Ancient Iberian DNA reveals how populations shifted after Rome

New rulers, old roots

Two medieval siblings were buried roughly 725 kilometres apart in ancient Iberia. Both carried genetic code tracing back to Central-Northern Europe. Yet their arrival did not rewrite the local community map.

When empires fall, old stories often describe hordes of invaders replacing the locals. By looking directly at ancient Iberian DNA, scientists found that political shifts did not always wipe out local folk. To track these changes, researchers read the genomes of 243 newly sequenced skeletons and 58 previously studied ones dating between 100 and 800 CE.

What the bones revealed

By comparing these genetic profiles step by step across time, the team traced ancient family trees. This method matters because bone shape alone cannot tell you where a person came from. The Roman era sparked major movement. The team found clear evidence of admixture, which means people from previously separated groups had children together. Travellers with roots in the Eastern Mediterranean arrived in large numbers. Many North Africans also moved in, mostly settling in the centre and south of the peninsula.

Things looked very different when the Western Roman Empire fell. Germanic and Alan rulers took political control in the early middle ages. Skeletons with Central-Northern European roots did appear from the 5th century. Importantly, this does not mean new rulers left no genetic mark. Rather, despite these arrivals, the established Hispano-Roman group stayed mostly the same over time. Scientists call this demographic continuity.

This outcome sets Iberia apart from other lands. In post-Roman Britain, imperial collapse triggered massive demographic change. The central Mediterranean also saw deep shifts. In Iberia, changing the rulers resembled changing the bosses at a big firm: new bosses ran things at the top, but the everyday workforce stayed.

What we still do not know

This genetic study only covers people who lived between 100 and 800 CE. North African roots appeared mainly in the centre and south, so other areas may show slightly different local stories.

Scientists also do not know the exact reasons why families moved, such as why those two siblings ended up buried hundreds of kilometres apart across the peninsula.