Ancient breeders dramatically shortened the natural generation times of horses starting about 4200 years ago, according to a genetic study of hundreds of ancient horses. This intensive breeding led to a massive expansion of those bloodlines across Eurasia within a few centuries, says“In other words, they controlled the reproduction of the horse,” he says. “So this tells us something about the process of breeding that was underlying the success of the expansion of horses around the world.
The DNA analysis revealed significant inbreeding 4200 years ago in the Pontic-Caspian steppe horses, probably because people aimed to develop specific traits that make high-quality riding and chariot horses, he says. “Right at the time of the domestication bottleneck, around 2200 BC, this is when breeders managed to control the reproduction of the horse so much that generations were ticking faster and faster,” says Orlando.