Horses had a huge impact on the success of many human societies. Now, scientists have found two key gene variants that helped paved the way for that equine role in human history. The pair made horses tamer and more rideable, researchers now report.

Ancient horse DNA suggests modern domesticated horses came from southwestern Russia more than 4,200 years ago. This research, published in 2021, revealed where and when humans had domesticated the animals. Ludovic Orlando led that study. A molecular archaeologist, he works at the Centre for Anthropobiology and Genomics. That’s in Toulouse, France.

What that work hadn’t shown was precisely what genetic changes in horses — mutations — might have led to these new traits.

Orlando and a team of scientists from China and Switzerland have now done that. They analyzed horse genomes, the full set of genetic instructions making up their DNA. In all, they compared the genomes of 71 horses from a range of breeds and time periods.

The team focused on 266 places in the genomes. From these, nine genes showed strong signatures of have been selected, or altered. That suggests the traits these genes produced in the horses may have been targeted by human breeders.

Two of these genes appear to have been heavily selected very early in horse taming.