CHAPTER VIII.
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 separatefamily. 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 thatin 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 betweenancestors 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 isone, 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 genusHomo.
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, thatman 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,285Darwin, 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 wordspontaneous generation, or rather,spontaneous genesis.286And 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 theegg 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.288The 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 bespontaneouslydeveloped 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 calledprotozoa. We can even ask, whether this latent primary life, this atomic life, has not always been the ruling life on our planet.289And since, when account is takenof 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 scholasticprestigewhich is explained by thewordclassical; it is only fit for universities. Cuvier proclaimed theimmutability of species, and wished that at every revolution of the globe (the word alone then made his fortune), a newfaunamight 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.”290This 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 dayofficial 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 thelastflood; in each of these centres would appear a special fauna, and also one of the species constituting the genushomo.
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 opinion292species 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,”293and 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,specieswill 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.”295Lamarck, to whom Isidore Geoffroy has rendered greater justice than any one else before or after him,296admitted theunlimited 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,297birds, 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 hisHistoire Naturelle Générale, where we find a complete and impartialchronological 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;300he 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 onlyrelative, 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’swhole systemof 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 wesee 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 theactionsandhabitsof 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.”303But it must not be thought that Lamarck gave anappreciablealteration 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 aninfinite timeis 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 almostdisposed 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 callsnatural 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 thischanceof 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 nativeindividualdisposition 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 beallthe 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 Geoffroy307continues 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 meanthat 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,308he 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 proportionallyweak, resulting less from sudden and powerful efforts than from those small and continuous actions309in 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 everyday 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, notvice 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,310in 1858, “when it will be proposed to strikeout 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 wordssome considerable time? This is a difficulty, we own, and we have just said so. We wish that the thirty thousand years,312the 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 nebuloussystem 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 thisembryowill 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;314or that there was a successiveevolution, 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 callindividual-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 timeand 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,315in 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 andalways multiplying themselves with more or less regularity, but so as to form an immense cone.316
Each of these straight lines would represent aspecific 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. Michelet317say, “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 sametime 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 ofmediumhave 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.318The 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.319And whilst all the specificvarieties 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: thedodohas disappeared some years ago, having been destroyed by the hand of man; they say that theapterixwill 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 Darwin320under the name ofvital competition. By this we see, even since the most ancient historic periods, that certain savage animals, like the lion,321crocodile,322and hippopotamus,323retire 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 allthings, 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 sameinferiorform, 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 genushomo. 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 differentspeciesof men designated by the name of races. So that all humanity would be in relationship, if the expression be allowed us, not in theserial sense, as monogenists take it, but in thecollateral 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 thepresenthuman 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 successionof 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, hamites324for 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 thisconsiderable timeof 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.325Nothing has appearedin order to justify this hypothesis, and everything seems to show that since that epoch the height of the genushomohas 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 ofevolution. 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,326a creator in his turn, he may not one day breathe life into some new species, which will suddenly appear from his laboratories?