# Early Man in Britain and His Place in the Tertiary Period/Chapter 5

CHAPTER V.
BIOLOGICAL AND PHYSICAL CHANGES IN BRITAIN AT THE TIME OF THE ARRIVAL OF MAN.
We have arrived now at that stage in the inquiry when new mammals appear, belonging for the most part to living species; and we shall see in the course of this and the two succeeding chapters, that their remains are associated with human implements in such a manner as to show that man was a member of the fauna which characterises the Pleistocene period of this quarter of the world.
Definition of the Pleistocene Period.
The Pleistocene mammalia, found in the deposits of rivers and in ossiferous caverns, present a remarkable ​contrast to those which preceded them in Europe. Instead of the one or two living species of the Pleiocene age, there are many, and they preponderate greatly over the extinct, standing to them in the relation of fifty-five to twenty-two, out of a total of seventy-seven. They may be divided into groups, which throw great light on the climatal and geographical conditions under which man lived in Europe.
Survivals from Pleiocene Period.
The first group to be noted consists of survivals from the preceding age. One living species, now only found in Africa south of the Sahara, and seven extinct, survived the changes which caused the destruction of the rest of the Pleiocene mammals, as may be seen in the following list:—
Survivals from Pleiocene, Living Species=1.
Survivals from Pleiocene, Extinct Species=7.
Incoming Living Species of Temperate Habit.
The incoming Pleistocene species, constituting the second group, now found in the temperate zones of Europe, Asia, and America, consist of animals of widely-different habits and range. The musk shrew, now restricted in Europe to the streams of southern Russia, and especially to the region of the Don and Volga, haunted the rivers of Norfolk (Bacton) in the Pleistocene age. The pouched marmot, now ranging eastwards from Austria and Poland through southern Russia, the Crimea, and Siberia to Kamtchatka, hibernated in Wiltshire (Fisherton) and in Somerset (Mendip Caves); and the field vole of central Europe and western Siberia (Arvicola arvalis) ranged as far to the west as Bath. At the present time three species of pika or tailless hares inhabit Siberia, of which one (Lagomys pusillus) lives as far west as the Volga. In the Pleistocene age the genus ranged as far to the west as Gibraltar, and the above-mentioned species seems to me identical with the (Lagomys spelæus) cave-pika of Brixham and Kent's Hole. The saiga antelope, now found no farther to the west than Poland, and most abundant in the region between the Volga and the river Irtisch, south of 55° N. lat., migrated as far to the west as Auvergne (Caves of the Dordogne); and the fallow deer, now only indigenous in the warm regions of the Mediterranean, wandered as far north as Harwich, being represented by a variety ​(Cervus Browni) discovered at Clacton. The bison, now preserved from extermination in a half-wild state in the imperial forests in Lithuania, and living in freedom in the Urals and Caucasus, roamed over the whole of Europe, as far to the north-west as Yorkshire. Its bones and teeth, found in northern Siberia and in Eschscholtz Bay, and other localities in North America, prove that in former times the herds, now rapidly being destroyed by the hunters in the tract of country extending from New Mexico into the British Dominions, were conterminous
Fig. 20.—Canine of Grisly Bear, Windy Knoll, Castleton, 1/1
with those of Asia. From Behring's Straits to Italy and Spain the remains of the bison are very generally found with those of the horse. The latter animal, as well as the urus, now only lives under the care of man. Among the incoming carnivores belonging to the temperate zone, the most important is the grisly bear (Fig. 20), the fossil remains of which, according to Professor Busk, are met with from Gibraltar, in the south-west, as far to the north as Britain and Belgium. At the present time the brown and grisly bears inhabit the same regions in North America, and we need therefore feel no surprise that they should be found together in the Pleistocene ​strata of Europe. The wolf and tlie fox range throughout Europe, Asia, and North America, as far north as the Arctic Sea.
Incoming Species now Living in the Temperate Zone = 33.
The last and most important addition to be made to ​this list is the man of the river deposits, or the River-drift man, who differs, as we shall presently see, both in culture and in range, from the man of the caverns.
Incoming Arctic Species.
The third group to be considered consists of living species of northern habit (see Fig. 24).
Incoming Living Species of Northern Habit = 8.
The arctic lemming, an inhabitant of the circumpolar regions of Asia and America, and not found farther south in the latter continent than Unalaska in N. lat. 54°, lived in the Pleistocene age as far to the south as Quedlinburg in Saxony, and the valley of the Loire in France, and as far to the west as the caverns of the Mendip Hills; while the allied Norwegian species, now restricted to the Scandinavian peninsula and Russian Lapland, ranged as far south into Germany as Saxony, and into England as Somerset. The Russian vole, also, of Scandinavia, Lapland, northern Russia, and Kamtchatka, then lived in Somersetshire; and the varying hare (=the Irish hare=blue hare of Scotland), of the cold hilly districts of Britain and of the continent, as well as northern Europe and Asia as far as the Arctic Sea, has been discovered in the caverns of Suabia (Fraas) and Switzerland (Mawdach). ​At the present time the musk sheep, the elegant white arctic fox, the reindeer, and the glutton or wolverine (Fig. 21), live side by side in circumpolar America, and the three last range over the far north of Asia and Europe, the glutton, according to Zimmermann, having been caught as far south as Brunswick and Saxony. Of these the first two have been met with as far to the south-west as the Pyrenees; the third as far to the south as Switzerland; and the fourth as far to the west as the caves of Somersetshire, and to the south as Auvergne (E. Lartet).
Fig. 21.—Lower Jaw of Glutton, Plas Heaton Cave, 1/1.
To this division also must be added the Cave-man, who, as we shall see in the seventh chapter, is represented at the present time by the Eskimos, and differed from the Palæolithic man of the river deposits probably in race, and certainly in culture.
Incoming Species now restricted to Cold Mountainous Regions.
The preceding group of animals now living in an arctic climate was associated in Pleistocene Europe ​with those which enjoy the cold climate of the mountains not far removed from the snow line, viz.—
The first of these, now not found at a lower level than 3000 feet above the sea in the Alps, has been discovered by Dr. Forsyth Major at Levrange in Lombardy. The second, now haunting the higher Alps, Pyrenees, and Carpathians, in the Pleistocene ranged from the shores of the Mediterranean (Mentone) as far north as Belgium (Trou de Magrite, Dupont). The third, the chamois of the Alps, the izard of the Pyrenees, the steinbock of the Carpathians and the Caucasus, lived on the banks of the Meuse, the region drained by the Loire, and in Suabia; while the fourth, the bouquetin or ibex of the Alps, Carpathians, and Sierra Nevada in Spain, was found alike in Gibraltar (Busk), southern and central France (Mentone, Auvergne), Belgium, and Suabia (Fraas). The last species is probably identical with the Capra beden of Crete, of the Cyclades, of Syria, and of north-eastern Africa, as well as with the C. Sibirica of the Altai and Thibet, all of which appear to be varieties brought about by insulation of the breeds from each other.
In the Pleistocene age the ibex ranged from the border of the Mediterranean northwards over Spain, France, and Germany; and it would have free access to North Africa, the sea bottom in the Straits of Gibraltar then being a valley lifted up above the level of the sea (see Map, Fig. 24), as well as to Crete and the Cyclades, which were then ​lofty mountains overlooking the land connecting Asia Minor with Greece. When the present geographical and climatal conditions were brought about, the ibexes would naturally take refuge in the mountains, and in the long course of ages would be very likely to present those minute and unimportant varieties which are seen in wild isolated breeds. It must further be remarked, that although the ibex ranged as far south as Crete and the Atlas, the mountains of the former are covered with snow as late as the middle of June, and the climate of the latter has been sufficiently severe in ancient times to allow of glaciers extending down their flanks to within 6000 feet of the present level of the Mediterranean. When Morocco and the Grecian archipelago were lifted high above the present level of the sea—not less, as I have pointed out in my work on Cave-hunting, than 2400 feet (400 fathoms)—the climate would be far more severe than it is at present, and the ice and snow probably formed snow-fields and glaciers like those of the high Alps.
Incoming Species now found in Hot Climates.
The animals passed under review in the above pages inhabit, as we have seen, the temperate and cold regions of Europe, Asia, and America. The next division which comes before us has its headquarters in hot climates. It consists of the
The porcupine of northern Africa and the warmer European districts of the Mediterranean, as well as of Asia Minor, lived in the Pleistocene age as far north as the banks of the Meuse. The leopard or panther, common to Africa and the warmer regions of middle and northern Asia, also ranged through Europe as far to the north-west as the Mendip Hills (see Fig. 24). The discovery of its remains in the caves of Gibraltar, France, and Germany, proves that in the Pleistocene age it passed over into Spain, France, and Saxony, just as those in the Mendip caves show that it passed northwards over the area of the Channel, to prey upon the reindeer, bisons, and horses of Somersetshire. It was very rare as compared with the other carnivores of the period—lions, bears, and hyænas—and it was associated in its wanderings with the feline now found throughout Africa the Caffer cat. The lynx of northern Africa, Spain, Sardinia, Sicily, and the Levant, has been discovered in the caves of Gibraltar. The lion, now found only in the warm climates of Africa and southern Asia, hunted its prey as far north as Yorkshire (Kirkdale), and as far to the north-east as the frontiers of Poland. The spotted hyæna now lives only in Africa, south of the Sahara Desert: then it abounded in Spain, France, Germany, and in Britain, as far north as the vale of ​Pickering, as well as in southern Russia, as far to the east as the region of the Altai (Brandt). The striped hyæna of Africa, and the warmer climates of Asia, dwelt in the Lunel-viel in Provence, and the African elephant, now no longer found north of the Sahara, then passed from the present coast of Africa northwards to Sicily, and in Spain as far as the latitude of Madrid.
Incoming Extinct Species.
The above species, with the exception of some of the survivals of the Pleiocene age, are alive in some part of the world. With them are associated others which have become extinct.
| Cuvier's beaver................................................................................................................................................................................................................................................................................................................................................................................................ | | Trogontherium Cuvieri, Ow. |
| Gigantic dormouse................................................................................................................................................................................................................................................................................................................................................................................................ | | Myoxtis Melitensis, Falc. |
| Pouched marmot................................................................................................................................................................................................................................................................................................................................................................................................ | | Spermophilus erythrogenoides (?), Falc. |
| Straight-tusked elephant................................................................................................................................................................................................................................................................................................................................................................................................ | | Elephas antiquus, Falc. |
| Mammoth................................................................................................................................................................................................................................................................................................................................................................................................ | | E. primigenius, Blum. |
| Falconer's elephant................................................................................................................................................................................................................................................................................................................................................................................................ Pigmy elephant................................................................................................................................................................................................................................................................................................................................................................................................ | $\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right.}$ | E. Falconeri, Busk. |
| Falconer's elephant................................................................................................................................................................................................................................................................................................................................................................................................ Pigmy elephant................................................................................................................................................................................................................................................................................................................................................................................................ | $\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right.}$ | E. melitensis, Falc. |
| Falconer's elephant................................................................................................................................................................................................................................................................................................................................................................................................ Pigmy elephant................................................................................................................................................................................................................................................................................................................................................................................................ | $\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right.}$ | E. mnaidrensis, Adams. |
| Woolly rhinoceros................................................................................................................................................................................................................................................................................................................................................................................................ | | Rhinoceros tichorhinus, Cuv. |
| Small-nosed rhinoceros................................................................................................................................................................................................................................................................................................................................................................................................ | | R. leptorhinus, Ow. |
| Deer of the Carnutes................................................................................................................................................................................................................................................................................................................................................................................................ | | Cervus Carnutorum. |
| Thick-antlered deer................................................................................................................................................................................................................................................................................................................................................................................................ | | C. verticornis, Dawk. |
| Irish elk................................................................................................................................................................................................................................................................................................................................................................................................ | | Megaceros hibernicus, Owen. |
| Pigmy hippopotamus................................................................................................................................................................................................................................................................................................................................................................................................ | | Hippopotamus Pentlandi, Falc. |
| Cave bear................................................................................................................................................................................................................................................................................................................................................................................................ | | Ursus spelæus, Goldf. |
Among the rodents the large extinct beaver, and among the deer the Cervus Carnutorum and the C. ​verticornis, are found in Britain and France, the giant dormouse and the three kinds of pigmy elephant in Malta.
Fig. 22.—Mammoth engraved on Ivory by cave-man, La Madeline.
​The mammoth (Fig. 22) is very abundant in the caverns and river deposits of Britain and of France, and is known to have ranged over the Pyrenees into Spain, from the discovery of specimens in the zinc-mines of Santander. It has been proved by Prof. E. Lartet and Dr. Falconer to have lived in the neighbourhood of Rome at a time when the volcanoes of central Italy were active, and poured currents of lava and threw clouds of ashes over the site of the imperial city. It is common in northern and southern Germany, but it has not been found in Europe north of a line passing through Hamburg, or in any part of Scandinavia or Finland. It occurs in the auriferous gravels of the Urals; and in Siberia, as is well known, it formerly existed in countless herds, being buried in the morasses in large numbers, in the same manner as the Irish elks at the bottom of the Irish peat-bogs. The admirable preservation of some of the carcases is undoubtedly due to their having been entombed directly after death, and then quickly frozen up, a process which need not necessarily imply climatal conditions unlike those of the present time in Siberia. In unusually hot spring times, the warm waters borne down by the great rivers from their southern feeders thaw the frozen morasses with incredible rapidity, so that the hard ice- bound "tundra" becomes quickly converted into a treacherous bog. In the exceptionally warm season of 1846, the mammoth discovered by Lieut. Benkendorf on the banks of the Indigirka was thawed out of the tundra until it was revealed to the astonished eyes of the beholder, standing on its feet in the position in which it had been bogged. Had any elks or reindeer been on ​that spot at that time they might have been entombed in the same way, and preserved by the frosts of the winter till they were liberated again by the rare chance of their place of sepulture being invaded by warm floods from the south. The thaw in that year proceeded so rapidly that Lieut. Benkendorf and his Cossacks narrowly escaped the alternative of being entombed in the soft morass, or of being swept out northwards into the Arctic Sea, as his mammoth was, to join the vast assembly of mammoths and reindeer and other animals which have been swept down in a similar fashion.
The remains of the animal occur throughout Russian Asia; and the singular notice of fossil ivory being brought for sale to Khiva, by an enterprising Arabian traveller, Abou-el-Cassim, in the middle of the tenth century, applies to the mammoth ivory from the old Bulgaria on the Lower Volga.
We learn from the recent researches of M. Chabas that an elephant was living in the valley of the Euphrates in the sixteenth century B.C., when that district was invaded by the Egyptians, since a great hunting of elephants by the Pharaoh Thothmes III. in the neighbourhood of Nineveh has been recorded in an Egyptian inscription. This important notice shows that the fossil and living elephants of Asia in ancient times were not separated from each other by impassable geographical barriers or wide spaces of mountain and desert. Those hunted may have been either the fossil (E. armeniacus) Armenian, or the Indian species. On taking a survey of the whole evidence as to the range of the mammoth ​and its relation to the Indian elephant, it appears to me very probable that they are two well-marked varieties rather than two extinct species, and that the latter has derived those trifling characters by which it is distinguished from the former in the untold ages of its sojourn in the tropical forests of India. The possession of hair and wool so remarkable in the Siberian mammoth depends mainly upon the climate, and cannot therefore be taken to be a specific character. It is very probable that the mammoth in Italy, and in the districts bordering on the Gulf of Mexico, presented as great a contrast in those respects with the mammoth of the north as the Thibetan mastiff and goat, which lose their fine wool when brought down from the Himalaya to Kashmir.
Fig. 23.—Upper Canine of Cave-bear, Wookey Hole, 1/1.
The mammoth was accompanied in its wanderings from the high northern latitudes of Asia by the woolly ​rhinoceros as far as the Alps and the Pyrenees. A straight-tusked elephant abounded in Italy, and is found through France and Britain as far north as Yorkshire, being very generally associated with a southern form of rhinoceros, the small-nosed species of Professor Owen. The gigantic Cave-bear (Fig. 23) haunted the caves of Italy, France, and Britain, as well as those of Germany; while the Irish elk fell a prey to the hyænas in all these countries, and was found as far to the east as the mountains of the Altai. The pigmy hippopotamus, on the other hand (H. Pentlandi), like the living dwarf species of Africa, has a comparatively restricted range, being found in Sicily, Malta, and Crete, and on the mainland of the Peloponnese at Megalopolis.
These groups of animals, man being omitted, stand to each other in the following relation:—
Survivals from Pleiocene—
Evidence from Distribution of Animals as to European Geography.
This remarkable association of animals in Pleistocene Europe, some of which are now only alive in widely ​remote parts of the world, points with unerring certainty to great geographical and climatal changes. Nearly all the temperate, northern, and mountainous species can be traced to northern and central Asia, and for their migration it is necessary to suppose that a very close connection With Asia was caused by the elevation of land at the close of the Pleiocene age.
This, probably, is indicated by the low tract of country uniting the northern end of the Caspian with the Sea of Aral, and reaching through the salt steppes of Ishim into the valley of the Irtisch, and thence to the Gulf of Obi and the Arctic Sea. Britain also formed part of the mainland, and the bottom of the Pleiocene sea (Fig. 10) became the feeding-grounds of the animals which have left their remains in the forest bed of Nor- folk and Suffolk, as well as in the Dogger Bank off Yar- mouth. Ireland also must have been united to Britain to have allowed of their finding their way so far to the west. The elevation above the present sea-level, necessary to account for this distribution of the animals, is not less than 600 feet or 100 fathoms. At this depth the soundings show the presence of a line of submarine cliffs which form the margin of the plateau of the British Isles, and which mark the probable Atlantic coast-line of north-western Europe, during a large part of the Pleistocene age, as represented in the accompanying map (Fig. 24).
Fig.—24. Pleistocene Europe, showing range of Northern and Southern Mammals.
Caffer cat and African lynx and spotted hyæna sought their prey in the Iberian peninsula. Nor could Sicily have been separated from Africa on the one hand and Italy on the other, when the African elephant lived on that island, and the striped hyæna passed into the south of ​France. Malta, Sicily, and Crete must have been the higher portions of a continent, now submerged, when the pigmy hippopotamus lived in all three; and the Apennines, the mountains of Sardinia, Greece, Asia Minor, and the Atlas, must have been connected by land with the mountains of Crete and the Cyclades to allow of the distribution of the living ibexes. For all these animals to have arrived at the places where they are found, it is necessary that the whole Mediterranean area should be lifted up 400 fathoms above its present level, which would result in its being reduced to the two deep land-locked seas of Fig. 24, divided from each other by the belt of land reaching from Cape Bon (Tunis) to Malta, Sicily, and Calabria. It may further be remarked that, while a large portion of the present Mediterranean was dry land, the Sahara was occupied by a prolongation of the Atlantic far into the region south of the Atlas mountains.
From these considerations it is evident that Pleistocene Europe must be looked upon as intimately connected with Africa on the south and with Asia on the east, and that it offered no barriers to the migration of Asiatic and African animals as far to the west as Britain and Ireland.
Evidence as to Climate.
The range of the northern and southern mammalia over Pleistocene Europe is indicated respectively by the horizontal and vertical dotted lines in the above Map (Fig. 24), and from their examination it will be seen that Europe is divided into three distinct zones; 1st, the northern, into which the southern animals never ​penetrated, comprising the region north of a line passing from Yorkshire eastwards through Hamburg and Russia; 2d, the middle zone, common to both groups of animals, extending south of this line as far as the Pyrenees, the Alps, and Hungary; and lastly, the southern, into which the northern animals never penetrated, or Spain, Italy, and Greece. It must further be observed that the range of the mountainous species, such as the ibex, into the region of the southern animals—into the Apennines, the Sierra Nevada—the Atlas, and the mountains of Sardinia, of Crete, and Anatolia,—shows that the distribution of the Pleistocene mammalia was regulated by climate rather than by physical barriers.
From this distribution we may infer that the climate was severe in the north and warm in the south, while in the middle zone, comprising France, Germany, and the greater part of Britain, the winters were cold, and the summers warm as in middle Asia and North America, where large tracts of land extend from the Polar region towards the equator, and offer no barrier to the swinging to and fro of the animals. In the summer time the southern species would pass northwards, and in the winter time the northern would swing southwards, and thus occupy at different times of the year the same tract of ground, as is now the case with the elks and reindeer.
It must not, however, be supposed that the southern animals migrated from the Mediterranean area as far north as Yorkshire in the same year, or the northern as far south as the Mediterranean. There were, as we shall see presently, secular changes of climate in Pleistocene Europe, and while the cold was at its maximum the arctic animals arrived at the southern limit, and while it was at its ​minimum the spotted hyæna and hippopotamus and other southern animals roamed to their northern limit. Thus every part of the middle zone has been successively the frontier between the northern and southern groups, and consequently their remains are mingled together in the caverns and river deposits, under conditions which prove them to have been contemporaries in the same region. In some of the caverns, such as that of Kirkdale, the hyæna preyed upon the reindeer at one time of the year and the hippopotamus at another. In this manner the association of northern and southern animals may be explained by their migration according to the seasons, and their association over so wide an area as the middle zone by the secular changes of climate, by which each part of the zone in turn was traversed by the advancing and retreating animals.
Climatal and Geographical Changes in Britain marked by Glacial Phenomena.
Secular changes of climate in the Pleistocene age are clearly marked in Britain north of a line connecting the Bristol Channel with the valley of the lower Thames, and passing due eastward into Germany and Russia, by the traces of glaciation, by the erratics, or blocks of stone transported far away from the rocks from which they were torn, and by the accumulations of clay and sand known as the glacial drift. They imply the following ​series of climatal and geograpliical changes, affecting the area of Britain north of the above line, those which are purely local being omitted.
1. The First Glaciation a Period of Elevation.
At the beginning of the Pleistocene age the temperature was lowered in northern Asia and Europe, and ultimately became sufficiently severe to allow of glaciers descending from the hills in Britain and Ireland, and covering large tracts of the lower grounds, like the con- fluent glaciers concealing a large portion of Greenland. One of these systems of glaciers covered the greater part of Scotland, another the mountains of Cumberland and Westmoreland, a third the Pennine chain, and a fourth the greater part of Wales, and they have left their marks behind in all these districts in the ice-moulded contours of the hills, and in the grooves cut in the
​rocks. In some cases, as near Liverpool, these grooves are found near the present sea-level, and in others they pass far below it. It is very probable that the ice may have arrived at the Atlantic shore at a considerable distance from the present coast-line, and that it may have been continuous with that of Scandinavia, where similar traces have been met with.
The ice at this time was sufficiently thick to override Schihallion in Perthshire at a height of 3500 feet, and the hills of Galway and Mayo at 2000 feet. Its southern limit in Britain is uncertain. According to Professor Ramsay and Dr. James Geikie it extended as far south as the latitude of London: but the hypothesis upon which this southern extension is founded—that the boulder clays have been formed by ice melting on the land—is open to the objection that no similar clays have been proved to have been so formed, either in the Arctic regions, where the ice-sheet has retreated, or in the districts forsaken by the glaciers in the Alps or Pyrenees, or in any other mountain chain. Similar deposits, however, have been met with in Davis Straits and in the North Atlantic, which have been formed by melting icebergs, and we may therefore "conclude that the boulder clays have had a like origin.
To this ice-sheet may be referred the groovings in the rocks underlying the lowest boulder clays of Britain and Ireland, as well as the lines of erratics which sometimes can be traced in directions not coinciding with the present valleys, as, for example, those at Norber, near ​Ingleborough, in Yorkshire. The tough clays with scratched stones, sometimes so hard to work that it is necessary to employ gunpowder, are considered by Dr. James Geikie to be the débris underneath the ice-sheet accumulated on land, and termed by the Swiss geologists "moraine profonde." These are met with chiefly in Scotland, but they have been observed by Mr. De Rance in South Lancashire, and at the Little Ormes Head in North Wales.
The climate must have been arctic in its severity during this period of glaciation, and this may have been partially due to the fact of the land standing at a higher level above the sea, and being lifted up into the colder regions of the atmosphere. It cannot, however, be wholly so explained, since it was the culmination of a series of changes by which the tropical climate of the Eocene passed into the warm Meiocene and temperate Pleiocene climates.
2. The Icebergs—a Period of Depression.
Then followed a period of depression beneath the sea. The glaciers, which had before carried their burdens of sand, clay, and stone far away from the present seaboard of Britain, now ended at the retreating shoreline, giving rise to icebergs, which deposited the lower boulder clay as they melted, and drifted as far to the south as the valley of the Thames. The mountains were ​reduced to clusters of glacier-covered islands rising from the sea, which, in Lancashire and Yorkshire, was not less than 300 feet above its present level. The drift of the icebergs at this time was mainly in a south-easterly direction, as is indicated by rocks derived from Cumberland, Westmoreland, and perhaps Scotland, and dropped, as they melted, over Lancashire, Cheshire, and Shropshire.
3. The Depression continued. Climate Temperate.
At the close of this period the climate grew warmer, and banks of shingle and sand were accumulated, instead of boulder clays, constituting "the Middle drift sand and gravels." The glaciers disappeared, and the sea beat upon an archipelago of islands, which gradually sank beneath the sea to a depth of from 2300 feet below their present level on the flanks of Snowdon, to 1200 feet at Vale Royal, on the road between Buxton and Macclesfield, and to about 1400 feet in Scotland. And as this took place, the sands and shingle gradually arrived at those altitudes, resting on the lower boulder clay in the lower and on the glaciated surface of the older rocks in the higher, grounds. The climate may be inferred to have been temperate, not merely from the absence of icebergs, but from the presence of mollusca now living in the adjacent seas.
4. A Reversion to a Severe Climate.
The next change was one of climate, which reverted to the cold condition of the second of these divisions. Glaciers again covered the higher grounds, and icebergs again floated over the lower grounds, still submerged, depositing as they melted the upper boulder clay, which rises as high as 500 feet above the sea-level in Lancashire and Yorkshire (Hull). The drift of the icebergs was south-easterly, since the peculiar altered chalk of Antrim, in the north of Ireland, is scattered over Lancashire and Cheshire, and as far south as Ironbridge in Shropshire.
5. Period of Elevation—Climate becoming Temperate.
Then followed an upward movement of the land, until the upper boulder clay became dry land, and Britain and Ireland became part of the mainland of Europe, as is represented in the Map (Fig. 32). Glaciers still remained on the higher hills in Scotland, Wales, and Cumbria, leaving in their retreat the old moraines, so conspicuous in those regions. The climate was less severe than in the preceding period, and was gradually again becoming temperate. As the upper boulder clay deposited on the sea-bottom became lifted up, it was gradually covered by forests of yew, Scotch fir, oak, ash, and alder, in which the Pleistocene mammalia found ample food in the eastern and midland counties.
Climatal Change on the Continent, and in Asia and Africa.
Similar climatal changes have left their mark upon the higher mountains of Europe, Asia Minor, and North ​Africa. During the period of maximum cold, the glaciers of Auvergne joined those of the Jura, in the valley of the Rhone, and those of the Alps extended far down into Lombardy, France, Switzerland, and Germany. From the Pyrenees, also, glaciers found their way as far as Toulouse, and from the snowy tops of the Atlas and of the Lebanon they descended to the level of 6000 feet, and from the mountains of Lazistan to that of 4500 feet above the sea.
This period of maximum cold in the south of Europe coincided with a period of high elevation, in which the Mediterranean area was lifted up not less than 2400 feet above the sea, so as to allow of Europe joining Africa by way of Gibraltar and of Sicily and Malta, as we have seen in this chapter. The Alps also, at the beginning of the Pleistocene, according to Professor Gastaldi, stood 1312 feet higher than they were in the Pleiocene age.
Variation of Climate in the Alps.
These climatal changes are traceable in the Alps by the advance and retreat of the glaciers, and in some Alpine districts there is evidence of a reversion to a temperate climate. On the borders of the lake of Zurich, for example at Utznach and Dürnten, a bed of lignite intercalated between two glacial accumulations proves that a forest occupied the same tract of ground which before and after was covered by a glacier.
Relation of Mammalia to Glacial Phenomena.
The complicated glacial phenomena summed up in the preceding pages imply not merely a change from a temperate to a cold climate of extreme severity, but they show a climatal fluctuation of the sort which might be expected from the examination of the Pleistocene mammalia. When the reindeer inhabited the south of France the cold was at its maximum, and when the hippopotamus lived in England the cold was probably at its minimum. Each of these changes was probably brought about during a long series of ages, and each has left its mark in the mixed fauna of the middle zone of the map (Fig. 24).
The lowering of the temperature was probably the cause of the immigration into Europe of the Asiatic species. As the cold increased in Asia, and the warm Pleiocene climate of northern and central Europe gradually became cool, the animals which had been living in Asia for an unknown series of years poured in, a way being opened to them by the elevation of a low-lying tract of land at the head of the Caspian and the Gulf of Obi, which had probably hitherto been the bottom of a shallow sea cutting them off from Europe. It must be remarked that a change towards cold conditions has already been indicated by the ice-borne blocks of stone met with on the Pleiocene sea-shore of Suffolk. A vast migration of animals set in from Asia, analogous in every respect to that by which the European peoples arrived at their present homes, and following for the most part the same route, between the Caspian Sea and the Ural mountains (see Fig. 24, p. 111).
The Three Divisions of the Pleistocene Age.
As the climate in Europe changed, the Pleiocene species yielded place to those which were better adapted to the new conditions, either retreating southwards or becoming extinct. The first division of the Asiatic invaders is composed of the animals forming the temperate group above mentioned; they are found in the early Pleistocene strata, in Britain and in France, side by side with the survivals from the Pleiocene age. No arctic mammalia had as yet arrived. The next stage in the migration is that in which the temperate group of animals had for the most part replaced the Pleiocene survivals, in Britain and France, and the arctic mammalia begin to appear, but only in small numbers. This constitutes the middle Pleistocene division. The third stage in the migration is indicated by the presence in full force of the arctic species in the area north of the Alps and Pyrenees. They are not, however, met with south of this boundary, and therefore this classification does not apply to the deposits of Spain, or the other portions of the southern zone.
It must also be noted that the temperate group of the Asiatic invaders found their way over the whole of southern Europe, and along the Mediterranean shores, as far south as Palestine and the Sahara Desert—Sicily and Malta affording one line of migration southwards, and the land barrier then stretching across the Straits of Gibraltar offering another.
Pleistocene Mammalia in Britain before, during, and after the Glacial Period.
The Pleistocene mammalia might reasonably be expected, from the manner in which the Asiatic migration took place, to have been in Europe before, during, and after the Glacial period. As the ice advanced southwards it pushed the arctic mammalia southwards, and caused them to encroach on the temperate and southern mammalia. When it retreated northwards the animal life swung northwards. These considerations, necessary from the facts brought forward in the preceding pages, will be found in the next chapter to be proved by a critical examination of the river deposits and the contents of caverns.
From the large percentage of living species which we have noted in the preceding chapter, we might have inferred that the time was at hand for the arrival of man. The greater part of the living European mammalia were present, and the world was then in the stage of evolution in which man might be expected to play his part. In the next two chapters we shall see at what stage of the Pleistocene age he appears, and we shall examine the evidence from which it may be concluded that there were two races—the River-drift men and the Cave-men—in Europe during the long series of ages represented by the Pleistocene period.
* ↑ In working out the ranges of the animals in this chapter, I have chiefly used works of the following authors:—Blackmore and Alston, "Arvicolidæ," Proceed. Zool. Soc., 1874, p. 460; Bell, British Quadrupeds, 8vo, 1837; Blasius, Fauna der Wirbelthiere Deutschlands, 8vo, 1857; Busk, Trans. Zool. Soc., x. Part II.; Clermont, Lord, Quadrupeds and Reptiles of Europe, 8vo; Dawkins and Sanford, "British Pleistocene Mammalia," Palæont. Soc., 1866; Desmarest, Mammalogie, 4to, Paris, 1820; Falconer, Palæontographical Memoirs, 2 vols. 8vo, 1868; Fischer, Synopsis Mammalium, 8vo, Stutgart., 1830; Forsyth. Major, Atti Soc. Tosc. Sc. Nat. Pisa, iii. 1876-9; Murray, Geographical Distribution of Animals, 4to; Pallas, Zoographia Rosso-Asiatica, 3 vols. 4to, Spicilegia Zoologica, 4to, 1777; Pennant, Arctic Zoology, 2 vols. 4to, 1784; Owen, British Fossil Mammalia, 8vo, 1846, Palæontology, 8vo, 1860; Richardson, Sir John Fauna Boreali-Americana, 4to; Zimmerman, Specimen Zoologiæ, 4to, 1777.
* ↑ Atti Soc. Tosc. Sc. Nat., Nov. 1876.
* ↑ I saw the top of Mount Ida covered with deep snow in June 1875.
* ↑ Schmerling, Recherches sur les Oss.-Foss., decouverts dans les Cavernes de la Province de Liège, 4to, 1833-34.
* ↑ Dawkins and Sanford, British Pleistocene Mammalia. Palæont. Soc., 1871. Part IV.
* ↑ Op. cit. Part III.
* ↑ Marcel de Serres, Mem. du Mus., xvii. Pl. 25.
* ↑ Falc., Palæont. Memoirs, ii. p. 283.
* ↑ This is separated from the living S. erythrogenys by Dr. Falconer, but it is by no means certain that it belongs to an extinct species.
* ↑ See Dawkins, Quart. Journ. Geol. Soc. Lond., xxxv. 138, for the references to the range of the mammoth.
* ↑ Chabas, Études sur l'Antiquité historique d'après les sources égyptiennes, 2d edit., p. 124. It must be remarked that this notice stands alone, and is as yet not confirmed by any Assyrian or Babylonian records.
* ↑ Falconer, Nat. Hist. Rev., 1862, p. 113. On the variability in the development of hair and wool, see Darwin, Variation under Domestication, ii. p. 278.
* ↑ Dawkins' Cave-hunting, p. 362 et seq.
* ↑ For proof of this see Cave-hunting, chap. x.
* ↑ The term glacial, used in a varying sense by different writers, is employed in these pages merely to express the marks of the presence of ice in the shape of glaciers and icebergs in the areas where they are no longer found. For purposes of geological classification over wide areas an appeal to the purely local phenomena of glacier or iceberg is useless, because they tell us nothing as to the contemporary fauna and flora, by which alone all geological periods have hitherto been determined. I am unable, therefore, to agree with Dr. James Geikie in treating the Pleistocene period as the equivalent of "the Ice age."   It is foreign to the plan of this work to discuss the much debated cause of the Glacial period, as the lowering of the temperature in the Pleistocene age is frequently termed. Was it due to a change in the oceanic currents? or to a movement in the axis of the earth? or to a variation in the heating power of the variable star on which our universe depends? The question opens a vast field for speculation, on which the reader may consult Dr. Croll's Climate and Time, Sir John Lubbock's Prehistoric Times, and Sir Charles Lyell's Antiquity of Man.   The best account of the complex phenomena of the Glacial period is to be found in Lyell's Antiquity of Man, 4th edit. c. xil-xviii. See also The Great Ice Age of Dr. James Geikie, as well as the essays of Jamieson, Searles Wood, Harmer, Hull, De Rance, and others, in the Geological Magazine, the Quarterly Journal of the Geological Society, and the Memoirs of the Geological Survey.
* ↑ Jamieson, Quarterly Journal of Geological Society, Lond., xxi. p, 165.
* ↑ Kinahan and Close, General Glaciation of lar-Connaught and its Neighbourhood, Dublin, 1872, p. 16.
* ↑ See Bonney, Geological Magazine, ii. Vol. iii., "Some Notes on Glaciers."
* ↑ The English boulder clays, as a whole, differ from the moraine profonde in their softness and the large area which they cover. Strata of boulder clay at all comparable to the great clay mantle covering the lower grounds of Britain north of the Thames are conspicuous by their absence from the glaciated regions of central Europe and the Pyrenees, which were not depressed beneath the sea.
* ↑ For the geography of Britain at this time, see Lyell, Antiquity of Man, Fig. 43.
* ↑ See Lyell, Antiquity, Fig. 42.
* ↑ See Dawkins' Cave-hunting, p. 382 et seq.
* ↑ Atti della Reale Accademia delle Scienze de Torino, vol. x. 21.
* ↑ Heer, Primeval World in Switzerland, ii p. 149