Stephanie Tucker, age 11, of Heber, Utah, for her question:

How far back can they trace the horse family?

Some 50 million years ago, herds of little horses scampered around the land that is now Utah. Most likely you would not. have recognized them as ancestors of our magnificent modern horses. Almost certainly you would not have recognized the landscape as the central region of North America. The horses were no bigger than our fox terriers and they ran on soft toed feet. Even then they were strict vegetarians. The climate was moist and very mild and an endless carpet of tender green grasses covered the rolling landscape.

The first mammals were mousy little creatures who arrived on earth some 200 million years ago. Through the ages, of course, they changed and improved. The successful ones became the ancestors of our present mammals and many of their bones fossilized in the ground. Through the ages they left a record of their achievements    and their failures. But tracing the history of their family trees is not as simple as it sounds. For example, a certain ancestral mammal of 40 million years ago gave rise to both the bears and the dogs.

Tracking down the horse’s family began with a whopping error. In 1838, fossil hunters mistakenly thought they had found remains of early ancestral horses in England. But later it was established for certain that the horse family got its start right here in North America. In the 1870s, a fossil with horsy features was found in Wyoming. But many other fossil remains were needed to verify it and trace the horse’s family tree through its long series of improvements. Paleontologists now place the original ancestors back in the Eocene Period of 50 million years ago.

The earliest known fossil with recognizable horsy features is so different from the modern horse that he was given a name of his own. The small, soft toed ancestor is Eohippus, the Dawn Horse. And in Eocene days the eohippus was very plentiful in North America, his one and only original homeland. He was about a foot high and less than two feet long. Even then, his slender legs were designed for speed. His neck was too short and his teeth too soft. But his spine showed the beginning of a graceful, horsy curve.

Fossil records reveal clearly how the descendants of eohippus improved to keep pace with the changing times. To escape their meat hungry enemies they grew larger and stronger. To gain still more speed, they stood ready to run on tip toe and very gradually one toe on each foot became a hard hoof. Their teeth grew tougher to cope with tougher grasses. About a million years ago, the wild herds of North America were at last recognizable horses.

For some reason nobody knows, tragedy struck the North American horses and they were wiped out. But fortunately, some members of the horse family had already left this continent and had spread to Asia, Europe and Africa. Thus the horses you see here today are the descendants of a race that started here, moved away and then, thanks to man, returned.