Extinct species

“ Let us now look to the mutual affinities of extinct and living species. All fall into a few grand classes; and this fact is at once explained on the principle of descent. The more ancient any form is, the more, as a general rule, it differs from living forms. But, as Buckland long ago remarked, extinct species can all be classed either in still existing groups, or between them. That the extinct forms of life help to fill up the intervals between existing genera, families, and orders, is certainly true ”

“ With extinction rates now exceeding natural background rates by a factor of 100 to 1,000 [30] , our results also suggest that this slow advance in the description of species will lead to species becoming extinct before we know they even existed. High rates of biodiversity loss provide an urgent incentive to increase our knowledge of Earth's remaining species. ”

“ Cause of the Extinction of Species.—There is good reason to believe that the most effective agent in the extinction of species is the pressure of other species, whether as enemies or merely as competitors. If therefore any portion of the earth is cut off from the influx of new or more highly organised animals, we may there expect to find the remains of groups which have elsewhere become extinct. ”

“ Besides the many extinct species, and extinct genera of Mammalia that are enumerated in this list, the occurrence of nine or ten extinct species of fossil Birds in the Eocene period of the tertiary series, forms a striking phenomenon in the history of organic remains. ”

“ It had now become clearly evident, moreover, that the fossils from the older formations were all extinct species, and that only in the most recent deposits were there remains of forms still living. The equally important fact had been established that in several groups of both animals and plants the extinct forms were vastly more numerous than the living, while several orders of fossil animals had no representatives in modern times. Human remains had been found mingled with those of extinct animals, but the association was regarded as an accidental one by the authorities in science ”

“ These faunas are far stranger than the corresponding ones of North America and differ more radically from those of modern times, since they include a much larger proportion of extinct types, and the extinctions have swept away not only species and genera, but families and orders as well. ”

“ They maintain that certain species, which formerly existed, have become extinct, or are now unknown, although formerly known. The assumption of so much recent extinction is no difficulty in their eyes; for they do not judge of its probability by the facility or difficulty of the extinction of other closely-allied wild forms. ”

“ Nor could it be in doubt that the successive faunas, whose individual remains have been preserved in myriads, representing extinct species by thousands and tens of thousands, must have required vast periods of time for the production and growth of their countless generations. ”

“ In the changes, the development and extinction, of species we must remember that such expressions as ‘a new species,’ or as ‘a species becoming extinct,’ are each commonly and indiscriminately used to express totally different and opposite meanings. Of course the ‘new’ species is not new in the sense that its ancestors appeared later on the globe’s surface than those of any old species tottering to extinction. ”

“ Were the extinct species taken into account, it would be seen that they fill in the intervals separating one living form from another, and that they grow more and more like the living forms as they approach nearer to the present day. ”

“ The same causes continuing in action, the parent species would next suffer, would gradually diminish in numbers, and with a recurrence of similar unfavourable conditions might also become extinct. The superior variety would then alone remain, and on a return to favourable circumstances would rapidly increase in numbers and occupy the place of the extinct species and variety. ”

“ To admit that species generally become rare before they become extinct—to feel no surprise at the comparative rarity of one species with another, and yet to call in some extraordinary agent and to marvel greatly [Pg 94] when a species ceases to exist, appears to me much the same as to admit that sickness in the individual is the prelude of death—to feel no surprise at sickness—but when the sick man dies to wonder, and to believe that he died through violence." [69]
Geographical distribution is an important element in this question of extinction. ”

“ In the cases where we can trace the extinction of a species through man, either wholly or in one limited district, we know that it becomes rarer and rarer, and is then lost: it would be difficult to point out any just distinction [13] between a species destroyed by man or by the increase of its natural enemies. The evidence of rarity preceding extinction is more striking in the successive tertiary strata, as remarked by several able observers; it has often been found that a shell very common in a tertiary stratum is now most rare, and has even long been thought to be extinct. ”

“ Thus the naturalist finds in the bowels of the earth species as well defined as, and in some groups of animals more numerous than, those which breathe the upper air. But, singularly enough, the majority of these entombed species are wholly distinct from those that now live. Nor is this unlikeness without its rule and order. As a broad fact, the further we go back in time the less the buried species are like existing forms; and, the further apart the sets of extinct creatures are, the less they are like one another. ”

“ In this collection there are extinct species of all the thirty-two genera, excepting four, of the terrestrial quadrupeds now inhabiting the provinces in which the caves occur; and the extinct species are much more numerous than those now living: there are fossil ant-eaters, armadillos, tapirs, peccaries, guanacos, opossums, and numerous South American gnawers and monkeys, and other animals. ”

“ The absolute extermination of a species means that not one individual of it remains alive. Judgment to this effect is based upon the lapse of time since the last living specimen was observed or killed. When five years have passed without a living "record" of a wild specimen, it is time to place a species in the class of the totally extinct. ”

“ The affinities of all the beings of the same class have sometimes been represented by a great tree. I believe this simile largely speaks the truth. The green and budding twigs may represent existing species; and those produced during former years may represent the long succession of extinct species. At each period of growth all the growing twigs have tried to branch out on all sides, and to overtop and kill the surrounding twigs and branches, in the same manner as species and groups of species have at all times overmastered other species in the great battle for life. ”

“ Further, it brings before us this remarkable fact, that while in the older periods all the animals whose remains we find are extinct as species, so soon as we enter on the Neozoic we find some which still continue to our time—at first only a very few, but in later and later beds in gradually increasing percentage, till the fossil and extinct wholly disappear in the recent and living. ”

“ First one then another of its component species will dwindle away and become extinct, till at last only a few species remain. Sometimes these soon follow the others and the whole genus dies out, as thousands of genera have died out during the long course of the earth's life-history; but it will also sometimes happen that a few species will continue to maintain themselves in areas where they are removed from the influences that exterminated their fellows. ”

“ In the Post-Pliocene formations, while all the Mollusca belong to existing species, most of the Mammals belong to extinct species. In the Recent period, the quadrupeds, as well as the shells, belong to living species.
The above, with some modifications, was the original classification proposed by Sir Charles Lyell for the Tertiary rocks, and now universally accepted. More recent researches, it is true, have somewhat altered the proportions of existing species Page 287 to extinct, as stated above. The general principle, however, of an increase in the number of living species, still holds good ”

“ In accordance with this, we in fact no longer find forms of transition leading to those groups which are becoming extinct, as, for example, among birds, are the ostriches; and among mammals, the elephants, giraffes, Semi-apes, Edentata, and Ornithorhyncus. The groups of forms approaching their extinction no longer produce new varieties, and naturally the species are what is called “good,” that is, the species are distinctly different from one another. ”

“ This is proved to have been the case in Europe, and is supported by much evidence both as regards North and South America.
It is clear that so complete and sudden a change in the higher forms of life, does not represent the normal state of things. Species and genera have not, at all times, become so rapidly extinct. ”

“ The general laws of distribution also lead us to expect such phenomena. Very rare and very local species are such as are becoming extinct; and it is among insects, which are so excessively varied and abundant, which present so many isolated forms, and which, even on continents, afford numerous examples of very rare species confined to restricted areas, that we should have the best chance of meeting with every degree of rarity down to the point of almost complete extinction. ”

“ On a continent, the process of extinction will generally take effect on the circumference of the area of distribution, because it is there that the species comes into contact with such adverse conditions or competing forms as prevent it from advancing further. A very slight change will evidently turn the scale and cause the species to contract its range, and this usually goes on till it is reduced to a very restricted area, and finally becomes extinct. ”

“ We can see that any form which is represented by few individuals will run a good chance of utter extinction, during great fluctuations in the nature or the seasons, or from a temporary increase in the number of its enemies. But we may go further than this; for as new forms are produced, unless we admit that specific forms can go on indefinitely increasing in number, many old forms must become extinct. That the number of specific forms has not indefinitely increased, geology plainly tells us ”

“ If, then, a carnivorous species become extinct, the species on which it has fed will so multiply as to prove great nuisances, and to produce wide disorder among many species, not only of animals, but of plants. And often has man, in this way, by the extermination of species, in particular districts, unwittingly brought a powerful reaction on himself. ”

“ If there be any result which has come more clearly out of geological investigation than another, it is, that the vast series of extinct animals and plants is not divisible, as it was once supposed to be, into distinct groups, separated by sharply-marked boundaries. There are no great gulfs between epochs and formations—no successive periods marked by the appearance of plants, of water animals, and of land animals, 'en masse'. ”

“ The fact that a large proportion pf these remains belong to extinct genera, and almost all of them to extinct species, that lived and multiplied and died on or near the spots where they are now found, shows that the strata in which they occur were deposited slowly and gradually, during long periods of time, and at widely distant intervals. ”

“ It is a fact, that many species of the lower order of animals which once existed are now extinct. It has been asserted and denied, that fossil remains of man have been found, indicating that races which once existed have disappeared from the face of the earth. ”

“ A survey of the known fossil and living forms shows that not only have old species constantly become extinct during the progress of geological time, but new species have been as frequently appearing. This is equally true of genera, families, orders or even classes. ”

“ From these several considerations I think it inevitably follows, that as new species in the course of time are formed through natural selection, others will become rarer and rarer, and finally extinct. The forms which stand in closest competition with those undergoing modification and improvement, will naturally suffer most. ”

“ THE LARGER ZOOLOGICAL AND BOTANICAL GROUPINGS SURVIVE LONGER THAN THE SMALLER. Species are so short-lived that a single geological epoch may be marked by several more or less complete extinctions of the species of its fauna-flora and their replacement by other species. A genus continues with new species after all the species with which it began have become extinct. Families survive genera, and orders families. ”

“ The consequence is, that, while every individual animal and plant dies, the species survives. In the whole history of the animals and plants now existing on the globe, only eight or ten certain examples are on record in which a species has become extinct, and those are some large birds, such as the dinornis and dodo, once inhabitants of the Isle of Bourbon and New Zealand. Every one of the human family, every elephant, every ox, every lion, &c., die, but man, as a species, still lives ”