Transitional fossil

“ But it has its limitations, and it goes without saying that the more complete the fossil skeleton of a vertebrate, or the remains of an arthropod, the more complete will be our conception of the form of the extinct organism. It may be misleading in the numerous cases of convergence and of generalized forms which now abound in our palæontological collections. We can well understand how guarded one must be in working out the restorations of dinosaurs and fossil birds, of the Permian and Triassic theromorphs, and the Tertiary creodonts as compared with existing carnivora. ”

“ Thus, the same fossil, occurring in successive groups of strata, and with the merely trivial and varietal differences due to the gradual change in its environment, has been repeatedly described as a distinct species, with a distinct name, in every bed in which it was found. We know, however, that many fossils range vertically through many groups of strata, and there are some which even pass through several formations. The mere fact of a difference of physical position ought never to be taken into account at all in considering and determining the true affinities of a fossil. ”

“ Fossils as Guides to Age of Strata.—
In passing from fossil deposits of fairly recent origin to those of older date, we find the proportion of living species gradually diminish, being replaced by forms now extinct. After this the genera themselves are replaced by more ancient types, and if we penetrate still deeper into the series of geological strata, even families and orders of animals and plants give place to others entirely unknown at the present day. ”

“ The fifth and most critical flaw in the fossil “evidence” for evolution is to be found in the anomalies of the actual distribution of fossils in time. It is the boast of evolutionary Palæontology that it is able to enhance the cogency of the argument from mere structural resemblance by showing, that, of two structurally allied forms, one is more ancient than the other, and may, therefore, be presumed to be ancestral to the later form. ”

“ But it must be confessed that the logical extension of this broad view of the fossils, and the projection of our modern zoological provinces and zones back into the fossil world would mean the death-blow to the life succession theory, and might have a very disturbing effect upon certain theories about human origins and other genetic relationships which have grown quite popular since the middle of the last century. ”

“ Besides, were we to consider it in this view, the recent and fossil remains would be found to throw a mutual light upon each other, and the naturalist would not be so often at a loss to class every new fossil acquisition, of which the recent specimen is not to be found, especially whenever the fossil has any thing seemingly æquivocal in its formation, so as on a superficial imspection to render the matter doubtful, whether the body belongs to the animal or vegetable kingdoms, or indeed to either of them. ”

“ The succession of fossil remains throughout the whole geological series of rocks is the record of the change; and it became easy to see that the extreme slowness of these changes was such as to allow ample opportunity for the continuous automatic adjustment of the organic to the inorganic world, as well as of each organism to every other organism in the same area, by the simple processes of "variation and survival of the fittest." ”

“ In other cases, though practically the real body it represents, all the cavities of the fossil, down to its minutest recesses, may have become infiltrated with mineral matter. It need hardly be added, that it is in the more modern rocks that we find the fossils, as a rule, least changed from their former condition; but the original structure is often more or less completely retained in some of the fossils from even the most ancient formations. ”

“ All those who are entitled to speak on this head are agreed that the introduction of new and the destruction of old species have been slow and gradual processes, in no sense of the term "catastrophistic." Most are also willing to admit that "Evolution" has taken place in the past, to a greater or less extent, and that a greater or less number of so-called species of fossil animals are really the modified descendants of pre-existent forms. ”

“ But hardly more than two centuries have elapsed since this fundamental problem was first exhaustively treated; it was only in the last century that the archaeological value of fossils—their importance, I mean, as records of the history of the earth—was fully recognised; the first adequate investigation of the fossil remains of any large group of vertebrated animals is to be found in Cuvier's "Recherches sur les Ossemens Fossiles," completed in 1822 ”

“ To conclude, it appears that, in going back from the recent to the Eocene period, we are carried by many successive steps from the fauna now contemporary with man to an assemblage of fossil species wholly different from those now living. In this retrospect we have not yet succeeded in tracing back a perfect transition from the recent to an extinct fauna; but there are usually so many species in common to the groups which stand next in succession as to show that there is no great chasm, no signs of a crisis when one class of organic beings was annihilated to give place suddenly to another. ”

“ Further, we know from the evidence of fossil remains that the animals existing in former periods were very different from those existing now, and that many of the existing forms, such as man, mammals, birds, bony fishes, can only be traced back in the succession of stratified rocks to the later strata or to those about the middle of the series, evidence of their existence in the periods represented by the most ancient strata being entirely absent. Existing types then must have arisen by evolution, by changes occurring in the succession of generations. ”

“ As it is, we have fossil remains of perhaps only about one out of each thousand extinct species, a mere random sampling of the types that prevailed during the various past ages. Considering how many factors have been at work to prevent fossilization of large groups of species and how erosion and metamorphosis have worked together to destroy those fossils already preserved, we marvel that our fossil record is sufficiently complete to tell any sort of sequential story. ”

“ This is true in many cases, no doubt, yet one frequently comes across the remains of plants and animals that [10] have undergone very little change, and have, as it were, been simply sealed up. The state of a fossil depends on several circumstances, such as the soil, mud, or other medium in which it may happen to be preserved. Again, the newest, or most recent, fossils are generally the least altered. We have fossils of all ages, and in all states of preservation. ”

“ Fossils were accurately determined, comparisons were made with living forms, and the species named according to the binomial system. However, every species, recent and extinct, was regarded as a separate creation, and because of the usually sharp separation of the superposed fossil faunas and floras, these were held to have been destroyed through a series of periodic catastrophes of which the Noachian deluge was the last. ”

“ This has been to a great extent dredged from the rivers; and thus remains of Pleistocene and of Tertiary animals have been mixed indiscriminately together. It is often impossible to determine to what formation a fossil may belong. To add to the difficulty of the palæontologist, the vertebrate remains are sometimes found washed out and mingled with bones or teeth of what appear to have been domestic animals. ”

“ Thus, for instance, in the long series of the mesozoic formations, in the different strata of the Trias, Jurassic, and Chalk formations, for the deposition of which a lapse of many millions of years has been required, we find absolutely no remains of fossil mammalia beyond lower jaws; seek where we will, nothing is anywhere to be found but lower jaws, and no other bones whatever. ”

“ All of which tends to show how unreliable are those assertions commonly found in the text-books about all the species of the so-called "older" rocks being extinct. It is only with hesitation that such specific distinctions are surrendered even to-day, though during the last few decades a steady progress has been made in bringing the palaeontology of the higher vertebrates into line with our increased knowledge of zoology, thus breaking down many of the specific distinctions which have long been maintained between the fossil and the living forms. ”

“ Yet countless millions of creatures are annually dying, ready and willing to become fossils. Fossils, however, they do not become, simply because other creatures eat them up. For this reason alone, not one in ten thousand of any particular terrestrial species is likely to become fossil, because to some creature or another it is almost sure to be good eating, and therefore in the living state or the dead, sure to be ravenously seized upon and devoured.
Some forms of marine life are indeed represented by a wonderful number of specimens or fragments of specimens. ”

“ The long succession of these strata, in connection with the evidences of their slow accumulation, observed in the undisturbed condition of the fossil remains which they contained, bore witness to long periods occupied in the production of a single group of strata constituting but a minor division of one of the formations. The lapse of long periods was also indicated by the fossils found in beds of older date becoming constantly more and more unlike existing species. ”

“ Go deeper still, and the kinds of animals change further. Fewer and fewer resemble those which now range the earth; more and more belong to other species.
Descend through layer after layer till we come to rocks built in earliest ages and not one fossil shall we find precisely the same as one animal living now.
So not only are the rocks built in successive order, stratum after stratum belonging to age after age in the past, but fossil-remains also are found in successive order, kind after kind belonging to past age after age. ”

“ Numbers of rare specimens must continually be consigned to the furnace and the limekiln, or buried under mounds and hills of refuse. Sometimes the character of the matrix, by its hardness or its softness, makes it impossible to disengage the fossil without complete disfigurement; sometimes the fossil itself is so fragmentary as rather to confuse than to teach. ”

“ If, for reasons before stated, we assume a continual extinction of species and appearance of others on the globe, it will then follow that the fossils of strata formed at two distant periods on the same spot will differ even more certainly than the mineral composition of those strata. For rocks of the same kind have sometimes been reproduced in the same district after a long interval of time; whereas all the evidence derived from fossil remains is in favour of the opinion that species which have once died out have never been reproduced. ”

“ In the last fifty years the number of known fossil remains of invertebrated animals has been trebled or quadrupled. The work of interpretation of vertebrate fossils, the foundations of which were so solidly laid by Cuvier, was carried on, with wonderful vigour and success, by Agassiz in Switzerland, by Von Meyer in Germany, and last, but not least, by Owen in this country, while, in later years, a multitude of workers have laboured in the same field. In many groups of the animal kingdom the number of fossil forms already known is as great as that of the existing species. ”

“ It is nevertheless remarkable, that on the continent of Europe, as in England, the fossil remains of mammalia belong almost exclusively to those of the Newer Pliocene and Post-Pliocene periods, and not to the Miocene or Eocene epochs, and when they are accompanied by land or river shells, these agree in great part, or entirely, with recent species. ”

“ His studies led him to infer that the fossils contained in the oldest rocks are very different from any of the species of the present time; that the newer the formation, the more do the remains approach in form to the organic beings of the present creation, and that in the very latest formations, fossil remains of species now existing occur. ”

“ The earliest representatives of organic life were doubtless of such a perishable nature that their remains could not be preserved in a fossil state even under the most favourable conditions. Such organisms, whether plants or animals, as possessed any resistant tissues or hard skeletons might be preserved in the oldest rocks, but as these strata became involved in earth-foldings or were penetrated by injections of igneous eruptions, the relics of life would be entirely destroyed. ”

“ The break will then be rendered wider, for it will intervene between man in a more civilised state, as we may hope, than the Caucasian, and some ape as low as a baboon, instead of as at present between the negro or Australian and the gorilla.
With respect to the absence of fossil remains, serving to connect man with his ape-like progenitors, no one will lay much stress on this fact, who will read Sir C. Lyell’s discussion,271 in which he shews that in all the vertebrate classes the discovery of fossil remains has been an extremely slow and fortuitous process. ”