolutely irreducible to any invertebrate type whatsoever, contrary
to Lamarck’s opinion. A vertebrate is to an invertebrate as two first
numbers are to one another; all the vertebrata, on the contrary, are
one to another as a simple number raised to different powers; they can
all be brought back to their origin, and both the most complicated and
the most elevated of the series are only the most simple ones arrived
at a state of considerable perfection.
A still weaker side of Lamarck’s theory is certainly the decided
influence which he attributes to the _actions_ and _habits_ of
organised beings, so as to modify them by their own means. The pedantic
caprice of his enemies has always hit on this point. “The habit of
exercising an organ,” he says, “makes it acquire developments and
dimensions which insensibly change it, so that in time it becomes very
different. On the contrary, the faulty continual exercise of an organ
impoverishes it gradually, and ends by destroying it.”[303] But it must
not be thought that Lamarck gave an _appreciable_ alteration to the
organ,--an alteration sufficiently rapid to be noticed by ourselves.
If some passages of his works make the reader think so, it is plain
that they are only the wanderings of a great mind, always weak on the
side of the ideas which he has created, and which he cherishes. Lamarck
knew very well that an _infinite time_ is the condition of unlimited
variability.[304]
Darwin is the direct successor of Lamarck, and, in our opinion, the
success of his book both in England and France is an index of the
progress which scientific ideas have made, since the days of Cuvier,
in the path of liberty and independence. Darwin, like Lamarck, admits
unlimited variety; he thinks that all animals must descend from four
or five primitive types, and plants from about an equal number; he
is almost disposed to admit but one primordial type for all organic
nature.[305]
Darwin, however, seems to us to have fallen into a grievous
exaggeration, or error of interpretation, formerly laid to Lamarck’s
charge, while he is at the same time defending an excellent cause.
Without speaking here of the relationship (forced, in our opinion)
which Darwin makes out between wild and domestic animals (of which we
have before spoken), the learned Englishman seems to have accorded too
much to individual action in the production of specific modification.
He sees a powerful activity, which he calls _natural selection_, where
we can only see absolute passiveness. We will explain what we mean:
in the midst of this vital concurrence, which he has in part so well
described,--in the midst of this immense struggle, where all which
has life on our planet is engaged in combat one against the other, or
against all, on this eternal field of battle, where the victors become
the victims, Darwin supposes that an animal brings into the world with
him, _by chance_, some psychological modification, or some anatomical
disposition, which is individually advantageous to him in the great
struggle for life; after this he will have a chance of being among the
victors, of uniting himself to another animal as happily endowed by
birth by having also conquered; they will together leave a numerous
posterity, and there is every chance that some of the descendants of
such a couple may inherit either the same instinctive disposition or
the same conformation; definitively, and by the repeated action of
this natural proceeding, a new variety can be formed, and may either
supplant the parent species or coexist with it.[306]
Such is, in a few words, the theory of natural selection. In our ideas,
there is here a false interpretation of facts; we do not believe in
this _chance_ of a native disposition, which thus transmits itself in
order to become in time a specific characteristic. We have shown,
while speaking of hybridity, that a native _individual_ disposition
ought always to disappear by the mere fact of its being individual;
it quickly disappears through cross-breeding at the tenth generation,
if not at the first, in the midst of a population which does not
possess it. We fully admit, like Lamarck, that species are formed from
one another by the appearance of organic modifications, more or less
decided; but we do not leave anything to chance in this phenomenon, as
Darwin does, and we can only see there the application of general laws.
It is not one or two animals, born with some special psychological or
anatomical disposition, who are destined to generalise themselves by
generation: it will be _all_ the individuals of the same species in a
certain radius, who will be born with a scarcely appreciable organic
modification, resulting, as far as we can tell, in an action of the
medium also nearly inappreciable by ourselves, but which long ago
will have made itself felt by the parents. The new variety will be
propagated quite naturally, since it is general, and can but increase
with each generation as long as the modifying cause continues to act.
Étienne Geoffroy had been the worthy successor of Lamarck, with
a larger and more philosophical mind. He never fell into his
exaggerations, nor into the restrictive applications of the system,
like Darwin. Let us see how Isidore Geoffroy[307] continues his
father’s theory: “Species is variable under the influence of the
ambient medium; differences, more or less considerable according to the
power of the modifying causes, may in time be produced, and the present
beings may be the descendants of the former being.” This doctrine is
our own also.
As to the idea of limited variety, propounded by Isidore Geoffroy,
we can only see in it an unfortunate restriction of his father’s
theory,--one of those errors into which even the most judicious minds
are liable to fall. Limited! Does he mean that there is a point where
these variations stop, and consequently a point where they have
commenced? Does he mean that some neighbouring animal species are
derived from a given prototype, similar to themselves, and without
any antecedents in the organic world? This is to return to Cuvier!
Limited! Does he mean that the modifications will not be considerable
in the present state of things, on account of this present state being
more or less modified? It comes to nothing directly we admit variety
as a consequence of the medium. Étienne Geoffroy was led by this kind
of idea, when, limiting his view to the short period of historical
time, and thinking he had discovered that our present climates do not
sensibly alter existing species,[308] he asked, “if there had not been
on the earth revolutions and disturbances of so vast a character that
their influence may not have been enormous; whilst in our days, changes
may have been according to the power of their effects, that is to say,
almost nothing.” And he explained everything by this convenient theory
of geological floods.
Before going farther, let us consider what we ought to think about
the disturbances of the terrestrial globe thus invoked by Étienne
Geoffroy. Now, to our mind, we have no authentic proof that the past of
our planet has really been marked by such frightful revolutions, and
geology does not make the tradition as clear as some have desired. We
think, although this is not the place to prove it, that if the changes
which have happened to the surface of the globe have been considerable,
they ought to be proportionally _weak_, resulting less from sudden and
powerful efforts than from those small and continuous actions[309] in
which nature puts forth its most formidable energies, but the progress
of which is not to be measured by the memory of man. In general, our
mind seizes but badly the notion of duration beyond certain limits. It
is not the same with the notion of force. Hence, the belief in floods.
In the presence of gigantic effects, the mind, in the appreciation of
the movers of this effect, has done what we have done every day in
mechanics. “It has changed mind into force.” It is certain that weak
but continuous forces (everywhere, however, the most powerful) have
been able to play a grander part in the history of our globe, than
these disturbances which we are in the habit of seeing everywhere.
We consider that there ought to be an entire revolution in the system
of geological research; it ought to commence at ancient times, and
come down to the present day, not _vice versâ_; we ought, in fact, to
substitute synthetic for analytical geology. After having carefully
noticed contemporaneous phenomena, we should doubtless be in time able
to read simply the trace of a feeble revolution in the geological
past, accomplished under the government of the same forces which are
daily preparing new lands, new elevations, new depressions, and a new
organic world on the surface of the globe, for the future. If it is
probable that the atmosphere has changed within certain limits, if
the nature of the waters has also been altered,--at least all these
geological phenomena, these abysses, chains of mountains, and submerged
continents, can only be the result of the forces now at work under our
own eyes,--the comparison of animals which formerly existed with those
which exist at the present day, shows, as we shall see farther on, that
the conditions of life have not sensibly changed on the surface of the
globe since the formation of the rocks subjacent to the metamorphous
rocks.
We deny that the earth is actually passing through a period of repose,
and we do not believe that it has ever formerly been more disturbed.
Since the age of the first vestiges of the organic life, which we find
in the most ancient rocks, we think that our planet has not ceased to
move in a calm and continuous march of existence; we think, in fact,
that geological phenomena of all sorts, which we hear of now-a-days,
are the exact history of the past, during which some volcanic phenomena
have also taken place, but in an entirely sporadic manner. “The day
is, perhaps, not very distant,” said M. Lartet, at the Institute,[310]
in 1858, “when it will be proposed to strike out the word ‘flood’
from the vocabulary of positive geology.” This day approaches still
nearer.[311]
Before mooting, in our turn, a theory about the vertebrate animal
kingdom (the only one which ought to occupy our attention) on the
surface of the globe, we simply ask, what is meant by Étienne Geoffroy
by the words _some considerable time_? This is a difficulty, we own,
and we have just said so. We wish that the thirty thousand years,[312]
the maximum time which we give to the farthest origin of man, should be
considered as being the age which separates us from the first organic
matter cast into the bosom of the waters, in the same proportion as the
radius of the earth is to the distance which separates our sun from the
most distant star of the most distant nebulous system which the best
telescope can observe. The extent alone of the heavens can give us an
idea of the extent of the past.
This being granted, let us see how we can represent the history of
organic development upon the earth in a few words, without hiding from
ourselves the immense obscurity which covers all origins. We are here
expressing merely a hypothesis. It will suffice us to see if this
hypothesis will agree in a satisfactory manner with the facts noticed
at the present day, on the surface and in the interior of the globe.
At the origin of the vertebrate world, since we are only examining
this, it seems rational to admit a primordial commencement, which
nothing prevents us from considering as a new and special combination
of organic matter, derived from the invertebrate world, which we may
believe to have formerly existed. In the heart of this _embryo_ will
have appeared, by spontaneous generation, the first organism connected
with the vertebrate type. This was, doubtless, a simple anatomical
element, like that which histologists see every day formed in certain
granular liquids.
We do not imagine that the origin of life can be otherwise represented;
for to admit, as Isidore Geoffroy has done in certain passages of his
works, that the will of a God peopled the earth suddenly with perfect
beings, fit for producing other beings like themselves, would be to
admit a miracle, and science teaches us at the present day what to
think of all divine interventions, either past or present.[313]
We defy anyone to get out of this alternative,--either that there
was an instantaneous and miraculous creation of a certain number of
perfect animals;[314] or that there was a successive evolution, which
is Lamarck’s idea, modified by the sense of the new knowledge which we
have at the present day, arising, on the one hand, from geology, and on
the other, from philosophical anatomy.
Let us return to this primordial anatomical element which we may
call _individual-element_. It virtually represents a vertebrate
animal just as the ovum detached from the ovary of the female
represents a man, who is only waiting for favourable circumstances
in order to develope himself. This individual-element, according
to our hypothesis, is at first simply reproduced; then, after some
considerable time, its descendants, will, little by little, in their
own sphere of activity, give birth to other elements in juxtaposition
to themselves, in this manner perfecting it and identifying it more and
more with the vertebrate type which it offers for our consideration.
After some considerable time vertebrates of as simple an organism
as mixinæ and lampreys will have thus appeared. Then, again, after
another considerable lapse of time--millions of centuries, rather
than thousands--these animals with elementary vertebra will have
successively produced, by transformation, all the vertebrata which
stock the globe at the present day.
We must here make an important remark. We have inferred by all which
precedes this, that the vertebrata of the present day and the fossil
vertebrata all descend from the same individual-element prototype,
whose existence we have admitted. In one word, we think that all
the vertebrata, both present and past, have the same genealogy, and
are all relations. That may doubtless be the case; but nothing will
make us admit that there once existed on our planet conditions fit
for the birth of this individual-element prototype, and that these
circumstances have never since been represented; so that the most
simple vertebrata of our time may very well descend from a less ancient
spontaneous genesis than the mammalia and man himself. Nothing hinders
such a supposition. It does not cost us any more to admit that one day
or other a simple organic element is formed, endowed with a life of
its own, and, even more, with a latent life, which it can, by means of
time and circumstances, diffuse around it; it does not cost us more to
admit this than to admit that similar elements have arisen at different
periods of time. This last supposition may even be regarded as so much
more probable, that we must renounce entirely, in order to explain
specific transformations, the influence of the geological revolutions
of which Étienne Geoffroy took so much account. We have seen higher up
that these were far from being proved; we can add, in support of our
assertion, a fact which we think has not been sufficiently remarked. If
these revolutions ever existed, we have a strong proof that they have
only very slightly altered the conditions of life on the surface of
the globe, at least since the ancient periods during which the first
alluvium was deposited; if we dredge some yards deep in the ocean,
the drag brings up terebratulæ and encrini; that is to say, animals
identical with those which we find in the most ancient alluvia. Is
it not remarkable that the lowest placed fossil in the stratigraphic
ladder of the beds of the terrestrial surface, the most ancient fossil
which we know, is precisely this same terebratula, which still lives
in our seas? What must we hence conclude? That there once existed on
the globe, at least to a certain extent, conditions of aquatic life
sensibly identical with those which exist at the present day.
Whether all the species of vertebrata descend from one original
spontaneous beginning, or from many successive ones, signifies very
little, since, in the second case, the primordial individual-elements
which have thus appeared at various times, would always show a great
analogy to one another.
Now, after all that we have said, this is how we may, in our opinion,
represent by a graphic figure the whole of the vertebrate kingdom,[315]
in the present and in the past. Let us image a conical figure: the
individual-element of which we have spoken will occupy its summit.
From this point a number of straight lines, few at first, will start,
branching off and always multiplying themselves with more or less
regularity, but so as to form an immense cone.[316]
Each of these straight lines would represent a _specific modification_,
accomplished after a certain number of generations under the combined
influence of the ambient medium and of some considerable time: in other
terms, each ramification would represent a species having once existed
or now existing on our planet. The length of each line would measure
the time which the species in question has existed. These lines would
never converge, because we do not believe in the creation of permanent
species by means of hybridity.
Now the mind must admit here all possible combinations; certain species
have disappeared without producing any others after them:--others exist
actually without our having any idea of one of the intermediary species
which have been allied to primitive species;--others have subsisted
slightly or not at all altered from the remotest antiquity up to our
own days, thus becoming through contemporaneous time the transformed
descendants of fossil species, of which they were also formerly the
contemporaries; it is even not impossible but that certain species
succeeding one another may have presented a retrograde evolution,
so that we must not always conclude that because one animal is only
inferior to another, it has therefore preceded it:--without going so
far as all this, the evolution of certain species may have presented
a long time of cessation whilst all others were progressing around
them, so that they appear to have retrograded. This is what has made
M. Michelet[317] say, “Nature has not progressed with a continuous
flow, but with retrograde movements, and stoppages, which allow her to
harmonise everything.” These times of repose in a specific evolution,
as well as the hypothesis of successive geneses which are already
admitted, explain how the stratified beds of the earth’s surface, in
showing from low to high what we may call more perfect organic means,
unveil at the same time to our eyes here and there a certain number of
species, inferior in organisation to those in the most ancient rocks.
As to explaining how a part of the ancient species has been able to
modify itself whilst another has remained stationary, we must admit
that all these influences of _medium_ have always been exclusively
local, so that all the coexisting vertebrata have never been able
to submit at once to its influence. We must understand by medium,
_the whole of the circumstances, past or present, which are able to
influence organism mediately or immediately in any manner whatsoever_.
The ancestors of an animal, as well as the sun which warms it, and the
parasites which devour it, make up a part of this medium.
But if it is easy to explain variety by the medium, it is a difficulty
against which the mind struggles. How can we explain ascending and
progressive variety? must we believe in some finality, an end settled
beforehand? We do not think so. Finality is a sort of divine prevision,
and the world as regards this hypothesis is still in tutelage; we
would rather believe in a creating intelligence. A simple example will
make our meaning understood. In the vegetable world this strikes us
forcibly:--the most simply formed plants are precisely those which
approach most nearly to animals by reason of their physiological
manifestations.[318] The plants which they call superior, by placing
them in an organographic point of view, are in reality inferior,
so that these plants are simple in reference to the dicotyledons
which have necessarily succeeded them, and there has been in reality
a retrograde march of life, instead of the ascending march of the
animal kingdom. Must we seek for the reason of this difference in the
presence of a nervous system? We think so. We then would admit that
organism would tend to modify itself by an inconscient act of the will,
analogous to those which rule most physiological actions; this would be
something like the possible increase or growth of the head by reason
of the influence of civilisation of which we have before spoken.[319]
And whilst all the specific varieties would result among plants from
the influence of the physical medium, we must add to the notion of this
medium, as regards animals, the nervous activity of the ancestors.
By the side of this creating influence we must recognise in the medium
a parallel destructive influence. Now, we can appreciate this every
day. The present tells us about the past; we cannot doubt but that
species formerly disappeared exactly as we see them still disappear
under our eyes by the manifestation of some new condition of the
medium; these may be sudden; volcanic phenomena, floods, extreme
variations of temperature, diseases, famines, enemies--all these
hypotheses are possible, and all equally reasonable: the _dodo_ has
disappeared some years ago, having been destroyed by the hand of
man; they say that the _apterix_ will soon disappear in the same
way, devoured by cats. But actions only moderately destructive were
doubtless otherwise very important, and we find here all the phenomena
which have been so well described, and so well explained by Darwin[320]
under the name of _vital competition_. By this we see, even since
the most ancient historic periods, that certain savage animals, like
the lion,[321] crocodile,[322] and hippopotamus,[323] retire before
mankind; that the black rat is disappearing in Europe to give place
to the field mouse, and that a race of savages disappears when their
country begins to be inhabited by a more civilised race, even when the
victors in this organic, as well as political, struggle, are not able
to reproach themselves with any cruelty.
Now, let us apply to man the theory of the origin of species which we
wish to be dominant, for there is no reason to think that man forms
any exception to the common rule. Before all things, we must remember
that human races cannot lend themselves to any classification in
natural series. It is also as impossible for the naturalist to point
out a race at the present day from which all the others are derived,
either parallelly or successively, as for the historian to discover
in the past any trace of a homogeneous humanity. If even such an
uniformity had ever existed, how would the remembrance of it have been
kept, for it is evident that this primitive form, constituting at the
beginning all the human genus, would be the same _inferior_ form, such
as the Negro or the Bosjesman, for instance, nature rising in general
from inferiority to perfection. This was for a long time Prichard’s
idea, and certain monogenists think the same at the present day. This
hypothesis, entering at its basis into the doctrine of evolution, has
nothing in itself which is startling; we can only say one thing against
it, and that is in its admitting as proved that filiation which would
connect one with the other all the groups composing in our times the
genus _homo_. For our part, we wish simply to extend the same manner
of viewing the matter, to generalise it, and to place it in relation
with this immense unknown which is behind us, and of which monogenists
do not take enough notice. We maintain that there has existed in the
night of time a certain species, less perfect than the most imperfect
man, remounting by a certain number of intermediary species, of whose
nature it is impossible for us at present to form any idea,--to
this primordial vertebrate animal which we admit. This species, a
rough outline of what man now is, gave birth, after a considerable
time, to many other species, whose parallel and unequal evolution,
following what we have said concerning animals, has at the present
day as contemporaneous (but not the last) illustration, the different
_species_ of men designated by the name of races. So that all humanity
would be in relationship, if the expression be allowed us, not in the
_serial sense_, as monogenists take it, but in the _collateral sense_,
and at a degree which we cannot determine; the prognathous races
probably less deviated from the former type, the others more separated
from this type, and more perfect.
It may be seen, and we are bound to make the remark, that we no more
pretend to make man a descendant of the ape, than a white man a
descendant of a Negro; but it is not impossible, in our opinion, that
species of men, as well as the great apes whose relationship hurts our
vanity so much, may remount infinitely far in the past to an unknown
single species, whose descendants, submitted to multiplied influences,
might be modified in different ways by reason of these different
influences.
We admit, then, that species is an instant of a constant evolution;
that it does not exist by itself; and that it is only an appreciation
of our senses, localised by time. In our opinion, if species is fixed,
it is fixed after the manner of the sun. That is to say, that we cannot
perceive any movement in it beyond the merest trifle.
It requires thousands of years to discover either solar displacement or
specific alteration. This is what makes the determination of species so
difficult; some of which may be considered as in progress of formation
in reference to others. The difficulty is the same with mankind as it
is with animals. We would not dare to contradict, for instance, the
opinions of those who see in the Hindú, German, and Celtic population
three species in course of formation, all three being probably derived
from a species anterior to that which history endeavours at the present
day to name; that Aryan race of which such a noble picture is made,
and which we believe to be primitive because it is in the horizon of
history, just as the ancients saw in the ocean the limits of the world.
In a short time, perhaps, some discovery in a poor Asiatic field will
take away from the Aryas the characteristic nobility and intelligence
which we give to them with so much satisfaction. It belongs to human
palæontology alone to enlighten us upon the origin of the _present_
human types; it alone can lead us in a sure path towards the great
problem of their origin.
But both geology, and palæontology which depends on it, have the
singular destiny of showing at one and the same time both great
certainties and insoluble doubts. The stratification of rocks, for
example, gives us very clearly the notion of the succession of
these rocks with regard to one another. But it leaves us in absolute
ignorance of all which has passed between the deposit of one stratum
and the deposit of that which we meet with above it; in this unknown
time all may take place, ten series of rocks may have been placed upon
it, and then have been so well mingled together that we cannot discover
their individual trace. Who will tell us about the continents engulphed
by the sea; has it not already ground up under its waves those
memorials of ancient days, which would be so useful to us as a means of
reconstructing the history of man? Geology is a gigantic inscription
lacerated for ever: each age will decipher some fragment, but we shall
never be able to read it in its perfect state.
Besides its great advantages, palæontological inquiry has its great
inconveniences. Its advantages are the studying of animal forms
which are fixed for ever, and not seeing the field of such studies
continually increasing on our view. The limit of its inquiries is the
origin of the alluvium; all the facts which we are thereby called
upon to study are within this boundary. Palæontology alone, among the
sciences of the present day, knows the extent of its domain.
But palæontology, proceeding step by step, by blows of the pickaxe in
an otherwise inaccessible mass, is composed of two orders of facts,
which must be distinguished one from the other, resting either on
affirmative evidence (the existence of organic remains in a rock) or
on negative evidence (the absence of organic remains in a rock). Human
palæontology itself has its own inconveniences. A bone or a skull of
a man are things which are well known; they have not that strange
appearance in the eyes of the crowd which makes them take ammonites
for petrified serpents, hamites[324] for leeches, radiated animals for
stars; when we dig up some singular bone, some carapace of a lizard, a
fish, or of some unknown animal, we pick it up, and take great care of
it. But if it is a man’s head, it is generally replaced religiously in
the earth, and these remains are for ever lost to the scientific world.
There result from all this two sorts of ideas in palæontology, the one
positive, the other negative: it is true, however, that the latter
diminish continually the profit we obtain from the former, and it is
important to remember that this negative evidence is the only basis
upon which rests the hypothesis that man is so new to our globe as some
imagine. Every moment we may expect to see the interior of the earth
prove the contrary. Instead of discoveries following one another, and
being linked together as in other sciences, forming a whole which hangs
together by itself, palæontology goes on from hand to mouth, as it
were, at the caprice of whatever may happen, without knowing the wonder
which is about to be revealed, perhaps at a few steps from a path which
millions of men have passed by.
It is very true that the human bones which have hitherto been found
in the ground in caverns seem to proceed from a form but slightly
different from our own; but all this is very recent, relatively to this
_considerable time_ of which we have before spoken. Who can say but
that we may find very soon a skull which must be classed, whether one
will or not, between the anthropomorphous apes and man?
Étienne Geoffroy, led by the logical nature of his ideas, naturally
admitted this intermediary form, anterior to our own; but seeing the
mammalia of the last geological ages generally larger than those
which are contemporary with ourselves, he concluded besides that our
immediate ancestors were giants, and that we have degenerated, like the
descendants of the bears and hyenas found in caverns.[325] Nothing has
appeared in order to justify this hypothesis, and everything seems to
show that since that epoch the height of the genus _homo_ has not much
altered, whilst the size of the different genera of ferines, ruminants,
and pachyderms has positively varied.
_Recapitulation._ Since we have found that man is comparable in all
points to animals, we ought to seek for him and for them a common
origin, and the difficulty of admitting an initial miracle has led us
to the idea of _evolution_. If in the science of observation it is
permitted to refer to general ideas, assuredly it is so in this case;
philosophy commences where science ends, and it belongs to it to give
us an explanation of the matter; but we must wait for the future for a
true positive solution of the problem, perhaps from advanced geology,
perhaps from experiments. The genius of man has no bounds, who can say
to what it may reach? who knows whether, like a new Prometheus,[326]
a creator in his turn, he may not one day breathe life into some new
species, which will suddenly appear from his laboratories?