The genomic history of the Iberian Peninsula over the last 8000 years

We assembled genome-wide data from 271 ancient Iberians, of whom 176 are from thelargely unsampled period after 2000 BCE, thereby providing a high-resolution time transectof the Iberian Peninsula. We document high genetic substructure between northwesternand southeastern hunter-gatherers before the spread of farming. We reveal sporadiccontacts between Iberia and North Africa by ~2500 BCE and, by ~2000 BCE, thereplacement of 40% of Iberia’s ancestry and nearly 100% of its Y-chromosomes by peoplewith Steppe ancestry. We show that, in the Iron Age, Steppe ancestry had spread not onlyinto Indo-European–speaking regions but also into non-Indo-European–speaking ones, andwe reveal that present-day Basques are best described as a typical Iron Age population without the admixture events that later affected the rest of Iberia. Additionally, we documenthow, beginning at least in the Roman period, the ancestry of the peninsula was transformedby gene flow from North Africa and the eastern Mediterranean