The evolution of the horse occurred over a period of 50 million years, transforming the small, dog-sized, forest-dwelling Eohippus into the modern horse. Paleozoologists have been able to piece together a more complete outline of the modern horse's evolutionary lineage than that of any other animal.
The horse belongs to the order Perissodactyla (odd-toed ungulates), the members of which all share hooved feet and an odd number of toes on each foot, as well as mobile upper lips and a similar tooth structure. This means that horses share a common ancestry with tapirs and rhinoceroses. The perissodactyls arose in the late Paleocene, less than 10 million years after the Cretaceous–Paleogene extinction event. This group of animals appears to have been originally specialized for life in tropical forests, but whereas tapirs and, to some extent, rhinoceroses, retained their jungle specializations, modern horses are adapted to life on drier land, in the much-harsher climatic conditions of the steppes. Other species of Equus are adapted to a variety of intermediate conditions.
The early ancestors of the modern horse walked on several spread-out toes, an accommodation to life spent walking on the soft, moist grounds of primeval forests. As grass species began to appear and flourish, the equids' diets shifted from foliage to grasses, leading to larger and more durable teeth. At the same time, as the steppes began to appear, the horse's predecessors needed to be capable of greater speeds to outrun predators. This was attained through the lengthening of limbs and the lifting of some toes from the ground in such a way that the weight of the body was gradually placed on one of the longest toes, the third.
Indigenous modern horses died out in the New World at the end of the Pleistocene, about 12,000 years ago, and thus were absent until the Spanish brought domestic horses from Europe, beginning in 1493. Escaped horses quickly established large wild herds. In the 1760s, the early naturalist Buffon suggested this was an indication of inferiority of the New World fauna, but later reconsidered this idea. William Clark's 1807 expedition to Big Bone Lick found "leg and foot bones of the Horses", which were included with other fossils sent to Thomas Jefferson and evaluated by the anatomist Caspar Wistar, but neither commented on the significance of this find.
The first equid fossil was found in the gypsum quarries in Montmartre, Paris in the 1820s. The tooth was sent to the Paris Conservatory, where it was identified by Georges Cuvier, who identified it as a browsing equine related to the tapir. His sketch of the entire animal matched later skeletons found at the site.Read more ...
Scientists recover ancient DNA from a bizarre Ice Age mammal that stumped Darwin and discover it is related to horses and rhinos - 180 years after it was first found by the naturalist Daily Mail - June 27, 2017
For the first time, scientists have recovered ancient DNA from one of the more puzzling species to have lived during the last Ice Age, a creature named Macrauchenia patachonica. The DNA allows researchers to finally map the mammal's relationships and place it within a group that includes horses, rhinos, and tapirs. One of the last 'South American native ungulates,' or SANUs, this animal likely weighed as much as 500 kilograms (1,100lbs) and had baffled biologists, including its discoverer Charles Darwin, for more than 180 years.
Ancient horse-like fetus discovered in Germany BBC - October 8, 2015
A fossilized fetus belonging to an early relative of the horse has been described by scientists. The unborn foal was identified among the remains of its mother - a 48-million-year-old horse-like animal found in Germany's Messel pit in 2000. The mare probably fell into a lake shortly before birth - which led to outstanding preservation of the soft tissue from the fetus.
Reshaping the horse through millennia: Sequencing reveals genes selected by humans in domestication Science Daily - December 15, 2014
Whole genome sequencing of modern and ancient horses unveils the genes that have been selected by humans in the process of domestication through the last 5,500 years, but also reveals the cost of this domestication. An international research group reports that a significant part of the genetic variation in modern domesticated horses could be attributed to interbreeding with the descendants of a now extinct population of wild horses. This population was distinct from the only surviving wild horse population.
Unborn Foal Discovered In 47-Million-Year-Old Horse Fossil Huffington Post - November 10, 2014
When paleontologists discovered the 47-million-year fossil of a prehistoric horse in 2000, they didn't yet realize a rare treasure was hidden inside. Now, high-resolution X-ray technology has revealed the Eurohippus messelensis mare was pregnant. In fact, the size of the unborn foal discovered in the fossil indicates that it was close to term, and its position in the mother's uterus indicates the mother and foal did not die during labor. During the analysis, the researchers detected the remains of the ancient mare's uterine wall and the broad ligament, which connects the uterus to the backbone. The researchers also identified the horse's placenta, making it the second known example of a fossil with this structure preserved. These structures indicate that reproduction in the tiny ancient horse, which was roughly the size of a terrier, was similar to reproduction in horses today, according to the researchers.
Ancient horse bone yields oldest DNA sequence BBC - June 27, 2013
A fragment of a fossilized bone thought to be more than 700,000 years old has yielded the genome of an ancient relative of modern-day horses. This predates all previous ancient DNA sequences by more than 500,000 years. A remnant of the long bone of an ancient horse was recovered from the Thistle Creek site, located in the west-central Yukon Territory of Canada. Paleontologists estimated that the horse had last roamed the region sometime between a half to three-quarters of a million years ago. An initial analysis of the bone showed that despite previous periods of thawing during inter-glacial warm periods, it still harbored biological materials - connective tissue and blood-clotting proteins - that are normally absent from this type of ancient material.
Ancient horse bones tell story behind the Tibetan plateau NBC - April 24, 2012
A newly discovered skeleton from an ancient three-toed horse not only provides information about ancient Tibetan wildlife, but it also sheds light on the habitat and elevation of Tibet nearly 5 million years ago. This area of the world, called the Tibetan plateau, is the youngest and highest plateau on Earth, its average elevation exceeding 14,800 feet (4,500 meters), but researchers don't know exactly when this happened. Some researchers think that 5 million years ago, the plateau was once much higher than it is today, but others think it was much lower.
Ancient horses' spotted history reflected in cave art BBC - November 7, 2011
Scientists have found evidence that leopard-spotted horses roamed Europe 25,000 years ago alongside humans. Until now, studies had only recovered the DNA of black and brown colored coats from fossil specimens. The result suggests that the dappled horses depicted in European cave art were inspired by real life, and are less symbolic than previously thought.
Saudi find shows horses used 9,000 years ago PhysOrg - August 25, 2011
Saudi Arabia has found traces of a civilization that was domesticating horses about 9,000 years ago, 4,000 years earlier than previously thought, the kingdom said. "This discovery shows that horses were domesticated in the Arabian Peninsula for the first time more than 9,000 years ago, whereas previous studies estimated the domestication of horses in Central Asia dating back 5,000 years. The remains of the civilization were found close to Abha, in southwestern Asir province, an area known to antiquity as Arabia Felix. The civilization, given the name al-Maqari, used methods of embalming that are totally different to known processes. Among the remains found at the site are statues of animals such as goats, dogs, hawks, and a metre-tall bust of a horse. An international team of archaeologists published an article in January that suggested human beings could have been present on the Arabian Peninsula about 125,000 years ago.
Discovery at al-Maqar
Horses: Finding the First Horse Whisperers Live Science - November 27, 2009
Paleolithic hunters in Europe and Asia began exploiting horses for meat thousands of years ago when the last continental glaciers disappeared, yet the origin of horse domestication long has eluded archaeologists - for some captivating reasons. One of the biggest reasons is that for many centuries, horse skeletons did not significantly differ in size or physical structure from those of their wild ancestors, making early taming and use of the animal more difficult to identify.
Artist's impression of the ancient Clovis people
May 3, 2001 - Calgary News
Canadian scientists have uncovered what they say is the first unequivocal evidence that prehistoric North Americans hunted and butchered now-extinct horses. University of Calgary scientists discovered the pony-sized horses while excavating the dry bed of the St. Mary Reservoir in southern Alberta. The site is one of the richest archeological fields in North America. It is now protected under the Alberta Historical Resources Act. The discovery adds weight to the theory that overhunting played a major role in the extinction of North American horses about 10,000 years ago.
The University of Calgary team also found footprints of woolly mammoths and a now-extinct North American camel. The site provides "an astonishingly detailed picture of what the New World was like during the late Pleistocene Era," said University of Calgary archeologist Dr. Brian Kooyman.
The link between the Equus conversidens horse and human hunters was established after team members unearthed a skeleton of an extinct horse at the site. Several of the horse's vertebrae were smashed and it had what appeared to be butcher marks on a number of its bones.
Some 500 metres from the skeleton, they also discovered several Clovis spearheads. Protein residue testing and examination of the spearheads confirmed the artifacts had been used to hunt the extinct horse. Although archaeologists have long suspected the "big game" hunters of the Clovis period (9000-10000 BC) of hunting the horses, there has been little evidence to support this theory until now. Spanish Conquistadors reintroduced horses to the Americas during the 16th century.
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