Cave Hunting / Researches on the evidence of caves respecting the early inhabitants of Europe

by William Boyd Dawkins

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. hemitœchus), 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 and 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, leaving 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 mountains of Wales were submerged to a height of at least 1,300 feet; and the waves of the sea washed out of the pre-existing glacial detritus the shingle and sand, termed the “middle drift,” which occurs also in Scotland and Ireland.[265] Then the land was re-elevated above the waves, and a second period of glaciers set in, traces of which occur abundantly in Wales, Scotland, and Ireland, in the white areas in [Fig. 126]. They were, however, of far less extent than those which preceded them, occupying isolated areas instead of forming one continuous icy covering to the country. The glacial phenomena may be briefly summed up as follows: 1. As the pleiocene temperature was lowered, the glaciers crept down from the tops of the mountains, until at last they united to form one continuous ice sheet, moving resistlessly over the smaller hills and valleys to the lower grounds, and the first ice or glacial period set in. 2. Then followed the era of depression beneath the sea. 3. And, lastly, on the land re-emerging from the sea the second ice or glacial period began. The climate during the marine depression must obviously have been milder than that of either of the glacial periods, because of the moderating effect of the wide extent of sea.

The exact relation of the boulder clays with marine shells, in the centre and south of Britain, to the detritus left behind by the ice-sheet in the north, has not as yet been satisfactorily ascertained. It is very probable that the elevation of land in the north was simultaneous with a southern depression, which allowed of icebergs depositing their burdens in the eastern counties, in the valley of the Thames, and as far south as Selsea, on the coast of Sussex.

Three Climatal Changes represented on the Continent.

These changes of climate have also been observed on the continent of Europe. The Swiss geologists have shown that the Alpine glaciers extended farther than they do at the present time, and that they present two stages of extension, the first of which is of greater magnitude than the second. The Alpine blocks and moraines have been traced far down into the plains of Lombardy, northwards into the valley of the Rhine, and in France as far south in the valley of the Rhone as Valence. The admirable essay and map brought by MM. Falsan and Chantre, before the meeting of the French Association for the Advancement of Science at Lyons, in 1873, show that there were two periods of glaciation in the valley of the Rhone, the one being due to the movement of an ice-sheet irrespective of the lower hills, the other being merely the work of the glaciers localized in the valleys. These in all probability correspond in point of time with the like stages of the complicated glacial phenomena in Britain. At this time the glaciers of the Pyrenees, now so small, extended at least from thirty to forty miles from their present position down into the plains, leaving behind most astounding evidences of their presence in the valley of the Garonne and elsewhere. On the Spanish frontier, for example, one of the precipitous sides of the valley, near the Pont du Roy, is so smoothed and polished that it is bare of vegetation except in the deep grooves, which offer a precarious support to the roots of ferns and of dwarf beeches. The hills of Dauphiny also and Auvergne were crowned with glaciers, and those of the latter have been shown by MM. Falsan and Chantre to have been conterminous with those of the Alps.