By SUE MILLER Advanced PATH International Instructor at High Horses Therapeutic Riding in Sharon, Vermont
I find it amazing that the horses you see today are a marvel of qualities that have adapted from descendants some 56-million years ago. What is astonishing to me is that the horse started off as something so far removed from the magnificent, majestic creature we know today. Horses have been called the noblest of creatures, and it’s easy to see why. Depending on which scientific accounts you believe, horses have been one of man’s best friends since anywhere from 4000 to 2000 B.C. They’ve taken us wherever we’ve asked them to including the fields of battle.
The domestic horse is an innovation – a never ending process of modification. From caterpillar to butterfly if you will. Watching horses is an invitation to fall in love with them, but also their long-term evolution.
Horses have been shaped and reshaped by ice ages, heat spikes, volcanic eruptions and tectonic forces. Horses can live in the most challenging of environments. Horses are resilient and malleable to their surroundings.
The first horses were more the size of a fox and had toes. The front legs of the dawn horse, called Eohippus found around the time of the Eocene stage had four-fingered toes on each fore-limb and three-fingered toes on each hind limb making them an odd toed ungulate. Today, horses have the largest eyes of any land mammal.
It’s hard to believe that Eohippus that stood not much more than 14 inches at the shoulder and was about 2 feet long could one day become the size of a Shire draft horse standing some 5 foot 6 inches at the shoulder and weighing close to a ton.
It is the large middle toe that was key to the horse’s survival. Over time horses placed more weight on the middle toes, until the other toes became useless. The vestigial toes are still present on horses today. They have become the chestnut and the ergot respectfully. The wart like areas on the inside of each of the horse’s legs and the small growth at the back of the pastern, above the hoof on each leg.
The five major changes that brought about modifications in the horse started with Eohippus at about 50 million years ago. Mesohippus had a larger body with longer limbs than its predecessor (Eohippus), it stood about 2 feet tall. Gradually it improved its body features suitable for running faster. The face of Mesohippus became longer and larger and teeth evolved suited to grind grass. Next came the Merychippus at about 10 million years ago.
Merychippus lived in the middle of Miocene to Pliocene age. This was thought to have been the first horse to have grazed. In this version of our equine friend their middle toe started to become a hoof and the side toes began to recede. This was followed by the Pliohippus at about 5 million years ago. Pliohippus became the first horse in the evolution with a single toe (hoof). With its long and slim limbs, Pliohippus was able to run faster than other creatures, had teeth similar to modern day horses and stood a little over three feet tall.
It was originally thought that no horses had roamed the American West before the Spaniards brought over horses in the 1400’s during their explorations, some of which escaped to roam free eventually becoming the American Mustang. However, fossil findings in Wyoming and the Rocky Mountain regions of the west dispel that notion. While the area was once covered by the sea, it now shares a plethora of history about the horse. Scientists think that much of equine evolution took place in North America. Horses became extinct around 10,000 years ago during another tectonic shift. Horses may have stepped onto a floating land mass and not arrived back to North America until humans began to explore the world and bring their steadfast companions with them.
It is interesting to note that along with the earliest known horse fossil, paleontologists found in the same time period the earliest known fossil of what is thought to have evolved into man. It seems that horses and humans have always shared a bond as evidenced in the cave drawings of France’s Chauvet Cave, dated to at least 32,000 years ago. Perhaps at some point in time past, horse & human were closer kin. Perhaps the visceral bond modern day humans feel toward their noble horses is a more tangible DNA particle found deeply in the bone. Perhaps time will tell.