Horses revolutionized human history through fast mobility. A study analyzing 475 ancient horse genomes reveals that reproductive control of the domestic lineage emerged around 2200 BCE, marked by close-kin mating and shortened generation times. This period followed a domestication bottleneck starting no earlier than 2700 BCE and coincided with a sudden expansion of horses across Eurasia, replacing local lineages. This expansion marked the rise of widespread horse-based mobility, refuting the idea that large horse herds accompanied the Yamnaya migration around 3000 BCE. The study also detected shortened generation times in Botai around 3500 BCE, a site associated with horse-based subsistence. This supports early horse husbandry before the rise of modern domestic bloodlines. The genetic makeup of modern domestic horses (DOM2) emerged in the western Eurasian steppes during the third millennium BCE. The spread of DOM2 horses, alongside the development of Sintashta spoke-wheeled chariots, indicates that long-distance horse-based mobility developed no earlier than the late third millennium BCE. The study challenges the notion that DOM2 horseback riding drove the spread of steppe-related ancestry in Europe. However, recent population models suggest significant DOM2 genetic ancestry in European horses associated with the Corded Ware complex. Bone pathologies potentially from horseback riding are found in about 5% of human skeletons from the Carpathian Basin. These findings support theories linking horseback riding to the Yamnaya expansion. The study also shows that the spread of DOM2 horses in Europe was not driven by horseback riding but by other factors. The genetic makeup of ancient European horses does not support widespread horse-driven mobility before the end of the third millennium BCE. The study provides evidence for a strong domestication bottleneck in horses during the 75 generations preceding the DOM2 expansion. The time when steppe people migrated did not coincide with expanding, but rather plummeting, availability of DOM2 reproductive horses, aligning with horses not driving Yamnaya-related steppe migrations. The study also shows that DOM2 generation times contracted around 2200 BCE, indicating new reproductive control practices aimed at faster productivity. The study highlights the importance of horse husbandry in the Botai culture, where shortened generation times and demographic expansion occurred. The findings suggest that the domestication process in Botai was regional and not aimed at global production. The study provides new insights into the timing and context of horse domestication, emphasizing the role of reproductive control and shortened generation times in the development of horse-based mobility. The study also expands the bioarchaeological toolkit to detect molecular evidence of reproductive control, offering new perspectives on the timing of animal husbandry in human history. The study's findings have significant implications for understanding the role of horses in human history and the spread of Indo-European languages.Horses revolutionized human history through fast mobility. A study analyzing 475 ancient horse genomes reveals that reproductive control of the domestic lineage emerged around 2200 BCE, marked by close-kin mating and shortened generation times. This period followed a domestication bottleneck starting no earlier than 2700 BCE and coincided with a sudden expansion of horses across Eurasia, replacing local lineages. This expansion marked the rise of widespread horse-based mobility, refuting the idea that large horse herds accompanied the Yamnaya migration around 3000 BCE. The study also detected shortened generation times in Botai around 3500 BCE, a site associated with horse-based subsistence. This supports early horse husbandry before the rise of modern domestic bloodlines. The genetic makeup of modern domestic horses (DOM2) emerged in the western Eurasian steppes during the third millennium BCE. The spread of DOM2 horses, alongside the development of Sintashta spoke-wheeled chariots, indicates that long-distance horse-based mobility developed no earlier than the late third millennium BCE. The study challenges the notion that DOM2 horseback riding drove the spread of steppe-related ancestry in Europe. However, recent population models suggest significant DOM2 genetic ancestry in European horses associated with the Corded Ware complex. Bone pathologies potentially from horseback riding are found in about 5% of human skeletons from the Carpathian Basin. These findings support theories linking horseback riding to the Yamnaya expansion. The study also shows that the spread of DOM2 horses in Europe was not driven by horseback riding but by other factors. The genetic makeup of ancient European horses does not support widespread horse-driven mobility before the end of the third millennium BCE. The study provides evidence for a strong domestication bottleneck in horses during the 75 generations preceding the DOM2 expansion. The time when steppe people migrated did not coincide with expanding, but rather plummeting, availability of DOM2 reproductive horses, aligning with horses not driving Yamnaya-related steppe migrations. The study also shows that DOM2 generation times contracted around 2200 BCE, indicating new reproductive control practices aimed at faster productivity. The study highlights the importance of horse husbandry in the Botai culture, where shortened generation times and demographic expansion occurred. The findings suggest that the domestication process in Botai was regional and not aimed at global production. The study provides new insights into the timing and context of horse domestication, emphasizing the role of reproductive control and shortened generation times in the development of horse-based mobility. The study also expands the bioarchaeological toolkit to detect molecular evidence of reproductive control, offering new perspectives on the timing of animal husbandry in human history. The study's findings have significant implications for understanding the role of horses in human history and the spread of Indo-European languages.