Sivatherium Giganteum.
Sivatherium Giganteum.
A Great Ruminant of the Miocene of India.
Copied by special permission of James Murie, M.D., F.G.S., &c.
Theincoming of that highest order of animals in which man himself, in so far as his physical nature is concerned, takes his place, presents some features which, though not unparalleled in the history of other forms of life, are still very striking. The modern Mammalia are somewhat sharply divided into three very unequal groups. First, those which present in their full perfection the property of producing fully developed young, which is one of the distinctive characters of the class. These are the Placental Mammals. Secondly, those in which the young are produced in a very imperfect condition, and are usually nourished for a time in a marsupium or pouch. These are hence called Marsupials. They are for the most part confined to Australasia, though a few occur in America; and are decidedly inferior in rank to the ordinary mammals. Thirdly, those in which there is a bird-like bill, and also certain bird-like or reptilian peculiarities of skeleton and of the alimentary canal. These are the Monotremes, represented by a very few species in Australia and New Guinea.
In geological history, so far as the facts are at present known, the second group, that of the Marsupials, antedated the others by a vast lapse of time. The Marsupials appear in the Trias, near the beginning of the Mesozoic period. The Placentalsare not found until we reach the beginning of the Tertiary. The Monotremes would seem to be a comparatively modern degraded type. Thus the Marsupials existed throughout the reptilian age, and this in those countries of the northern hemisphere in which they are not now found. The Mesozoic Marsupials were, it is true, of small size, but there were probably numerous species, and though unable to cope with the great reptiles that swarmed by the shores and on the plains, they may have found abundant scope in the upland and interior regions of the continents.
The Upper Trias of Germany has afforded to Professor Pleininger two teeth of a small mammal, to which the name ofMicrolestes antiquushas been given, under the impression that it was carnivorous, though it now seems more likely that it was a vegetable feeder. In rocks of nearly the same age in America, Emmons found a jaw-bone of another species (Dromatherium sylvestre), which has been supposed to be a near ally of the existingMyrmecobius fasciatusof Australia (Figs. 166, 167). In the Stonesfield slate, a member of the English Jurassic, several other species have been found (Fig. 168), and a still larger number in the freshwater beds of the Upper Purbeck. Marsh has obtained many others from the Jurassic of America. None appear to have yet been found in the Cretaceous, but they reappear in the Eocene Tertiary, and continue to the modern time. Their absence in the Cretaceous is probably a mere accident, and they present an illustration of a very permanent type little changed since its first introduction. Lyell enumerates in all thirty-three species from the Mesozoic, all of them of small size, and all more or less nearly related to existing Australian Marsupials, though differing much among themselves, and including both carnivorous and herbivorous forms (Fig. 169). Marsh has recently suggested a somewhat new interpretation of these interesting mammalian remains.79He considers them divisible into two groups, one allied tothe modern Insectivora (Moles, Shrews, Hedgehogs, &c.), but of generalized forms. For these he constitutes a new order (Pantotheria, Marsh). The other group is less numerous and is Marsupial (Allotheria, Marsh). The jaws inFigs. 166 and 168belong to the former group, that inFig. 169to the latter. We should thus have both placental and Marsupial mammals in the Mesozoic. Marsh remarks that the descent of these different types from a common ancestry would require us to trace mammals back into the Palæozoic, that is, on the doctrine of gradual evolution.
Jaw of Dromatherium sylvestre.
Fig. 166.—Jaw ofDromatherium sylvestre(Emmons). From the Trias of North Carolina.
A modern Australian marsupial.
Fig. 167.—Myrmecobius fasciatus.A modern Australian marsupial, allied to Mesozoic species.
So soon as the palæontologist passes from the Upper Cretaceous to the Eocene, he finds himself in the domain of the placental mammals, which appear in numerous and large species, and this, not merely in one region, but in every part of the world in which these deposits are known to exist.
Jaw, and enlarged molar of Phascolotherium Bucklandi.
Fig. 168.—Jaw, and enlarged molar ofPhascolotherium Bucklandi. Stonesfield slate. England.—After Phillips.
Plagiaulax Becklesii. Jaw, and pre-molar enlarged.
Fig. 169.—Plagiaulax Becklesii.Jaw, and pre-molar enlarged, showing flat surface, with ridges.—Purbeck.
Indeed, the recent discoveries in America and in the east of Europe have almost thrown into the shade those researches of Cuvier in the Paris basin which first brought this important fact to light. The Eocene mammals, like the Carboniferous amphibians, the Mesozoic reptiles, and the Cretaceous forests, appear to spring full-grown from the earth, and this at nearly the same time in every part of the northern hemisphere. It has been suggested that they may have come in gradually without our knowledge in the Cretaceous period; but if so, we should have found some of their remains along with those of the Upper Cretaceous plants. But the prevalence of the great reptiles up to the close of the Cretaceous would seem to render the co-existence of large mammals unlikely. It has further been supposed that geological changes in the southernand northern hemispheres may have alternated with each other, so that there may be in the former Cretaceous beds in which the remains of ancestors of the Eocene mammals may be found. But we do not as yet know of such deposits. We may be content, therefore, to suppose that at the close of the Cretaceous there was established somewhere a sort of Eden for the first placental mammals, in which they were introduced and could live unharmed by the decaying monsters of the reptilian age, until the time came when they could increase and multiply and replenish the earth. The nearest approach to such a centre of mammalian life is perhaps to be found in those great American lake basins embedded in the mountains of the West, which have been so well described by Hayden and Newberry, and which have yielded so many animal remains to the researches of Leidy, Marsh, and Cope.
Restoration of Palaeotherium magnum.
Fig. 170.—Restoration ofPalæotherium magnum. Eocene.—After Cuvier and Owen.
The typical deposits of the Early Eocene have long been those of the Basin of Paris, where thick and highly fossiliferous deposits of this age rest on the more or less denuded surface of the Upper Chalk, and have afforded a rich harvest ofremains of about fifty species of placental quadrupeds, whose bones have been found in the gypsum quarries of Montmartre. The great majority belong to the Ungulates, or hoofed animals, and the most abundant genera are those called by CuvierPalæotherium(Fig. 170) andAnoplotherium, of which there are several species, and which have affinities with the modern Tapirs on the one hand, and with the Horse on the other. Of the Unguiculate or clawed orders there are carnivorous forms allied to the Hyæna and the Fox, a Bat and a Squirrel; and the Marsupials are represented by an Opossum. Lyell describes a bed of clay associated with the gypsum, in which are numerous footprints, probably produced on the margin of a lake. Many of these might be referred to the Palæothere and its allies; but there are others belonging to quadrupeds yet unknown, and there are also tracks of tortoises, crocodiles, and lizards, and of a large wading bird. Such a bed, perhaps deposited on the margin of a salt lake, resorted to as a “lick” by herbivorous animals, and by the carnivorous species which preyed on them, is well fitted, by the thronging life which it indicates, to teach how little we can know of the actual number and variety of the old inhabitants of the earth.
In England, Eocene beds of the age of those of Paris, occupy the valley of the Thames and the Isle of Wight and neighbouring parts of Hants. They have afforded mammalian fossils similar to those of Paris, though less abundantly, but they are rich in remains of marine animals and of land plants.
Instead of describing the well-known animals of the French and English Tertiaries, from these Eocene deposits upwards, I shall shortly sketch the succession in America, as worked out by Marsh and Cope, with the aid of the admirable summary given by Gaudry of the present state of knowledge with reference to the sequence of mammalian life from its appearance in the Early Eocene up to the present time.80
Eocene mammals, especially those gigantic whale-likecreatures calledZeuglodon(Fig. 180), have been found in Eastern North America, but the most remarkable discoveries have been made in the Western Territories, where vast numbers of bones are imbedded in certain ancient and wide-spread lacustrine beds. It may be well to premise here that though the division into Eocene, Miocene, and Pliocene is recognised in America as well as in Europe, the limits of these groups may not precisely correspond with those in the Old World. Still we have this certain point of departure, that the Eocene begins where the peculiar animals of the Cretaceous end, and that the drying up of the later Cretaceous sea and the establishment of the Eocene land were probably nearly contemporaneous in both continents. It is true, however, in animals as in plants, that in the successive periods of the Tertiary, America presents an older aspect than Europe, just as its modern fauna still contains such old forms as the opossum.
It would seem that as the mountain-ranges and table-lands of Western America emerged from the Cretaceous waters, they became clothed with Eocene forests and inhabited by Eocene mammals. But the waters, dammed up by surrounding ridges, formed large lake basins, which were drained only by the slow excavation of “cañons” as the land rose still higher. In the successive deposits formed in these lakes both by ordinary deposition of silt and by paroxysmal showers of volcanic ashes were entombed great numbers of the animals which fed on their banks. It appears that these deposits, which in some places are estimated at not less than 8000 feet in thickness, hold the remains of three successive faunas, differing materially from each other, and representing the Lower, Middle, and Upper Eocene. On the flanks of the elevated region supporting the beds formed in the Eocene lakes, are other later lake basins of Miocene age, also abounding in animal remains. East of the Rocky Mountains, and also on the Pacific coast, are still later Pliocene depositsholding other and more modern Mammalia. The vast area of these formations and the complete sequence which they show are scarcely equalled elsewhere.
Coryphodon Hamatus.
Fig. 171.—Coryphodon Hamatus.A Lower Eocene Perissodactyl skull, greatly reduced, showing small size of brain,a.—After Marsh.
As in the Paris basin, the large Ungulates constitute the most conspicuous feature. The great group is now usually divided into those that are odd-toed (Perissodactyl) and those that are even-toed (Artiodactyl). Though these are apparently arbitrary characters, they correspond with other more fundamental differences. The first includes such modern animals as the Rhinoceros, Tapir, and Horse. The second includes two somewhat distinct assemblages—that with mammillated teeth, of which the Hog and Hippopotamus are types (Bunodonts), and that with crescental plates of enamel in the teeth, of which the Ruminants like the Deer, Ox and Camel, are examples (Selenodonts).
Fore-foot of Coryphodon.
Fig. 172.—Fore-foot ofCoryphodon. Greatly reduced.—After Marsh.
The most characteristic animals of the lowest Eocene belong to the genusCoryphodon(Figs. 171, 172), which so abounded in Eocene America that bones of about 150 individuals were found by the Wheeler Expedition in one year in the Eocene beds of New Mexico. These animals in their dentition approached the American tapirs, except that they had great canines like the bear, while their feet resembled those of the elephant, and some of them attained the dimensions of the ox.Coryphodonis thus, as might be expected in a primal placental mammal, a creature of somewhat generalised type. Another point in which it resembles some at least of its early Tertiary contemporaries is the small size of the brain, especially in those parts of it supposed to minister to the intelligence and higher instincts (Fig. 171,a). It is certainly remarkable that as Tertiary time went on the successive groups of mammals were gifted with brains of larger and larger size, fitting themfor higher functions; and ultimately for associating with man. Animals thus low in development of brain were probably slow and sluggish and stubbornly ferocious, and dependent on brute force for subsistence and defence; and they would have been altogether unsuitable for domestication had they lived to the present time.
Skull of an Upper Eocene Perissodactyl.
Fig. 173.—Skull of an Upper Eocene Perissodactyl (Dinoceras mirabilis), showing three pairs of horn-bases. Greatly reduced.—After Marsh.
In the Middle Eocene, the place ofCoryphodonwas taken byDinocerasand allied forms. Some of the species nearly equalled the elephant in size, but had shorter and stouter limbs, each supported on five great toes—the most perfect possible sort of pedestal foot (Figs. 172, 174). They were heavily armed with immense canines on the upper jaws, and two or even three pairs of horns or hard protuberances on the head (Fig. 173). Creatures so supported and so armed, andliving where food was plentiful, might well dispense with any great degree of intelligence, and their development of brain is consequently little better than that ofCoryphodon. These great and characteristic Eocene families have no known successors; and in the Miocene age their place is taken by a very different group, that of whichBrontotheriumis the type (Fig. 175). They are creatures of huge size, with a pair of horn-cores on the nose, and feet with four toes in front and three behind, resembling in form those of the rhinoceros.
Fore-foot of Dinoceras.
Fig. 174.—Fore-foot ofDinoceras. Greatly reduced.—After Marsh.
Skull of Brontotherium ingens.
Fig. 175.—Skull ofBrontotherium ingens(Marsh). Greatly reduced. A Miocene Perissodactyl.
Series of Equine Feet.
Fig. 176.—Series of Equine Feet.—After Marsh.
a,Orohippus, Eocene.b,Miohippus, Miocene.c,Protohippus, Lower Pliocene.d,Pliohippus, Upper Pliocene.e,Equus, Post-Pliocene and Modern.
While these gigantic Perissodactyles have no successors as yet known to us, another and less conspicuous Eocene type can be traced onward to modern times by a chain of successors which the imagination of evolutionists has converted into a veritable genetic series, to which they appeal as a “demonstration” of the process of descent with specific modifications. In the Lower Eocene are found the remains of a diminutive ungulate (Eohippus), of the stature of a moderately-sized dog. It has four toes and a rudiment of a fifth in front, and three toes behind; and has teeth slightly resembling those of the horse, but more simple and shorter in the crown. In this creature it has been supposed that we have a direct ancestor of the modern horse. A very similar genus (Orohippus), lacking only the fifth rudimentary toe, replacesEohippusin the Middle Eocene.Mesohippusof the Lower Miocene is as large as a sheep, and has only three toes on the fore-foot and a splint bone, while its teeth assume a more equine character (Fig. 176). In the Upper MioceneMiohippuscontinues the line, whileProtohippusof the Lower Pliocene is still more equine and as large as an ass, and corresponds with the EuropeanHipparionin having the middle toe of each foot alone long enough to reach the ground. In the Upper Pliocene true horses appear with only a single toe, and splint bones instead of the others. In America, though the horse wasunknown at the time of the discovery of the continent, several species occur in the Tertiary and Post-Pliocene, showing that the genus existed there up to a comparatively late period; and when re-introduced it has thriven and run wild in the more temperate regions. What cause could have led to its extinction in Post-Glacial times is as yet a mystery. This genealogy of the horse, independently of its evolutionist application, is very interesting. It shows that some Eocene types were suited to continuance, and even adapted for extension, while others were destined to become altogether extinct at an early date. It shows farther that the power of continuance resided not so much in the gigantic and prominent species as in smaller forms. It is to be observed, however, that Gaudry and other orthodox evolutionists in Europe deduce the horse, not fromEohippus, but fromPalæotherium, and that it is equally impossible to verify either phylogeny, since the mere sequence of more or less closely allied species in time does not prove continuous derivation. Nor indeed are we certain that one-toed horses like those now living did not exist on the dry plains in Eocene times, since the inhabitants of these plains are probably unknown to us. An amusing illustration of the probable reason of the disappearance of the missing links has recently been given by a writer not very favourable to the new philosophy. The several consecutive species may be represented by coins. We may suppose, for example, sixpences to have been coined first, then sevenpenny and eightpenny pieces, and so on up to a shilling, then pieces representing thirteen, fourteen and fifteen pence, and so on up to a half-crown or crown; but all the intervening denominations between the sixpence and the shilling, and between the shilling and the half-crown, were found practically of little use. Hence few were coined, and they soon became obsolete. Thus the antiquary would find only a few denominations, and those connecting them would be seldom or never found. It is plain that if we could suppose that nations constructed theircoinage after this unthinking and empirical fashion, and that if we were justified in ascribing a similar procedure to the Creator, it might help to account for the facts as we find them, otherwise we should rather suppose that in both cases something like plan and calculation determined the selection of the species produced, whether of coins or animals. But Chance is a blind goddess, and if we instal her as creator, we must expect the work to proceed by a series of abortive experiments.
The Perissodactyls are not numerous at present. The three groups represented by the Horse, Rhinoceros, and Tapir constitute the whole; and the two latter forms can be traced back to predecessors in Eocene times, even more closely resembling them than those supposed to be ancestors of the horse resemble that animal. But the few species now living have thus a vast surplusage of possible ancestors. Many species and genera are dropped without any modern representatives, so that the tendency has been to a gradual elimination of surplus types, until only a few isolated and somewhat specialised forms remain at present. Yet this process of elimination is not necessarily an evolution or survival of the fittest, in the sense of modern derivationists. It rather implies that in certain past states of the earth the conditions of life afforded scope for many forms not now required, or replaced by other types more suited to the advanced and specialised nature of the world.
On the other hand, the Artiodactyls have gained in numbers and importance, in comparison with their odd-toed comrades; and this, though an odd number, namely five, was the typical number with which the earliest quadrupedal forms began life far back in the Palæozoic. The typical Artiodactyls are those that cleave the hoof, and many of which also chew the cud; and they are of all others, the horse perhaps excepted, those that are most valuable to man. The lower type (Bunodont), to which the hog belongs, is the older; and many hog-likeanimals occur from the earlier Tertiary upwards. In the Upper Eocene, even-toed species appear with an approach at least to the crescent-shaped teeth of the modern deer and oxen. Some of the species are obviously forerunners of the modern antelopes and deer, though as yet destitute of horns or antlers. Others, likeOreodon, are of more hog-like aspect, though believed to have been ruminants (Fig. 177). These are characteristic of the Middle Miocene, at which stage true deer appear in Europe (Dicroceras), though they are not known in America until the Pliocene period. The earliest deer have small and simple antlers, these ornaments becoming larger and more elaborate in approaching the modern era. The hollow-horned ruminants appear for the first time in America in the Lower Pliocene; and no ancestry has so far been attempted to be traced for them. The antelopes of this group, as well as the giganticSivatheriumof India,81allied to the modern prong-horned antelope of North America, were prominent in the Old World in the Miocene.
Oreodon major.
Fig. 177.—Oreodon major.A generalised Miocene ruminant, with affinities to the Deer, Camel, and Hog. Greatly reduced.—After Leidy.
Lower Jaw of Megatherium.
Fig. 178.—Lower Jaw ofMegatherium. Greatly reduced. Post-Pliocene of South America.—After Owen.
Ungual Phalanx and Claw-core of Megatherium.
Fig. 179.—Ungual Phalanx and Claw-core ofMegatherium. Greatly reduced.
A very noteworthy and specially American group of mammals is that of theEdentates, the Sloths and Ant-eaters, a group whichà prioriwe should have supposed would have been one of the earliest in time. They appear, however, first in the Miocene, without even any suggested ancestry, and are represented from the first by large species, though they attain their grandest stature in theMegatheriumandMylodonof the Post-Pliocene (Figs. 178, 179), which were sloths of so gigantic size that they must have pulled down trees to feed on their leaves, unless, indeed, there were trees equally colossal for them to climb. But before the modern time, like the American horses, the larger herbivorous forms suddenly disappear, and are now represented only by a few diminutive South American species, which can scarcely, by any stretch of imagination, be supposed to be descendants of their gigantic predecessors. The history of these animals, like those of the great Tertiary marsupials ofAustralia and the many Miocene elephants of India, affords a remarkable illustration of the persistence of similar groups of creatures in successive ages in the same region, along with diminution in magnitude and number of species toward the modern times.
Tooth of Eocene Whale.
Fig. 180.—Tooth of Eocene Whale (Zeuglodon cetioides). One-half natural size.
The Whale-tribe (Cetaceans) at once in the earliest Eocene takes the place of the great Sea-lizards of the Cretaceous; and the oldest of the whales are in their dentition more perfect than any of their successors, since their teeth are each implanted by two roots, and have serrated crowns, like those of the Seals. The great Eocene whales of the Southern Atlantic (Zeuglodon) (Fig. 180), which have these characters, attained the length of seventy feet, and are undoubtedly the first of the whales in rank as well as in time. This is perhaps one of the most difficult facts to be explained on the theory of evolution. Allied to the whales is the small and peculiar group of theSea-cows or Dugongs (Sirenians). These creatures, highly specialised and very distinct from all others, appear in the Early Tertiary in forms very similar to those which now exist, and probably in much more numerous species, and they pursue the even tenor of their way down to modern times without perceptible elevation or degradation. “We have questioned,” says Gaudry, when speaking of the Tertiary Cetaceans, “these strange and gigantic sovereigns of the Tertiary oceans as to their progenitors—they leave us without reply.” Their silence is the more significant as one can scarcely suppose these animals to have been nurtured in any limited or secluded space in the early stages of their development. The true Seals, which are more elevated than the Whales, and very different in type, appear much later, and without any probable ancestry.
The Elephants, two or three species of which constitute in the modern world the sole representatives of an order, are a remnant of an ancient race once vastly more numerous. They appear in Europe and Asia in the Miocene, when they were represented by three distinct genera (Elephas,Mastodon, andDinotherium). The second genus (Fig. 181) differs from the proper Elephants in having tuberculated teeth, indicating a more swinish habit, and probably a more fierce disposition. The third (Fig. 182) is remarkable for the immense size of some of its species, far exceeding the modern Elephants, and has the farther peculiarity of a pair of descending tusks on the lower jaw, constituting a strong and heavy grubbing-hoe, with which it could probably dig deeply for roots. So important was the group in Miocene times that seven elephants are already known from this formation in India alone, besides three species of Mastodon. Four or five Miocene Mastodons are known in Europe, besides twoDinotheria; and the true Elephants appear there in the Pliocene, and continue to the beginning of the Modern. The elephantine animals are not known in America till the Pliocene, but in that and the Pleistocene, and perhaps up to the human period, the western continent, now altogetherdestitute of elephants, possessed several species both ofElephasandMastodon, which extended, as in Siberia, even into the Arctic regions; and, as we know from specimens preserved in a frozen state in the latter region, some of the species were so protected by dense fur as to be able to endure extreme cold. The candid Gaudry closes his summary of the history and affinities of the elephantine animals with the words: “However, the sum of the differences compared with that of the resemblances is too great to permit us to indicate any relation of descent between the proboscidians and the animals of other orders known to us at present.” So these greatest of all the animals of the land, with their strangely specialised forms and almost human sagacity, stand alone, without father or mother, without descent.
Mastodon ohioticus.
Fig. 181.—Mastodon ohioticus.An American Elephant. Post-Glacial.
Head of Dinotherium giganteum.
Fig. 182.—Head ofDinotherium giganteum. Greatly reduced. Miocene of Europe.
Wing of Vespertilio aquensis.
Fig. 183.—Wing ofVespertilio aquensis. An Eocene Bat. After Gaudry.
The Rodents, or gnawing animals, appear in the Early Eocene on both continents in familiar forms allied to our Squirrels andRats. Porcupines and Beavers are added in the Miocene. This group seems thus to have continued much as it was; and it is still perhaps represented by as many species as at any previous time. Many of the ancient forms were, however, much larger than any modern species, and some of these larger forms82present singular points of approach to very distinct types, as, for example, to that of the Bears; but these large and composite species are long since extinct. The insectivorous mammals have much the same history with the Rodents. Such highly specialised and abnormal forms as the Bats might be supposed to be modern. But, strange to say, they appear with fully developed wings both in Europe and America in the Eocene (Fig. 183). Gaudry thinks that it is “natural to suppose” that there must have been species existing previously with shorter fingers and rudimentary wings; but there are no facts to support this supposition, which is the more questionable since the supposed rudimentary wings would be useless, and perhaps harmful to their possessors. Besides, if from the Eocene to the present the Bats have remained the same, how long would it take to develop an animal with ordinary feet, like those of a shrew, into a bat?
The Early Eocene was not altogether a time of peace in the animal world. The old carnivorous Saurians were dead and buried, but their place was taken by carnivorous mammals, allied to our modern Tigers, Hyænas, Foxes, and Weasels. The Carnivora, however, were subordinate in the Eocene, and, as already remarked, some of them appear to be intermediate between marsupial and placental forms—a fact which evolutionists have noticed with much satisfaction. They appear to attain to their culmination in the Miocene, when their powers seem to be proportionate to those of the great and well-armed quadrupeds they had to deal with. To this age belongs the introduction of the terrible “Cymetar-toothed Tiger” (Machairodus,Fig. 184). Its huge tusk-like canines and powerful limbs seem to fit it more than any other of the cat family for destructive efficiency. Yet ordinary cat-like animals were contemporary with it, and have survived it, since Machairodus disappears in the Post-Pliocene, though in previous periods it had been very widely distributed on both continents. It is a curious fact, perhaps of more significance in various ways than we yet understand, that the Dog-bear (Arctocyon), of the oldest French Eocene, believed to be the oldest placental mammal known, though technically placed among the Carnivora, has a kind of dentition indicating that, like the modern Bears, it was really omnivorous; and its skull shows some peculiarities tending to those of the Marsupials.
Skull of a Cymetar-toothed Tiger.
Fig. 184.—Skull of a Cymetar-toothed Tiger (Machairodus cultridens). Pliocene, France. Reduced.
Lower Jaw of Dryopithecus Fontani.
Fig. 185.—Lower Jaw ofDryopithecus Fontani. An Anthropoid Ape of the Middle Miocene of France. Natural size.
Much interest attaches to the first appearance of the order of Apes (Quadrumana), or, if we take the somewhat deceptive classification favoured by some modern zoologists, thePrimates,including the apes and man. They begin in the Eocene, both in Europe and America, with the lowest tribe, that of the Lemurs, now confined to the island of Madagascar and parts of Africa and Southern Asia, and which may, Gaudry thinks, be modified Marsupials, though he admits that this is hard to understand. He mentions the resemblance of the teeth of monkeys to those of some hog-like animals, a resemblance, however, merely marking a similarity of food, and suggests on this ground that some of the primitive ancestors of the hog may have also given rise to the Monkeys. In the Miocene of Europe and Asia we have true Apes; and one of these, which rivals man in stature (Dryopithecus), belongs to the group of the gibbons, or long-armed apes, one of the higher families of the modernQuadrumana(Fig. 185). This animal presents, indeed, the nearest approach to man made by any Tertiary mammal. Still the differences are great, as, for instance, in the much larger size of the canines and premolars. Yet so much confidence has Gaudry in the resemblances, that he even venturesto suggest that certain flint chips found in the Miocene of Thenay, and which have been supposed to indicate human workmanship, may have been chipped by the hands ofDryopithecus. Should this view be adopted by evolutionists, it will at least have the effect of preventing flint chips from being received as evidences of the antiquity of man.
It is scarcely necessary to sum up this review of the history of the Tertiary mammals. Much that has been said may be modified or changed by future discoveries; but the great facts of the late appearance of the placental mammals, of their rapid introduction, with their ordinal differentiation nearly complete over all the continents, of the speedy culmination and early decadence of many types, and of the unchanged permanence of others, must in the main be sustained. It is not too much to say that to account for these facts the evolutionist must abandon the idea of gradual change, and adopt that of “critical periods” when sudden changes occurred. The history becomes inexplicable, unless with Mivart, Le Conte, and Saporta, we admit “periods of rapid evolution” alternating with others of stagnation or retrogression; and if we admit these, we practically fall back on the old idea of creation; only it may perhaps be “Creation by Law.”
Contemporaries of Post-Glacial Man.
Contemporaries of Post-Glacial Man.From a painting by Waterhouse Hawkins.
Hithertowe have met with no trace of man or of his works. Yet there have been in our upward progress from the dawn of life mute prophecies of his advent. Man is in his bodily frame a vertebrate animal and a mammal; and when first the Amphibians were introduced in the Palæozoic, the framework of man’s body was already sketched out and its principles settled. Those great reptilian lords, the biped Saurians of the Mesozoic, already foreshadowed his erect posture, though their limbs may have been more ornithic than mammalian. The gradual advance in the brain-development of the Tertiary mammals presaged a coming time when mind would obtain the mastery over claw and tooth and horn; and in the Miocene ages there was already some hint of the precise style of structure in which this new creative idea would be realised. Yet it might have been impossible to imagine beforehand the vast changes which this new idea would inaugurate. In the lower animals such intelligence as they possess is so tied to the physical organisation that it manifests itself as a mechanical unvarying instinct. Man bursts this bond, and in doing so revolutionises the whole scheme of nature. Old things are now put to new uses, the face of nature is changed, varied arts are introduced, and thought enters into the domain ofgeneral and abstract truth. Objects are arranged, classified, understood, and while in some respects the whole creation is made to groan under the tyrannous inventions of man, yet these are the inventions of imagination and design. They are the triumph, not of brute force, but of will and intelligence.
That man was not in all the earlier ages of the world, except in these prophecies of his coming, geology assures us. That he is, we know. How he came to be, is, independently of Divine revelation, an impenetrable mystery—one which it is doubtful if in all its bearings science will ever be competent to solve. Yet there are legitimate scientific questions of great interest relating to the time and manner of his appearance, and to the condition of his earlier existence and subsequent history, which belong to geology, and in which so great stores of material have been accumulated that a treatise rather than a chapter would be required for their discussion. We may endeavour to select a few of the more important points.
One of the first questions meeting us is that which relates to the point in geological time signalised by the advent of our species. In the Eocene period our continents were being gradually raised out of the ocean, and were still in great part under the waters, which several times returned upon the land, and seemed ready again to engulf it. In this period not only have we no traces of man, but all the higher animals of that age are now extinct. In the later Eocene and Miocene the extent of land became greater, but it was so disposed as to allow the influx into the Arctic Sea of vast volumes of heated water from the equatorial regions; and there may have been also astronomical causes at work to increase this influx of warm water, and so to raise the temperature of the Arctic regions still higher.83The middle period of the Tertiary was undoubtedly a time very favourable to the wide distribution of the higher forms of life both animal and vegetable. But we cannot traceman or any of the contemporary mammals back to the Miocene. In the Pliocene the continents had attained to their present elevations, and climates were not dissimilar from those prevailing at present; but still we have no certain indication of the presence of man; and if other modern mammals extend back to this period their number is very small. In this age also the greater part of the continents must have been covered with a great thickness of soil and disintegrated rock favourable to vegetation, and there seemed nothing to preclude the introduction of man. But a new and at first sight most unfavourable change was to intervene. Whether through internal changes affecting the distribution of land and water, or through astronomical vicissitudes, the northern hemisphere, and possibly the whole world, entered on an era of refrigeration, the so-called “Glacial Age” of the Post-Pliocene or Pleistocene period. That in this period our continents as far south as the latitude of 40° were overwhelmed with ice or ice-laden seas is rendered evident by the fact that the whole surface up to several thousands of feet above the sea-level has been bared of its accumulateddébrisand polished and grooved by ice, and laden with boulders and other glacial deposits, while in many places at heights of even 1,000 or 1,200 feet these deposits contain sea-shells of species now living in the colder parts of the ocean. These phenomena do not exist in the tropical regions, except in the vicinity of high mountains, but they recur in the southern hemisphere. It is still uncertain whether the period of greatest cold in the two hemispheres was at the same time or in successive ages. Geologically, however, they are approximately contemporaneous, both occurring between the end of the Pliocene and the modern period; but nevertheless they may not have coincided in absolute date.
Very different views have been held as to the precise condition of the continents in the Glacial Age, though all agree in the prevalence of cold and the action of ice, and in the fact of a great submergence at one or more stages of the period.My own conclusions, which I have advocated elsewhere,84and which are based on extensive study of the northern parts of America, where the deposits of this age are more widely developed than elsewhere, are that there was one great subsidence, leading to a condition in which the lower levels of the continents were covered with ice-laden water and the higher regions were occupied with permanent snow and glaciers. This submergence went on till even high mountains 4,000 feet or more in elevation were under water. Then there was a gradual though intermittent elevation, during which the climate became ameliorated, and lastly there was a condition in which the land of the northern hemisphere stood higher than at present, and which immediately preceded the modern period. As these conditions have great significance in relation to the appearance of man, I have tabulated them for reference as they occur in Scandinavia, Great Britain, and North America. The so-called “Interglacial Periods” of some geologists are in reality local results of the stages of intermittent elevation in which were deposited beds which in some cases, as in Scotland, Sweden, and Eastern Canada, hold sea-shells, and in others, as in the central areas of North America, contain remains of plants of northern species.
We shall name, for convenience, the parts of this Pleistocene revolution which include the great subsidence and glaciation, theGlacialAge, that extending from the re-elevation to the modern thePost-glacial.
The Glacial Age proved fatal to a large proportion of the land life of the previous periods. According to Professor Boyd Dawkins, out of fifty-three species known in Britain in the Post-glacial, only twelve are survivors of the Pliocene; and probably the proportions would not be greater in any part of the northern hemisphere. Some, however, did survive, either by migrating southward or by being inhabitants of places less severely affected than most by the general cold andsubmergence. There was thus no absolute break in the chain of life effected by the Glacial Age.
Valley-clays and Heath-sands of Sweden. (No fossils.)
Hoxne Deposits and Upper Terrace Gravels. Palæolithic Implements.
Terrace Gravels and Loess Deposits.
Terrace-gravels of Norway and Sweden. (No fossils.)
Upper Glacial Beds. Bridlington Beds. Upper Boulder Beds.
Placer Gravels of West.
Do. Sand and Gravel, Newer Boulder Drift.
Dryas-clay with Fossil plants of northern species.
So-called “Interglacial” Deposits.
So-called Interglacial Beds, with Plants, &c. Loess Deposits of Mississippi.
Uddevalla beds with Boreal Marine shells.
Clyde Beds and Marine Clays.
Upper Leda Clay and Champlain Clay, with Boreal Shells.White Silts of British Columbia.
Mid-Glacial Sands.
Erie Clays and similar Beds of West.
Yoldia Clay and Sand. Arctic Marine Shells.
Lower Leda Clay, with Arctic Shells.
Yellow Stony Clay and Sand, and Gravel of Scania.
Port Hudson Deposit of Mississippi.
“Syrtensian” Beds of New Brunswick.
Orange Sand of Mississippi.
“Moraines de Fond,” or Boulder Clay proper.
Till, or Older Boulder Clay.
Boulder Clays, with Local and some Travelled Boulders.
Ancient Diluvial Sand.
Pebbly Beds and Weyburne Sands, Lignitic Forest Beds.
Old Land Surfaces--Peat under Boulder Clay, Local Gravels and Sands.
Pre-glacial Gravels of British Columbia.
In what part of this sequence did man appear? In answer to this, I think it is now generally admitted that he is not certainly known earlier than the Post-glacial period. Various supposed indications of his presence in “Inter-glacial” Glacial, Pliocene, and even Miocene deposits have proved on examination to be unreliable. America has recently put forth claims to have been inhabited by man in the Pliocene, on the faith of remains found in auriferous gravels in the West. But the facts that the implements and bones found are modern in type, that the gravels were deeply mined by the Indians, and that the objects found, as mortars for dressing gravel, etc., are in many cases such as they would be likely to leave in their excavations, have discredited these supposed discoveries. Still more recently, chipped flints found in gravels in New Jersey, by Abbott, have been supposed to carry back the Indians of the East coast to the Glacial period. It is evident, however, from the description of these deposits by the late Mr. Belt and by Professor Cook, director of the Survey of New Jersey, that they are really Post-glacial, that their age must be estimated by study of the local conditions, and that there is no good ground for correlating them with the upper members of the true Glacial drift to the northwards, with which they had been somewhat rashly identified. Irrespective of the doubtful character of many if not all of the so-called implements, the deposits in which they are found is confessedly not a product of the ice of the Glacial period proper, whether that was, as some maintain, a period of land glaciation as far south as New Jersey or not. It belongs to a time of denudation by water, aided perhaps by floating ice, and is not necessarily older than the river gravels of the Somme, which, like it, contain boulders and imply conditions of torrential action and climate which have long since passed away. If, however, these implements are genuine, they would imply the presence of Palæocosmic or Antediluvian man in America. This would in itself be an important discovery.
For the present, therefore, man is geologically a Post-glacial species, and there is nothing unreasonable in supposing that he dates no farther back, since several animals his contemporaries are in the same case; and by supposing him to have originated after the Glacial age we avoid the difficulties attendant on his survival of that great revolution. The only necessity for supposing an earlier appearance arises from the requirements of the hypothesis of evolution. Those, however, who hold this theory, may with Haeckel take refuge in that shadowy continent supposed to have extended from Africa to Australia,85and to have sheltered man in his transition from the ape to humanity, in the Tertiary period. The name Lemuria is taken from the Lemurs, supposed ancestors of the Apes, which still haunt the margin of the Indian Ocean; but it may be taken also in its old Latin sense of ghosts of the evil dead; and as we are not likely to obtain any more tangible evidence of the old natives of Lemuria, perhaps we may hope that some spiritualist may succeed in charming them from the vasty deep for our enlightenment. Should this be so, it is to be hoped that no “drum ecclesiastic” will be beaten to drive them away till they have revealed all they can tell.
It may be well to add that, in addition to the negative evidence, there is at least one positive evidence of the recent origin of man which has been well urged by Le Conte. It is this: animals have continued long in geological time in the inverse ratio of their rank. Some Mesozoic protozoa still survive. So do many early Tertiary mollusks. But the mammals are of much less duration. No living species goes back farther than the Pliocene. Few extend farther than the Glacial age. On the same principle it is not to be expected that man, the highest of all animals, should extend far back in geological time.
Accepting the Post-glacial age as that of the advent of man, it may be interesting to ask what we know of the condition of our continents when he appeared. In Western Asia, in Europe, except in its more northern portions, and it would now seem also in America, man had been introduced at a time closely following the emergence of the land from the Glacial sea. At this time the land area of both continents was larger than it is at present, and the character of the fauna shows that much of the surface was occupied with great steppes or prairies, over which migration would be easy; while there were probably connections by land or chains of islands between the continents of the northern hemisphere. The land animals of the continents were more numerous and of greater stature than at present. Several species of elephants (Fig. 186) and a rhinoceros roamed over the plains. The formidableElasmotherium(Fig. 187),86an animal allied to the rhinoceros, but more fleet and active, and of immense size, inhabited Asia and Europe. Hippopotami, wild horses, the gigantic Irish stag, several species of wild cattle, and bisons of greater size than their successors, haunted the streams and steppes. The cave bear, the cave lion, the spotted hyæna, and possibly theMachairodus, were among the beasts of prey even in the temperate latitudes. The climate must have been a continental one, ranging through considerable extremes; but the conditions favoured migration of animals on the great scale, so as to avoid these extremes, and hence species of types now comparatively restricted enjoyed a wide distribution.