The horse’s evolution

If you go back in time, millions of years ago, you will not see the horse as we know it today. The horse has undergone many changes in those millions of years to become the modern horse we now know. It is often said that horses are typical examples of evolution, but what exactly does this mean? 

 

Evolution is described as a gradual process in which a species (plant or animal) changes into a different, usually more complex or better adapted, form. These changes are linked to the environment the species lives in. An animal that needs to survive in the desert will adapt differently than an animal that needs to survive in the Artic. The term ‘survival of the fittest’ is really all about ‘survival of the best adapted to their environment’. Because even if you take the strongest Polar Bear in the Artic, if you place it in the Sahara, it will probably not survive. This might be an extreme example, but as soon as an animal’s environment changes, the animal needs to change along with it, or risk rapid extinction. 

 

The first of the Equidae was a good example of these changes in the environment. They lived about 55 million years ago and were a small creature, about the size of a dog (50cm), with four toes on each foot. Probably it could walk, trot and canter like a horse, but it lived in the woods and ate the leaves of the trees and other plants. 

In the period from 55 million to 39 million years ago, drastic changes to the climate took place. There was less and less rain, and the woods perished to make way for grassy steppes. The forming of this grassland forced the horse’s ancestors to evolve both physically and psychologically. To be able to live off the grass, the head and nose became longer, and the eyes moved more towards the side of the head allowing for a broad field of vision while grazing. The teeth also evolved, adapting to grow continually to keep up with the wear from the grass. Internally, the caecum became bigger to allow for the digestion of grass. The horse migrated from sheltered, wooded areas to the wide open plains. There was no more hiding, so fleeing became the horse’s main defence mechanism. The horse in its entirety grew bigger. To be able to make a quick escape, the legs became taller and the four toes conjoined to grow into one single hoof. The hooves also became tougher and harder to be able to cope with the various sorts of terrain. The chest grew deeper, allowing more room for a bigger heart and bigger lungs. And to become more aware of their surroundings and potential predators, the sense sharpened. 

 

But on the inside as well, clear differences began to emerge, depending on the environment in which the horse lived. Just think of all the different breeds we know today. Many of these breeds have developed certain (external) characteristics for good reason, even long before man began to get involved in horse breeding. Horses living in cold, wet and marshy climates have a small, furry body with short legs and tiny ears. This evolved precisely in this way because spherical surfaces lose less heat to their environment than other shapes. And heat conservation is critically important in these cold climates. So the more spherical your body shape, the better you are able to keep yourself warm. A fine example of a breed with all these characteristics is the Shetland pony. On the other end of the spectrum, a horse that needs to survive in a hot, dry climate has other needs. Keeping warm is not the problem, but keeping cool. These breeds therefore developed a narrower, thin body with long legs and a finer coat, to better expel their heat. Just think of the Arabian horses. 

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