George Cameron, age 8, of Asbury Park, N.J., for his question:
WHERE DID THE HORSE ORIGINATE?
Scientists tell us that our modern horse's earliest ancestor was a small animal no more than 10 or 20 inches high. The tiny horse was called an Eophippus or Hydracotherium and it lived about 55 million years ago in what is now North America or Europe.
The tiny prehistoric horses had arched backs and snoutlike noses. They looked more like racing dogs, such as grayhounds or whippets, than like the straight backed, long faced modern horse.
Early horses had four toes on their front feet and three toes on their hind feet. Each toe ended in a separate small hoof. Large, tough pads similar to those on a dog's foot kept the toes off the ground. These pads bore the animal's weight.
Then about 35 million years ago, the modern horse's next important ancestor lived. Called the Mesophippus, this animal was about 20 inches high and had long, slender legs. Each foot had three toes, of which the middle toe was longest.
About 30 million years ago, Mesophippus gave way to a new horselike creature called the Miohippus. This animal stood from 24 to 28 inches tall and its middle toe was longer and stronger than that of its ancestors.
Horselike animals continued to develop. Then about 26 million years ago the Merychippus appeared. This was a ruminant or cud chewing horse and it grew to be about 40 inches high. Like the Miohippus, it had three toes on each foot. The side toes were almost useless, however, and the center toe grew long and strong. It ended in a large, curved hoof and it bore all of the animal's weight.
By about 1 million years ago, horses probably looked somewhat like modern horses. They grew larger than their ancestors: The side toes on their feet became short bones along the legs, leaving the strong center toe with its hoof to support the animals.
With the horse that evolved about 1 million years ago, the teeth developed greatly and its mouth was well fitted for eating grass. Scientists group these horses, along with the modern domestic horse, under the name Equus.
No one knows where horses originated. Fossils show that during the Ice Age horses lived on every continent except Australia. Great herds wandered throughout North and South America. Then, for some unknown reason, they disappeared from the Western Hemisphere.
Primitive man hunted horses and ate their meat. No one knows who first tamed horses and trained them for riding. Scientists discovered evidence in the ancient city of Susa in southwestern Asia that man most likely rode horseback more than 4,000 years ago.
Stone tablets show that the Hittites trained horses for sport and war about 1400 B.C. and that the Assyrians, in about 800 B.C., hunted lions in two wheeled chariots drawn by a pair of horses.
Ancient Romans and Greeks were expert horsemen and used horses for racing.