A new genetic study published in the journal Cell has uncovered a surprising truth about the history of the Iberian Peninsula: the Roman Empire had a more profound impact on the region’s ancestry than the major migrations that followed. The research, which analyzed DNA from 243 individuals spanning from 100 to 800 CE, shows that Roman rule introduced widespread ancestry from the eastern Mediterranean and North Africa, fundamentally altering the genetic makeup of Iberia. Later migrations, in contrast, introduced new ancestry without replacing the existing Hispano-Roman population on a large scale.
Major Genetic Shifts Under Roman Rule
Rome entered Iberia during the Second Punic War in the late 3rd century BCE. While its influence reshaped the region’s language, culture, and legal systems, the study reveals that this transformation also included significant demographic changes. The newly examined remains were collected at 31 archaeological locations, representing diverse settings and cultural contexts, including Hispano-Roman and Germanic-associated communities. When Iron Age populations were compared with Roman and late antique samples, researchers found major shifts in ancestry composition across three of the four regions studied.
Eastern Mediterranean-related ancestry was particularly widespread. It was detected in 83% of the 66 Roman-period individuals analyzed. This ancestry component made up an average of 4.1% of the genetic profile in Augusta Emerita, a former Roman provincial capital, but reached 34.6% in southeastern Iberia. The samples underwent enrichment using panels targeting approximately 1.2 million or 1.4 million single-nucleotide polymorphisms (SNPs). In contrast, ancestry directly linked to the Italian Peninsula was uncommon, suggesting migrants from the eastern Mediterranean were a primary driver of these changes.
Widespread North African Ancestry
North African ancestry was another major contributor during the Roman and late antique periods. In southeastern Iberia, 33 of 34 Roman-period individuals carried this ancestry, averaging 26.9%. The genetic signal of North African admixture extended to northeastern Iberia during Roman times and central Iberia during late antiquity, found in both provincial capitals and inland settlements.
One striking example comes from the Christian basilica of Cortijo Coracho, where 29 of 30 individuals had North African ancestry, often alongside local Iberian and Eastern Mediterranean lineages. This site also revealed a four-generation family network of 16 individuals, highlighting strong community ties and extensive admixture within this population. Yet control weakened during the 5th-century CE migration period as Germanic and Alan groups gained political influence.
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The study also identified a particularly notable finding: two siblings with entirely Central-Northern European-related ancestry who were buried approximately 725 km apart, likely connected by the Roman road network. This discovery suggests considerable mobility among migrant groups and the use of Roman-era infrastructure for long-distance movement.
Central-Northern European-related ancestry appeared more frequently during the migration period. It was found in 53 of 164 individuals from this era, compared with only six of 66 people who lived during Roman times. This ancestry was most common at Germanic-associated cemeteries. At these sites, 29 of 52 individuals carried CNE-related ancestry. Some of these were high-status burials, suggesting the newcomers held significant positions within these communities.
Even after excluding Germanic-associated cemeteries, 23 of 114 individuals still carried CNE-related ancestry, averaging 12.1% in this subset. This indicates that the new ancestry was not limited to specific burial groups. Instead, at sites with Germanic practices, individuals with predominantly CNE ancestry lived alongside people with local ancestry, showing evidence of admixture between the two groups.
Decline of Ancestry and Modern Connections
CNE-related ancestry later declined but did not disappear. Traces of it persisted into the medieval period. After applying sequencing coverage and contamination filters, the researchers included 212 newly analyzed individuals in the genetic comparisons. They obtained 35 additional radiocarbon measurements and drew on 32 dates reported in earlier research. The study compared the genetic profiles of ancient Iberians with present-day populations. This comparison revealed less variation in ancestry composition among modern Iberians.
The team compared genetic variation between ancient and present-day Iberians and analyzed regional populations from the 1000 Genomes Project to investigate whether genetic contributions from Central and Northern Europe remained detectable in modern Iberians. However, none of the ancestry models used in the study achieved a statistically acceptable fit for the modern data. Later historical movements, such as resettlement, likely contributed to these differences.