Horse Tale: Oriental Stallions Dominate Horse DNA, Gene Study Shows

Virtually all the horses who grace racetracks, horse shows, riding stables, and private farms around the world today descend from two lines of “Oriental” champions, researchers reported Thursday.

The genetic study sheds light on the long-withstanding effects of intensive breeding, which dates back just 700 years. Choices made then — during the height of the Medieval period in Europe and at the birth of the Ottoman Empire — live on today in the genes of horses found across the American West, in the stables of European royalty, and on the pampas of Argentina.

Image: A Lipizzan stallion named Conversano Sessana
A Lipizzan stallion named Conversano Sessana, born in 2001.The Y sequence that is needed as a template to detect variants in any horse is generated from a stallion of this breed. Spanische Hofreitschule Wien

A group of researchers led by Barbara Wallner of the Institute of Animal Breeding and Genetics in Vienna, Austria sampled the genes of 52 modern horses representing 21 different breeds for their study. They included the famous white dancing Lipizzaners, quarter horses, cobs, Thoroughbreds and Arabians.

The team focused on the male specific Y chromosome, which males pass down virtually unchanged from father to son. While the chromosome only carries a few essential genes, it does provide a clear road map of male heredity.

The findings were startling. Most of the horses in common use descend from just two lineages, the Arabian lineage from the Arabian Peninsula and the Turkoman lineage from the steppes of Central Asia, also widely known as "Oriental" among horse breeders, as reported in the Journal of Current Biology.

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"Apart from stallion lines in Northern European breeds, all stallion lines detected in other modern breeds derive from more recently introduced Oriental ancestors," Wallner said.

It’s not surprising that a few studs would have a large number of progeny. Females can have one or two foals a year, while males can sire many.

It seems medieval horse breeders made great use of a few very strong specimens, Wallner said, breeding them with local mares.

The qualities they were looking for are still the same qualities people still admire today.

“They wanted them because they were beautiful. They wanted them to be faster and stronger and lighter,” Wallner told NBC News.

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There’s plenty of history about horse breeding and it’s no secret that Arabian stallions were desired and shipped long distances for breeding.

“Of particular importance was the trend to import stallions from foreign studs to improve local herds. In central Europe, this practice started in the 16th century with the popularity of Spanish and Neapolitan stallions. Until the end of the 18th century, the Central European horse population was shaped by the introduction of ‘Oriental stallions’,” they wrote.

Image: A person riding a Lipizzan stallion
A person riding a Lipizzan stallion. They perform in the Spanish Riding School in Vienna. Spanische Hofreitschule Wien

Wallner’s study shows just how few male lines ended up surviving the process.

Other research has looked at mitochondrial DNA, which females pass down virtually unchanged to their children. This collection of DNA is particularly diverse in horses, demonstrating that many, many mares are ancestors of modern horses.

Now Wallner wants to collect DNA from the remains of ancient horses to see if she can determine when wild horse were first domesticated, and where.

Similar recent studies have shown the surprising origins of domestic dogs and show evidence that suggests that wildcats were tamed into pussycats more than once.