The genomic history of Iberian horses since the last Ice Age

Horses have inhabited Iberia (present-day Spain and Portugal) since the Middle Pleistocene, shaping a complex history in the region. Iberia has been proposed as a potential domestication centre and is renowned for producing world-class bloodlines. Here, we generate genome-wide sequence data from 87 ancient horse specimens (median coverage = 0.97X) from Iberia and the broader Mediterranean to reconstruct their genetic history over the last ~26,000 years. Here, we report that wild horses of the divergent IBE lineage inhabited Iberia from the Late Pleistocene, while domesticated DOM2 horses, native from the Pontic-Caspian steppes, already arrived ~1850 BCE. Admixture dating suggests breeding practices involving continued wild restocking until at least ~350 BCE, with IBE disappearing shortly after. Patterns of genetic affinity highlight the far-reaching influence of Iberian bloodlines across Europe and north Africa during the Iron Age and Antiquity, with continued impact extending thereafter, particularly during the colonization of the Americas.