Where did the horse come from? Evolution…

Leave a Comment / By Sian Sync / 4 December 2022

A little bit about the evolution of the horse

Did you know that the horse has one of the best evolutionary lineages documented in palaeontology? (Paleontology is the study of ancient life, from dinosaurs to prehistoric plants, mammals, fish, insects, fungi, and even microbes [1]).

*Hyracotherium, or Eohippus, Encyclopædia Britannica*

The first ‘horse’ known as the Hyracotherium or Eohippus (conceptualised image and fossil image above) existed around 56 million years ago and wouldn’t be recognisable as the present-day horse. As browser feeders they would mainly have fed on leaves, fruits, shoots and shrubs. They would not have grazed on grass and other low-lying vegetation like the modern horse.

Figure: The Hyracotherium was around 4.2 – 5 hands tall and had padded feet with four hooves on the front and three on the hind.

The Mesohippus was the next ancestor of the horse, they were alive 33.9 million years ago. They had a lot more in common with the modern horse than the Hyracotherium, with longer slender legs, the average height was around 6 hands high, the snout had developed into more of a muzzle and they remained browsing animals. The brain size increased and the fourth toe was made redundant, so all feet had a footpad and three toes.

*The ancestral horse Miohippus, in an artist’s conception, Encyclopædia Britannica.*

*The ancestral horse Merychippus, in an artist’s conception, Encyclopædia Britannica.*

The next key stage of evolution was during the Miocene around 23 million years ago. The Merychippus properly looked like the modern pony, they had become grazing animals and their teeth had adjusted as such. They were approximately 10 hands high and the lower leg bones had fused, like the modern horse and was an adaptation for a quick getaway. The foot no longer had the footpad, but it still had three toes, although the two outer toes had become smaller so the central toe bore the majority of the animal’s weight.

Domestication is likely to have taken place around 6,000 years ago in modern-day Ukraine and Kazakhstan. It is thought that humans spread domestic horses from Western Europe and that the domestic populations were often bred with wild populations which increased the diversity of the genetics. Unlike a lot of other species there was not just a single domestication event but multiple over time.

*Origin of horse domestication, Encyclopædia Britannica.*

*5 Detail of cave painting © Bridgeman Images.*

Modern day horse

There are over 200 breeds [3] of modern day horse from the Abyssinian to the Zhemaichu. The majority of horses in the world today are used for sports (racing, dressage, show jumping etc) or as a hobby. The human/horse interaction has changed dramatically since the invention of the motor vehicle in the late 1800’s. The 19th-century population was reliant on the horse in so many ways, they were used for transportation, farm work, mail delivery, war, hunting and sport.

Summary – how has the horse changed?

Over millions of years, the ‘horse’ evolved gradually from a four-toed to one-toed animal, they grew in size, reduction in the number of toes, lost the footpads, lengthened the legs, fused the independent bones of the lower legs, elongated the muzzle, increased the size and complexity of the brain, and developed crested, high-crowned teeth suited to grazing.

So it is important to note and think that the horse is an ancient animal with strong instincts dating back millions of years, when the world was a much different place. Yes they have long since been domesticated, but they are still prey animals with natural instincts.