However, in regard to the history of elephants, the upshot of Dr. Andrews' most important discoveries is that we find living here in the Upper Eocene period (which is older than the age in which the Tetrabelodon Mastodon was found) an elephant ancestor of the kind to which Dr. Andrews gave the name of Palæomastodon or "ancient mastodon." We thus arrive at an ancestral elephant-like creature which serves to join the elephant stock on to more ordinary mammals. This beast was not so very big, perhaps about the same size as an ordinary cart-horse.
Dr. Andrews' further triumph was the additional discovery of the rather smaller animal which he called the Meritherium, and which was undoubtedly an elephant of sorts, though at first sight it has no resemblance to one, and probably had no trunk at all. It certainly had no big tusks; but its teeth make us certain that it belonged to the elephant family. "Here, then," says Sir E. Ray Lankester, "we have arrived at a form which undoubtedly was closely related to the ancestors of all the elephants, if not actually itself that ancestor, and in it we see the origin of the elephants peculiar structure. From this comparatively normal pig-like Meritherium, the wonderful elephant, with his upright face, his dependent trunk, and his huge spreading tusks has been gradually, step by step, produced. And we have seen some, at least, of the intermediate steps—the lengthening of the jaws and the increase in the size of the teeth in the Palæomastodon—carried still further on by the Tetrabelodon, and then followed by a shrinkage of the lower jaw and final evolution of the middle part of the face and upper jaw into the drooping, wonderful, prehensile trunk."
The long-chinned elephant requires, however, a few moments' consideration from an altogether different point of view. This species appears to have had the widest geographical distribution of any member of the family, of which it may be regarded as the great colonising or emigrant representative. First developed in North Africa, where its remains occur in the early Miocene strata of Mogara and Tunisia, this species ranged right across Europe to the confines of North-Western India, having probably reached Italy from Africa by means of a land-bridge by way of Sicily, and thence travelling through Greece into Asia. On the latter continent it appears to have given rise to the modern elephants, as remains of the former are unknown in any other part of the world.
If this be true, it follows that elephants of the modern type subsequently migrated into Europe and thence to Africa, while in the other direction they wandered by way of Behring Strait to America. Hence we are led to the remarkable conclusion that while the first elephants appeared in Africa, the modern African elephant is of Asiatic parentage, and a comparatively recent immigrant into the land of its forefathers. Next to man and the carnivora, elephants appear to have been the greatest travellers the world has ever produced, for, starting from their North African birthplace, they reached by the Behring Strait route nearly to the extremity of South America, while to the north they penetrated the Arctic circle, and to the south, on their return journey, reached the coast in the neighbourhood of Cape Town.
Another great traveller was the horse. The first undoubted horse-like animal was Eohippus, a little creature about eleven inches in height at the shoulder, and in general rather more like the flesh-eaters than the horses of the present day. The back was arched, the head and neck were short, and the limbs of moderate length, showing no remarkable adaptation for speed. This genus had a remarkable range, having apparently originated in England (then a part of Western Europe), and migrated by way of Europe and Asia, and what is now Behring Strait, to America, where it got as far east as New Mexico. This migration of Eohippus shifted the scene of evolution to the western hemisphere, for while examples of it are continually and continuously found there in succeeding strata it only appears occasionally in Europe, as if the remains there had been those of mere emigrants.
Later on the horse developed in America, growing larger till it was first as big as a collie-dog, with signs of being more adapted for speed. It then had four toes on its foot. It continued, though very gradually, to grow larger, and even more gradually its unnecessary toes grew fewer and fewer till at last they disappeared.
At length appeared the horse which had only one toe. This type, that of the modern horse, first becomes known in the Upper Pliocene beds of Europe, and represents the culmination of the race. The completeness of the record of the evolution of the horse tells us something of the enormous numbers of ancestral forms which must have existed in the more than two million years that have elapsed since the first diminutive horse appeared in North America. While not strongly given to migration, in the course of time these animals wandered over the entire world, with the exception of such inaccessible places as Australia and the Oceanic Islands.... It would seem that the original stock was of Eurasian derivation, though the great theatre of the evolutionary drama was soon transferred to North America, the Eurasian, African, and South American horses which appear from time to time being in all probability of North American origin. The ultimate fate of the horses in both North and South America was extinction, all wild horses of our own time, including the asses and zebras, being confined to Asia and Africa. The apparently wild bands of the American western plains, and those which roam over the pampas of South America, are the descendants of domestic horses that have escaped from human bondage, largely from the early Spanish explorers.
The rhinoceroses of to-day, the one-horned Indian variety and the two-horned African rhinoceros, were preceded by a whole regiment of rhinoceroses in the Tertiary period. One such was dug out in Fleet Street during the excavation for the Daily Chronicle office. This rhinoceros had a hairy coat like the Mammoth which lived much later, and in Siberia is found sometimes side by side with the later quadruped. Many of the extinct rhinoceroses had two horns like the African square-mouthed rhinoceros, which is sometimes misleadingly called the white rhinoceros. One great extinct beast, the Elasmotherium, allied to them, had a great horn carried on a huge boss in the middle of its head instead of on the nose, while another still huger animal called the Titanotherium and found in North America had a pair of horns perched on either side of its nose. As large as the rhinoceros but having a very different arrangement of the bones of its ankles and wrists and very different teeth and horns are the extraordinary creatures known as Dinoceras, whole skeletons of which have been disinterred from the Eocene strata of Wyoming in the United States by Professor Marsh. These creatures had three pairs of horns on the top of the head and a pair of great tusks as well. Nearly all these animals, though they were more brainy than the reptiles, had much smaller brains in proportion to their size than the bulk of the animals which now roam the earth, from which we may surmise that though a small brain suffices to guide a great animal machine in established ways, yet in order to learn new things in its lifetime an animal must have a big brain.
The last great mammal we must mention in this series is the Arsinoitherium, which was found only a few years ago by Dr. Andrews in Egypt, in the same strata whence he obtained the fossil ancestors of the elephant. It was so called because it was found near the palace of Arsinoë, the name of the Egyptian queen of Greek race. But Arsinoitherium was far from being a graceful ladylike creature, and, resembling in general appearance a rhinoceros, had two enormous bones, which grew out of its nose on either side of it. The bones were hollow and were probably covered with skin in life; and Arsinoitherium had a wonderful and wonderfully even set of teeth. To conclude, we must add a representative mammal of this period, the Sivatherium, found in India, and the Samotherium, found in the Isle of Samos, which were like giraffes, and the beginning of the sloth-like animals, whose appearance we must, however, deal with in another chapter.
