It will be necessary before we examine the group of caves used by man in prehistoric times, to point out the important difference in the measurement of time within and beyond the borders of history. When we speak, for example, of the date of the Norman Conquest, we imply that we can ascertain by historical records, not merely that it succeeded the invasion of Britain by the English or Danes, and happened before our own time, but that the interval which separates it from those events can be accurately measured by the unit of years. If, however, we attempt to ascertain the date of any event which happened outside the historical limit, we shall find that it is a question solely of relation. When we speak, for example, of the neolithic age, we merely mean a certain stage of human progress which succeeded the palæolithic, and preceded the bronze age, but we have no proof of the length of the interval dividing it from the one or the other. The historic “when?” implies “how long ago?” the prehistoric “when?” merely implies a definition before and after certain events, without any idea of the measurement of the intervals.
An attempt to ascertain the absolute date of prehistoric events must of necessity fail, since it is based on the improbable assumption that the physical agents have acted uniformly, and that therefore the results may be used as a natural chronometer. The present rate of the accumulation of débris, as at the Victoria Cave of the preceding chapter, or of that of silt in the deltas of rivers, such as the Nile, or the Tinière, may convey a rough idea of the high antiquity of prehistoric deposits; but a slight change either of the climate, or of the rainfall, would invalidate the conclusion. When the greater part of Europe lay buried under forest, when Palestine supported a large population, and when glaciers crowned some of the higher mountains of Africa, such as the Atlas, the European and Egyptian climates were probably moister than at the present time, and the rainfall and the floods greater, and consequently the accumulation of sediment quicker than the observed rate under the present conditions. And in the same way all estimates of the lapse of past time, based upon the excavation of a river valley, or the retrocession of a waterfall, such as Niagara, lie open to the same kind of objection. It is not at all reasonable to suppose that the complex conditions which regulate the present rate of erosion, have been the same during the time the work has been done, and it therefore follows that the work done is a measure of the power employed, and not of the length of time during which it has been in operation. We must, therefore, give up the idea of measuring the past beyond the memory of man, as represented in historical documents, by the historic unit of years. We can merely trace a definite sequence of events, separated one from another by uncertain intervals. And for that series of events which extends from the borders of history back to the remote age where the geologist, descending the stream of time, meets the archæologist, I have adopted the term prehistoric.[85]
The Prehistoric Fauna.
The prehistoric period is characterized by the arrival of the domestic animals in Europe, under the care of man. The dog, swine, horse, horned-sheep, goat, Bos longifrons, and the larger ox descended from an ancestor, according to Professor Rütimeyer, of the type of the great Urus, make their appearance together, in association with the remains of man, in the neolithic stage of civilization.[86] Subsequently they spread over the whole of our continent, for the most part under the care of man. The Bos longifrons, however, and possibly also the Urus, reverted to feral conditions, just as the horses and oxen, in the Americas and Australia, have done at the present time, and their remains are therefore frequently found in association with animals undoubtedly wild. The domestic horse, the variety of hog descended from the wild boar, and the domestic cattle derived from the Urus, may possibly have passed under the yoke of man, in Europe, since their wild stocks were to be found in that area, both in the prehistoric and pleistocene times. This, however, cannot be affirmed of the swine descended from the southern variety of Sus Indica, or of the Celtic shorthorn, of the sheep, or goat, since their wild ancestors were not indigenous in Europe. These animals must have been domesticated in some area outside Europe; and since central Asia is the region where the wild stocks still exist, from which all the domestic animals are descended, it is reasonable to suppose that they were domesticated in that region, and thence introduced, by a race of shepherds and herdsmen, into our quarter of the world.
This conclusion is considerably strengthened by the evidence which Professor Heer has advanced, as to the vegetables used by the dwellers on piles in the Swiss lakes, among which some, such as the two kinds of millet, the six-rowed barley (hordeum hexastichon), the Egyptian wheat (triticum turgidum), and a weed (Silene cretica), accidentally brought along with them, are distinctively of southern derivation.
The most important wild animals living in this country during the prehistoric period are the urus, the gigantic skulls of which occur in the peat bogs of England and Scotland, the Irish elk, the moose (Cervus alces), and the reindeer. The two last are far more abundant in the north than in the south of Britain; their remains have been discovered in the neighbourhood of London, those of both animals at Walthamstow, and those of the latter at Crossness in Kent, on the banks of the Thames. The remains of the bison have not been recorded from any prehistoric deposit in this country.
The Irish elk is the only animal which has become extinct; while the moose, or true elk, is the only wild species which has not been proved to have been living in the preceding age. The stag was very abundant.
The prehistoric fauna is distinguished from that of the pleistocene not merely by the appearance of the animals above mentioned, which were hitherto unknown, but by the absence of many species which were living during the latter period. The cave bear, woolly rhinoceros, and mammoth, for example, became extinct, the musk-sheep and lemming were banished from a temperate latitude to take refuge in the regions of the north, while the spotted hyæna, the hippopotamus, and Felis caffer, retired to the warm regions of Africa, where they are still living.
The Archæological Classification.
The prehistoric period has been classified by the archæologists according to the stages of human progress which it presents. At the frontier of history, in each country, we find that the dwellers were acquainted with the use of iron, and had found it to be the most convenient material for the manufacture of cutting weapons and implements. Before this the voice of tradition points out that bronze was the only material used for these purposes, and stone before bronze. These three stages of human culture, or the ages of iron, bronze, and stone, have been fully verified by investigations which have been made in various parts of Europe, into the prehistoric habitations and burial-places of man.