For thousands of years, the grassy plains of Europe and Asia were home to a mosaic of genetically distinct horse lineages. But only one line galloped forward to overtake and replace all the other wild horses. This domesticated line has become the horse of our modern imagination: slender legs, a muscular back and a mane that sparkles in the wind.
For decades, scientists have tried to find out when and where modern horses were first domesticated, but had yet to find the smoking hoof they needed.
Now in an article published in the newspaper on Wednesday Nature, scientists have finally solved the mystery. After collecting and sequencing 273 ancient horse genomes, a team of 162 authors concluded that modern horses were domesticated about 4,200 years ago in the steppes of southern Russia near the intersection of the Volga and Don.
This new article comes as close as possible today to solving the mystery of the origins of the domestic horse, according to Peter Heintzman, a paleogenomic researcher at the Tromsø campus of the University of the Arctic of Norway, who was not involved in the research. . “It’s a monumental effort,” said Dr Heintzman, noting that they had collected a “wall of data” from “hundreds of horses.”
Ludovic Orlando, paleogeneticist and research director of the Toulouse Anthropobiology and Genomics Center in France and author of the article, has been studying this question for a decade.
In recent years, scholars have settled in a Botai settlement in the Kazakh steppes that was teeming with fragments of horse bones and clay pots covered in what appeared to be mare’s milk. It was the first archaeological evidence for the domestication of horses and held promise as the birthplace of modern horses.
But in 2018, a team of researchers including Dr Orlando sequenced the genomes of horse bones in Botai. To researchers’ surprise, the Botai horses did not give birth to modern horses, but were rather the direct ancestors of the Przewalski horses, a stocky line originally considered to be the last wild horses on the planet. They revealed that the Przewalskis were not wild after all, but rather the wild descendants of servants. The enigma of the origins of modern horses therefore remained unsolved. “Every time I expected something it was wrong,” said Dr. Orlando.
He said that to solve the mystery, “we decided to be exhaustive and to really look everywhere.”
Everywhere, in this case, meant across Eurasia. Starting in 2016, Dr Orlando collected samples from across the region from archaeological collections and new excavations, essentially any ancient horse bones they could get their hands on.
To preserve the remains for the future, researchers drilled tiny holes in the inner ears, teeth and other bones of ancient horses to retrieve tiny samples.
As researchers mapped the genomes of horses across time and space, the picture became sharper. A little over a year ago, they were able to pinpoint the location precisely: the Volga-Don region in present-day Russia.
With such a gargantuan data set, researchers ended up answering additional historical details about the horses. They found that modern horses had two marked genetic differences from other ancient bloodlines – a gene linked to docility and another to a stronger spine – which may have facilitated the animals’ spread.
Domestic horses have transformed human history, enabling people to travel great distances and develop new technologies of warfare. “Everyone wanted the horse,” said Dr. Orlando.
As a result, the article’s genetic findings “constitute major advances in our understanding of the human societies that bred these horses,” said Pauline Hanot, postdoctoral researcher at the French National Center for Scientific Research who was not involved in the research.
The study also overturned ideas about the role of horses in earlier human history. For example, a pre-existing theory suggested that a pastoral people called Yamnaya were able to migrate on horseback in large numbers to Europe about 5,000 years ago. But the new genetic map found no evidence; the researchers point out that the oxen, and not the horses, could have been the driving factor of their expansion.
The new article also reveals domestic horses widespread throughout Eurasia as well as the Sintashta culture of the Bronze Age, which possessed wire-wheeled chariots around 3,800 years ago.
After getting to grips with all this horse data, Dr Orlando embarked on a new hobby – he started taking riding lessons.
Like all other humans, he rides domestic horses, descendants of ancient animals that galloped in southern Russia.
“I wouldn’t dare approach a Przewalski horse,” said Dr Orlando. “They kill wolves. I’m not such a fast runner.