(ORDO NEWS) — How horses left their ancient ancestral home and returned to it already domesticated. Evolution and history of the main helpers of man, starting with the first equids.
There are hardly any animals that have influenced the history of mankind more than they. Until the Industrial Revolution, horses replaced everything that today relates to transport, engineering and agricultural machinery, were tanks, racing cars, all-terrain vehicles and luxury supercars.
For thousands of years they pulled wagons and turned gates, carried, carried, delivered people and goods. We still measure power in horsepower. However, their history began with small, three or four-toed inhabitants of the rainforests of North America – the ancient ancestral home of horses, which they lost and found again.
Most modern ungulates rely on the third and fourth toes, which have evolved into thick horn supports for fast running. Camels and pigs, giraffes and hippos, cows, rams and goats – a large and diverse group of artiodactyls dominates vast expanses of land.
But the heyday of artiodactyls has long passed. Today, only 18 species from three families live on Earth: rhinos, tapirs and, in fact, horses (which also include donkeys and zebras). However, traces of hundreds of species of odd-toed ungulates, representatives of a dozen families that flourished in past eras, have been preserved in the fossil record.
Their lineage emerged about 65 million years ago, shortly after the Cretaceous-Paleogene extinction event that wiped out the flightless dinosaurs. And already 10 million years later, the oldest equids, such as gyracotherium, spread throughout the Northern Hemisphere.
They didn’t even look like horses. Hyracotheria were no larger than a cat, fed on soft fruits and foliage, and had four toes on their feet. Even their name is derived from the root hyrax, as hyraxes are called in Latin, small herbivorous mammals, for which the bones of hyracotherium were at first taken.
That was the warm epoch of the Paleocene-Eocene thermal maximum. Most of the land was covered with swampy broad-leaved forests, and under their dense crowns early equids prospered. In North America, orogippuses and eogippuses arose – the first direct ancestors of horses.
However, they were still far from horses. The small teeth of these animals could only cope with fairly soft food, the forelimbs ended in four, and the hind limbs ended in three large fingers with separate horn “hats” on each. However, years passed, the climate changed, it became colder, drier and more uncomfortable.
Around 49 million years ago, dense forests of trees everywhere began to give way to vast open plains. Endless forests have become archipelagos scattered among a sea of young grass. Odd-toed ungulates had to adapt to new conditions, to new food and never-before-seen predators.
The open space did not allow hiding from danger, leaving only one way – to become faster than the pursuer and run away from him. Therefore, the body size of the following horses increased, the bones and ligaments of the limbs became more massive and stronger, and the teeth became larger in order to grind tough vegetation.
The modern horse and several of its notable ancestors. Showing changes in body size, structure of limbs and molars
Mesogippus, who inhabited the grassy plains of North America about 38 million years ago, could already be mistaken for small horses.
Their spine became straighter, better adapted for running horizontally, the number and size of teeth increased, the height at the withers exceeded 60 cm, and the “forest” camouflage coloration almost disappeared. This trend continued: the myohippus, which separated from the mesohippus after several million years, became even more massive.
It was they who managed to survive the cold era of the Oligocene, which began about 33 million years ago, and 10 million years later, when grassy plains covered most of the continent, their descendants flourished here, perfectly adapted to life on the prairie.
The teeth of these animals were finally adapted to feeding on grass and could grow as they wore out when grinding abrasive vegetation; this turned out to be a really strong evolutionary advantage.
There were a few steps left before real horses: a large elongated head (like that of the merigippus) and, finally, a full-fledged one-toed (starting with the dinohippus).
Powerful legs and decent size helped them to escape from the large predators of the time – and single hooves provided reliable support for the body and a dangerous weapon in case you can’t hide.
Most likely, from dinohippus about 4 million years ago, when Australopithecus lived in Africa, the first representatives of the genus Equus, real horses, appeared in North America.
Dinohippus: reconstruction. These animals reached already 1.5 m at the withers
Equus simpicidens is one of the candidates for the “first true horses”. The remains of these animals are found throughout North America and show that they even had such a feature of horses as a “standing apparatus” (or “static apparatus”).
It includes a whole set of details in the structure of the skeleton, joints and ligaments, allowing the animal to stand upright, with little or no effort and without expending energy, transferring the load from one leg to the other.
In this position, the horses doze lightly, although from time to time they still need to sleep fully, lying down. Equus simpicidens were partly striped, like zebras, but their muzzle was shorter than that of a horse, like donkeys.
The “design” of these animals turned out to be extremely successful for the new era. Grassy plains spread everywhere, and horses settled with them. About 3 million years ago they moved to South America, and half a million years later they crossed the Bering Strait, reaching the great steppes of Eurasia and even the African savannas.
At the height of its history, the family included more than a dozen species found throughout the northern hemisphere. Their diversity declined sharply with the advent of the Pleistocene and the new Ice Age. And about 10 thousand years ago, horses completely died out in their “historical homeland”.
The reason for this is not exactly known, although the lion’s share of the megafauna in North America disappeared during that period. Perhaps a whole range of factors contributed to this, including climate warming, the spread of artiodactyl bison competitors, and, of course, the appearance on the continent of the first people who actively hunted all large animals for their meat and skins.
One way or another, but the remains of horses testify that then they were rapidly shrinking, their range was reduced to the most inaccessible areas, until the animals disappeared altogether. But their relatives, who emigrated to Eurasia in time, were destined for a different fate.
Thanks to the static apparatus, the horse keeps its massive body upright even in sleep, without much effort
Two cultures of the Eurasian Copper Age, the Yamnaya and the Botai, compete for supremacy in the domestication and domestication of horses. The Yamnaya culture, which existed in the Black Sea-Caspian steppes about 5000 years ago, is considered Proto-Indo-European.
They were nomads, pastoralists, and the first four-wheeled carts and the remains of horses are found in their burials. It was for a long time believed that it was these technological innovations that served as the basis for the rapid spread of the Indo-Europeans and their dominance throughout Europe.
However, the Botai, who are more related to the Ural peoples, could have domesticated the horse even earlier.
The Botai people lived in the steppes in the north of modern Kazakhstan, and judging by the archaeological finds, they actively hunted horses. Among other bones at their sites, horse teeth are also found, dating back to about 5500 years old and retaining characteristic traces of wear from the use of bits.
And in 2009, traces of horse milk were also found in one of the Botai vessels. However, not everything is so clear-cut here.
Already in 2018, French scientists conducted a genetic study comparing the DNA of ancient and modern horses, and found that all today’s horses come from animals that were bred by representatives of the Yamnaya culture.
More recently, this version was confirmed by the analysis of genomes isolated from ancient remains of horses. The Botai horses turned out to be closer to the semi-wild horses of Przewalski.
It is possible that horses were domesticated twice – as they settled North America twice. In the Botai culture, this was achieved a little earlier, but not as successfully as in the pit. Perhaps they borrowed the idea from their neighbors, but used for this local wild animals, genetically separate from the Botai.
It was they who became the progenitors of billions of horses, which have been bred since then for thousands of years. During this time, different peoples have created breeds adapted for different tasks, from hardy and unpretentious Mongolian horses to mighty percheron heavy trucks and horses as fast as the wind.
Wild horses in the steppes of Kakhastan
They ended up in their ancestral home, in North America, only in the 15th century, transported by European conquistadors and colonists. Here the horses met almost ideal conditions for themselves: free prairies, endless plains of lush grass – and soon some of them, having escaped from the paddocks, became wild again.
Already in the middle of the XVI century. there are reports of encounters with their herds in the vicinity of Mexico City. The story is closed – but not in vain. Thanks to man, horses have returned to their homeland already as one of the most successful and numerous species of mammals on Earth.
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