One of the most famous and most studied of paleontological evidence of evolution is the phylogenetic series of modern unicorn ungulates. Multiple paleontological findings and identified transitional forms create the scientific evidence base of this series. Described by the Russian biologist Vladimir Onufrievich Kovalevsky back in 1873, the phylogenetic series of the horse remains today an “icon” of evolutionary paleontology.
Evolution through the Ages
In evolution, phylogenetic series are successive transitional forms that have led to the formation of modern species. By the number of links, the series can be complete or partial, however, the presence of successive transitional forms is a prerequisite for their description.
The phylogenetic row of a horse is classified as evidence of evolution precisely because of the presence of such successive forms that replace each other. The multiplicity of paleontological finds gives it a high degree of reliability.
Examples of phylogenetic series
A number of horses are not the only among the described examples. The phylogenetic series of whales and birds is well studied and has a high degree of reliability. And the controversial in scientific circles and the most used for various populist insinuations is the phylogenetic series of modern chimpanzees and humans. Disputes over the missing links here do not subside in the scientific community. But no matter how many points of view, the importance of phylogenetic series as evidence of the evolutionary adaptability of organisms to changing environmental conditions remains indisputable.
The link between horse evolution and the environment
Numerous studies by paleontologists have confirmed the theory of O.V. Kovalevsky about the close relationship of changes in the skeleton of the ancestors of horses with environmental changes. The changing climate led to a decrease in forests, and the ancestors of modern one-toed ungulates adapted to living conditions in the steppes. The need for quick movement provoked modifications in the structure and number of fingers on the limbs, a change in the skeleton and teeth.
The first link in the chain
In the early Eocene, more than 65 million years ago, the first great ancestor of the modern horse lived. This “low horse” or Eohippus, which was the size of a dog (up to 30 cm), rested on the entire foot of the limb, on which there were four (front) and three (rear) fingers with little hooves. Eogippus ate shoots and leaves and had tuberous teeth. Bulan color and sparse hair on a moving tail - this is the distant ancestor of horses and zebras on Earth.
Intermediate links
About 25 million years ago, the climate on the planet changed, and the steppe expanses began to replace forests. In the Miocene (20 million years ago), mesogippus and parahippus, already more similar to modern horses, appear. And the first herbivorous ancestor in the phylogenetic row of the horse is considered to be the merikippus and pliogippus, which enter the arena of life 2 million years ago. Hipparion - the last three-fingered link
This ancestor lived in the Miocene and Pliocene on the plains of North America, Asia and Africa. This three-toed horse, resembling a gazelle, had no hooves yet, but could run fast, ate grass and it was she who occupied vast territories.
One-Toed Horse - Plyogippus
These one-fingered representatives appear 5 million years ago in the same territories as the hipparions. Environmental conditions change - they become even drier, and the steppes grow significantly. This is where one-toedness turned out to be a more important sign for survival. These horses were up to 1.2 meters high at the withers, had 19 pairs of ribs and strong leg muscles. Their teeth acquire long crowns and folds of enamel with a developed cement layer.
The horse we know
The modern horse as the final stage of the phylogenetic series appeared at the end of the Neogene, and at the end of the last ice age (about 10 thousand years ago) millions of wild horses already grazed in Europe and Asia. Although the efforts of primitive hunters and the reduction of pasture made a wild horse a rarity already 4 thousand years ago. But her two subspecies - the tarpan in Russia and Przhevalsky's horse in Mongolia - managed to hold out much longer than everyone else.
Wild horses
Today, these wild horses are almost gone. The Russian tarpan is considered an extinct species, and Przhevalsky’s horse does not occur under natural conditions. Herds of horses that graze freely are wild, domesticated forms. Such horses, although quickly returning to wild life, are still different from truly wild horses.
They have long manes and tails, and they are of different sizes. The exceptionally mulled Przewalski’s horses and mousy tarpans have, as it were, trimmed bangs, manes and tails.
In Central and North America, wild horses were completely exterminated by the Indians and appeared there only after the arrival of Europeans in the 15th century. The wild descendants of the horses of the conquistadors gave rise to numerous herds of mustangs, the number of which is now controlled by shooting.
In addition to the mustangs in North America, there are two types of wild island ponies - on the islands of Assatig and Sable. The semi-wild herds of horses of the Camargue are found in the south of France. In the mountains and swamps of Britain, you can also find some wild ponies.
Our beloved horses
The man tamed the horse and brought more than 300 of its breeds. From heavyweights to miniature ponies and handsome race breeds. In Russia, about 50 horse breeds are bred. The most famous of them is the Oryol Trotter. Exceptionally white suit, excellent lynx and agility - these qualities were so appreciated by Count Orlov, who is considered the founder of this breed.