Everyone's heard about the terrifying giant insects and birds of the prehistoric era, but not every species lived so large in the long ago. The earliest known horses, for example, stood nowhere near as tall as those we know today. Fossils from the early Eocene Epoch, which took place between 33.9 million and 56 million years ago, are evidence that the first known horse reached only about 20 inches (50.8 cm) in height, at most. Known commonly as Eohippus, or the "dawn horse," the hoofed mammal lived in North America and Europe but looked considerably different from the noble steeds we recognize today. In fact, it wasn't until more recent fossils were uncovered that the link was made certain. Over time, paleontologists were able to sketch the changes that horses have undergone over the past 50 million years or so. They grew taller, with larger brains, longer legs, and bigger muzzles. They also lost some hoof mass along the way, and their teeth became better equipped for eating grain.
To get a clear idea of the remarkable growth of the horse, one need only look at the Shire horse, which would make those first horses quiver. The largest horse breed in the world, the Shire weighs up to 2,400 pounds (1100 kg) and stands 6 feet (1.8 m) tall, on average.
- A horse's teeth take up more space in its head than its brain does.
- Horses often look like they are laughing, but they are actually testing the air to determine whether a smell is good or bad.
- Most horses live between 25 and 33 years, but an English horse known as Old Billy died in 1822 at the record age of 62.