In the ancestors of horses, extra toes played an important role in helping the legs withstand a lot of stress while running, but then all but the middle toe became simply superfluous.

On each leg modern horses only one finger - but what a! (Photo: virgonira / Depositphotos .)

The very first ancestors of modern horses lived about 50 million years ago. These were small animals, the size of a dog, they ran through the forests and on their feet they had four and three fingers (four on the back, three on the front).

Then climate change happened, and the next varieties of horses came out into open spaces. Then they began to increase in size, began to run faster, in their anatomy there were major changes- so, among other things, all fingers except the middle one gradually disappeared, and hooves appeared - horny formations, the equivalent of our nail, completely covering the finger.

The evolution of horses is well understood thanks to the many bones left over from a wide variety of ancient species. In the open space of the steppes, savannahs and meadows, horses needed to move quickly, and those individuals that were larger gained an advantage, and the disappearance of the lateral toes coincides well with the increase in body weight and lengthening of the legs. And yet - why only one finger?

Horse toe structure, i.e., the area of ​​the putovoy, coronoid and hoof-shaped bones, is very difficult. There are peculiarities in the location and shape of the bones, a large number of ligaments running in different directions, powerful tendon endings of the muscles, a highly developed elastic crumb that softens shocks and tremors when the limbs are leaning on the ground, and a strong, insensitive horn capsule that protects the tissues enclosed in it. from damage.

Trimming and shoeing of the hoof affect, to one degree or another, the condition and function of the entire lower limb. In diseases of the hoof, pathological processes often spread upward, to neighboring areas of the finger. Therefore, in order to substantiate the rules of shoeing and for orientation in hoof diseases, knowledge is required the anatomical structure of the horse's toe in general and in particular the topographic relationship of its individual parts.

Ancestors horses were five-toed plantigrade animals. They leaned on the ground with five outstretched rays of the paw, i.e., the hand and foot participated in the support.

In the process historical development there was a gradual transformation of the paw and raising it above the ground; in parallel, the rays of the paw, not involved in resting on the ground, were reduced. Thus, in the horse, the metacarpus (tarsus) and the first two phalanges of the third finger turned out to be elevated above the ground (the horse rests on the ground only with the last phalanx of the third finger) and became part of the main column of the free limb supporting the body. The resulting elongation of the limb contributed to the capture of more space during movement, hence the speed and ease of running.

Simultaneously with the skeleton of the paw, other organs of this area were rebuilt. The lower part of the horse's limbs consists of a bone skeleton, ligaments and tendons, dressed in a skin with a strongly keratinized epidermis at the distal end. The short muscles of the fingers found in other animals are absent in the horse.

The skin of the finger also underwent changes. A special adaptation at the distal end of the finger in the form of elastic crumbs for stepping and touch, quite clearly expressed in predatory animals (finger crumbs), in the horse lost its tactile functions to a large extent and took the form of a wedge forked by a longitudinal groove, which acts as an elastic body at various gaits. .

For horses characteristic is the presence of another formation that is absent in other animals - flank cartilage; they cover the crumbs from the sides and soften the impact of the hoof on the ground.

In predatory animals, a hard, keratinized dermal tip, curved in a hook, forms a case of the last phalanx of the finger and is adapted for climbing and tearing food. At horses it acquired the shape of a truncated cone, turned base down, with a clearly defined plantar surface in the form of an open circle, creating a fairly perfect support for the limb.

Changes in the histological structure of the skin are especially pronounced in the area of ​​the third phalanx and led mainly to an increase in the strength and elasticity of the skin tip.

When the question arises of how many toes a horse has, what comes to mind? Horse's toes? Well, maybe one ... However, in fact, this is not entirely true. Although, even if you have your own horse, it still won’t work to count more than one finger. Here the matter is much more complicated. Although scientists themselves are still arguing about this. However, this is definitely not one finger with a hoof.

What scientists say

According to research published in the journal Royal Society Open Science, the assumption that a horse's hoof consists of one toe is false. Scientists have proven that these animals still have missing fingers, but they have merged into a hoof. This was due to the need to adapt, which is subject to all living things over time on our planet. The reason for this, first of all, is the change in climatic conditions.

The ancestors of horses had five fingers on one limb. They have survived to this day, as evidenced by the skeleton of the animal. Five fingers merging into one hoof can be felt through soft tissues animal. However, over time, they are somewhat deformed and are no longer complete.

Researching

The toes of horses have not been lost in the course of evolution. They just changed their shape. This has been proven by studies. The middle, largest, finger forms the hoof, two more are located slightly above the hoof in a rudimentary, that is, underdeveloped state, as well as on the upper edges of the metacarpal bone. However, it is impossible to see these four fingers with the naked eye.

When scientists cut open the hoof, they saw separately two and three more sections with phalanges, implying five fingers that are hidden. It was also possible to find that there are much more nerves and arteries than previously thought. And the vascular network is characteristic precisely for the presence of five fingers.

The study of ancestors

Bone structures that corresponded to such a number of fingers were also found in the studied remains. One copy lived 35 million years ago, the second - 5 million years.

Mesogippus from the horse family, like dinohippus, did not have hooves. They relied on three fingers, the middle of which had big size. At the same time, they were quite capable of moving at a trot, like modern horses. Their ancestors were only the size of a fox.

The first ancestors of horses appeared in North America. Previously, the Bering Strait did not exist, and in its place there was a land bridge. It was on it that the ancient horses moved to Europe. Over time, individuals developed, new species became larger. The toes were replaced with hooves to adapt to the new conditions of the changing climate.

Eohippus were even more ancient ancestors of horses. They lived about 50 million years ago. Ancient animals had spotted coloration to blend in with the terrain while hiding from predators. In size, they were no larger than the most ordinary domestic cat, but outwardly they still looked like a horse. The animal could run very fast thanks to its long legs. Of course, he didn’t have any hooves, but he had widely spaced fingers. There were still five of them on each leg, although the fifth was located higher than the others and was much shorter.

Thus, it can be traced that with the development of each subsequent equine species, their limbs changed, the fingers became smaller, some remained in an underdeveloped state. And the size of individuals became more and more.

Most scientists are confident in the existence of one ancestor of mammals, which was five-fingered, and many animals familiar to us, including horses, have already descended from it.

Animal features

These animals have very large eyes and excellent vision. However, there are some problems with color recognition of browns and grays.

Their hearing is also excellent. To listen to sounds from all directions, horses can rotate their ears.

Their sense of smell is no better than that of other animals, but it is much higher than that of a human.

The first ancestors of horses arose on our earth ten million years after the extinction of the dinosaurs.

Underdeveloped four fingers, represented by residual bones, often cause injuries to the fibula.

The milk of these animals contains little fat and protein, but a lot of lactose and has a useful vitamin composition. Koumiss, a fermented milk drink, is of particular benefit.

These representatives of the animal world can live up to 25 years or more.

In the ancestors of horses, extra toes played an important role in helping the legs withstand a lot of stress while running, but then all but the middle toe became simply superfluous.

The very first ancestors of modern horses lived about 50 million years ago. These were small animals, the size of a dog, they ran through the forests and on their feet they had four and three fingers (four on the back, three on the front).

Then climate change happened, and the next varieties of horses came out into open spaces. Then they began to increase in size, began to run faster, serious changes took place in their anatomy - so, among other things, all the fingers except the middle one gradually disappeared, and hooves appeared - horny formations, the equivalent of our nail, completely covering the finger.

The evolution of horses is well understood thanks to the many bones left over from a wide variety of ancient species. In the open space of the steppes, savannahs and meadows, horses needed to move quickly, and those individuals that were larger gained an advantage, and the disappearance of the lateral toes coincides well with the increase in body weight and lengthening of the legs. And yet - why only one finger?

In an article in Proceedings of the Royal Society B Harvard researchers are analyzing the history of horses in terms of biomechanics. Stephanie Pierce ( Stephanie Pierce) and her colleagues used computed tomography to evaluate how the leg bones of thirteen extinct species coped with stress.

As a result, the authors of the work came to the conclusion that the lateral fingers played a rather significant role in early horses. For example, Parahippus, which lived just at the time when forests were decreasing and vast plains were appearing, had three toes on each foot, although they were merged together and protected by one hoof (although not as developed as those of the following horses) . Parahippus was already quite large, about a meter at the withers, and two lateral fingers helped to distribute the load so as to prevent injuries - cracks, bone fractures, etc.

But the horses continued to grow, their mass increased, their legs lengthened, they ran faster, and the load on the fingers became stronger. The growing load was primarily felt by the middle finger, which gradually became larger. In the end, horses appeared that had a very overgrown, massive middle finger, and the side fingers, at best, remained either in the form of rudiments or completely disappeared. When researchers tried to attach normal, well-developed additional toes to the legs of such “one-fingered” horses, it turned out that from a biomechanical point of view, they did not give almost any advantage - the middle finger itself learned to cope with the entire load.

That is, it cannot be said that the fate of the lateral fingers in horses was predetermined from the very beginning - for the time being, they worked in the same way as the middle finger, taking on part of the weight and protecting the bones of the limbs from injury. But the horses were getting bigger and faster, and at some point it became clear that the middle finger became the main one, and the very small benefit that the side fingers can bring no longer justifies the resources that need to be spent on them.