The proportion of the Pleistocene which is covered by the Old Stone Age is variously estimated. Some geologists will not allow the undisputed Palæolithic to have extended over more than the last tenth of the Pleistocene: the rivers have not changed their beds enough to permit the assumption of a longer period. This allowance would give the Palæolithic a duration of perhaps a hundred thousand years, which is the figure here followed. Those who place the beginning of the European Palæolithic in the second instead of the third interglacial period, would have to admit a considerably longer duration.
The geologist, because he deals with such enormous durations, has to operate on a broad-gauge scale, and usually disdains to commit himself to close estimates of years. To measure the lapse of time within the Pleistocene, he has found it most useful to avail himself of the evidences left by the great glaciers which repeatedly covered parts of several continents during the Pleistocene, and he has therefore given this period its popular name of “glacial epoch.” These glaciations must be imagined as having occurred on a much larger scale than one might at first infer from the shrunken remnants of the glaciers that persist in the Alps and other mountains. The Pleistocene glaciers were vast sheets, hundreds of feet in thickness, sliding uniformly over valleys, hills, and mountains except for an occasional high peak. Modern Greenland, which except at the edges is buried under a solid ice cap, evidently presents a pretty fair picture of what the northern parts of Europe and North America repeatedly looked like during the Pleistocene.
Four such glaciations, or periods of maximum extent of the continental ice, have been distinguished, and more or less correlated, in Europe and North America. In Europe they have been designated as the Günz, Mindel, Riss, and Würm glaciations respectively ([Fig. 5]). Each of these is the name of a locality in the Alps at which typical moraines or erosions produced by the ice of that period have been carefully observed.
Between these four successive advances of the ice sheets there fell more temperate eras, some of them rather arid, and others moist and almost tropical even in the latitude of Europe. These mild intervals are known as the interglacial periods. That Europe was free from ice during these interglacial periods is shown not only by facts of a purely geological nature but by the occurrence in these periods of fossils of a semi-tropical fauna which included elephants, rhinoceroses, lions, and the like.
Coming now to a consideration of the relation of man to these ice eras, we find that the first, second, and probably the third glaciations passed without leaving sure evidence of manufactured stone implements. In the last interglacial period, that which falls between the Riss and the Würm glaciations, the so-called “Chellean picks” appear; and from then on the record of artifacts is a continuous one. Considerable parts of Europe remained habitable all through the fourth and last glaciation, the Würm period, as the implements discovered prove. Gradually, although irregularly and with three minor advances and recessions, always diminishing in rigor, however, this last predominance of the ice died away; until, by the time its effects had wholly disappeared, and the geologically “Recent” era was inaugurated, human civilization had evolved to a point where it began to enter the New Stone Age.
The animals whose fossils are found in the same deposits with human skeletons and artifacts have been of the greatest assistance in the determination of the periods of such remains. The fossils are partly of extinct species until toward the very end of the Pleistocene, when exclusively living types of animals begin wholly to supersede the earlier ones. While the identification of the various species, and the fixation of the age of each, is the work of the specialist in palæontology, the results of such studies are all-important to the historian of man’s beginnings, because they help to determine chronology. If artifacts are found in association with fossil remains of an extinct animal such as the mammoth or the woolly rhinoceros, they are obviously older than artifacts that are accompanied only by the bones of the reindeer, the dog, or other living species. For this reason, although the history of mammalian life in the past is a science in itself, it also has close relations with human prehistory. Some of the most characteristic animals of the later Pleistocene, and the successive stages of human cultural development with which they were associated, are listed on the following page.
70. Subdivisions of the Palæolithic
The places at which the men of the Stone Age lived and where their debris accumulated are known as “stations.” The word was first employed in this sense in French, but has been taken over into other languages. A “station” then is simply a spot at which prehistoric remains of human occupation are found. At least a thousand of these have been discovered in western Europe. In general they divide into two classes. One kind is in the open, mostly in the gravels laid down by streams. These are therefore known as “River Drift” or simply “Drift” stations. The other kind is found in caves or under sheltering rocks. The majority of Drift stations have proved to be from the earlier or Lower Palæolithic, whereas the Cave stations date mostly from the later or Upper Palæolithic. The Drift and the Cave periods are therefore often distinguished within the Old Stone Age, especially by English archæologists. French, German, and American students generally use the terms “Lower Palæolithic” and “Upper Palæolithic,” whose reference is to periods of cultural development rather than type of locality inhabited, and which carry more significance. French archæologists also speak of the Upper Palæolithic as the Reindeer Age.
The Later Glacial Fauna of Western Europe