 This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org. Recorded by Julian Jamison. The Origin of Species by Means of Natural Selection or The Preservation of Favored Races in the Struggle for Life. Sixth London Edition by Charles Darwin. Chapter Number Ten, Part B. On the absence of numerous intermediate varieties in any single formation. From these several considerations, it cannot be doubted that the geological record, viewed as a whole, is extremely imperfect. But if we can find our attention to any one formation, it becomes much more difficult to understand why we do not therein find closely graduated varieties between the allied species which lived at its commencement and at its close. Several cases are on record of the same species presenting varieties in the upper and lower parts of the same formation. Thus, Trouchhold gives a number of instances with ammonites. And Hilgendorf has described a most curious case of ten graduated forms of planorbis multiformis in the successive beds of a freshwater formation in Switzerland. Although each formation has indisputably required a vast number of years for its deposition, several reasons can be given why each should not commonly include a graduated series of links between the species which lived at its commencement and close. But I cannot assign due proportional weight to the following considerations. Although each formation may mark a very long lapse of years, each probably is short compared with the period requisite to change one species into another. I am aware that two paleontologists whose opinions are worthy of much deference, namely Braun and Woodward, have concluded that the average duration of each formation is twice or thrice as long as the average duration of specific forms. But in supervol difficulties, as it seems to me, prevent us from coming to any just conclusion on this head. When we see a species first appearing in the middle of any formation, it would be rash in the extreme to infer that it had not elsewhere previously existed. So again, when we find a species disappearing before the last layers have been deposited, it would be equally rash to suppose that it then became extinct. We forget how small the area of Europe is compared with the rest of the world, nor have the several stages of the same formation throughout Europe been correlated with perfect accuracy. We may safely infer that with marine mammals of all kinds, there has been a large amount of migration due to climatol and other changes. And when we see a species first appearing in any formation, the probability is that it only then first immigrated into that area. It is well known, for instance, that several species appear somewhat earlier in the Paleozoic Beds of North America than in those of Europe, time having apparently been required for their migration from the American to the European seas. In examining the latest deposits in various quarters of the world, it has everywhere been noted that some few still existing species are common in the deposit, but have become extinct in the immediately surrounding sea, or conversely, that some are now abundant in the neighboring sea, but are rare or absent in this particular deposit. It is an excellent lesson to reflect on the ascertained amount of migration of the inhabitants of Europe during the glacial epoch, which forms only a part of one whole geological period, and likewise to reflect on the changes of level, on the extreme change of climate, and on the great lapse of time all included within this same glacial period. Yet it may be doubted whether, in any quarter of the world, sedimentary deposits, including fossil remains, have gone on accumulating within the same area during the whole of this period. It is not, for instance, probable that sediment was deposited during the whole of the glacial period near the mouth of the Mississippi, within that limit of depth at which marine animals can best flourish, for we know that great geographical changes occurred in other parts of America during this space of time. When such beds as were deposited in shallow water near the mouth of the Mississippi, during some part of the glacial period shall have been upraised, organic remains will probably first appear and disappear at different levels, owing to the migrations of species and to geographical changes. And in the distant future, a geologist examining these beds would be tempted to conclude that the average duration of life of the embedded fossils had been less than that of the glacial period, instead of having been really far greater, that is extending from before the glacial epoch to the present day. In order to get a perfect gradation between two forms in the upper and lower parts of the same formation, the deposit must have gone on continuously accumulating during a long period, sufficient for the slow process of modification. Hence, the deposit must be a very thick one, and the species undergoing change must have lived in the same district throughout the whole time. But we have seen that a thick formation, fossiliferous throughout its entire thickness, can accumulate only during a period of subsidence, and to keep the depth approximately the same, which is necessary that the same marine species may live in the same space, the supply of sediment must nearly counterbalance the amount of subsidence. But the same movement of subsidence will tend to submerge the area once the sediment is derived, and thus diminish the supply, whilst the downward movement continues. In fact, this nearly exact balancing between the supply of sediment and the amount of subsidence is probably a rare contingency, for it has been observed by more than one paleontologist that very thick deposits are usually barren of organic remains, except near their upper or lower limits. It would seem that each separate formation, like the whole pile of formations in any country, has generally been intermittent in its accumulation. When we see, as is so often the case, a formation composed of beds of widely different mineralogical composition, we may reasonably suspect that the process of deposition has been more or less interrupted. Nor will the closest inspection of the formation give us any idea of the length of time which its deposition may have consumed. Many instances could be given of beds only a few feet in thickness, representing formations which are elsewhere thousands of feet in thickness, and which must have required an enormous period for their accumulation. Yet no one ignorant of this fact would have even suspected the vast lapse of time represented by the thinner formation. Many cases could be given of the lower beds of a formation having been upraised, denuded, submerged, and then recovered by the upper beds of the same formation. Facts showing what wide yet easily overlooked intervals have occurred in its accumulation. In other cases we have the plainest evidence in great fossilized trees, still standing upright as they grew, of many long intervals of time and changes of level during the process of deposition, which would not have been suspected had not the trees been preserved. Thus Sir C. Lyell and Dr. Dawson found carboniferous beds 1,400 feet thick in Nova Scotia, with ancient root-bearing strata, one above the other, at no less than 68 different levels. Hence, when the same species occurs at the bottom, middle, and top of a formation, the probability is that it has not lived on the same spot during the whole period of deposition, but has disappeared and reappeared, perhaps many times, during the same geological period. Consequently, if it were to undergo a considerable amount of modification during the deposition of any one geological formation, a section would not include all the fine intermediate gradations, which must, on our theory, have existed, but abrupt, though perhaps slight, changes of form. It is all important to remember that naturalists have no golden rule by which to distinguish species and varieties. They grant some little variability to each species, but when they meet with a somewhat greater amount of difference between any two forms, they rank both as species, unless they are enabled to connect them together by the closest intermediate gradations. And this, from the reasons just assigned, we can seldom hope to affect in any one geological section. Supposing B and C to be two species, and a third, A, to be found in an older and underlying bed, even if A were strictly intermediate between B and C, it would simply be ranked as a third and distinct species, unless at the same time it could be closely connected by intermediate varieties with either one or both forms. Nor should it be forgotten, as before explained, that A might be the actual progenitor of B and C, and yet would not necessarily be strictly intermediate between them in all respects, so that we might obtain the parent species and its several modified descendants from the lower and upper beds of the same formation, and unless we obtained numerous transitional gradations, we should not recognize their blood relationship and should consequently rank them as distinct species. It is notorious on what excessively slight differences many paleontologists have found in their species, and they do this the more readily if the specimens come from different substages of the same formation. Some experienced conchologists are now thinking many of the very fine species of Durbinier and others into the rank of varieties, and on this view we do find the kind of evidence of change which on the theory we ought to find. Look again at the later tertiary deposits, which include many shells believed by the majority of naturalists to be identical with existing species. But some excellent naturalists, as Agassiz and Pikte, maintain that all these tertiary species are specifically distinct, though the distinction is admitted to be very slight. So that here, unless we believe that these eminent naturalists have been misled by their imaginations, and that these late tertiary species really present no difference whatever from their living representatives, or unless we admit in opposition to the judgment of most naturalists that these tertiary species are all truly distinct from the recent, we have evidence of the frequent occurrence of slight modifications of the kind required. If we look to rather wider intervals of time, namely to distinct but consecutive stages of the same great formation, we find that the embedded fossils, though universally ranked as specifically different, yet are far more closely related to each other than are the species found in more widely separated formations. So that here again we have undoubted evidence of change in the direction required by the theory. But to this latter subject, I shall return in the following chapter. With animals and plants that propagate rapidly and do not wander much, there is reason to suspect, as we have formerly seen, that their varieties are generally at first local and that such local varieties do not spread widely and supplant their parent form until they have been modified and perfected in some considerable degree. According to this view, the chance of discovering in a formation in any one country all the early stages of transition between any two forms is small for the successive changes are supposed to have been local or confined to some one spot. Most marine animals have a wide range and we have seen that with plants it is those which have the widest range that oftenest present varieties. So that with shells and other marine animals it is probable that those which had the widest range, far exceeding the limits of the known geological formations in Europe, have oftenest given rise first to local varieties and ultimately to new species. This again would greatly lessen the chance of our being able to trace the stages of transition in any one geological formation. It is a more important consideration leading to the same result as lately insisted on by Dr. Falconer, namely that the period during which each species underwent modification, though long as measured by years, was probably short in comparison with that during which it remained without undergoing any change. It should not be forgotten that at the present day with perfect specimens for examination two forms can seldom be connected by intermediate varieties and thus proved to be the same species until many specimens are collected from many places and with fossil species this can rarely be done. We shall perhaps best perceive the improbability of our being enabled to connect species by numerous fine intermediate fossil links by asking ourselves whether for instance geologists at some future period will be able to prove that our different breeds of cattle, sheep, horses, and dogs are descended from a single stock or from several aboriginal stocks. Or again whether certain seashells inhabiting the shores of North America which are ranked by some congeologists as distinct species from the European representatives and by other congeologists as only varieties are really varieties or are as it is called specifically distinct. This could be affected by the future geologist only by his discovery in a fossil state numerous intermediate gradations and such success is improbable in the highest degree. It has been asserted over and over again by writers who believe in the immutability of species that geology yields no linking forms. This assertion as we shall see in the next chapter is certainly erroneous. As Sir Jay Lubbock has remarked every species is a link between other allied forms. If we took a genus having a score of species recent and extinct and destroy four fifths of them, no one doubts that the remainder will stand much more distinct from each other. If the extreme forms in the genus happen to have been destroyed, the genus itself will stand more distinct from other allied genera. What geological research has not revealed is the former existence of infinitely advanced gradations as fine as existing varieties connecting together nearly all existing and extinct species. But this ought not to be expected, yet this has been repeatedly advanced as a most serious objection against my views. It may be worthwhile to sum up the foregoing remarks on the causes of the imperfection of the geological record under an imaginary illustration. The Malay Archipelago is about the size of Europe from the North to the Mediterranean, and from Britain to Russia, and therefore equals all the geological formations which have been examined with any accuracy accepting those of the United States of America. I fully agree with Mr. Godwin Austin that the present condition of the Malay Archipelago with its numerous large islands separated by wide and shallow seas probably represents the former state of Europe while most of our formations were accumulating. The Malay Archipelago is one of the richest regions in organic beings, yet if all the species were to be collected which have ever lived there, how imperfectly would they represent the natural history of the world. But we have every reason to believe that the terrestrial productions of the archipelago would be preserved in an extremely imperfect manner in the formations which we supposed to be there accumulating. Not many of the strictly latoral animals, or of those which lived on naked submarine rocks would be embedded, and those embedded in gravel or sand would not endure to a distant epoch. Wherever sediment did not accumulate on the bed of the sea, or where it did not accumulate at a sufficient rate to protect organic bodies from decay, no remains could be preserved. Formations rich in fossils of many kinds, and of thickness sufficient to last to an age as distant in futurity as the secondary formations lie in the past would generally be formed in the archipelago only during periods of subsidence. These periods of subsidence would be separated from each other by immense intervals of time during which the area would be either stationary or rising. Whilst rising, the fossiliferous formations on the steeper shores would be destroyed, almost as soon as accumulated, by the incessant coast action, as we now see on the shores of South America. Even throughout the extensive and shallow seas within the archipelago, sedimentary beds could hardly be accumulated of great thickness during the periods of elevation, or become capped and protected by subsequent deposits, so as to have a good chance of enduring to a very distant future. During the periods of subsidence, there would probably be much extinction of life. During the periods of elevation, there would be much variation, but the geological record would then be less perfect. It may be doubted whether the duration of any one great period of subsidence over the whole or part of the archipelago, together with a contemporaneous accumulation of sediment, would exceed the average duration of the same specific forms. And these contingencies are indispensable for the preservation of all the transitional gradations between any two or more species. If such gradations were not all fully preserved, transitional varieties would merely appear as so many new, though closely allied, species. It is also probable that each great period of subsidence would be interrupted by oscillations of level, and that slight climatical changes would intervene during such lengthy periods. And in these cases, the inhabitants of the archipelago would migrate, and no closely consecutive record of their modifications could be preserved in any one formation. Very many of the marine inhabitants of the archipelago now range thousands of miles beyond its confines, and analogy plainly leads to the belief that it would be chiefly these far-ranging species, though only some of them, which would oftenest produce new varieties. And the varieties would at first be local or confined to one place. But if possessed of any decided advantage, or when further modified and improved, they would slowly spread and supplant their apparent forms. In such varieties returned to their ancient homes, as they would differ from their former state in a nearly uniform, though perhaps extremely slight degree, and as they would be found embedded in slightly different sub-stages of the same formation, they would, according to the principles followed by many paleontologists, be ranked as new and distinct species. If then there be some degree of truth in these remarks, we have no right to expect to find in our geological formations an infinite number of those fine transitional forms, which, on our theory, have connected all the past and present species of the same group into one long and branching chain of life. We ought only to look for a few links, and such assuredly we do find, some more distantly, some more closely related to each other. And these links let them be ever so close if found in different stages of the same formation would by many paleontologists be ranked as distinct species. But I do not pretend that I should ever have suspected how poor was the record in the best preserved geological sections, had not the absence of innumerable transitional links between the species which lived at the commencement and close of each formation pressed so hardly on my theory. On the sudden appearance of whole groups of allied species. The abrupt manner in which whole groups of species suddenly appear in certain formations has been urged by several paleontologists, for instance by Agassiz, Pikte, and Sedgwick, as a fatal objection to the belief in the transmutation of species. If numerous species belonging to the same genera or families have really started into life at once, the fact would be fatal to the theory of evolution through natural selection. For the development by this means of a group of forms, all of which descended from some one progenitor must have been an extremely slow process, and the progenitors must have lived long before their modified descendants. But we continually overrate the perfection of the geological record, and falsely infer because certain genera or families have not been found beneath a certain stage that they did not exist before that stage. In all cases, positive paleontological evidence may be implicitly trusted. Negative evidence is worthless, as experience has so often shown. We continually forget how large the world is, compared with the area over which our geological formations have been carefully examined. We forget that groups of species may elsewhere have long existed, and have slowly multiplied before they invaded the ancient archipelagos of Europe and the United States. We do not make due allowance for the enormous intervals of time which have elapsed between our consecutive formations. Longer, perhaps in many cases, than the time required for the accumulation of each formation. These intervals will have given time for the multiplication of species from some one parent form, and in the succeeding formation such groups or species will appear, as if suddenly created. I may here recall a remark formerly made, namely that it might require a long succession of ages to adapt an organism to some new and peculiar line of life, for instance to fly through the air. And consequently, that the transitional forms would often long remain confined to some one region. But that, when this adaptation had once been affected, and a few species had thus acquired a great advantage over other organisms, a comparatively short time would be necessary to produce many divergent forms, which would spread rapidly and widely throughout the world. Professor Pikde, in his excellent review of this work, in commenting on early transitional forms and taking birds as an illustration, cannot see how the successive modifications of the interior limbs of a supposed prototype could possibly have been of any advantage. But look at the penguins of the Southern Ocean. Have not these birds their front limbs in this precise intermediate state of, quote, neither true arms nor true wings? Yet these birds hold their place victoriously in the battle for life, for they exist in infinite numbers and of many kinds. I do not suppose that we here see the real transitional grades through which the wings of birds have passed. But what special difficulty is there in believing that it might profit the modified descendants of the penguin, first to become unable to flap along the surface of the sea, like the logger-headed duck, and ultimately to rise from its surface and glide through the air. I will now give a few examples to illustrate the foregoing remarks and to show how liable we are to error in supposing that whole groups of species have suddenly been produced, even in so short an interval as that between the first and second editions of Piquetet's great work on paleontology, published in 1844-46, and in 1853-57, the conclusions on the first appearance and disappearance of several groups of animals have been considerably modified, and a third edition would require still further changes. I may recall the well-known fact that in geological treatises, published not many years ago, mammals were always spoken of as having abruptly come in at the commencement of the tertiary series. And now, one of the richest known accumulations of fossil mammals belongs to the middle of the secondary series. And true mammals have been discovered in the new red sandstone, and nearly the commencement of this great series. Cuvier used to urge that no monkey occurred in any tertiary stratum. But now extinct species have been discovered in India, South America, and in Europe, as far back as the Miocene stage. I had not been for the rare accident of the preservation of footsteps in the new red sandstone of the United States, who would have ventured to suppose that no less than at least 30 extinct bird-like animals, some of gigantic size, existed during that period. Not a fragment of bone has been discovered in these beds. Not long ago paleontologists maintained that the whole class of birds came suddenly into existence during the Eocene period. But now we know, on the authority of Professor Owen, that a bird certainly lived during the deposition of the upper green sand. And still more recently, that strange bird, the Archaeopteryx, with a long, lizard-like tail bearing a pair of feathers on each joint, and with its wings furnished with two free claws has been discovered in the oolytic slates of Solenhofen. Hardly any recent discovery shows more forcibly than this how little we as yet know of the former inhabitants of the world. I may give another instance, which from having passed under my own eyes has much struck me. In a memoir on fossil-sessile objects, I stated that from the large number of existing and extinct tertiary species, from the extraordinary abundance of the individuals of many species all over the world, from the arctic regions to the equator, inhabiting various zones of depths, from the upper tidal limits to fifty fathoms, from the perfect manner in which specimens are preserved in the oldest tertiary beds, from the ease with which even a fragment of a valve can be recognized. From all these circumstances I inferred that had sessile syrups existed during the secondary periods they would certainly have been preserved and discovered. And as not one species had then been discovered in beds of this age, I concluded that this great group had been suddenly developed at the commencement of the tertiary series. This was a sore trouble to me, adding, as I then thought, one more instance of the abrupt appearance of a great group of species. But my work had hardly been published when a skillful paleontologist, Monsieur Bosquet, sent me a drawing of a perfect specimen of an unmistakable sessile syruped which he had himself extracted from the chalk of Belgium. And as if to make the case as striking as possible, this syruped was a thamilus, a very common, large, and ubiquitous genus of which not one species has as yet been found even in any tertiary stratum. Still more recently, a pyrgoma, a member of a distinct sub-family of sessile syrupeds, has been discovered by Mr. Woodward in the upper chalk, so that we now have abundant evidence of the existence of this group of animals during the secondary period. The case most frequently insisted on by paleontologists of the apparently sudden appearance of a whole group of species is that of the teleostein fishes low down, according to Agassiz, in the chalk period. This group includes the large majority of the remaining species. But certain Jurassic and Triassic forms are now commonly admitted to be teleostein, and even some paleozoic forms have thus been classed by one high authority. If the teleosteins had really appeared suddenly in the northern hemisphere at the commencement of the chalk formation, the fact would have been highly remarkable. But it would not have formed an insuperable difficulty unless it could likewise have been shown that at the same period the species were suddenly and simultaneously developed in other quarters of the world. It is almost superfluous to remark that hardly any fossil fish are known from south of the equator. And by running through Pictay's paleontology, it will be seen that very few species are known from several formations in Europe. Some few families of fish now have a confined range. The teleostein fishes might formerly have had a similarly confined range, and after having been largely developed in some one sea, have spread widely. Nor have we any right to suppose that the seas of the world have always been so freely open from south to north as they are at present. Even at this day, if the Malay archipelago were converted into land, the tropical parts of the Indian Ocean would form a large and perfectly enclosed basin in which any great group of marine animals might be multiplied. And here they would remain confined until some of the species became adapted to a cooler climate and were enabled to double the southern capes of Africa or Australia, and thus reach other and distant seas. From these considerations, from our ignorance of the geology of other countries beyond the confines of Europe and the United States, and from the revolution in our paleontological knowledge affected by the discoveries of the last dozen years, it seems to me to be about as rash to dogmatize the notion of organic forms throughout the world as it would be for a naturalist to land for five minutes on a barren point in Australia and then to discuss the number and range of its productions. On the sudden appearance of groups of allied species in the lowest known fossiliferous strata. There is another and allied difficulty which is much more serious. I allude to the manner in which species belonging to several of the main divisions of the animal kingdom suddenly appear in the lowest known fossiliferous rocks. Most of the arguments which have convinced me that all the existing species of the same group are descended from a single progenitor apply with equal force to the earliest known species. For instance, it cannot be doubted that all the Cambrian and Celerian trilobites are descended from some one crustacean which must have lived long before the Cambrian age and which probably differed greatly from any known animal. Some of the most ancient animals as the nautilus, lingula, etc. do not differ much from living species and it cannot on our theory be supposed that these old species were the progenitors of all the species belonging to the same groups which have subsequently appeared for they are not in any degree intermediate in character. Consequently if the theory be true it is indisputable that before the Cambrian stratum was deposited long periods elapsed as long as or probably far longer than the whole interval from the Cambrian age to the present day and that during these vast periods the world swarmed with living creatures. Here we encounter a formidable objection for it seems doubtful whether the earth in a fit state for the habitation of living creatures has lasted long enough. Sir W. Thompson concludes that the consolidation of the crust can hardly have occurred less than 20 or more than 400 million years ago but probably not less than 98 or more than 200 million years. These very wide limits show how doubtful the data are and other elements may have hereafter to be introduced into the problem. Mr. Kroll estimates that about 60 million years have elapsed since the Cambrian period but this judging from the small amount of organic change since the commencement of the Glacial Epic appears a very short time for the many and great mutations of life which have certainly occurred since the Cambrian formation and the previous 140 million years can hardly be considered as sufficient for the development of the varied forms of life which already existed during the Cambrian period. It is however probable as Sir William Thompson insists that the world at a very early period was subjected to more rapid and violent changes in its physical conditions than those now occurring and such changes would have tended to induce changes at a corresponding rate in the organisms which then existed. To the question why we do not find rich fossiliferous deposits belonging to these assumed earliest periods prior to the Cambrian system I can give no satisfactory answer. Several eminent geologists with Sir R. R. Murchison at their head were until recently convinced that we beheld in the organic remains of the lowest Celerian stratum the first dawn of life. Other highly competent judges as Lyell and E. Forbes have disputed this conclusion. We should not forget that only a small portion of the world is known with accuracy. Not very long ago Mr. Barand added another and lower stage abounding with new and peculiar species beneath the then known Celerian system. And now still lower down in the lower Cambrian formation Mr. Hicks has found south Wales beds rich in trilobites and containing various mollusks and analytes. The presence of phosphatic nodules and bituminous matter even in some of the lowest azotic rocks probably indicates life at these periods and the existence of the eosone in the Laurentian formation of Canada is generally admitted. There are three great series of stratum beneath the Celerian system in Canada in the lowest of which the eosone is found. Sir W. Logan states that their quote, united thickness may possibly far surpass that of all the succeeding rocks from the base of the Paleozoic series to the present time where thus carried back to a period so remote that the appearance of the so-called primordial fauna of Burand may by some be considered as a comparatively modern event. The eosone belongs to the most lowly organized of all classes of animals but is highly organized for its class. It existed in countless numbers and as Dr. Dawson has remarked certainly preyed on other minute organic beings which must have lived in great numbers. Thus the words which I wrote in 1859 about the existence of living beings long before the Cambrian period and which are almost the same with those since used by Sir W. Logan have proved true. Nevertheless, the difficulty of assigning any good reason for the absence of vast piles of strata rich in fossils beneath the Cambrian system is very great. It does not seem probable that the most ancient beds have been quite worn away by denudation or that their fossils have been fully obliterated by metamorphic action. For if this had been the case we should have found only small remnants of the formations next succeeding them in age and these would always have existed in a partially metamorphosed condition. But the descriptions which we possess of the Silurian deposits over immense territories in Russia and in North America do not support the view that the older a formation is the more invariably it has suffered extreme denudation and metamorphism. The case at present must remain inexplicable and may be truly urged as a valid argument against the views here entertained to show that it may hereafter receive some explanation I will give the following hypothesis. From the nature of the organic remains which do not appear to have inhabited profound depths in the several formations of Europe and of the United States and from the amount of sediment miles in thickness of which the formations are composed we may infer that from first to last large islands or tracts of land once the sediment was derived occurred in the neighborhood of the now existing continents of Europe and North America. This same view has since been maintained by Agassiz and others. But we do not know what was the state of things in the intervals between the several successive formations whether Europe and the United States during these intervals existed as dry land surface near land on which sediment was not deposited or as the bed of an open and unfathomable sea. Looking to the existing oceans which are thrice as extensive as the land we see them studded with many islands but hardly one truly oceanic island with the exception of New Zealand if this can be called a truly oceanic island is as yet known to afford even a remnant of any paleozoic and secondary formation. Hence we may perhaps infer that during the paleozoic and secondary periods neither continents nor continental islands existed where our oceans now extend. For had they existed paleozoic and secondary formations would in all probability have been accumulated from sediment derived from their wear and tear and would have been at least partially upheived by the oscillations of level which must have intervened during these periods. If then we may infer anything from these facts we may infer that where our oceans now extend oceans have extended from the remotest period of which we have any record. And on the other hand that where continents now exist large tracts of land have existed subjected no doubt to great oscillations of level since the Cambrian period. The coloured map appended to my volume on coral reefs led me to conclude that the great oceans are still mainly areas of subsidence the great archipelagos still areas of oscillations of level and the continents areas of elevation. But we have no reason to assume that things have thus remained from the beginning of the world. Our continents seem to have been formed by preponderance during many oscillations of level of the force of elevation. But may not the areas of preponderant movement have changed in the laps of ages at a period long antecedent to the Cambrian epoch continents may have existed where oceans are now spread out and clear and open oceans may have existed where our continents now stand. Nor should we be justified in assuming that if for instance the bed of the Pacific ocean were now converted into a continent we should there find sedimentary formations in recognizable condition older than the Cambrian strata supposing such to have been formerly deposited for it might well happen that strata which had subsided some miles nearer to the center of the earth and which had been pressed on by an enormous weight of super incumbent water might have undergone far more metamorphic action than strata which have always remained nearer to the surface. The immense areas in some parts of the world for instance in South America of naked metamorphic rocks which must have been heated under great pressure have always seemed to me to require some special explanation and we may perhaps believe that we see in these large areas the many formations long anterior to the Cambrian epic in a completely metamorphosed and denuded condition. There's several difficulties here discussed namely that though we find in our geological formations many links between the species which now exist and which formerly existed we do not find infinitely numerous fine transitional forms closely joining them all together. The sudden manner in which several groups of species first appear in our European formations the almost entire absence as at present known of formations rich in fossils beneath the Cambrian strata are all undoubtedly of the most serious nature. We see this in the fact that the most eminent paleontologists namely Kuvier, Agassiz, Barand, Pikte, Falconer, e-forbes etc. and all our greatest geologists as Lyell, Murchison, Sedgwick, etc. have unanimously often vehemently maintained the immutability of species but Sir Charles Lyell now gives the support of his high authority to the opposite side and most geologists and paleontologists are much shaken in their former belief. Those who believe that the geological record of the degree perfect will undoubtedly at once reject my theory. For my part, following out Lyell's metaphor, I look at the geological record as a history of the world imperfectly kept and written in a changing dialect. Of this history we possess the last volume alone relating only to two or three countries. Of this volume only here and there a short chapter has been preserved and of each page only here a few lines. Each word of the slowly changing language more or less different in the successive chapters may represent the forms of life which are entombed in our consecutive formations and which falsely appear to have been abruptly introduced. On this view the difficulties above discussed are greatly diminished or even disappear. End of chapter 10 Part B All LibriVox recordings are in the public domain. For more information or to volunteer visit LibriVox.org The Origin of the Species by Natural Selection or The Preservation of Favored Races in the Struggle for Life 6th London Edition by Charles Darwin Chapter 11 The Geological Succession of Organic Beings Part 1 Contents of this chapter include of the slow and successive appearance of new species on their different rates of change species once lost do not appear groups of species follow the same general rules in their appearance and disappearance as do single species on extinction on simultaneous changes in the forms of life throughout the world on the affinities of extinct species to each other and to living species on the state of development of ancient forms of the succession of the same types within the same areas summary of preceding and present chapter Let us now see whether the several facts and laws relating to the geological succession of organic beings accord best with the common view of the immutability of species or with that of their slow and gradual modification through variation and natural selection new species have appeared very slowly one after another both on the land and in the waters Lyle has shown that it is hardly possible to resist the evidence of this head in the case of the several tertiary stages and every year tends to fill up the blanks between the stages and to make the proportion between the lost and existing forms more gradual in some of the most recent beds though undoubtedly of high antiquity if measured by years only one or two species are extinct and only one or two are new having appeared there for the first time either locally or as far as we know on the face of the earth the secondary formations are more broken but as Braun has remarked neither the appearances nor disappearance of the many species embedded in each formation has been simultaneous species belonging to different genera and classes have not changed at the same rate or in the same degree in the older tertiary beds a few living shells may still be found in the midst of a multitude of extinct forms Faulkner has given a striking instance of a similar fact for an existing crocodile is associated with many lost mammals and reptiles and the sub-hemalayan deposits the Cylurian lingula differs but little from the living species of this genus whereas most of other Cylurian molests and all the crustaceans have changed greatly the productions of the land seem to have changed at a quicker rate than those of the sea of which a striking instance has been observed in Switzerland there is some reason to believe that organisms high in the scale change more quickly than those that are low though there are exceptions to this rule the amount of organic change as Pictit has remarked is not the same in each of so called formation yet if we compare any but the most closely related formulations all the species will be found to have undergone some change when a species has once disappeared from the face of the earth we have no reason to believe that the same identical form ever reappears the strongest apparent exception to this letter rule is called colonies of M. Barande which intrude for a period in the midst of an older formation and then allow the pre-existing fauna to reappear but Lyle's explanation namely that it is a case of temporary migration from a distinct geographical province seems satisfactory these several facts accord well with our theory includes no fixed laws of development causing all the inhabitants of an area to change abruptly or simultaneously or to an equal degree the process of modification must be slow and will generally affect only a few species at the same time for the variability of each species is independent of that of all others whether such variations or individual differences will arise will be accumulated through natural selection in a greater or less degree thus causing a greater or less amount of permanent modification will depend on many complex contingencies on the variations being of beneficial nature on the freedom of intercrossing on the slowly changing physical conditions of the country on the immigration of new colonists and on the nature of the other inhabitants with which the varying species come into competition hence it is by no means surprising that one species should retain the same identical form much longer than others or if changing should change in a less degree we find similar relations between the existing inhabitants of distinct countries for instance the land shells coeliopterous insects of Madera have come to differ considerably from their nearest allies on the continent of Europe whereas the marine shells and birds have remained unaltered we can perhaps understand the apparent quicker rate of change in terrestrial and in more highly organized productions compared with marine and lower productions by the more complex relations of higher beings to their organic and inorganic conditions of life as explained in a former chapter when many of the inhabitants of any area have become modified and improved we can understand on the principle of competition and from the all important relations of organism to organism and the struggle for life that any form which did not become in some degree modified and improved would be liable to extermination hence we see why all the species in the same region do at last if we look to long enough intervals of time become modified for otherwise they would become extinct in members of the same class the average amount of change during long and equal periods of time may perhaps be nearly the same but as the great accumulation of enduring formations rich in fossils depends on great masses of sediment being deposited on subsiding areas our formations have been almost necessarily accumulated at wide and irregularly intermittent intervals of time consequently the amount of organic change exhibited by the fossils embedded in consecutive formations is not equal each formation on this view does not mark a new and complete act of creation but only an occasional scene taken almost at hazard in an ever slowly changing drama we can clearly understand why a species when once lost should never reappear even if the very same conditions of life organic and inorganic occur for though the offspring of one species might be adapted and no doubt this has occurred in innumerable instances to fill the place of another species in the economy of nature and the supplanted yet the two forms the old and the new would not be identically the same for both would almost certainly inherit different characters from their distinct characters and organisms already differing would vary in a different manner for instance it is possible if all our fantail pigeons were destroyed that fanciers might make canoe breed hardly distinguishable from the present breed but if the parent rock pigeon were likewise destroyed and under nature we have every reason to believe that parent forms are generally supplanted and exterminated by their improved offspring it is incredible that a fantail identical with the existing breed could be raised from any other species of pigeon or even from any other well established race of the domestic pigeon for the successive variations would almost certainly be in some degree different and the newly formed variety would probably inherit from its progenitor some characteristic differences groups of species that is genera and families follow the same general rules in their appearance and disappearance as do single species changing more or less quickly and in a greater or lesser degree a group when it has once disappeared never reappears that is its existence as long as it lasts is continuous I am aware that there are some apparent exceptions to this rule but the exceptions are surprisingly few so few that E. Forbes picked it and Woodward though all strongly opposed to such views as I maintain admit its truth and the rule strictly accords with the theory for all the species of the same group however long it may have lasted are the modified descendants one from the other and all from a common progenitor and the genus lingula for instance the species which have successively appeared at all ages must have been connected by an unbroken series of generations from the lowest silurian stratum to the present day we have seen in the last chapter that whole groups of species sometimes falsely appear to have been abruptly developed and I have attempted to give an explanation of this fact which if true would be fatal to my views but such cases are certainly exceptional the general rule being a gradual increase in number until the group reaches its maximum and then sooner or later a gradual decrease if the number of species included within a genus or the number of the genera within a family be represented by a vertical line of varying thickness ascending through the successive geological formations in which the species are found the line will sometimes falsely appear to begin at its lower end not in a sharp point but gradually it then gradually thickens upwards often keeping of equal thickness for a space and ultimately thins out in the upper beds marking the decrease in final extinction of the species this gradual increase in the number of the species of a group is strictly conformable with the theory for the species of the same genus increase only slowly and progressively the process of modification and the production of a number of allied forms necessarily being a slow and gradual process one species first giving rise to two or three varieties these being slowly converted into species which in their turn produced by equally slow steps other varieties and species like the branching of a great tree from a single stem till the group becomes large on extinction we have as yet only spoken incidentally of the disappearance of species and of groups of species on the theory of natural selection the extinction of old forms in the production of new and improved forms are intimately connected together the old notion of all the inhabitants of the earth being swept away by catastrophes at successive periods is very generally given up even by those geologists as Ellie de Beaumont Richardson Barond etc whose general views would naturally lead them to this conclusion on the contrary we have every reason to believe in the study of the tertiary formations that species and groups of species gradually disappear one after another first from one spot then from another and finally from the world in some few cases however as by the breaking of an isthmus and the consequent eruption of a multitude of new inhabitants into an adjoining seat or by the final subsistence of an island the process of extinction may have been rapid both single species and whole groups of species last for very unequal periods some groups as we have seen have endured from the earliest known dawn of life to the present day some have disappeared before the close of the Paleozoic period no fixed law seems to determine the length of time during which any single species or any single genus endures there is reason to believe that the extinction of a whole group of species is generally a slower process than their production if their appearance and disappearance be represented as before by a vertical line of varying thickness the line is found to taper more gradually at its upper end which marks the progress of extermination then at its lower end which marks the first appearance and the early increase in number of the species in some cases however the extermination of whole groups as of emanates toward the close of the secondary period has been wonderfully sudden the extinction of species has been involved in the most gratuitous mystery some authors have even suppose that as the individual has a definite length of life so have species a definite duration no one can have marveled more than I have done at the extinction of species when I found in La Plata the tooth of a horse embedded with the remains of mastodon perium and other extinct monsters which all coexisted with still living shells at a very late geological period I was filled with astonishment for seeing that the horse since its introduction by the Spaniards into South America has run wild over the whole country and has increased in numbers at an unparalleled rate I asked myself what could so recently have exterminated the former horse under conditions of life apparently so favorable but my astonishment was groundless Professor Owen soon perceived that the tooth though so like that of the existing horse belonged to an extinct species had this horse been still living but in some degree rare no naturalist would have felt the least surprise at its rarity for rarity is the attribute of a vast number of species of all classes in all countries if we ask ourselves why this or that species is rare we answer that something is unfavorable in its conditions of life but what that something is we can hardly ever tell on the supposition of the fossil horse still existing as a rare species we might have felt certain from the analogy of all other mammals even of the slow breeding elephant and from the history of the naturalization of the domestic horse in South America that under more favorable conditions it would in a very few years have stocked the whole continent but we could not have told what the unfavorable conditions were which checked its increase whether some one or several contingencies and at what period of the horse's life and in what degree they severally acted if the conditions had gone on however slowly becoming less and less favorable we assuredly would not have perceived the fact yet the fossil horse would certainly have become rarer and rarer and finally extinct its place being seized on by some more successful competitor it is most difficult always to remember that the increase of every living creature is constantly being checked by unperceived hostile agencies and that these same unperceived agencies are amply sufficient to cause rarity and finally extinction so little is this subject understood that I have heard surprise repeatedly expressed at such great monsters as the mastodon and the more ancient donessorians having become extinct as if mere bodily strength gave victory in the battle of life mere size on the contrary would in some cases determine as has been remarked by Owen quicker extermination from the greater amount of requisite food before man inhabited India or Africa some cause must have checked the continued increase of the existing elephant a highly capable judge doctor falconer believes that it is chiefly insects which from incessantly harassing and weakening the elephant in India checked its increase and this was Bruce's conclusion with respect to the African elephant in Abyssinia it is certain that insects and blood sucking bats determine the existence of the larger naturalized quadrupeds in several parts of South America we see in many cases in the more recent tertiary formations that rarity precedes extinction and we know that this has been the progress of events with those animals which have been exterminated either locally or wholly through man's agency I may repeat what I published in 1945 namely that to admit that species generally become rare before they become extinct to feel no surprise at the rarity of a species and yet to marvel greatly when the species ceases to exist is much the same as to admit that sickness in the individual is the forerunner of death to feel no surprise at sickness but when the sick man dies to wonder and to suspect that he died by some deed of violence the theory of natural selection is grounded on the belief that each new variety and ultimately each new species is produced and maintained by having some advantage over those with which it comes into competition and the consequent extinction of less favored forms almost inevitably follows it is the same with our domestic productions when a new and slightly improved variety has been raised it at first supplants the less improved varieties in the same neighborhood when much improved it is transported far and near like our short horn cattle and takes the place of other breeds in other countries thus the appearance of new forms and the disappearance of old forms both those naturally and artificially produced are bound together in flourishing groups the number of new specific forms which have been produced within a given time has at some periods probably been greater than the number of the old specific forms which have been exterminated but we know that species have not gone on indefinitely increasing at least during the later geological ethics so that looking to later times we may believe that the production of new forms has caused the extinction of about the same number of old forms the competition will generally be most severe as formerly explained and illustrated by examples between the forms which are most like each other in all respects hence the improved and modified descendants of a species will generally cause the extermination of the parent species and if many new forms have been developed from any one species the nearest allies of that species that is the species of the same genus will be the most liable to extermination thus as I believe a number of new species descended from one species that is a new genus comes to supplant an old genus belonging to the same family but it must often have happened that a new species belonging to some one group has seized on the place occupied by a species belonging to a distinct group and thus have caused its extermination if many allied forms be developed from the successful intruder many will have to yield their places and it will generally be the allied forms which will suffer from some inherited inferiority in common but whether it be species belonging to the same or to a distinct class which have yielded their places to other modified species a few of the sufferers may often be preserved for a long time from being fitted to some peculiar line of life or from inhabiting some distant and isolated station where they will have escaped severe competition for instance some species of trigonium a great genus of shells in the secondary formations survive in the Australian seas and a few members of the great and almost extinct group of ganoid fishes still inhabit our fresh waters therefore the utter extinction of a group is generally as we have seen a slower process than its production with respect to the apparently sudden extermination of whole families or orders as of trilobites at the close of the Paleozoic period and of ammonites at the close of the secondary period we must remember what has been said already on the probable wide intervals of time between our consecutive formations and in these intervals there may have been much slow extermination moreover when by sudden immigration or by unusually rapid development many species of a new group have taken possession of an area many of the older species will have been exterminated in a correspondingly rapid manner and the forms which thus yield their places will commonly be allied for they will per take of the same inferiority in common thus as it seems to me the manner in which single species and whole groups of species become extinct accords well with the theory of natural selection we need not marvel at extinction if we must marvel let it be at our presumption in imagining for a moment that we understand the many complex contingencies on which the existence of each species depends if we forget for an instant that each species tends to increase inordinately and that some check is always in action yet seldom perceived by us the whole economy of nature will be utterly obscured whenever we can precisely say why this species is more abundant in individuals than that why this species and not another can be naturalized in a given country then and not until then we may justly feel surprise why we cannot account for the extinction of any particular species or group of species on the forms of life changing almost simultaneously throughout the world scarcely any paleontological discovery is more striking than the fact that the forms of life change almost simultaneously throughout the world thus our European chalk formation can be recognized in many distant regions under the most different climates where not a fragment of the mineral chalk itself can be found namely in North America in Equatorial South America in Tierra del Fuego at the Cape of Good Hope and in the Peninsula of India for at these distant points the organic remains in certain beds present an unmistakable resemblance to those of the chalk it is not that the same species are met with for in some cases not one species is identically the same but they belong to the same families in sections of genera and sometimes are similarly characterized in such trifling points as mere superficial sculpture moreover other forms which are not found in the chalk of Europe but which occur in the formations either above or below occur in the same order at these distant points of the world in the several successive paleologic formations of Russia, Western Europe and North America a similar parallelism in the forms of life has been observed by many authors and so it is according to Lyle with the European and North American tertiary even if the few fossil species which are common to the old and new worlds were kept wholly out of view the general parallelism in the successive forms of life in the paleozoic and tertiary stages would still be manifest and the several formations could be easily correlated these observations however relate to the marine inhabitants of the world we have not sufficient data to judge whether the productions of land and of fresh water at distant points change in the same parallel manner we may doubt whether they have thus changed if the Megatherium Myladon Macrochenea and Toxodon were brought to Europe from La Plata without any information in regard to their geological position no one would have suspected that they had coexisted with seashells all still living but as these anomalous monsters coexisted with the mastodon and horse it might at least have been inferred that they had lived during one of the later tertiary stages when the marine forms of life are spoken of as having changed simultaneously throughout the world it must not be supposed that this expression relates to the same year or even to the same century or even that it has a very strict geological sense for if all of the marine animals now living in Europe and all those that lived in Europe during the Pleistocene period a very remote period as measured by years including the whole glacial epic were compared with those now existing in South America or in Australia the most skillful naturalist would hardly be able to say whether the present or the Pleistocene inhabitants of Europe resembled most closely those of the southern hemisphere so again several highly competent observers maintain that the existing productions of the United States are more closely related to those which lived in Europe during certain later tertiary stages then to the present inhabitants of Europe if this be so it is evident that fossiliferous beds now deposited on the shores of North America would hereafter be liable to be classed with somewhat older European beds nevertheless looking to a remotely future epic there can be little doubt that all the more modern marine formations namely the upper Pleocene the Pleistocene and strictly modern beds of Europe North and South America and Australia from containing fossil remains in some degree allied and from not including those forms which are found only in the older underlining deposits would be correctly ranked as simultaneous in a geological sense the fact of the forms of life changing simultaneously in the above large sense at distant parts of the world has greatly struck those admirable observers Meshur's Der Wunei and Dacharjak after referring to the parallelism of the paleozoic forms of life in various parts of Europe they add quote if struck by this strange sequence we turn our attention to North America and there discover a series of analogous phenomena it will appear certain that all these modifications of species their extinction and the introduction of new ones cannot be owing to mere changes in marine currents or other causes more or less local and temporary but depend on general laws which govern the whole animal kingdom close quote Meshur Baran has made forcible remarks to precisely the same effect it is indeed quite futile to look to changes of currents climate or other physical conditions as the cause of these great mutations in the forms of life throughout the world under the most different climates we must as Baran has remarked look to some special law we shall see this more clearly when we treat of the present distribution of organic beings and how slight is the relation the physical conditions of various countries and the nature of their inhabitants this great fact of the parallel succession of the forms of life throughout the world is explicable on the theory of natural selection new species are formed by having some advantage over older forms and the forms which are already dominant or have some advantage over the other forms in their own country give birth to the greatest number of new varieties or incipient species we have distinct evidence on this head in the plants which are dominant that is which are commonest and most widely diffused producing the greatest number of new varieties it is also natural that the dominant varying and far spreading species which have already invaded to a certain extent the territories of other species should be those which would have the best chance of spreading still further and of giving rise in new countries to other new varieties and species the process of diffusion would often be very slow depending on climatial and geographical changes on strange accidents and on the gradual climatization of new species to the various climates through which they might have to pass but in the course of time the dominant forms would generally succeed in spreading and would ultimately prevail the diffusion would be slower it is probable with the terrestrial inhabitants of distinct continents than with the marine inhabitants of the continuous sea we might therefore expect to find as we do a less strict degree of parallelism in the succession of the productions of the land than with those of the sea thus as it seems to me the parallel and taken a large sense simultaneous succession of the same forms of life throughout the world accords well with the principle of new species having been formed by dominant species spreading widely and varying the new species thus produced being themselves dominant owing to their having had some advantage over their already dominant parents as well as over other species and again spreading varying and producing new forms the old forms which are beaten and which yield their places to the new and victorious forms will generally be allied in groups from inheriting some inferiority in common and therefore as new and improved groups spread throughout the world old groups disappear from the world and the succession of forms everywhere tends to correspond both in their first appearance and final disappearance there is one other remark connected with this subject worth making I have given my reasons for believing that most of our great formations rich in fossils were deposited during periods of subsidence and that blank intervals of vast duration as far as fossils are concerned occurred during the periods when the bed of the sea was either stationary or rising and likewise when sediment was not thrown down quickly enough to embed and preserve organic remains during these long and blank intervals I suppose that the inhabitants of the region underwent a considerable amount of modification and extinction and that there was much migration from other parts of the world as we have reason to believe that large areas are affected by the same movement it is probable that strictly contemporaneous formations have often been accumulated over very wide spaces in the same quarter of the world but we are very far from having to conclude that this has invariably been the case and that large areas have invariably been affected by the same movements when two formations have been deposited in two regions during nearly but not exactly the same period we should find in both from the causes explained in the foregoing paragraphs the same general succession in the forms of life but the species would not exactly correspond for there will have been a little more time in the one region than in the other for modification, extinction and immigration I suspect that cases of this nature occur in Europe Mr. Prestwich in his admirable memoirs of the Eocene deposits of England in France is able to draw a close general parallelism between the successive states in the two countries but when he compares certain stages in England with those in France although he finds in both a curious accordance in the numbers of the species belonging to the same general yet the species themselves differ in a manner very difficult to account for considering the proximity of the two areas unless indeed it be assumed that an isthmus separated two seas inhabited by distinct but contemporaneous faunas Lyell has made similar observations on some of the later tertiary formations Baran also shows that there is a striking general parallelism in the successive Silurian deposits of Bohemia and Scandinavia nevertheless he finds a surprising amount of difference in the species if the several formations in these regions have not been deposited during the same exact periods a formation in one region often corresponding with a blank interval in the other and if in both regions the species have gone on slowly changing during the accumulation of the several formations and during the long intervals of time between them in this case the several formations in the two regions could be arranged in the same order in accordance with the general succession of the forms of life and the order would falsely appear to be strictly parallel nevertheless the species would not all be the same in the apparently corresponding stages in the two regions end of chapter 11 part 1 recorded by Dennis Sayers Modesto California winter 2006