Many domestic horses run in a smooth motion, in what is known as an “ambling” gait, perfect for people who ride on them. While you might be forgiven for thinking that this movement developed long before mankind intervened, it turns out that this gait can be traced to a single gene involved in the coordination of limb movement, and may have been selected for by early humans. Nowadays, the same mutation in this gene appears widely around the globe, yet where it originated has been a bit of a mystery.

Now, researchers have conducted genetic analysis on the remains of horses dating from 8,000 to 1,000 years old and discovered something intriguing: The Vikings might be responsible for the modern-day prevalence of ambling horses. Previous research has found that the gene responsible for the gait is a mutated form of DMRT3, which is thought to be expressed in the animals’ spinal cord interneurons, and plays a role in the development of the coordination of the limbs.  

By looking for the mutated version of this gene – known as an allele – in the historic remains of horses, the team were able to trace the mutation to its origin and then follow its spread. They found that it all began in Medieval England between 850 and 900 CE, where the mutation cropped up in two horses from this period. Within the next few decades, they then detected the allele in Icelandic horses, strongly suggesting that it was the Norse settlers of both islands who had taken the animals from England to Iceland, and then selected for the animals' movement that made riding them more effortless.

“Considering the high frequency of the ambling allele in early Icelandic horses, we believe that Norse settlers selected for this comfortable mode of horse riding soon after arrival,” the researchers write in their paper published in Current Biology. “The absence of the allele in samples from continental Europe (including Scandinavia) at this time implies that ambling horses may have spread from Iceland and maybe also the British Isles across the continent at a later date.”

This account matches with the historical records of the movement of the Norse settlers though Northern Europe at this period of time. From Scandinavia, the Vikings came to settle in northern England, especially around the city of York, where the two remains of horses carrying the original mutation were also discovered. The Norse then moved north, and apparently took the horses with them.

So advantageous was this ambling gait for early riders, it seems to have been selected for fairly rapidly, and has spread around the world ever since.