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

Abstract

We assembled genome-wide data from 271 ancient Iberians, of whom 176 are from the largely unsampled period after 2000 BCE, thereby providing a high-resolution time transect of the Iberian Peninsula. We document high genetic substructure between northwestern and southeastern hunter-gatherers before the spread of farming. We reveal sporadic contacts between Iberia and North Africa by ~2500 BCE and, by ~2000 BCE, the replacement of 40% of Iberia's ancestry and nearly 100% of its Y-chromosomes by people with Steppe ancestry. We show that, in the Iron Age, Steppe ancestry had spread not only into Indo-European-speaking regions but also into non-Indo-European-speaking ones, and we 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 document how, beginning at least in the Roman period, the ancestry of the peninsula was transformed by gene flow from North Africa and the eastern Mediterranean.

Fig. 1.. Overview of the Ancient Iberian Genetic Time Transect.

(A) Geographic distribution and (B) dates of new and previously reported samples. Random jitter is added for sites with multiple individuals. Sites mentioned in the text are labeled. (C) Principal Component Analysis of 989 present-day west Eurasian individuals (grey dots), with ancient individuals from Iberia and other regions (pale yellow) projected onto the first two principal components. (D) Section of the PCA in (C). (E) Schematic representation of events documented in this study.

Fig. 2.. Genome-wide admixture proportions using qpAdm.

(A) Modeling Mesolithic, Neolithic and Copper Age populations as a mixture of Anatolia_N, El Mirón and KO1. Percentages indicate proportion of El Mirón + KO1 ancestry. (B) Proportion of ancestry derived from central European Beaker/Bronze Age populations in Iberians from the Middle Neolithic to the Iron Age (table S15). Colors indicate the Y-chromosome haplogroup for each male (table S4). (C) Ancestry proportions for individuals from three sites in northeast Iberia dated between the 6th and 12th centuries CE. (D) Ancestry proportions for individuals from southeast Iberia from the 3–16th centuries CE (tables S20-S21). Each bar represents one individual with associated mtDNA (top) and Y-chromosome (bottom). In bold, haplogroups with a likely recent non-local origin.