AT the same time there were living a great number of mammals, grass-eating and flesh-eating, whose descendants are the kinds we know to-day. The grass-eating ones were pigs, some of which grew to a considerable size, rhinoceroses, antelopes, okapis, and smallish three-toed horses, of which we must write later. The carnivorous mammals that preyed upon them were wolves, hysnas, bears, and the sabre-toothed cats. Most of these forms were so much like those we know to-day that there is no need to discuss them. The sabre-toothed cats, however, are not so well known, and their common name is rather misleading.
)They were not true cats, but only related to them, and they were certainly not tigers, the name often applied to them. Equal to a lion in size, but of slightly heavier build and with
shorter and stouter limbs, Macharodus, a typical representative, possessed an unusually powerful neck and two tremendous fangs in the upper jaw. These fangs were like sabres, wide and thin, and had faint saw-like markings on the hinder margin. Their use is something of a mystery, for although we know that the jaws opened very widely, they cannot have opened so widely as to allow these fangs to be used like ordinary teeth. Most probably they were used to tear the flesh and cut the blood-vessels of the victim—to kill, and to reduce the food to the proper size.
This fauna, diverse in characters and widespread over Europe and Asia, continued to flourish greatly until the close of the Pliocene. Then it passed slowly southwards into Africa, where much of it, a little modified, remains. Its place in the North was occupied by true horses and true elephants, and by many kinds of deer, about which something must now be said.
THE HORSE’S LITTLE FIVE-TOED ANCESTORS THE evolution of both the horses and the elephants makes fascinating stories which have often been told. It is hardly correct to call them evolutionary stories because, though we know most of the stages, a great many links are not in our possession.
The horses of to-day have specialised teeth and hoofed feet which are composed of only one toe. If we go right back in the records of the Tertiary age, we can gradually see a series in which progressive alteration of the tooth structure and reduction of the number of toes has taken place. In the Eocene, for example, the first-recognised horse forms appear to have been little animals the size of foxes. Like most of the other Eocene hoofed-creatures, they were five-toed, and their appearance and structure would make it difficult to think of them as being related to the horses at all were it not for the fact that we know of intervening, later forms.
In the related forms of the Upper Eocene and later ages, we see that not only are the animals becoming larger in size but that they are changing the form and shape of the teeth, which are becoming suited to a less succulent diet. The toes are only three in number, and the side ones are gradually seen losing their connection with the ground.
In the Pliocene age, a genus named Hipparion was widely established, for fossilised remains are known from England,
France, Germany, Spain, Italy, India, Greece and Persia. Hipparion, though not quite so large as the typical modern species, was in all essentials a true horse, but it had a toe on each side of the main, or middle, toe. Gradually these side-toes disappeared, becoming the mere splints of bone we know in the living horse.
The true, one-toed, horse is of Lower Pleistocene age, and first appears in such widely separated places as Norfolk, Central France, and North America. To-day the wild horses are found only in Africa and Asia, while the North American ones are extinct. The distribution of horses is now man-made, the result of domestication, and the American horses now living have been transported there.