The changing climate
As the slow tremendous change of the Earth's climate narrowed the forest, there was no longer food for all the woodland animals, and some of them ventured out into the open glades. Here was a final parting of the ways between the tapir who stayed in the woods and the horse-ancestor who went out into the open. He was as yet no bigger than a sheep, and still wore three toes on each foot, but the grass diet agreed with him, for his tribe soon grew to the size of an English donkey. The firmer ground no longer needed a wide tread to the foot. Slowly the second and fourth toes shrank away up the leg, and hung there like the dew claw of a dog, sometimes surviving more or less even in human times, as with Julius Cæsar's charger. The next ages evolved an animal the size of our ponies, running on one toe hardened to the hoof we know to-day. The snout diminished, while the tail became a fly whisk.
Varieties of the horse
So we have the beginning of a group of animals the tarpan (Prejevalski) zebra, quagga and ass. They are so much alike that one cannot easily tell from the bones to which kind a skeleton belongs. We must think of them, then, as varieties of the horse.
CHAPTER II.
THE ORIGIN OF HORSE VARIETIES.
PROPOSITIONS. In the study of any subject, if we can only begin by clearing our vision, we shall have a sporting chance of avoiding muddle.
The horse, like man or any other animal, reflects his environment in times past and present.
1. If all countries had equal lighting, all horses would reflect one colour.