In the older geological formations no remains of man or of his works have been found. Nor do we expect to find them, for none of the animals more nearly related to man then existed, and the condition of the earth was probably not suited to them. Nor do we find human remains even in the earlier Tertiary. Here also we do not expect them, for the Mammalia of those times were all specifically distinct from those of the modern world. It is only in the Pliocene period that we begin to find modern species of mammals. Here, therefore, we may look for human remains; but we do not find them as yet, and it is only at the close of the Pliocene, or even after the succeeding Glacial period, that we find undoubted traces of man. Let us glance at the significance of this.
Mammalian life probably culminated or attained to its maximum in the Miocene and the early Pliocene periods. Then there were more numerous, larger, and better-developed quadrupeds on our continents than we now find. For example, the elephants, the noblest of the mammals, are at present represented by two species confined to India and parts of Africa.[8] In the Middle Tertiary there were, in addition to the ordinary elephants, two other genera, Mastodon and Dinotherium, and there were many species which were distributed over the whole northern hemisphere. The sub-Himalayan deposits of India alone have, I believe, afforded seven species, some of them of grander dimensions than either of those now existing. We have no trustworthy evidence as yet that man lived at this period. If he had, he either would have required the protection of a special Eden, or would have needed superhuman strength and sagacity.
But the grand mammalian life of the Middle Tertiary was destined to die out. At the close of the Pliocene came an age of refrigeration, when arctic cold crept down over our continents far to the south, and when most of the animals suited to temperate climates were either frozen out or driven southward. During, or closing, this period was also a great submergence of the continents, which must have been equally destructive to mammalian life, and which extended over both Eurasia and America till the summits of some of the highest hills were under water. Attempts have been made to show that man existed before or during the Glacial Age, but this is very unlikely, and, as I have elsewhere argued, the evidence adduced to prove so great antiquity of man, whether in America or Europe, has altogether broken down.[9]
At the close of the Glacial period the continents re-emerged and became more extensive than at present. Survivors of the Pliocene species, as well as other species not previously known, spread themselves over this new land. It would appear that it was in this "Post-Glacial" period that man made his appearance, and that he was then contemporary with many large animals now extinct, and was the possessor of wider continental areas than his descendants now enjoy. To this age belong those human bones and implements found in the older cave and gravel deposits of Europe, and which are referred to those palæolithic or palæocosmic ages which preceded the dawn of history in Europe and the arrival therein of the present European races. The occupation of Europe, and probably of Western Asia, by these oldest tribes of men was closed by a subsidence or submergence at the end of that "second continental period," as it has been called by Lyell,[10] in which they lived. When the land was restored to its present condition, they were replaced by the ancestors of the present European races.
It may be well here to tabulate that later portion of the earth's geological history in which man appeared, more especially as it is sometimes arranged in a manner not suited to convey a correct impression of the actual succession. It will be seen by the general table given in the last lecture that the latest of the Tertiary ages is that known as the Pleistocene or Post-Pliocene, and this, with the succeeding modern period, may be best arranged as follows:
I. Pleistocene, including—
(a) Early Pleistocene, or First Continental Period. Land very extensive, moderate climate.
(b) Later Pleistocene, or Glacial (including Dawkins' "Mid-Pleistocene"). In this there was a great prevalence of cold and glacial conditions, and a great submergence of the northern land.
II. Modern, or Period of Man and Modern Mammals, including—
(a) Post-Glacial, or Second Continental Period, in which the land was again very extensive, and palæocosmic man was contemporary with some great mammals—as the mammoth, now extinct—and the area of land in the northern hemisphere was greater than at present. (This represents the Late Pleistocene of Dawkins.) It was terminated by a great and very general subsidence, accompanied by the disappearance of palæocosmic man and some large Mammalia, and which may be identical with the historical deluge.[11]
(b) Recent, when the continents attained their present levels, existing races of men colonized Europe, and living species of mammals. This includes both the Prehistoric and the Historic Period.
The palæocosmic men of the above table are the oldest certainly known to us, and it has been truly said of them that they are so closely related to modern races that, on any hypothesis of gradual evolution, we must look for the transition from apes to men not merely in the Eocene Tertiary, but even in the Mesozoic—that is, in formations vastly older than any containing any remains so far as known either of man or of apes. That these most ancient men were in truth most truly human, and that they presented no transition to lower animals, will appear from the following notices, which I condense from a work of my own in which these subjects are more fully treated:
The beautiful work of Lartet and Christy has vividly portrayed to us the antiquities of the limestone plateau of the Dordogne—the ancient Aquitania—remains which recall to us a population of Horites, or cave-dwellers, of a time anterior to the dawn of history in France, living much like the modern hunter-tribes of America, and, as already stated, possibly contemporary—in their early history, at least—with the mammoth and its extinct companions of the later Post-Pliocene forests. We have already noticed the arts and implements of these people, but what manner of people were they in themselves? The answer is given to us by the skeletons found in the cave of Cro-magnon. This cavern is a shelter or hollow under an overhanging ledge of limestone, and excavated originally by the action of the weather on a softer bed. It fronts the south-west and the little river Vezère; and, having originally been about eight feet high and nearly twenty deep, must have formed a cosey shelter from rain or cold or summer sun, and with a pleasant outlook from its front. All rude races have much sagacity in making selections of this sort. Being nearly fifty feet wide, it was capacious enough to accommodate several families, and when in use it no doubt had trees or shrubs in front, and may have been further completed by stones, poles, or bark placed across the opening. It seems, however, in the first instance to have been used only at intervals, and to have been left vacant for considerable portions of time. Perhaps it was visited only by hunting- or war-parties. But subsequently it was permanently occupied, and this for so long a time that in some places ashes and carbonaceous matter a foot and a half deep, with bones, implements, etc., were accumulated. By this time the height of the cavern had been much diminished, and, instead of clearing it out for future use, it was made a place of burial, in which four or five individuals were interred. Of these, two were men, one of great age, the other probably in the prime of life. A third was a woman of about thirty or forty years of age. The other remains were too fragmentary to give very certain results.
These bones, with others to be mentioned in connection with them, unquestionably belong to the oldest human inhabitants known in Western Europe. They have been most carefully examined by several competent anatomists and archæologists, and the results have been published with excellent figures in the Reliquiæ Aquitanicæ. They are, therefore, of the utmost interest for our present purpose, and I shall try so to divest the descriptions of anatomical details as to give a clear notion of their character. The 'Old Man of Cro-magnon' was of great stature, being nearly six feet high. More than this, his bones show that he was of the strongest and most athletic muscular development—a Samson in strength; and the bones of the limbs have the peculiar form which is characteristic of athletic men habituated to rough walking, climbing, and running, for this is, I believe, the real meaning of the enormous strength of the thigh-bone and the flattened condition of the leg in this and other old skeletons. It occurs to some extent, though much less than in this old man, in American skeletons. His skull presents all the characters of advanced age, though the teeth had been worn down to the sockets without being lost; which, again, is the character of some, though not of all, aged Indian skulls. The skull proper, or brain-case, is very long—more so than in ordinary modern skulls—and this length is accompanied with a great breadth; so that the brain was of greater size than in average modern men, and the frontal region was largely and well developed. In this respect this most ancient skull fails utterly to vindicate the expectations of those who would regard prehistoric men as approaching to the apes. It is at the opposite extreme. The face, however, presented very peculiar characters. It was extremely broad, with projecting cheek-bones and heavy jaw, in this resembling the coarse types of the American face, and the eye-orbits were square and elongated laterally. The nose was large and prominent, and the jaws projected somewhat forward. This man, therefore, had, as to his features, some resemblance to the harsher type of American physiognomy, with overhanging brows, small and transverse eyes, high cheek-bones, and coarse mouth. He had not lived to so great an age without some rubs, for his thigh-bone showed a depression which must have resulted from a severe wound—perhaps from the horn of some wild animal or the spear of an enemy.