The next mastodon to appear on the scene was the so-called Missourium of Albert Koch, which he constructed somewhat as he did the Hydrarchus (see p. 61) of several individuals pieced together, thus forming a skeleton that was a monster in more ways than one. To heighten the effect, the curved tusks were so placed that they stood out at right angles to the sides of the head, like the swords upon the axles of ancient war chariots. Like Peale"s specimen this was exhibited in London, and there it still remains, for, stripped of its superfluous bones, and remounted, it may now be seen in the British Museum.
Many a mastodon has come to light since the time of Koch, for while it is commonly supposed that remains of the animal are great rarities, as a matter of fact they are quite common, and it may safely be said that during the seasons of ditching, draining, and well-digging not a week pa.s.ses without one or more mastodons being unearthed. Not that these are complete skeletons, very far from it, the majority of finds are scattered teeth, crumbling tusks, or ma.s.sive leg-bones, but still the mastodon is far commoner in the museums of this country than is the African elephant, for at the present date there are eleven of the former to one of the latter, the single skeleton of African elephant being that of Jumbo in the American Museum of Natural History. If one may judge by the abundance of bones, mastodons must have been very numerous in some favored localities such as parts of Michigan, Florida, and Missouri and about Big Bone Lick, Ky. Perhaps the most noteworthy of all deposits is that at Kimmswick, about twenty miles south of St. Louis, where in a limited area Mr. L. W. Beehler has exhumed bones representing several hundred individuals, varying in size from a mere baby mastodon up to the great tusker whose wornout teeth proclaim that he had reached the limit of even mastodonic old age. The spot where this remarkable deposit was found is at the foot of a bluff near the junction of two little streams, and it seems probable that in the days when these were larger the spring floods swept down the bodies of animals that had perished during the winter to ground in an eddy beneath the bluff. Or as the place abounds in springs of sulphur and salt water it may be that this was where the animals a.s.sembled during cold weather, just as the moas are believed to have gathered in the swamps of New Zealand, and here the weaker died and left their bones.
The mastodon must have looked very much like any other elephant, though a little shorter in the legs and somewhat more heavily built than either of the living species, while the head was a trifle flatter and the jaw decidedly longer. The tusks are a variable quant.i.ty, sometimes merely bowing outwards, often curving upwards to form a half circle; they were never so long as the largest mammoth tusks, but to make up for this they were a shade stouter for their length. As the mastodon ranged well to the north it is fair to suppose that he may have been covered with long hair, a supposition that seems to be borne out by the discovery, noted by Rembrandt Peale, of a ma.s.s of long, coa.r.s.e, woolly hair buried in one of the swamps of Ulster County, New York. And with these facts in mind, aided by photographs of various skeletons of mastodons, Mr. Gleeson made the restoration which accompanies this chapter.
[Ill.u.s.tration: Fig. 40.--The Mastodon. _From a drawing by J. M.
Gleeson._]
As for the size of the mastodon, this, like that of the mammoth, is popularly much over-estimated, and it is more than doubtful if any attained the height of a full-grown African elephant. The largest femur, or thigh-bone, that has come under the writer"s notice was one he measured as it lay in the earth at Kimmswick, and this was just four feet long, three inches shorter than the thigh-bone of Jumbo. Several of the largest thigh-bones measured show so striking an unanimity in size, between 46 and 47 inches in length, that we may be pretty sure they represent the average old "bull" mastodon, and if we say that these animals stood ten feet high we are probably doing them full justice. An occasional tusk reaches a length of ten feet, but seven or eight is the usual size, with a diameter of as many inches, and this is no larger than the tusks of the African elephant would grow if they had a chance.
It is painful to be obliged to scale down the mastodon as we have just done the mammoth, but if any reader knows of specimens larger than those noted, he should by all means publish their measurements.[20]
[20] _As skeletons are sometimes mounted, they stand a full foot or more higher at the shoulders than the animal stood in life, this being caused by raising the body until the shoulder-blades are far below the tips of the vertebrae, a position they never a.s.sume in life._
The disappearance of the mastodon is as difficult to account for as that of the mammoth, and, as will be noted, there is absolutely no evidence to show that man had any hand in it. Neither can it be ascribed to change of climate, for the mastodon, as indicated by the wide distribution of its bones, was apparently adapted to a great diversity of climates, and was as much at home amid the cool swamps of Michigan and New York as on the warm savannas of Florida and Louisiana. Certainly the much used, and abused, glacial epoch cannot be held accountable for the extermination of the creature, for the mastodon came into New York after the recession of the great ice-sheet, and tarried to so late a date that bones buried in the swamps retain much of their animal matter. So recent, comparatively speaking, has been the disappearance of the mastodon, and so fresh-looking are some of its bones, that Thomas Jefferson thought in his day that it might still be living in some part of the then unexplored Northwest.
It is a moot question whether or not man and the mastodon were contemporaries in North America, and while many there be who, like the writer of these lines, believe that this was the case, an expression of belief is not a demonstration of fact. The best that can be said is that there are scattered bits of testimony, slight though they are, which seem to point that way, but no one so strong by itself that it could not be shaken by sharp cross-questioning and enable man to prove an alibi in a trial by jury. For example, in the great bone deposit at Kimmswick, Mo., Mr. Beehler found a flint arrowhead, but this may have lain just over the bone-bearing layer, or have got in by some accident in excavating. How easily a mistake may be made is shown by the report sent to the United States National Museum of many arrowheads a.s.sociated with mastodon bones in a spring at Afton, Indian Territory. This spring was investigated, and a few mastodon bones and flint arrowheads were found, but the latter were in a stratum just above the bones, although this was overlooked by the first diggers.[21] Koch reported finding charcoal and arrowheads so a.s.sociated with mastodon bones that he inferred the animal to have been destroyed by fire and arrows after it became mired. It has been said that Koch could have had no object in disseminating this report, and hence that it may be credited, but he had just as much interest in doing this as he did in fabricating the Hydrarchus and the Missourium, and his testimony is not to be considered seriously. It seems to be with the mastodon much as it is with the sea-serpent; the latter never appears to a naturalist, remains of the former are never found by a trained observer a.s.sociated with indications of the presence of man. Perhaps an exception should be made in the case of Professor J.
M. Clarke, who found fragments of charcoal in a deposit of muck under some bones of mastodon.
[21] _This locality has just been carefully investigated by Mr. W. H.
Holmes of the United States National Museum who found bones of the mastodon and Southern Mammoth a.s.sociated with arrowheads. But he also found fresh bones of bison, horse, and wolf, showing that these and the arrowheads had simply sunk to the level of the older deposit._
We may pa.s.s by the so-called "Elephant Mound," which to the eye of an unimaginative observer looks as if it might have been intended for any one of several beasts; also, with bated breath and due respect for the bitter controversy waged over them, pa.s.s we by the elephant pipes. There remains, then, not a bit of man"s handiwork, not a piece of pottery, engraved stone, or scratched bone that can _unhesitatingly_ be said to have been wrought into the shape of an elephant before the coming of the white man. True, there is "The Lenape Stone," found near Doyleston, Pa., in 1872, a gorget graven on one side with the representation of men attacking an elephant, while the other bears a number of figures of various animals. The good faith of the finder of this stone is unimpeachable, but it is a curious fact that, while this gorget is elaborately decorated on both sides, no similar stone, out of all that have been found, bears any image whatsoever. On the other hand, if not made by the aborigines, who made it, why was it made, and why did nine years elapse between the discovery of the first and second portions of the broken ornament? These are questions the reader may decide for himself; the author will only say that to his mind the drawing is too elaborate, and depicts entirely too much to have been made by a primitive artist. A much better bit of testimony seems to be presented by a fragment of Fulgur sh.e.l.l found near Hollyoak, Del., and now in the United States National Museum, which bears a very rudely scratched image of an animal that may have been intended for a mastodon or a bison. This piece of sh.e.l.l is undeniably old, but there is, unfortunately, the uncertainty just mentioned as to the animal depicted. The familiar legend of the Big Buffalo that destroyed animals and men and defied even the lightnings of the Great Spirit has been thought by some to have originated in a tradition of the mastodon handed down from ancient times; but why consider that the mastodon is meant? Why not a legendary bison that has increased with years of story-telling? And so the co-existence of man and mastodon must rest as a case of not proven, although there is a strong probability that the two did live together in the dim ages of the past, and some day the evidence may come to light that will prove it beyond a peradventure. If scientific men are charged with obstinacy and unwarranted incredulity in declining to accept the testimony so far presented, it must be remembered that the evidence as to the existence of the sea serpent is far stronger, since it rests on the testimony of eye-witnesses, and yet the creature himself has never been seen by a trained observer, nor has any specimen, not a scale, a tooth, or a bone, ever made its way into any museum.
_REFERENCES_
_There are at least eleven mounted skeletons of the Mastodon in the United States, and the writer trusts he may be pardoned for mentioning only those which are most accessible. These are in the American Museum of Natural History, New York; the State Museum, Albany, N. Y.; Field Columbian Museum, Chicago; Carnegie Museum, Pittsburg; Museum of Comparative Zoology, Cambridge, Ma.s.s. There is no mounted skeleton in the United States National Museum, nor has there ever been._
_The heaviest pair of tusks is in the possession of T. O. Tuttle, Seneca, Mich., and they are nine and one-half inches in diameter, and a little over eight feet long; very few tusks, however, reach eight inches in diameter. The thigh-bone of an old male mastodon measures from forty-five to forty-six and one-half inches long, the humerus from thirty-five to forty inches. The height of the mounted skeleton is of little value as an indication of size, since it depends so much upon the manner in which the skeleton is mounted. The grinders of the mastodon have three cross ridges, save the last, which has four, and a final elevation, or heel. This does not apply to the teeth of very young animals. The presence or absence of the last grinder will show whether or not the animal is of full age and size, while the amount of wear indicates the comparative age of the specimen._
_The skeleton of the "Warren Mastodon" is described at length by Dr. J.
C. Warren, in a quarto volume ent.i.tled "Mastodon Giganteus." There is much information in a little book by J. P. MacLean, "Mastodon, Mammoth, and Man," but the reader must not accept all its statements unhesitatingly. The first volume, 1887, of the New Scribner"s Magazine contains an article on "American Elephant Myths," by Professor W. B.
Scott, but he is under an erroneous impression regarding the size of the mastodon, and photographs of the Maya carvings show that their resemblance to elephants has been exaggerated in the wood cuts. The story of the Lenape Stone is told at length by H. C. Mercer in "The Lenape Stone, or the Indian and the Mammoth."_
[Ill.u.s.tration: Fig. 41.--The Lenape Stone, Reduced.]
XII
WHY DO ANIMALS BECOME EXTINCT?
"_And Sultan after Sultan with his Pomp Abode his destined Hour and went his way._"
It is often asked "why do animals become extinct?" but the question is one to which it is impossible to give a comprehensive and satisfactory reply; this chapter does not pretend to do so, merely to present a few aspects of this complicated, many-sided problem.
In very many cases it may be said that actual extermination has not taken place, but that in the course of evolution one species has pa.s.sed into another; species may have been lost, but the race, or phylum endures, just as in the growth of a tree, the twigs and branches of the sapling disappear, while the tree, as a whole, grows onward and upward.
This is what we see in the horse, which is the living representative of an unbroken line reaching back to the little Eocene Hyracothere. So in a general way it may be said that much of what at the first glance we might term extinction is really the replacement of one set of animals by another better adapted to surrounding conditions.
Again, there are many cases of animals, and particularly of large animals, so peculiar in their make up, so very obviously adapted to their own special surroundings that it requires little imagination to see that it would have been a difficult matter for them to have responded to even a slight change in the world about them. Such great and necessarily sluggish brutes as Brontosaurus and Diplodocus, with their tons of flesh, small heads, and feeble teeth, were obviously reared in easy circ.u.mstances, and unfitted to succeed in any strenuous struggle for existence. Stegosaurus, with his bizarre array of plates and spines, and huge-headed Triceratops, had evidently carried specialization to an extreme, while in turn the carnivorous forms must have required an abundant supply of slow and easily captured prey.
Coming down to a more recent epoch, when the big t.i.tanotheres flourished, it is easy to see from a glance at their large, simple teeth that these beasts needed an ample provision of coa.r.s.e vegetation, and as they seem never to have spread far beyond their birthplace, climatic change, modifying even a comparatively limited area, would suffice to sweep them out of existence. To use the epitaph proposed by Professor Marsh for the tombstone of one of the Dinosaurs, many a beast might say, "I, and my race perished of over specialization." To revert to the horse it will be remembered that this very fate is believed to have overtaken those almost horses the European Hippotheres; they reached a point where no further progress was possible, and fell by the wayside.
There is, however, still another cla.s.s of cases where species, families, orders, even, seem to have pa.s.sed out of existence without sufficient cause. Those great marine reptiles, the Ichthyosaurs, of Europe, the Plesiosaurs and Mosasaurs, of our own continent, seem to have been just as well adapted to an aquatic life as the whales, and even better than the seals, and we can see no reason why Columbus should not have found these creatures still disporting themselves in the Gulf of Mexico. The best we can do is to fall back on an unknown "law of progress," and say that the trend of life is toward the replacement of large, lower animals by those smaller and intellectually higher.
But _why_ there should be an allotted course to any group of animals, why some species come to an end when they are seemingly as well fitted to endure as others now living, we do not know, and if we say that a time comes when the germ-plasm is incapable of further subdivision, we merely express our ignorance in an unnecessary number of words. The mammoth and mastodon have already been cited as instances of animals that have unaccountably become extinct, and these examples are chosen from among many on account of their striking nature. The great ground sloths, the Mylodons, Megatheres, and their allies, are another case in point. At one period or another they reached from Oregon to Virginia, Florida, and Patagonia, though it is not claimed that they covered all this area at one time. And, while it may be freely admitted that in some portions of their range they may have been extirpated by a change in food-supply, due in turn to a change in climate, it seems preposterous to claim that there was not at all times, somewhere in this vast expanse of territory, a climate mild enough and a food-supply large enough for the support of even these huge, sluggish creatures. We may evoke the aid of primitive man to account for the disappearance of this race of giants, and we know that the two were coeval in Patagonia, where the sloths seem to have played the role of domesticated animals, but again it seems incredible that early man, with his flint-tipped spears and arrows, should have been able to slay even such slow beasts as these to the very last individual.
Of course, in modern times man has directly exterminated many animals, while by the introduction of dogs, cats, pigs, and goats he has indirectly not only thinned the ranks of animals, but destroyed plant life on an enormous scale. But in the past man"s capabilities for harm were infinitely less than now, while of course the greatest changes took place before man even existed, so that, while he is responsible for the great changes that have taken place in the world"s flora and fauna during recent times, his influence, as a whole, has been insignificant.
Thus, while man exterminated the great northern sea-cow, Rytina, and Pallas"s cormorant on the Commander Islands, these animals were already restricted to this circ.u.mscribed area[22] by natural causes, so that man but finished what nature had begun. The extermination of the great auk in European waters was somewhat similar. There is, however, this unfortunate difference between extermination wrought by man and that brought about by natural causes: the extermination of species by nature is ordinarily slow, and the place of one is taken by another, while the destruction wrought by man is rapid, and the gaps he creates remain unfilled.
[22] _It is possible that the cormorant may always have been confined to this one spot, but this is probably not the case with the sea-cow._
Not so very long ago it was customary to account for changes in the past life of the globe by earthquakes, volcanic outbursts, or cataclysms of such appalling magnitude that the whole face of nature was changed, and entire races of living beings swept out of existence at once. But it is now generally conceded that while catastrophes have occurred, yet, vast as they may have been, their effects were comparatively local, and, while the life of a limited region may have been ruthlessly blotted out, life as a whole was but little affected. The eruption of Krakatoa shook the earth to its centre and was felt for hundreds of miles around, yet, while it caused the death of thousands of living beings, it remains to be shown that it produced any effect on the life of the region taken in its entirety.
Changes in the life of the globe have been in the main slow and gradual, and in response to correspondingly slow changes in the level of portions of the earth"s crust, with their far-reaching effects on temperature, climate, and vegetation. Animals that were what is termed plastic kept pace with the altering conditions about them and became modified, too, while those that could not adapt themselves to their surroundings died out.
How slowly changes may take place is shown by the occurrence of a depression in the Isthmus of Panama, in comparatively recent geologic time, permitting free communication between the Atlantic and Pacific, a sort of natural inter-oceanic ca.n.a.l. And yet the alterations wrought by this were, so to speak, superficial, affecting only some species of sh.o.r.e fishes and invertebrates, having no influence on the animals of the deeper waters. Again, on the Pacific coast are now found a number of sh.e.l.ls that, as we learn from fossils, were in Pliocene time common on both coasts of the United States, and Mr. Dall interprets this to mean that when this continent was rising, the steeper sh.o.r.e on the Pacific side permitted the sh.e.l.l-fish to move downward and adapt themselves to the ever changing sh.o.r.e, while on the Atlantic side the drying of a wide strip of level sea-bottom in a relatively short time exterminated a large proportion of the less active mollusks. And in this instance "relatively short" means positively long; for, compared to the rise of a continent from the ocean"s bed, the flow of a glacier is the rapid rush of a mountain torrent.
Then, too, while a tendency to vary seems to be inherent in animals, some appear to be vastly more susceptible than others to outside influences, to respond much more readily to any change in the world about them. In fact, Professor Cook has recently suggested that the inborn tendency to variation is sufficient in itself to account for evolution, this tendency being either repressed or stimulated as external conditions are stable or variable.
The more uniform the surrounding conditions, and the simpler the animal, the smaller is the liability to change, and some animals that dwell in the depths of the ocean, where light and temperature vary little, if any, remain at a standstill for long periods of time.
The genus Lingula, a small sh.e.l.l, traces its ancestry back nearly to the base of the Ordovician system of rocks, an almost inconceivable lapse of time, while one species of brachiopod sh.e.l.l endures unchanged from the Trenton Limestone to the Lower Carboniferous. In the first case one species has been replaced by another, so that the sh.e.l.l of to-day is not exactly like its very remote ancestor, but that the type of sh.e.l.l should have remained unchanged when so many other animals have arisen, flourished for a time, and perished, means that there was slight tendency to variation, and that the surrounding conditions were uniform.
Says Professor Brooks, speaking of Lingula: "The everlasting hills are the type of venerable antiquity; but Lingula has seen the continents grow up, and has maintained its integrity unmoved by the convulsions which have given the crust of the earth its present form."
Many instances of sudden but local extermination might be adduced, but among them that of the tile-fish is perhaps the most striking. This fish, belonging to a tropical family having its headquarters in the Gulf of Mexico, was discovered in 1879 in moderately deep water to the southward of Ma.s.sachusetts and on the edge of the Gulf Stream, where it was taken in considerable numbers. In the spring of 1882 vessels arriving at New York reported having pa.s.sed through great numbers of dead and dying fishes, the water being thickly dotted with them for miles. From samples brought in, it was found that the majority of these were tile-fish, while from the reports of various vessels it was shown that the area covered by dead fish amounted to somewhere between 5,000 and 7,500 square miles, and the total number of dead was estimated at not far from _a billion_. This enormous and widespread destruction is believed to have been caused by an unwonted duration of northerly and easterly winds, which drove the cold arctic current insh.o.r.e and southwards, chilling the warm belt in which the tile-fish resided and killing all in that locality. It was thought possible that the entire race might have been destroyed, but, while none were taken for many years, in 1899 and in 1900 a number were caught, showing that the species was beginning to reoccupy the waters from which it had been driven years before.
The effect of any great fall in temperature on animals specially adapted to a warm climate is also ill.u.s.trated by the destruction of the Manatees in the Sebastian River, Florida, by the winter of 1894-95, which came very near exterminating this species. Readers may remember that this was the winter that wrought such havoc with the blue-birds, while in the vicinity of Washington, D. C., the fish-crows died by hundreds, if not by thousands.
Fishes may also be exterminated over large areas by outbursts of poisonous gases from submarine volcanoes, or more rarely by some vast lava flood pouring into the sea and actually cooking all living beings in the vicinity. And in the past these outbreaks took place on a much larger scale than now, and naturally wrought more widespread destruction.
A recent instance of local extermination is the total destruction of a humming-bird, _Bellona ornata_, peculiar to the island of St. Vincent, by the West Indian hurricane of 1898, but this is naturally extirpation on a very small scale.
Still, the problems of nature are so involved that while local destruction is ordinarily of little importance, or temporary in its effects, it may lead to the annihilation of a species by breaking a race of animals into isolated groups, thereby leading to inbreeding and slow decline. The European bison, now confined to a part of Lithuania and a portion of the Caucasus, seems to be slowly but surely approaching extinction in spite of all efforts to preserve the race, and no reason can be a.s.signed for this save that the small size of the herds has led to inbreeding and general decadence.
In other ways, too, local calamity may be sweeping in its effects, and that is by the destruction of animals that resort to one spot during the breeding season, like the fur-seals and some sea-birds, or pa.s.s the winter months in great flocks or herds, as do the ducks and elk. The supposed decimation of the Moas by severe winters has been already discussed, and the extermination of the great auk in European waters was indirectly due to natural causes. These birds bred on the small, almost inaccessible island of Eldey, off the coast of Iceland, and when, through volcanic disturbances, this islet sank into the sea, the few birds were forced to other quarters, and as these were, unfortunately, easily reached, the birds were slain to the last one.
From the great local abundance of their remains, it has been thought that the curious short-legged Pliocene rhinoceros, _Aphelops fossiger_, was killed off in the West by blizzards when the animals were gathered in their winter quarters, and other long-extinct animals, too, have been found under such conditions as to suggest a similar fate.
Among local catastrophes brought about by unusually prolonged cold may be cited the decimation of the fur-seal herds of the Pribilof Islands in 1834 and 1859, when the breeding seals were prevented from landing by the presence of ice-floes, and perished by thousands. Peculiar interest is attached to this case, because the restriction of the northern fur-seals to a few isolated, long undiscovered islands, is believed to have been brought about by their complete extermination in other localities by prehistoric man. Had these two seasons killed all the seals, it would have been a reversal of the customary extermination by man of a species reduced in numbers by nature.
In the case of large animals another element probably played a part. The larger the animal, the fewer young, as a rule, does it bring forth at a birth, the longer are the intervals between births, and the slower the growth of the young. The loss of two or three broods of sparrows or two or three litters of rabbits makes comparatively little difference, as the loss is soon supplied, but the death of the young of the larger and higher mammals is a more serious matter. A factor that has probably played an important role in the extinction of animals is the relation that exists between various animals, and the relations that also exist between animals and plants, so that the existence of one is dependent on that of another. Thus no group of living beings, plants or animals, can be affected without in some way affecting others, so that the injury or destruction of some plant may result in serious harm to some animal.
Nearly everyone is familiar with the cla.s.sic example given by Darwin of the effect of cats on the growth of red clover. This plant is fertilized by b.u.mble bees only, and if the field mice, which destroy the nests of the bees, were not kept in check by cats, or other small carnivores, their increase would lessen the numbers of the bees and this in turn would cause a dearth of clover.
The yuccas present a still more wonderful example of the dependence of plants on animals, for their existence hangs on that of a small moth whose peculiar structure and habits bring about the fertilization of the flower. The two probably developed side by side until their present state of inter-dependence was reached, when the extinction of the one would probably bring about that of the other.