Last updated March 8, 2018 at 10:09 am
There are no more ‘wild’ horses in the world. They haven’t turned over a new leaf – they just don’t exist.
A herd of Przewalski’s horses on the prairie. Credit: iStock
It has long been assumed that Przewalski’s horses, native to the Eurasian steppes, are the last wild horse species on Earth, but new research shows they may be feral and not actually wild.
Instead, they are descended from the earliest-known instance of horse domestication by the Botai people of northern Kazakhstan some 5,500 years ago.
“There are a lot of equine biologists who have been studying Przewalskis and this will be a big shock to them,” says co-author Professor Sandra Olsen, curator-in-charge of the archaeology division of the Biodiversity Institute and Natural History Museum at the University of Kansas.
“They thought they were studying the last wild horses. It’s not a real loss of biodiversity, but in our minds, it is. We thought there was one last wild species, and we’re only just now aware that all wild horses went extinct.”
The Botai horses
That isn’t the only disappointing surprise. The research also shows that modern domesticated horses didn’t descend from the Botai horses.
“I was confident soon after we started excavating Botai sites in 1993 that we had found the earliest domesticated horses,” Olsen says. “We went about trying to prove it, but based on DNA results Botai horses didn’t give rise to today’s modern domesticated horses – they gave rise to the Przewalski’s horse.”
Many of the horse bones and teeth that Olsen excavated at two Botai sites in Kazakhstan, called Botai and Krasnyi Yar, were used in the latest phylogenetic analysis.
An international team sequenced the genomes of 20 horses from the Botai and 22 horses from across Eurasia then compared these ancient genomes with already published genomes of 18 ancient and 28 modern horses.
New facts about domesticated horses
Phylogenetic reconstruction confirmed that domestic horses do not form a single monophyletic group as expected if descending from Botai. Earliest herded horses were the ancestors of feral Przewalski’s horses but not of modern domesticates.
Olsen says the findings give rise to a new scientific quest: locating the real origins of today’s domesticated horses.
“It’s thought that modern-day domesticated horses came from Equus ferus, the extinct European wild horse. The problem is they were thought to have existed until the early 1900s. But, the remains of two individuals in St. Petersburg, Russia, are probably feral, too, or at least probably had some domesticated genes.”
The researchers believe Przewalski’s horses likely escaped from domestic Botai herds in eastern Kazakhstan or western Mongolia.
A wild appearance
“They started developing a semi-wild lifestyle like our mustangs, but they still have a wild appearance,” Olsen said. “This is partly why biologists assumed they were genuinely wild animals. They have an upright mane, something associated with wild equids. They also have a dun coat, like the ones you see in the Ice Age cave paintings in France and Spain made when horses were wild. Their size, however, is very similar to what you see at Botai and other sites.”
By 1969, Przewalski’s horses were declared extinct in the wild, and all living today originated from just 15 individuals captured around 1900.
Today, there are approximately 2,000 Przewalski’s horses, all descended from those captured horses, and they have been reintroduced on the Eurasian steppes.
The paper published in Science.
