In the course of the pliocene the previously high temperature of the northern hemisphere was sensibly lowered, and at its close the pleistocene period introduced a cold and wintry climate, along with gradual and unequal subsidence of the land, the whole producing that most dismal of the geological ages, known as the 'glacial period.' At this time much of the lower land of the continents was submerged and the mountains became covered with snow and ice, leaving space for vegetable and animal life only toward the south and in a few favoured spots in the higher latitudes. There is much difference of opinion among geologists as to the extent, duration and vicissitudes of this reign of ice, but there can be no doubt that it destroyed much of the animal and vegetable life of the pliocene, or obliged it to migrate to the southward. In this period great deposits of mud, sand and gravel were laid down, which prepared the world for a new departure in the succeeding age. This we may name the post-glacial, or early modern period, and in it we have the most certain evidence of the existence of man, though the geographical arrangement of our continents and their animal inhabitants were in many respects different from what they now are. If geologists are right in the conclusion already stated, that the close of the glacial period is as recent as 7,000 years ago, this will give us a narrow limit in time for the age of man, at least under his present conditions.
While, however, there is an absolute consensus of opinion among geologists as to the existence of man at or about the close of the glacial age, in the northern temperate regions at least, there are some facts which have been supposed to indicate a pre-glacial human period, or the advent of man even as early as the middle of the cenozoic time. These merit a short consideration.
THE EARLIEST TRACES OF MAN
In the eocene, or earliest cenozoic, it is not pretended by anyone that man existed, except inferentially, on the ground that if the remains we know in the earliest caves and gravels belong to men who were developed from apes on the method of natural selection, their ancestors must have existed, at least in a semi-human form, in the eocene. But no such precursors of man are yet known to us. It would have been pleasant to believe that man arrived in time to see the beautiful forests and to enjoy the mild climate of the golden age of the miocene, and this would have agreed with some human traditions; but the probabilities are against it, as we know no one species of higher animal of the many found in the miocene that has survived to our time. The privilege of enjoying the forests of the miocene age seems to have been reserved for some large and specialised monkeys, which even Darwinians can scarcely claim as probable ancestors of man. [6] It would appear also that owing to increasing refrigeration of climate these apes were either obliged to leave Europe for warmer latitudes or became extinct in the succeeding pliocene.
[6] Dryopithecus and Mesopithecus.
There are, however, in France two localities, one in the upper and the other in the middle miocene, which have afforded what are supposed to be worked flints. [7] The geological age of the deposits seems in both cases beyond question, but doubts have been cast, and this seemingly with some reason, on the artificial character of the flint flakes, while in the case of some examples which appear to be scrapers and borers, like those in use long afterward by semi-civilised peoples for working in bone and skin, there are grave doubts whether they actually came from the miocene beds. Lastly, it has even been suggested that these flints may be the handiwork of miocene apes, a suggestion not so unreasonable as at first sight it appears, when taken in connection with the working instincts of beavers and other animals. Monkeys, however, seem to have less of this gift as artificers than most other creatures. On the whole, we must regard the existence of miocene man as not proven, though, if it should prove to be a fact, it may be useful to some of the scoffers of these days to know that it would not be so irreconcilable with the Biblical account of creation as they seem to suppose. It might, however, prove a serious stumbling-block to orthodox Darwinians, and might raise some difficulties respecting antediluvian genealogies.
[7] Puy, Courny and Thenay.
In the pliocene of Europe there are alleged to be instances of the occurrence of human bones. One of these is that of the skull now in the museum of Florence, supposed to have been found in the pliocene of the Val d'Arno. It is, however, a skull of modern type, and may have been brought down from the surface by a landslip. But this explanation does not seem to apply to the human remains found in lower pliocene beds at Castelnedolo, near Brescia. They include a nearly entire human skeleton, and are said by good observers to have been imbedded in undisturbed pliocene beds. M. Quatrefages, who has described them, and whose testimony should be considered as that of an expert, was satisfied that the remains had not been interred, but were part of the original deposit. Unfortunately the skull of the only perfect skeleton is said to have been of fair proportions and superior to those of the ruder types of post-glacial men. This has cast a shade of suspicion on the discovery, especially on the part of evolutionists, who think it is not in accordance with theory that man should retrograde between the pliocene and the early modern period, instead of advancing. Still we may ask, why not? If men existed in the fine climates of the miocene and early pliocene, why should they not have been a noble race, suited to their environment; and when the cold of the glacial period intervened, with its scarcity and hardships, might they not have deteriorated, to be subsequently improved when better conditions supervened? This would certainly not be contradictory to experience in the case of varieties of other animals, however at variance with a hypothetical idea of necessarily progressive improvement. Let us hope that the existence of European pliocene man will be established, and that he will be found to have been not of low and bestial type, but, as the discoveries above referred to if genuine would indicate, a worthy progenitor of modern races of men.