THE EUROPEAN CLIMATE IN THE PLEISTOCENE AGE.

    The evidence of the Mammalia as to Climate.—The Southern Group.—The Northern Group.—Probable cause of Association of Northern and Southern Groups.—The Temperate Group.—Species common to Cold and Tropical Climates.—Extinct Species.—Two Periods of Glaciation in Britain.—Three Climatal Changes represented on the Continent.—Europe invaded by Pleistocene Mammals before the Glacial Period.—Mammals lived in Britain during the Second Ice or Glacial Stage.—The Glacial Period does not separate one Life-era from another.—Relation of Pal?olithic Man to Glacial Period.—Age of Contents of Caves in Glaciated Districts.

The Evidence of the Mammalia as to Climate.

In the last three chapters we have seen that the cave-mammalia throw great light on the pleistocene geography of Europe, and that there is reason for the belief that the land surface then extended northwards and westwards, so as to include Ireland; and southwards to join Africa, in the direction of Sicily, Malta, and Gibraltar. We must now pass on to the consideration of the climate on this great continental area, which would allow of so large and varied a fauna existing in our quarter of the world.

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The Southern Group of Animals.

The pleistocene fauna is remarkable for the mixture of species. It consists of forms now banished to South Africa, Northern Asia, and America, or to the severe climate of high mountains, mingled with those which lived in Europe in the historic age, and those which have wholly disappeared from the face of the earth. We will take the living species first.

The southern group consists of the following animals:—

Lion.
Caffir Cat.
Spotted Hy?na.
Striped Hy?na.
Serval.
Hippopotamus.
African Elephant.
Porcupine.

At the present day the lion ranges over the whole of Africa, with the exception of Egypt and the Cape Colony, whence it has been driven out by the hand of man. In Asia, the maneless variety inhabits the valley of the Tigris and Euphrates, and the districts bordering on the Persian Gulf; and in India, according to Mr. Blyth, the province of Kattywar in Guzerat. Although now only found in these hot regions, it is proved, by the concurrent testimony of Herodotus, Aristotle, Xenophon, ?lian, and Pausanias, to have inhabited the mountains of Thrace, and of Asia Minor, and it probably became extinct in Europe before the end of the first century after Christ.259 We may therefore infer that it possessed a sufficient elasticity of constitution to endure394 a considerable degree of cold, although its present distribution implies that it is better fitted to thrive in a tropical than in a cold climate. The Caffir cat (Felis caffer of Desmarest) is an African species, which has been discovered by Mr. Ayshford Sanford and myself, in Somersetshire; it also occurs in the caves of Germany, France, and Gibraltar. The spotted hy?na now lives only in South Africa, while the striped species ranges through Africa and the warmer regions of Asia. It was extremely rare in Europe in the pleistocene age, and has not been identified in any deposit further north than Lunelviel, in southern France. The hippopotamus, now found only in middle and southern Africa, is proved by its fossil remains to have formerly dwelt in the region of the Lower Nile, as well as in Algeria. The serval and African elephant have been found in the Iberian peninsula, and the latter in Sicily.

The evidence afforded by the animals, as to the pleistocene climate of those portions of Europe which they inhabited, differs considerably in point of value, but on the whole indicates that it was temperate, or comparatively hot; for although the elasticity of constitution which we know to have been possessed by the lion, was probably shared by the spotted hy?na, it is very unlikely that so aquatic an animal as the hippopotamus could have ranged from southern Europe, as far north as Yorkshire, under any other than temperate conditions. It could not have endured a winter sufficiently severe to cover the rivers with a thick coating of ice, without having its present habits profoundly modified; and such an alteration of habits would certainly leave its mark, in other modifications in the fossil skeleton than those minute differences which have been observed, when395 it is compared with that of the living Hippopotamus amphibius. The porcupine of southern Europe has been found as far north as the caves of Belgium (Schmerling).
The Northern Group.

The northern group consists of those animals which are now only to be met with in the colder regions of the northern hemisphere, either in low latitudes or at great altitudes.

Marmot.
Pouched Marmot.
Lemming.
Alpine Hare.
Tailless Hare.
Glutton.
Arctic Fox.
Musk-sheep.
Reindeer.
Ibex.
Chamois.

To this list the pal?olithic man of the caves must be added, since he is probably related by blood to the Eskimos, and appeared in Europe simultaneously with the arctic group of animals.

The testimony of these animals as to climate is directly opposed to that of the preceding group, since they now only flourish in the arctic regions, or in mountainous districts in which the climate is severe. The marmot, in the pleistocene age, lived in Belgium, and descended from the Alpine heights as far as the shores of the Mediterranean, where it has been met with in the caverns near Nice. The pouched marmot, Spermophilus citillus of the Don and Volga, penetrated as far to the west as Somersetshire. The Alpine hare, now found only in the colder climates of northern Europe, Asia, and America (with the solitary exception of Ireland), ranged as far down the valley of the Rhine as Schussenreid, in Suabia. The two carnivores now dwelling in the colder396 regions of the north, the glutton or wolverine, and the arctic fox, have been discovered, the one as far south as France, the other as far as Schussenreid, and both probably occupied the whole of Germany, and of northern Russia, in the pleistocene age.

The musk-sheep,260 the most arctic in its habit of all the herbivores, is, at the present time, restricted to the high latitudes of North America, where it thrives in the desolate, treeless, barren grounds, not even being driven from its haunts by the extreme severity of the winter. It has been traced, by its fossil remains, from its present abode, across Behring’s Straits, and through the vast Siberian steppes, into Russia in Europe, Germany, Britain, and as far south and west as the barrier offered by the Pyrenees. Throughout this large area its remains occur in association with the reindeer, and both these animals, as I have remarked above, were hunted by the pal?olithic dwellers in the caves of Aquitaine, just as they are now hunted by the Eskimos on the shores of the Arctic Ocean.

If the present habits of these animals be any index to their mode of life in the pleistocene age, their presence in the area north of the Alps and Pyrenees implies that the climate in France, Germany, and Britain was severe, or analogous to that which they now enjoy on the tops of lofty mountains, or in the northern Asiatic steppes, or the high northern latitudes of America. But this conclusion is diametrically opposed to that which is based on the evidence of the southern group of animals.397261 And the remains of the two groups of animals are so associated together in the caves, and river-deposits of Europe, north of the Pyrenees, that it is impossible to deny the fact that it was the common feeding-ground of both during the same era.262
Probable Cause of Association of Northern and Southern Groups.

Must we then infer that in the pleistocene age the present habits of the musk-sheep, the reindeer, chamois, or ibex, were so changed as to allow them to flourish side by side with the hippopotamus, or vice versa? Was the climate colder than it is now in Europe, or was it hotter? How was this singular association of northern and southern species brought about? The problem may be solved if we refer to the present distribution of animals in northern Asia and North America. As the winter comes on the arctic species gradually retreat southwards, and occupy the summer feeding-grounds of the elk, red-deer, and other creatures which are unable to endure the extreme severity of an arctic winter. In the spring the latter pass northwards, to enjoy the summer herbage of that area, which had been the winter-quarters of the arctic group of animals. Thus there398 is a continued swinging to and fro, over the same region, of the arctic and the temperate animals, and their remains must necessarily become more or less associated in the river-deposits, as well as in caves, where these last happen to occur. In northern Asia, and in America, the only boundary between the northern and temperate zoological provinces is that constituted by the fluctuating annual temperature, and there are no great hilly barriers running east and west, to prevent free migration to the north or south. If reference be made to the map, Fig. 126, it will be seen that these conditions were amply satisfied in the pleistocene age. There were no physical barriers to migration, from the shores of the Mediterranean, as far north as Ireland. If the winter cold were severe, the reindeer and musk-sheep might advance as far south as the Pyrenees, and if the summer heat were intense there would be nothing to forbid the hippopotamus and the African carnivores advancing northwards. It seems to me that this is the only hypothesis which will satisfy all the facts of the case. The traces of glaciers and snow-fields where they are no longer found prove that the winter was severe; while the warmth of the summer seems to be sufficiently demonstrated by the presence of African species. Such extremes of temperature are presented, more or less, by all continents extending from high to low latitudes. They are modified in Europe at the present time by the warm current of the Gulf Stream, by the large area now occupied by the Mediterranean Sea, and by the submergence of the pleistocene lowlands on the Atlantic border.

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The Temperate Group.

The third group of pleistocene mammalia consists of those still living in the temperate zones of Europe, Asia, and America:

Beaver.
Hare.
Rabbit.
Wild Cat.
Martin.
Stoat.
Weasel.
Otter.
Brown Bear.
Grizzly Bear.
Wolf.
Fox.
Horse.
Urus.
Bison.
Antelope saiga.
Wild Boar.
Stag.
Roe.

The range of many of these animals has been profoundly modified since the pleistocene age. The Antelope saiga of the Don and Volga lived as far to the west as Aquitaine. The grizzly bear, instead of being restricted to its American habitat in the Rocky Mountains, ranged over the whole of Siberia into Europe, as far to the south as the Mediterranean, and westwards as far as Gibraltar.

The urus263 still lives in the larger domestic cattle, and the bison is represented in Europe by those which are protected by the forest laws of Lithuania, and in North America by the vast herds which are rapidly being exterminated, like the red Indian, by the rifles of the settlers. The horse was as abundant, and as widely spread over Europe, as the urus and the bison; according to Prof. Brandt it now no longer lives in Siberia in a wild state.

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Species common to Cold and Tropical Climates.

The panther or leopard, which has been found alike in Britain, France, and Germany, has at the present day a most extended range through Africa, from Barbary to the Cape of Good Hope, and throughout Persia into Siberia. In this latter country Dr. Gothelf Fischer describes it as living in the same districts in the Altai Mountains, and in Soongaria, as the tiger. The fox and wolf are like instances of carnivores being able to endure great variations in temperature without being specifically modified. These three animals, therefore, tell us nothing as to the pleistocene climate.
Extinct Species.

The extinct pleistocene species may also be divided into the same classes as the living, by an appeal to their geographical distribution. Two out of the three species of rhinoceros found in the caves (R. megarhinus and R. hemit?chus), and an elephant with slightly curved tusks (E. antiquus), had their head-quarters south of the Alps and Pyrenees, whence they wandered northward as far as the latitude of Yorkshire. The pigmy elephant and the dwarf hippopotamus are peculiar to the south, and the Machairodus latidens, or large sabre-toothed felis, is a survival, from the pleiocene age, of a peculiarly southern type.

The woolly rhinoceros, on the other hand, may be viewed as a northern form, since it is met with in vast abundance in the arctic regions of Siberia, as well as in Europe, and has not been found south of the Alps and401 Pyrenees. The cave-bear has not been discovered either in the extreme north or in the south of Europe, and may therefore be considered of temperate range; and the Irish elk, identified by Prof. Brandt, from the caves of the Altai Mountains, had a similar range in middle Europe. The mammoth, endowed with an elastic constitution, was able to endure the severity of an arctic climate in Siberia and North America, and the temperature of the latitude of Rome and the Gulf of Mexico,264 and consequently tells us as little of the pleistocene climate as the panther, fox, or wolf.

The evidence, therefore, as to climate, offered by the extinct animals in the caves is of the same nature as that of the living. There is the same mixture of northern and southern forms, which can only be accounted for satisfactorily by seasonal migrations, according to the summer heat and winter cold, such as those which are now observed to take place in Siberia and North America.

Before we consider the relation of the pleistocene animals buried in the caves and river deposits to the glacial period, it is necessary to define what is meant by the term glacial.
Two Periods of Glaciation in Britain.

At the close of the pleistocene period the climate gradually became colder, until ultimately it was arctic in severity in northern Europe. The researches of many eminent observers prove that an enormous sheet of ice, like that under which Greenland now lies buried, extended over North Britain, Wales, and Ireland, leaving402 its mark in the far-travelled blocks of stone, the moraines, and the grooves which pass over the surface irrespective of the minor contours. The land then, most probably, as Prof. Ramsay and Sir Charles Lyell believe, stood higher than it does now. To this succeeded a period of depression, during which the mount............