THE REIGN OF MAMMALS.
The incoming 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 Placentals are 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 of _Microlestes antiquus_ has
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 existing _Myrmecobius fasciatus_ of 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
fresh-water 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.[79]
He considers them divisible into two groups, one allied to the 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
in Figs. 166 and 168 belong to the former group, that in Fig. 169 to 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
PalA|ozoic, that is, on the doctrine of gradual evolution.
[Illustration: FIG. 166.aEuro"Jaw of _Dromatherium sylvestre_ (Emmons). From
the Trias of North Carolina.]
[Illustration: FIG. 167.aEuro"_Myrmecobius fasciatus._ A modern Australian
marsupial, allied to Mesozoic species.]
So soon as the palA|ontologist 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.
[Illustration: FIG. 168.aEuro"Jaw, and enlarged molar of _Phascolotherium
Bucklandi_. Stonesfield slate. England.aEuro"After Phillips.]
[Illustration: FIG. 169.aEuro"_Plagiaulax Becklesii._ Jaw, and pre-molar
enlarged, showing flat surface, with ridges.aEuro"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 southern and
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.
[Illustration: FIG. 170.aEuro"Restoration of _PalA|otherium magnum_.
Eocene.aEuro"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 of remains 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 Cuvier
_PalA|otherium_ (Fig. 170) and _Anoplotherium_, 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 HyA|na 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 PalA|othere 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
aEurooelickaEuroŁ 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-like creatures called
_Zeuglodon_ (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 aEurooecaA+-onsaEuroŁ 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
deposits holding other and more modern Mammalia. The vast area of these
formations and the complete sequence which they show are scarcely
equalled elsewhere.
[Illustration: FIG. 171.aEuro"_Coryphodon Hamatus._ A Lower Eocene
Perissodactyl skull, greatly reduced, showing small size of brain,
_a_.aEuro"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 assemblagesaEuro"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).
[Illustration: FIG. 172.aEuro"Fore-foot of _Coryphodon_. Greatly
reduced.aEuro"After Marsh.]
The most characteristic animals of the lowest Eocene belong to the genus
_Coryphodon_ (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. _Coryphodon_ is
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 them
for 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.
[Illustration: FIG. 173.aEuro"Skull of an Upper Eocene Perissodactyl
(_Dinoceras mirabilis_), showing three pairs of horn-bases. Greatly
reduced.aEuro"After Marsh.]
In the Middle Eocene, the place of _Coryphodon_ was taken by _Dinoceras_
and allied forms. Some of the species nearly equalled the elephant in
size, but had shorter and stouter limbs, each supported on five great
toesaEuro"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, and living where food was
plentiful, might well dispense with any great degree of intelligence,
and their development of brain is consequently little better than that
of _Coryphodon_. 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 which _Brontotherium_ is 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.
[Illustration: FIG. 174.aEuro"Fore-foot of _Dinoceras_. Greatly
reduced.aEuro"After Marsh.]
[Illustration: FIG. 175.aEuro"Skull of _Brontotherium ingens_ (Marsh).
Greatly reduced. A Miocene Perissodactyl.]
[Illustration: FIG. 176.aEuro"Series of Equine Feet.aEuro"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 aEurooedemonstrationaEuroŁ 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, replaces
_Eohippus_ in the Middle Eocene. _Mesohippus_ of 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 Miocene _Miohippus_ continues the line, while _Protohippus_ of the
Lower Pliocene is still more equine and as large as an ass, and
corresponds with the European _Hipparion_ in 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 was unknown 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 from _Eohippus_,
but from _PalA|otherium_, 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 their coinage 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 PalA|ozoic. 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-like
animals 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, like _Oreodon_, 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 gigantic _Sivatherium_ of India,[81] allied to the modern
prong-horned antelope of North America, were prominent in the Old World
in the Miocene.
[Illustration: FIG. 177.aEuro"_Oreodon major._ A generalised Miocene
ruminant, with affinities to the Deer, Camel, and Hog. Greatly
reduced.aEuro"After Leidy.]
[Illustration: FIG. 178.aEuro"Lower Jaw of _Megatherium_. Greatly reduced.
Post-Pliocene of South America.aEuro"After Owen.]
[Illustration: FIG. 179.aEuro"Ungual Phalanx and Claw-core of
_Megatherium_. Greatly reduced.]
A very noteworthy and specially American group of mammals is that of the
_Edentates_, the Sloths and Ant-eaters, a group which _A priori_ we
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 the _Megatherium_ and _Mylodon_ of
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 of Australia 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.
[Illustration: FIG. 180.aEuro"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 the Sea-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. aEurooeWe have questioned,aEuroŁ says Gaudry,
when speaking of the Tertiary Cetaceans, aEurooethese strange and gigantic
sovereigns of the Tertiary oceans as to their progenitorsaEuro"they leave us
without reply.aEuroŁ 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_, and _Dinotherium_). 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
two _Dinotheria_; 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
altogether destitute of elephants, possessed several species both of
_Elephas_ and _Mastodon_, 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: aEurooeHowever, 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.aEuroŁ 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.
[Illustration: FIG. 181.aEuro"_Mastodon ohioticus._ An American Elephant.
Post-Glacial.]
[Illustration: FIG. 182.aEuro"Head of _Dinotherium giganteum_. Greatly
reduced. Miocene of Europe.]
[Illustration: FIG. 183.aEuro"Wing of _Vespertilio 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 and Rats.
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
forms[82] present 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 aEurooenatural to supposeaEuroŁ 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, HyA|nas,
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 formsaEuro"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 aEurooeCymetar-toothed
TigeraEuroŁ (_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.
[Illustration: FIG. 184.aEuro"Skull of a Cymetar-toothed Tiger (_Machairodus
cultridens_). Pliocene, France. Reduced.]
[Illustration: FIG. 185.aEuro"Lower Jaw of _Dryopithecus 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, the _Primates_, 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
modern _Quadrumana_ (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 ventures to 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 of _Dryopithecus_.
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 aEurooecritical periodsaEuroŁ when sudden
changes occurred. The history becomes inexplicable, unless with Mivart,
Le Conte, and Saporta, we admit aEurooeperiods of rapid evolutionaEuroŁ 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 aEurooeCreation by Law.aEuroŁ
[Illustration: CONTEMPORARIES OF POST-GLACIAL MAN. From a painting by
Waterhouse Hawkins.]