In the dense forests some of the vegetarian tribes of animals had on the face two little bags or glands, to hold a strong-smelling liquid. This perfume dropped on the herbage helped the members of the herd to scent one another's trails, and so keep together for company or defence. On the skulls of some kinds of horses there may still be seen the hollow where the sac used to be.
The bald skin of the pig is boldly painted in splashes of pink and brown to imitate the lights and shadows of forest undergrowth. The forest ancestors of the horse were bald, and painted just the same way; and their forest colouring may still be seen under the hairy coat, especially at the muzzle, where the hair is thin.
Of direct ancestors to the horse the earliest known was a little fellow called Hyracotherium, coloured no doubt like the pig or the hairless Mexican dog, and not bigger than a toy terrier. His range extended from England to New Mexico, across the old Atlantic continent. In him the original five toes had been reduced to four on the front foot, and three on the hind, as with the tapir, who is the very portrait of a horse-ancestor, although of larger growth.
The tapir
The tapir was ever a staunch conservative preferring death to reform. So he remains, one of the most ancient of all living animals, and relic of the long forgotten ages when the world was one big forest. Nowadays the tapir range which covered all the northern continents has shrunken to three districts widely sundered: Brazil, Mexico, and the Malay Peninsula. In all three he is dying out, and in a few more years will be extinct.
From the tapir's habits we may reason that the horse ancestors were creatures not only of the deep glades of the forest, but also of closely wooded mountain ranges. They were shy and harmless, feeding at night on buds, leaves and the tender shoots of bushes, not on grass. To this diet the horse reverts quite readily in times of famine, and in spring before the new grass sprouts, while the stable vice called cribbing develops when there is not enough bulk in his forage. The ancestors were fond of bathing, and when hunted would take refuge in the water. It will be noted that although wild horses do not bathe, the tame stock are excellent at swimming. The dappled skin of the tapir had grown a coat of hair, dark brown in the Americas, their original home. The long tail had shrunk, and in the tapir is reduced to a mere bud.
But the main interest is in the tapir's snout, which, like the elephant's trunk, has wonderful powers of holding and tearing down branches, of feeling, sensing, and handling. The horse-ancestor had a tapir snout of which the horse's upper lip is the survival. Play with any horse and you will notice how the lips try to curl round and grip one's fingers, to bring them within reach of the teeth. They will curl round, grip, and tear the bunch grass or pampas grass of the wild ranges. They are softer than velvet, delicate as a baby's hand, sensitive as the fingers of an artist, will caress like a woman's lips. The short hairs have an exquisite sense of touch, the beard bristles are used to sense grass with in the dark, and the whole instrument is wondrously designed to select sweet grasses, rejecting poisonous or unwholesome plants, so that feeding goes on through hours of total darkness.
The earlier world
Had the Earth remained an unbroken forest under a roof of cloud there had been no change since the Age of Dragons, no mighty drama of Creation lifting man and horse out of the shadows to work together as master and servant in the conquest and taming of the wilderness and final subjugation of the World.
The one great factor in Earth's history is the lessening of the sun's heat. Through long revolving ages the heat which the Earth received from the sun diminished. Ever less vapour was lifted from the Equatorial seas, the world-roof of cloud thinned out and disappeared; direct sunshine poured down instead of the endless rains; there was no moisture left to nourish the worldwide forest. Little by little glades opened in the woodlands caused by drought, savannahs replaced the timber, of tall jungle grasses, the openings widened into prairies, and vast grassy steppes, thousands of miles in breadth, evolved at their centres an aching core of desert. So we have reached the phase when forest, prairie and desert each claim one-third of the land surface. We are passing on to the phase, which Mars has reached, of world-wide desert, and beyond that is the far future when, like the Moon, our Earth will swing dead through the great deeps of space.