ology logo
card
292

horse

OLogy Series
animal
card
292

horse

OLogy Series
animal

A tiny, two-feet tall horse-like animal scampers through a forest, nibbling on leaves. This isn't a fairy tale, but a look back in time at Hyracotherium,
an ancient member of the horse family. For millions of years, many horse species in all shapes
and sizes roamed Earth's forests and grasslands. But only a very few that were adapted to the grasslands survived. All domestic horses belong
to a single species, Equus caballus.

Evolution of the Horse
The first members of the horse family, Equidae, appeared in North America about 55 million years ago. These small, leaf-eating horses thrived in the warm, wet forests that covered much of the continent.

Then, about 35 mya, global temperatures dropped and dry grasslands replaced much of the forest. Horses with traits that enable them to adapt to this new habitat survived. For example, some early horses had 3 or 4 toes, each ending in a small hoof. But those with bigger, strong-er middle toes were better adapted to run and stand on the harder soil of the prairie. This eventually led to the near-disappearance of the side toes. The remaining middle toe became the larger, broadened hoof that sported the horse's weight.

Horses of the grasslands also had longer teeth than horses of the forests. Short, broad teeth may have been fine for chewing soft leaves. But they would wear down quickly grazing on tough grasses. All these adaptations helped the grass-eating horses of the prairie to survive, as their
leaf-eating relatives of the forest slowly disappeared.

A thoroughbred racehorse is the same species as a:

zebra

donkey

Shetland pony

Are you right?

Correct!

Over the years, humans have bred horses for desired qualities, such as speed for racehorses or size and strength for workhorses. Today, there are over 200 horse breeds, all belonging to one species,
Equus caballus.

Humans have used horses for warfare, work, trade, and sports. For example, the Pony Express was launched in 1860 to:

carry settlers to the American West

entertain settlers in the American West

carry mail across the American West

Are you right?

Correct!

Horsemen raced day and night from Missouri to California, passing the mailbag to a new rider every 10 miles. Horse relays date back nearly 4,000 years and were used widely in ancient Babylonia, Persia, China, Mongolia, Egypt, Italy and France.

Scientists think horses were first domesticated around 6,000 years ago. What traits make horses good candidates for domestication?

horses are social creatures

horses are naturally submissive to a leader

both of these

Are you right?

Correct!

These are just two of the many traits that make horses natural candidates for domestication. Their behavior makes them easier to tame.

Sandra Olsen, zooarcheology

To my mind, horses have made a bigger impact on human society than any other animal. They provided the first means of fast travel, helped spread languages around the world, and helped people do work.

Sandra Olsen, zooarcheology

Today's horses represent just one tiny twig on an immense family tree that spans millions of years. All the other branches of the horse family, known as Equidae, are now extinct.

There are no wild horses living today.

Fact
or
Fiction
?

Fiction

The Przewalski horse of Mongolia is the only truly "wild" horse living today. "Feral" horses are descended from domestic ancestors.

Scientific name: Equus caballus
Number of breeds: over 200
Examples of breeds: Arabian, quarterhorse, thoroughbred, Shetland pony, Clydesdale
First domesticated: About 6,000 years ago
Diet: grasses
Gender names: mare (female); stallion (male)
Cool fact: Horseback riding first became common in Afghanistan and Iran, around 4,000 to 3,500 years ago.

Image credits: courtesy of AMNH; Sandra Olsen: courtesy of Sandra Olsen; Sandra Olsen: courtesy of Sandra Olsen.