Have Horses Always Been Large Animals?

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.

Horse sense:

• 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.

Frequently Asked Questions

How large were the earliest ancestors of modern horses?

The earliest known ancestor of the modern horse was Eohippus, also known as the "dawn horse," which lived approximately 55 million years ago. According to the fossil record, Eohippus was quite small, standing only about 12 to 14 inches at the shoulder, roughly the size of a small dog.

Did horse ancestors always have hooves?

No, the earliest horse ancestors did not have hooves. Eohippus had four toes on their front feet and three on their hind feet, with soft pads similar to those of modern dogs. Over millions of years, their descendants evolved into animals with a single, sturdy hoof on each foot, a trait characteristic of modern equines.

What factors contributed to the increase in size of horses over time?

Several factors contributed to the increase in horse size over time, including environmental changes and evolutionary pressures. As grasslands expanded, larger size likely helped horses cover greater distances in search of food and escape predators. Natural selection favored those with traits advantageous for survival in open habitats, such as increased body size and speed.

When did horses reach their current size?

Horses reached a size comparable to modern-day equines around 1 to 2 million years ago. The genus Equus, which includes modern horses, zebras, and donkeys, emerged during this period, and these animals had body sizes and limb proportions similar to those of today's domesticated horses.

Are there any small horse-like species alive today?

Yes, there are small horse-like species alive today, such as the Przewalski's horse, which is the only truly wild horse species remaining. Additionally, there are various breeds of domesticated horses that are quite small, like the Shetland pony, which stands about 10 hands (40 inches) tall at the withers.

How has domestication affected the size of horses?

Domestication has had a significant impact on the size of horses. Selective breeding by humans has led to a wide range of horse sizes, tailored to different uses and environments. From the large draft breeds like the Shire, bred for heavy work, to the smaller ponies bred for different climates and tasks, domestication has diversified the sizes of horse breeds.