It's an iconic scene in Western cinema: King Arthur and his band of knights prancing along to the clip-clop of coconuts. Equestrian viewers of Monty Python and the Holy Grail may have noticed that this coconut-banging follows a pattern indicative of a gallop—despite the fact that our heroes actually shuffle along at the speed of a trot, at best. Had Arthur and co. been astride actual horses, however, they probably would have preferred to amble.

Ambling—forms of which include racking, foxtrotting, Icelandic tölting and other intricate variations mostly known to equestrians—is a brisk four-beat gait faster than a walk but slower than a gallop. This more specialized gait makes for a far more comfortable and smoother ride. Unfortunately, even if they had horses, ambling would have been impossible for our heroes—because at that time, your average horse couldn’t amble.

The gaitedness of horses is controlled by a genetic mutation in a gene aptly called the “gaitkeeper,” which is present in many breeds around the world. Some horses with this mutated gene will amble naturally, while others require training, but if a horse doesn’t have the DMRT3, nothing in the world will make it amble. Today, gaitedness comes pre-programmed into the DNA of certain horse breeds. Yet until recently, researchers didn’t know how and when the gaitkeeper appeared.

In 2012, scientists found that gaitedness was associated with a mutation in the gene known as DMRT3, which is expressed in spinal cord neurons and is integral to the development of coordinated limb movements. Two years later, some of those same researchers tested DNA from 141 horse breeds to discover that just under half of them possessed the “gaitkeeper” gene. The gene now appears to be present globally, from the Hokkaido Horses of Japan to the Boer Ponies of South Africa to the Tennessee Walking Horse, the researchers found.

New research pinpoints when the gaitkeeper gene spread to all corners of the earth, and theorizes exactly how the leap happened. It turns out the gaitkeeper is a relatively recent addition to the equine genome, reports a study published today in Current Biology. In the study, researchers extracted DNA from the remains of 90 ancient horses from archaeological collections dating back as far as 6,000 BC to find that the gaitkeeper gene appeared around 850 or 900 AD. The earliest known copies of this gene come from two horses who lived in what is present day York, England.

So how did these smooth-running horses get from Ye Olde England to the rest of the world? Researchers have a theory. When they looked at the genome of 13 Icelandic horses from the 9th to the 11th century, they found that 10 of them possessed the gaitkeeper gene. Horses can swim, but not as far as England to Iceland, which means somebody had to have taken them on a boat. And who do we know to have been doing a lot of nautical looting and pillaging in this area at this time? That’s right: the Vikings.

Vikings had an on-again-off-again “trading” relationship with the British Isles for several centuries. At some point during that time, they came to appreciate that some of the Brits—technically Northumbrians at this point—had horses that made their home-grown steeds look like rough-riding jalopies. (No Scandinavian horses from this time period show the gaitkeeper gene.) So, by trade, murder or otherwise, they obtained a handful of these animals, and took them with them when they ventured out to Iceland.

Until the Vikings settled it, Iceland was an island devoid of horses. That meant that the gaitkeeping gene would have been bolstered and preserved within the new horse population, either from isolation or selective breeding. When the Vikings left Iceland, they took this new breed of ambling horse with them. Before long, the theory goes, horses around the globe could amble—making life a lot easier for riders in an era before cars.

This narrative is supported by the fact that Iceland had basically no roads at this time, says Michi Hofreiter, an evolutionary geneticist at the University of Potsdam in Germany and coauthor of the paper. “Anybody who has spent a day on horseback would for sure selectively breed for smoother gaits whenever possible,” Hofreiter says. But it’s still just one explanation. “We don't know if ambling horses were spread from Iceland or England or from both countries into the world,” admits Arne Ludwig, a geneticist at the Leibniz Institute for Zoo and Wildlife Research in Berlin and another author.

Back to the important part. Ludwig confirm that, indeed, it would be highly unlikely for King Arthur to have had a horse capable of ambling, given that gaitedness doesn’t appear in England until around 850 AD, and King Arthur was thought to have died in the early 6th century. And just think: If riding a horse without gaitedness is uncomfortable while wearing blue jeans and a using a modern saddle, we can only imagine what jangly hell the Knights of the Round Table must have endured in full armor.

No wonder Arthur and his trusty servant Patsy went with the coconuts.