Mitochondrial DNA diversity in northeast Iberians during the Iron Age

Iberian culture emerged along the Mediterranean coast of the Iberian Peninsula between the 8th and 6th century BCE, flourishing during the 5th-3rd BCE until the Roman conquest. Iberians engaged in metallurgy, agriculture, and livestock, and actively participated in Mediterranean commercial trade networks. Despite cremation being the predominant funerary practice, advances in ancient DNA techniques have enabled the recovery of mitochondrial DNA (mtDNA) from an increasing number of Iberian individuals. Here, we analyzed the remains of 31 newborns, successfully obtaining mtDNA profiles for 21 individuals (20 Iberians and 1 Late Roman). These data were merged with 41 previously published mtDNA profiles from unrelated Iberians across different tribes of the northeast of the Iberian Peninsula. Additional prehistoric data were compiled to contextualize Iberian haplogroups. We investigated maternal lineage diversity between tribes, temporal shifts in haplogroup composition, and signatures of long-distance female mobility. Our results revealed subtle differences in mtDNA haplogroup frequencies between groups, although genetic differentiation was not statistically significant. Mitochondrial diversity remained relatively high across all tribes, consistent with patrilocal mating systems and small-distance female migration that may have prevented strong matrilineal differentiation among tribes. A predominance of haplogroups H, J, K, HV0, and U was observed, most of which were already present in the Iberian Peninsula before the Iron Age. Haplogroup diversity remained stable over time, without population differentiation, suggesting maternal genetic continuity from the Bronze Age. However, the presence of some haplogroups pointed to occasional female-mediated gene flow from North Africa, the Near East, and Central Europe. Overall, this study provides the most comprehensive NGS-based assessment of maternal ancestry in Iron Age Iberians to date, revealing a genetic landscape shaped by local continuity alongside some long-distance female mobility linked to commercial trade and cultural interaction. • Ancient mtDNA reveals high maternal diversity in Iron Age Iberians. • Haplogroups show continuity from the Bronze Age to the Iron Age in northeast Iberia. • Subtle lineage differences found between Iberian groups, but no strong splits. • Local ancestry dominated, with long-distance contacts shaping diversity.