Researchers have found evidence of ancient horse domestication around four millennia ago, with genetic data pointing to Botai hunter-gatherers in Central Asia as the first to domesticate horses for milk and meat. The later domestication of horses north of the Caucasian Mountains changed the equine world dramatically, eventually leading to the modern domestic horse. This new research challenges long-held beliefs about early horseback riders, suggesting that the Yamnaya people were not the first to domesticate horses. Genetic evidence also indicates that people purposely started breeding horses, leading to the strong backs and tame temperaments we see in modern domestic horses today.
https://www.sciencenews.org/article/horses-domesticated-mobility-timing