The genomic history of Iberian horses from the last Ice Age to domestication and breeding

Horses have inhabited the region of Iberia (modern-day Spain and Portugal) from the Late Pleistocene until today. Iberian horse bloodlines are known to have expanded outside Iberia, especially during the American colonization. Whether Iberia represented an important horse breeding center in earlier time periods remains, however, unknown. Here, we generate genome-wide sequence data from 84 ancient horse specimens from Iberia and across the Mediterranean range to track the genetic history of Iberia horse populations over the last ~26 kyrs. We find that modern domesticated horses belonging the DOM2 lineage entered the region no later than ~1,600 BCE. Enduring traces of admixture support horse husbandry practices involving wild restocking until ~450 BCE, and the exrinction of wild local horses belonging to the IBE lineage shortly after. Geographic patterns of shared genetic affinity support a far-reaching influence of Iberian bloodlines across Europe and North Africa during the Iron Age and Antiquity, and until the Muslim expansion of the 7th century CE.