Y chromosome of horses reveals the global triumph of Oriental stallions

The horse is one of the most important domestic animals in human culture, and the history of the horse is inextricably linked to geopolitical developments. Past migratory movements, varied breeding goals and intensive stallion-centred breeding have created a complex mosaic of ancestry in the horse. The paternally inherited Y chromosome reflects the male side of population history and provides information about the origin and influence of stallions.

For their study, the researchers analysed a large number of modern breeds and reconstructed their paternal lineages over the last 1,500 years. The scientists identified three major recent breeding influences and highlighted two fundamental historical routes driving the spread of Oriental horses.

Oriental stallions with dominant influence on modern horses

The research team analysed datasets of patrilines comprising 1,517 stallions from 189 modern horse breeds, covering a broad phenotypic and geographic spectrum. The scientists were able to decipher the enormous influence of Oriental stallions over the last few hundred years, demonstrating the origin and widespread distribution of Arabian, English Thoroughbred and Coldblood stallions, and exposing the consequences of intense linebreeding.

“The majority of stallions worldwide carry Y lines that can be attributed to an only approximately 1,500-year-old so-called Crown haplogroup. The predominance of Crown lineages in modern horse breeds is the result of the enormous impact of stallions of “Oriental origin” in the past millennium,” as the study’s first author, Lara Radovic from the Centre for Biological Sciences at Vetmeduni, explains. “The spread of Oriental horses was complex and started with the Muslim expansion. The similar spectrum of paternal lines in horse breeds from the Iberian Peninsula and the New World confirms the enormous distribution of horses of Oriental origin via the Iberian Peninsula after the Middle Ages,” Radovic adds. The survey also revealed a second major historical dissemination of horses from Western Asia, accompanied by the expansion of the Ottoman Empire.

Inseparable bond between horses and human history

“Our study shows that MSY analysis can uncover the complex history of horse breeds,” says the study’s last author Barbara Wallner from the Centre for Biological Sciences at Vetmeduni. “By tracing the legacy of Oriental stallions, we have demonstrated the inseparability of horse and human history and deciphered former unknown connections between geographically and phenotypically different horse breeds. We have also highlighted the consequences of intensive animal breeding, which have led to the loss of breeding lines,” Wallner adds. The findings can be used to determine the ancestry of stallion lines in any horse breed of interest, which authors also exemplified in a population of European local breeds and ponies.

According to Wallner, the work also opens up new opportunities for capturing the historical development of breeding populations as a basis for meaningful decisions in breeding management in the future.