The domestication of the horse has been a mystery of science for generations. In Episode 2 of Equus, First Riders, anthropologist turned filmmaker Niobe Thompson travels to Kazakhstan to witness the groundbreaking discovery of a skeleton from the earliest culture ever to tame horses. In this episode, viewers get a set of genuine science scoops: we are the first to learn that our ancestors domesticated the horse twice and that early riders carried the world’s first pandemic of plague to Europe.