Europe Before the Arrival of Man

IN looking over any modern historical narrative — such, for example, as Knight’s History of England — one cannot fail to be struck by the disproportion between the amounts of space devoted respectively to ancient and to modern events. Of the eight bulky volumes of Knight, the first covers a period of 1432 years, from Cæsar’s invasion of Britain to the death of Edward III.; the second, bringing us down to the death of Henry VIII., covers 170 years; the third takes us 95 years further, to the beginning of the Great Rebellion; while five volumes are required to do justice to the two centuries intervening between the overthrow of Strafford and the repeal of the corn-laws. This is due partly to the greater complexity of modern life, and partly to the increasing abundance of our sources of information. It is true, we have to go back a long way before we encounter an absolute scarcity of information ; there was a great deal more literature in the Middle Ages than is commonly supposed, and it is possible to describe many long past events with great minuteness and accuracy. Mr. Freeman devotes the greater part of a volume of 768 pages to the political and military history of England during the single year 1066. But the history during the spring of 1815, if treated with equal thoroughness, would fill a good many volumes as big as this ; and this is owing largely to our increased wealth of materials. When we go back far enough and encounter a positive dearth of material, we can devote but a few pages to the history of a century, as in the case of the earliest Teutonic invasions of Britain ; or, as in the case of the long ages before Cæsar’s invasion, we can barely say that such and such races of men inhabited the island, and we can give little or no account of what they did. This is one reason why we find it so hard to form and preserve an accurate mental picture of the duration of past time. It requires a deliberate effort of the mind to realize, for example, that the interval between the proclamation of Constantine the Great by the Roman legions at York and the invasion of William the Conqueror was exactly equal to the interval between the latter event and the accession of George IV., or the adoption of the Missouri Compromise. We may know that it is so, but in order to make it seem so most people will have to stop and think.

The case is somewhat similar when we try to realize the relative duration of the successive geological epochs in the history of the earth’s crust. We are naturally inclined to overrate the relative duration of the later epochs. Familiar as we are with the established classification of periods as Primary, Secondary, and Tertiary, we fall naturally into a habit of regarding these three great groups of epochs as substantially equal in value, so that the beginning of the Tertiary period is apt to seem one third of the way back toward the first beginnings of fossil-bearing strata. Probably in our every-day thinking the Tertiary period occupies more than a third of the space that is occupied by the whole recorded life history of the earth, — mainly for the reason that it is so much more completely filled for us with familiar and well-ascertained facts. This may be partly because organic life has really been more complex and multiform since the beginning of the Tertiary period than it was in earlier ages ; but it is also, no doubt, because our sources of information are far more abundant. On the whole, the geologic record of the Tertiary period is much more completely preserved than that of the two earlier periods ; we see more clearly into the details of life at that time, and consequently have a more vivid picture of it before us ; and this more vivid picture, as is natural, usurps an undue place in our minds.

Copyright, 1882, by HOUGHTON, MIFFLIN & Co.

The force of these remarks will be obvious when it is stated that, in point of fact, the beginning of the Tertiary period carries us back barely one twentieth part of the way toward the first beginnings of fossil-bearing strata. In the table that follows, I have tried to give something like a just idea of the relative lengths of geological epochs, in accordance with the views now generally adopted by geologists. Let us first suppose the entire lapse of time since the oldest Laurentian strata began to be deposited, down to the present day, to be divided into ten equal periods, or æons, such as I have marked off on the table with dotted lines. Then the Laurentian epoch fills three of these great icons, to begin with. Here we find (with the exception of the Canadian eozoön, the organic nature of which has been disputed) only indirect traces of life, such as limestone, which probably came from shells. But, remembering how soft and perishable are all the lowest organisms, and remembering how considerably these oldest rocks have been affected by volcanic heat, we need not be surprised at finding the records of life in them very scanty and obscure. Next, the Cambrian epoch extends into the sixth æon, and then comes the Silurian, which takes us half-way through the seventh. Mollusks and crustaceans swarmed in the seas of the Cambrian epoch, but there are as yet no traces of fish before the upper Silurian. That is to say, three fifths of the whole duration of geological time had elapsed before the lowest vertebrate forms had begun to leave plentiful traces of themselves in the rocks. The Devonian epoch, in which we find the first record of insects, carries us half-way through the eighth æon ; and we are brought well on into the ninth by the Carboniferous age, in which appear the earliest air-breathing vertebrates in the shape of frog-like amphibians. The vegetation of this period consisted chiefly of ferns, club-mosses, and horse-tails, with araucarian pines. Nearly nine tenths of the past life history of our globe accomplished, and as yet no birds or mammals, perhaps no true reptiles, nor any tree save the araucaria or the arborescent fern! With the Permian epoch we reach the end of the Primary period and nearly complete our ninth æon, leaving for the whole of the Secondary and Tertiary periods only a little more than one æon to be divided between them. The oldest mammals and reptiles yet found belong to the Trias, or earliest Secondary epoch; yet so many small mammalia, inferior in type to the marsupials, have been found by Professor Marsh far down in the Trias as to warrant the belief that mammals had appeared on the scene toward the close of the Permian age ; and no doubt the same will prove true of reptiles. Some of the footsteps on the Triassic rocks of the Connecticut Valley are probably footsteps of great struthious birds ; but the oldest bird actually known belongs to the upper Jurassic strata. Throughout the Secondary period the real lords of the creation were the giant reptiles, stalking over the earth, splashing through the sea, and flying on swift bat-like wing overhead. Of these innumerable “ dragons of the prime,” the iguanodon, from fifty to seventy feet in length, used to be supposed the largest ; but Professor Marsh has lately discovered the atlantosaurus of Colorado, over sixty feet in length and thirty feet in height, — the largest land animal as yet known. The mammals contemporary with these monsters seem to have been mostly small insect-eating marsupials ; and the forests through which they roamed consisted mainly of palms, tree-ferns, and pines. In the Cretaceous epoch such deciduous trees as the oak and walnut had appeared on the scene, and the great reptiles had become less numerous. But it is not until we enter the Tertiary period, half-way through our tenth æou of geological time, that the face of the earth, with deciduous trees and flowering herbs, and mammals dominant in the animal world, could have begun to assume anything even distantly resembling the aspect under which we know it. Yet if we could be suddenly taken back, and permitted to inspect a landscape of the earliest Tertiary epoch, we should probably be far more forcibly struck with the differences than with the points of resemblance.

In this succinct view I have supposed the whole of the life history of our planet to be arbitrarily divided into ten equal periods. What, it may be asked, is supposed to have been the actual duration of one of these æons ? I am well aware that to such a question no definite answer can be given. The geologist deals only with relative, not with absolute, quantities of time : he can only say that the time has been long enough for a certain enormous amount of work to be performed, but he has nothing with which to measure its duration in years. Nevertheless, while fully admitting all this, one may perhaps venture to give a provisional answer for a provisional purpose. For the present it will be enough to recall Sir William Thomson’s ingenious speculations as to the limits of the antiquity of life upon the earth. Reasoning from the sources of the sun’s heat, and from the length of time which it would take a body like the earth to cool so as to produce the present increment of temperature as we go beneath the surface, Sir William Thomson concludes that the crust of the earth cannot possibly have existed in the solid state for more than 400,000,000 years, and in all probability has not been solidified and in fit condition for the support of vegetable and animal life for more than 100,000,000 or 200,000,000 years. This conclusion is largely speculative, including several data of which our knowledge is far from complete, and it is of course extremely indefinite. It makes a good deal of difference whether life has existed on the earth for one hundred million years or for two hundred millions, since one period is just twice as long as the other. Still, in spite of this indefiniteness, there is a growing disposition among geologists to accept Sir William Thomson’s estimate, as showing at least the order of magnitudes with which the geological chronologer must deal. That is to say, while it may not be clear whether life has existed for one or for two hundred millions of years, it is not at all probable that it has existed for a thousand millions or for any greater period. Even this amount of limitation is of some value as giving definite shape to our ideas, and as reminding us that geologists who have habitually reasoned as if there were an infinite fund of past time at their disposal have probably been in error. Provided we do not forget that Sir William Thomson’s conclusion contains more or less that is hypothetical, it is well enough to adopt it provisionally ; and I shall do so here. Of the ten æons, then, into which I have supposed geological time to be divided, we will suppose that each is about ten mill - ion years in duration; bearing in mind that, while it is highly improbable that the lapse of time has been very much less than this, it may not improbably have been considerably greater. According to this, the minimum antiquity for the beginning of the Eocene period would be about five million years.

If these periods seem short in comparison with the enormous quantity of work that has been done, both in the tearing down and rebuilding of the earth’s crust and in the modification of the forms of animals and vegetables, it is no doubt largely due — as both Mr. Darwin and Mr. Croll have reminded us — to the fact that it is almost impossible for us to frame an adequate conception of what is meant by a million years. We are wont to use these great arithmetical figures glibly, and without comprehending their import. Mr. Croll has done something to help us in this matter. “ Here is one way,” he says, “of conveying to the mind some idea of what a million of years really is. Take a narrow strip of paper, an inch broad or more, and 83 feet 4 inches in length, and stretch it along the wall of a large hall, or round the walls of an apartment somewhat over 20 feet square. Recall to memory the days of your boyhood, so as to get some adequate conception of what a period of a hundred years is. Then mark off from one of the ends of the strip 1/10 of an inch. The 1/10 of the inch will then represent one hundred years, and the entire length of the strip a million of years. It is well worth making the experiment, just in order to feel the striking impression that it produces on the mind.” Mr. Croll further reminds us that if we could see side by side a million of years as represented in figures and a million of years as represented in geological work, our respect for a unit with six ciphers after it would be notably increased. “ Could we stand upon the edge of a gorge a mile and a half in depth, that had been cut out of the solid rock by a tiny stream, scarcely visible at the bottom of this fearful abyss, and were we informed that this little streamlet was able to wear off annually only 1/10 of an inch from its rocky bed, what would our conceptions be of the prodigious length of time that this stream must have taken to excavate the gorge? We should certainly feel startled when, on making the necessary calculations, we found that the stream had performed this enormous amount of work in something less than a million of years.”¹

Now all the fossil-bearing rocks on the globe have been formed from the sediment brought down by rivers to the sea, and this sediment has been worn off from the hills and valleys and plains of ancient continents. In recent years it has been attempted to calculate the amounts of sediment worn off by various great rivers from the surface of the regions drained by them ; and the results are very interesting and instructive. The Mississippi, for example, draining a country with scanty rainfall, and having its sources in the Alleghanies and the Rocky Mountains, where there are no glaciers, performs its work of denudation slowly. The Mississippi wears off from the whole immense area drained by it about one foot in 6000 years. While the Po, on the other hand, having its sources in the glaciers of the Alps, works with great rapidity, and lowers the area drained by it at the rate of one foot in 729 years. The mean rate of denudation over the globe seems to be not far from one foot in 3000 years. Now at this rate, and from the action of rivers alone, it would take only two million years to wear the whole existing continent of Europe, with all its huge mountain masses, down to the sea-level, while North America, in similar wise, would be washed away in less than three millions.

But while the raindrops, rushing in rivers to the sea, are thus with tireless industry working to obliterate existing continents, their efforts are counteracted, here and there, and with more or less success, by slow upward thrusts or pulsations from the earth’s interior, which gradually raise the floors of continents. The general result of the struggle has been that, ever since the earliest geological periods, the surfaces of the great continents now existing have been subject to irregular oscillations ; now partially or almost entirely disappearing beneath the sea, now recovering ground as archipelagoes, or rising high and dry to great elevations, as in the case of Africa. The oscillations have not ordinarily exceeded from 6000 to 10,000 feet in vertical extent. There is no reason for supposing that the general relative positions of the great continents and great oceans have altered at all since the beginning of the Laurentian period. Since life began on the earth there is no reason for supposing that the bottoms of the stupendous abysses which hold the waters of the Atlantic, the Pacific, and the Indian oceans have ever been raised up so as to become dry land. Once geologists thought otherwise, and land was turned into sea and sea into land, by facile theorizers, as often as it was supposed to be necessary to account for the distribution of certain lizards or squirrels, or for changes in climate, such as have left marks behind in many parts of the earth. The greatest physical geologists now living, however, — such as Mr. Croll and the brothers Geikie, — are convinced that there has been no considerable change in the positions of the great oceans from the very beginning; and this view is ably sustained by Mr. Wallace — who is probably the highest living authority on the distribution of plants and animals — in his profound and fascinating treatise on Island Life, lately published.

Though the general relative positions of deep sea and continent have not altered, however, there have been frequent and striking changes in the superficial contour of land and sea. Every continent has been several times wholly or in part submerged, while shallow portions of what is now sea-bottom have been thrust up high and dry ; and in this way the climate and the mutual relations of floras and faunas have been variously and vastly affected. Thus, during the Silurian period, the dry land of Europe lay mostly in the north, over Finland, Scandinavia, and the German Ocean, covering also the British Islands, and stretching more than two hundred miles out into the Atlantic. The central and southern parts of Europe were then covered by a shallow sea, with islands on the sites of Bavaria and Bohemia. The duration of this state of things may be dimly imagined when we consider the enormous quantity of sediment worn off from this northern continent, and now constituting the Silurian rocks of Europe. If all this sediment were to be arranged in a longitudinal pile, according to Prof. Archibald Geikie, it would make a mountain ridge 1800 miles long, 33 miles wide, and somewhat higher than Mont Blanc. At the close of this long period ridges of land had begun to appear on the sites of Spain and Switzerland. By the Carboniferous period the central parts of Europe had risen so as to form an archipelago of low islands, surrounded by lagoons and salt marshes, covered with dense jungles of ferns and club-mosses. On the islets grew thick forests of pine, and as repeated epochs of submergence brought all this teeming vegetation under water, it became covered with detritus of mud and sand from the northern highlands, and in this way was preserved to form the coal-beds of Europe. By the Triassic period we find the general elevation of Europe increased, so that instead of an archipelago lying amid lagoons we have a continent thickly dotted over with salt lakes ; but in the next or Jurassic period the whole centre of the continent was laid under water again. The extent and shape of the European sea of the Cretaceous period are indicated by the extent of the chalk which was formed on its floor, and of which Professor Huxley has given such a graphic account in his lecture On a Piece of Chalk.² The greater part of Europe might then have been called a “ Mediterranean Sea,” extending from England far into central Asia. The western highlands of Scotland remained above water, but Bohemia, Switzerland, Spain, and the Caucasus seem to have been submerged, or reduced to islands. Still further submergence occurred during the Eocene period, and this in turn was followed by a long series of elevations, resulting in something like the configuration of Europe as we know it. Late in the Eocene period the Pyrenees, Apennines, Alps, Carpathians, and Caucasus had risen to their present or even to higher altitudes. While an inland sea flowed over the Netherlands and Normandy, the rest of Gaul was dry land, and at its northwestern extremity was joined to Britain. The British Islands, in turn, were joined to each other and to Scandinavia and Spitzbergen, as also to Iceland and Greenland. If Columbus had lived in those days, he could thus have walked on solid land all the way from Spain to the New World.

Two immediate consequences of this great upraising of land made the Eocene period an era of singular interest in the history of the European continent. The first was the invasion of Europe by placental mammals, which speedily supplanted the lower forms that had preceded them. The second was the immigration of deciduous trees from the polar regions. Before the Cretaceous period no such trees had been known in any part of the earth, and it is the opinion of Count Saporta that the habit of dropping the leaves was evolved in adaptation to the extreme differences between summer and winter temperatures which characterized the polar regions. However that may be, it is certain that during the Eocene and Miocene periods deciduous trees and shrubs advanced from Greenland and Spitzbergen into Europe, and rapidly covered the face of the country, evolving gradually a great diversity of forms. By the middle Eocene, along with cypresses, pines and yews, fan-palms and pandanus and cactus of giant size, the oak and the elm, the maple, willow, beech, and chestnut, as well as the gum and bread-fruit trees, flourished in Britain. The climate of western and central Europe was tropical, as is shown both by the abundance of palms and by the presence of crocodiles and alligators in large numbers, while the mollusks were such as are now found only in tropical waters.

But the most interesting feature of Eocene Europe was the peculiar character of its mammalian fauna. At first we find marsupials, and carnivora with marsupial affinities, showing that the order of carnivora was then only beginning to be evolved. Afterward came such creatures as the anchitherium, the ancestor of the horse, in general aspect somewhere between a Shetland pony and a pig, and with three separate hoofs on each foot. There were also the anoplotheria, or common ancestral forms of antelopes and deer, as yet without horns or antlers. The highest order of mammals, the Primates, — including man, ape, and lemur, — was then represented by the adapts of the Paris basin, the necrolemur of southern France, and the cœnopithecus of Switzerland. Now none of these Eocene primates answered to any living genus of lemur, though the lemurs are the least specialized of primates now existing ; but all these Eocene primates showed signs of relationship, in one way or another, to the hoofed quadrupeds living at that time, which, as we must not forget, were only on the way toward becoming hoofed quadrupeds such as we know. Cousinship, however remote, between such extremely specialized creatures as the horse and his rider seems odd to think of; yet the lemuroids of the Eocene furnish the link. And it is interesting to remember that, owing to the closeness of relationship, the lemuroid adapis was actually mistaken by Cuvier for an anoplotherium, or primitive antelope-deer. Of all anatomical contrasts, what can be greater than the contrast between a solid hoof and the flexible five-lingered hand of a Rubinstein ? Yet the Eocene greatuncle of our modern pianists could be mistaken for his contemporary great-uncle or great grandfather of our hoofed quadrupeds ! And this instance is but one fair sample out of many of the changes which the last five or six or eight million years have wrought. Speaking generally, it may be said that in the Eocene age there were carnivora, and there were ungulata, and there were primates ; but these orders were not so clearly distinguished from each other as they are to-day, and they were not so clearly distinguished from other orders, such as the rodents and insectivora, while in many cases they had not ceased to bear the marks of their marsupial ancestry. Or, to put the case in another way, in the Eocene period you have an instance of hoofed quadruped, but you don’t find an instance of any such special form as horse or deer or camel ; you find carnivora, but you don’t find a clear instance of felis or canis or ursus, — not even of hyæna, an earlier type than either of the others ; and you find primates, but among these there is nothing yet so clearly distinguished as a monkey. In short, the present species or genera of mammals had not come into existence in the Eocene period, but only the present orders and some of the present families; and even the orders were not clearly distinct from one another, as they are at present; but they were closely interlocked, very much as species are at present. In other words, the whole class of mammals in the Eocene age was far less highly specialized than it is at the present time.

From these premises Mr. Boyd Dawkins argues, with convincing force, that man could not possibly have existed in Europe, and probably nowhere on the earth, during the Eocene period. At a time when the order of ungulates had not clearly developed the distinction between camels and pigs and horses, and when the order of primates was only just beginning to be distinguished from other orders, so that Cuvier could even mistake a primate for an ungulate, — at such a time was it at all likely that man, the most highly specialized of all primates, or of all animals, could have existed ? Obviously, he could not have existed at such a time. The supposition is absurd on the face of it. As Mr. Boyd Dawkins says, “ to seek for highly specialized man in a fauna where no living genus of placental mammal was present would be an idle and hopeless quest.”

Coming to the Miocene age, we find traces of extensive submergences of parts of the European continent, followed by reëlevations. Considerable portions of Gaul and Italy were laid under water, and at one time the whole basin of the Danube was covered by a sea which connected with the Mediterranean near Berne, thus reducing Switzerland and Italy to an archipelago. The Alps, however, seem to have maintained a relative height as great as that of today, in comparison with the lands about them. The elevated position which Britain had occupied in the Eocene age seems to have been kept up during the Miocene. The whole of Britain and Ireland, with the English and Irish channels, the German Ocean, and the Atlantic ridge between Scotland and Greenland, stood at an average of nearly 3000 feet higher than they do to-day, so that the whole region remained dry land, and Gaul was still joined in this way to Scandinavia and North America. Above this high level the Scottish Highlands and the Welsh peaks rose to a height of some 7000 feet, having since been worn down to half that height by rain and ice. Many of these great mountains, thus standing nearly as high above sea-level as the Alps, were active volcanoes ; and this chain of volcanoes, of which Hecla is now the most famous remnant, extended across the Atlantic ridge, all the way from Wales to Greenland, which was then covered with a luxuriant vegetation of oaks and chestnuts, vines and magnolias. In the earlier part of the Miocene age the general climate of Europe resembled that of Algiers or Louisiana at the present day, but at the close of the period it had become somewhat cooler, though still subtropical. Gigantic conifers, like the famous trees of California, 400 feet in height and 25 or more in thickness, flourished all over Europe, from Italy to Norway. Along with these there were cycads, fan-palms, palmettos, figs, laurels and myrtles, poplars, oaks, lindens and maples, acacias and elms, camphors and cinnamons and sandalwood ; while ivies and biguonias grew in great luxuriance. Cranes, flamingos, and pelicans were common, as also geese, herons, pheasants, paroquets, and eagles. But the mammals, in this as in the preceding epoch, present the most instructive subject of study. Opossums were still present, but had vanished before the middle of the period; and a few existing genera of placental mammals had come upon the scene. There were tapirs and small rhinoceroses, as well as squirrels, moles, and hedgehogs, and carnivores similar to the weasels and civets. Collateral ancestors of the deer and antelope roamed about in large herds, and by the middle of the period had begun to acquire small horns and antlers. In mid-Miocene times the anchitheres disappeared, and were succeeded by the hipparion, much nearer in structure to the horse. The mastodon came in about the same time, and with him another elephant-like creature, the deinotherium, who lived in the water like a hippopotamus. Carnivores of the cat family reached their highest point of development as regards size and power in the middle and upper Miocene: the machairodus, or sabre-toothed lion, was much larger and more formidable than any lion or tiger now existing. The same period witnessed the arrival in Europe of true apes and baboons, and even of two species of anthropoid ape, allied to the gibbons, one of which, the dryopitheeus, was as large as a man, and has been regarded as in some respects superior to any modern anthropoid ape.

Mr. Boyd Dawkins — to whose admirable treatise on Early Man in Britain the present article is under great obligations— argues forcibly against the probability that man occupied Europe during any part of the Miocene period. All the species of Miocene land mammals, and several of the genera, are now extinct; and Mr. Dawkins urges that if man existed at that remote period it is incredible that he alone should have subsisted unchanged amid the destruction or metamorphosis of all other species. But it seems to me that Mr. Dawkins partly answers this argument himself when he observes that, “ were any man-like animal living in the Miocene age, he might reasonably be expected to be not man, but intermediate between man and something else, and to bear the same relation to ourselves as the Miocene apes, such as the mesopitheous, bear to those now living, such as the semnopithecus.” Why may not such a semi-human man have existed in the Miocene age, the race having undergone since then changes parallel to those which have affected the apes, or to those which have affected generally such Miocene genera as have survived down to our times ? No remains of any such creature have been found, but it is indisputable that artificially chipped flints and the artificially cut rib of an extinct species of manatee have been discovered in mid-Miocene strata in France. Mr. Dawkins is inclined to adopt M. Gaudry’s suggestion that the flints may have been chipped and the rib cut by the great man-like ape, the dryopitheeus ; for although it is not known that any existing apes are in the habit of chipping flints or cutting bones, yet it is not impossible that the dryopithecus may have somewhat surpassed the present apes in intelligence. On the other hand, M. de Mortillet regards these relics as conclusive proof of the existence of man in mid-Miocene Gaul. The question can hardly be decided at present; but it does not seem to me that Mr. Dawkins’s line of argument, which is so conclusive when applied to the Eocene age, is equally conclusive when applied to the Miocene. At an epoch when there were no true apes as yet to be found, when even the lemurs bore marks of kinship with the ancestors of ruminants and pachyderms, and when the carnivorous type was but half developed, it would clearly be idle to expect to find traces of man. But at an epoch when many modern genera had come into existence in all the principal orders, and when in particular there existed an ape as high, or higher, in organization than the modern chimpanzee or gorilla, I can see no such overwhelming improbability of the existence of man himself. No doubt, however, if the remains of Miocene man are ever to be found, they will disclose a type of humanity quite different from, and very likely much lower than, any that we now know. It is not at all improbable that such remains will by and by be discovered in some part of the earth, if not in Europe. By the time the strata of Africa have been explored with anything like the minuteness with which those of France and England have been examined, we shall be very likely to meet with clear indications of the former presence of halfhuman man, and it will not be strange if such indications lead us far back into the Miocene epoch.

In the Pliocene period the geographical structure of Europe began to be much more like what it is to-day. Hitherto, during the greater part of the Tertiary epoch, large portions of Russia and Siberia had been submerged, so that the continent of Asia did not extend nearly so far north as at present. A belt of sea appears to have stretched from the eastern Baltic across to the Persian Gulf, including the areas of the Black and Caspian Seas ; and another wide channel seems to have run west of the Ural Mountains, connecting the Caspian area with the Arctic Ocean, so that the warm waters of the Indian Ocean found a free passage to the very shores of Finland and Scandinavia. According to Prof. Archibald Geikie, these shallow seas disappeared early in Pliocene times, leaving the Aral, Caspian, and Black seas in something like their present isolation. While eastern Europe thus began to acquire its present contour, equally remarkable changes occurred at the same time in the west. The Atlantic ridge between Britain and Greenland was submerged, thus separating Europe from America, and the connections of Norway with Spitsbergen on the one hand and Scotland on the other were also severed by the encroachments of the North Sea. But the British Islands were still joined to each other and to the Gaulish mainland; the whole of Britain jutting out from the continent as a great triangular peninsula, with the Shetlands in its apex. The volcanoes of northwest Britain gradually lost their fires during the Pliocene age. Icebergs appeared in the North Sea, and the general climate of Europe, though still milder than to-day, was much colder than it had been during the Eocene and Miocene epochs. The vegetation began to lose its subtropical aspect. Bamboos, evergreen oaks, and magnolias still mingled with maples, willows, and poplars in the latitude of Lyons, but the cinnamon-trees and palms became restricted to Italy. Among mammalia, the first species that has continued to live down to the present time, namely, the African hippopotamus, appears in the upper Pliocene strata of Auvergne. The earliest true elephant, though of a species now extinct, appears at about the same time ; and contemporary with him were two species of mastodon, of enormous size, a rhinoceros, a tapir, two or more bears, the giant sabre-toothed lion, an ancestor of the panthers and lynxes, and two kinds of hyæna. There were many species of deer, with antlers, but for the most part unlike modern deer. The ox appears first in the upper Pliocene, but without horns. There were also wolves, and swine, and two kinds of ape. The hipparion still lived, but was becoming scarce, and along with him existed a horse, less specialized in teeth and feet than the modern horse.

Now from the fact that of these Pliocene mammals every one has long since become extinct except the hippopotamus, Mr. Dawkins again proceeds to argue that it is not likely that man inhabited Europe at that period. The alleged instances, three in number, of the occurrence of human remains in Pliocene strata of France and Italy he pronounces unsatisfactory ; and he does not even mention the brilliant investigations of the Geological Survey of Portugal, which have brought to light flint implements, of undoubted human workmanship, in great abundance in the Pliocene strata of that country, buried under 1200 feet of superincumbent rock. These discoveries, set forth by M. Ribeiro in 1871, are cited by Professor Whitney as furnishing conclusive evidence of the presence of man in Portugal during the Pliocene period. In his admirable memoir on The Auriferous Gravels of the Sierra Nevada, Professor Whitney has collected a great amount of evidence which seems to prove that man existed in California at an equally remote date. Now it is perfectly clear that the human race must have been in existence for a very long time before it could have become so widely dispersed over the earth as to occupy countries so distant from each other as California and Portugal. For the first appearance of man on the earth we must, therefore, go far back in the Pliocene period at any rate; and if we are to find traces of the “missing link,’’ or primordial stock of primates from which man has been derived, we must undoubtedly look for it in the Miocene.

Of the three stages of the Tertiary period here passed in review, we have seen that the Eocene was characterized by the entire absence of genera and species of mammals identical with those now living; in the Miocene there were genera, but no species, identical with those now living ; in the Pliocene there was at least one species in Europe that has survived to the present day. When we come to the Pleistocene age, we find a majority of the species identical with such as still exist. But in regard to this Pleistocene fauna there are some curious circumstances, which show that the climate of Europe had begun to be subject to vicissitudes such as it had not known in the earlier Tertiary epochs. Among the Pleistocene mammals of Europe we find such as are characteristic of warm climates, — as the lion, leopard, hyæna, elephant, rhinoceros, and hippopotamus ; and along with these we find such as characterize sub-arctic climates, — as the musk-sheep, reindeer, glutton, arctic fox, ibex, and chamois ; and yet again we find such denizens of the temperate zone as the bison, horse, deer, wild boar, brown and grizzly bears, wolf, and rabbit, to which may be added the mammoth and woolly rhinoceros. Now, as Mr. James Geikie has ably shown, this singular juxtaposition of northern, southern, and temperate forms points directly to great vicissitudes of climate. It is quite clear that when the reindeer came down as far as southern France, the climate must have been very different from what it was when the hippopotamus bathed in the Thames. We know Otherwise, from purely geologic evidence, that the Pleistocene climate was very extraordinary. Hitherto, during the Tertiary period, the temperature of Europe seems to have been steadily but slowly decreasing, from the Eocene epoch, when it was subtropical, to the end of the Pliocene, when it was temperate, though warmer than at present. But in the Pleistocene epoch there were at least four or five, and probably several more, extreme changes from a warm to a cold climate, and back again. This period, or the greater part of it, has been known as the “ Glacial Epoch ” or the “ Great Ice Age ; ” but recent researches have shown that over Britain and central Europe there were several glacial epochs, alternating with warm interglacial periods of long duration. When the cold was at its maximum, the whole area of Finland, Scandinavia, and Scotland, with the North and Baltic seas, was buried under a stupendous sheet of ice, varying from 1 000 to 2000 feet in thickness ; and this ice-sheet sent off glaciers as far east as Moscow and as far south as Dresden, while the Alps, the Pyrenees, and the mountains of Auvergne became centres of glaciation, inferior, indeed, to the great northern ice-sheet, but still immense in extent. While the climate of Pleistocene Europe thus came to be similar to that of modem Greenland, parallel phenomena were occurring all over the northern hemisphere. The continent of North America was deeply swathed in ice as far south as the latitude of Philadelphia, while glaciers descended into North Carolina. The valleys of the Rocky Mountains supported enormous glaciers, and the same was the case in Asia with the Himalayas. It was during these recurrent periods of arctic cold that the reindeer and musk-sheep found their way to the south of France, while over land-bridges at Gibraltar and Malta the leopard and elephant retreated to Africa. In the intervals between these glacial periods, when the climate became milder than it is at the present day, the arctic mammals traveled northward again, while the lion returned to chase the bison and elk in the forests of Yorkshire.

As the result of these prolonged and repeated climatic vicissitudes, and of the complicated migrations entailed by them, many of the Pliocene mammals still living in Europe at that time have become extinct,—such as the gigantic beaver, the cave-bear, the sabre-toothed lion, five species of deer, three species of elephant, and two of rhinoceros. One race of men — known as the “ men of the river drift ” — had taken up their abode in Europe when these great changes were beginning, and struggled with the extremes of climate like their enemies, the bears and hyænas. The discovery of flint knives has abundantly proved that man was living near the site of London before the big-nosed rhinoceros had become extinct, and before the arrival of the musk-sheep and the marmot in the valley of the Thames heralded the slow approach of the northern ice-sheet. But the fact that human remains of a date even more remote than this have also been found in Portugal and California shows, as I have said already, that man was then no new-comer upon the face of the earth, but must certainly have been in existence for many thousands of years, though as yet we are unable to assign either his primeval habitat or the precise epoch of his first appearance.

This “ man of the river-drift” seems to have become extinct during the Pleistocene period, like the great mammalia above mentioned ; and his place was supplied by a hardier race from the north, — the so-called “ cave-men,” of whom the modern Eskimos have been thought to be a surviving remnant. Of the Arrival of Man in Europe, and of the probable antiquity of this era of recurrent ice-sheets, at the beginning of which he made his appearance in Gaul and Britain, I shall have something to say in another paper.

John Fiske.