No need for The Rolling Stones to worry, there are no wild, wild horses left that could drag them away, according to the results of a new DNA study published on Thursday.

Researchers said the Przewalski's horse, which inhabits the grasslands of Mongolia, was thought to be the last remaining wild horse. But instead, they are a feral descendant of the earliest-known domesticated horses, according to the report in the journal Science.

"This was a big surprise," said the study's co-author, Sandra Olsen, from the University of Kansas, before admitting that the lack of remaining wild horses on earth was "the sad part."

Scientists studied the genomes of dozens of ancient and modern horses, before concluding that the Przewalski, which was saved from extinction in the 20th century, after being descended from horses domesticated in northern Kazakhstan some 5,500 years ago. Around 2,000 Przewalski's still exist.

The research showed that the Botai culture offers the earliest-known evidence for horse domestication, but that their animals were not the ancestors of modern domesticated breeds.

"The world lost truly wild horses perhaps hundreds, if not thousands of years ago, but we are only just now learning this fact, with the results of this research," said Olsen.

Read more: Preserving the world’s last wild horses

Another of the report's authors, archaeologist Alan Outram from Britain's University of Exeter, said the Przewalski's horse, named after a Russian who described them in the 19th century, is relatively small and stocky.

Some horses from the domesticated Botai herds escaped and became the feral Przewalski's horse, the researchers said. 

The study was conducted at two sites in northern Kazakhstan, where scientists found the earliest proof of horse domestication, going back more than 5,000 years.

Based on teeth and bones unearthed during archaeological digs, researchers sequenced the genomes of 20 horses from the Botai, along with 22 horses from across Eurasia. They then compared these ancient horse genomes with already published genomes of 18 ancient and 28 modern horses.

Przewalski's horses roamed Central Asia, Europe and China in prehistoric times. They are considered an endangered species by the International Union for Conservation of Nature and relied on a number of breed programs since the 1960s to boost their numbers.

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Scientists said they hope the research proves that all modern domesticated horses descend from animals first tamed in Botai.

"This means that we must continue the search for the true ancestors of modern breeds by gathering samples from places like Ukraine, western Russia, Hungary, Poland and that region," Olsen said.

mm/sms (AFP, Reuters)