The Iberian Peninsula has historically been a crossroads of civilizations. Iberians, Romans, Visigoths, Arabs, Jews, and many others have left their mark not only on the culture and language of the territory but also on the genomes of its native inhabitants.

Its geographical position, enclosed by the Pyrenees to the north and separated from Africa by the Strait of Gibraltar, could have led evolution on the Peninsula along different paths than the rest of Europe, with distinct population movements and admixtures, as well as the presence of possible specific selective factors. However, until now, it has been unknown whether large-scale migrations influenced the genetic adaptation of the Peninsula’s inhabitants to their environment.

Now, a research team at the Institute of Evolutionary Biology (IBE), a joint center of the Spanish National Research Council (CSIC) and Pompeu Fabra University (UPF), confirms that most genetic adaptations in Spaniards are found in other European populations and, as a whole, do not show a clear set of adaptation signals exclusive to the Iberian Peninsula.

Based on a dataset of more than 800 contemporary genomes from Catalan residents generated in the context of the GCAT project, the study reveals that there is no adaptive genetic trait that characterizes Catalans exclusively compared to Spaniards or other Europeans from an evolutionary perspective.

Furthermore, the research has identified new traits that may have benefited European populations in the past, possibly related to fat metabolism, influenza resistance, or a preference for spicy food.

The results suggest that large-scale migrations partially facilitated adaptation to the environment for the overall population of Europe. Despite historical borders, the evidence shows that genetically there are few differences between being Catalan, Spanish, or European.

Access to an unprecedented genetic database of Catalan residents

The team analyzed the genomes in the GCAT database to understand how historical migrations may have influenced the genetic adaptations of native populations. The database includes 800 high-quality complete genomes from Catalan residents aged 40 to 60. To create this biobank, the public health system recruited 20,000 volunteers and sequenced the genomes of 800 randomly selected individuals, including 141 with all four grandparents born in the same autonomous community—55 of them with four Catalan grandparents.

"The study reinforces the value of GCAT, showing that Catalans, like other analyzed populations in Spain, share a solid European genetic foundation. Current adaptive differences are mainly due to environmental and social factors. GCAT is thus established as a European reference cohort, indicating that future contrasts may emerge more from functional levels—such as epigenetics or gene regulation—than exclusively from genetic variants," says Rafael de Cid, head of GCAT and researcher at the Germans Trias i Pujol Research Institute (IGTP).

"Given Catalonia’s recent history, with significant migration flows, particularly from other parts of Spain, we can consider GCAT a suitable reference for the Spanish population," notes Francesc Calafell, principal investigator at the Institute of Evolutionary Biology (IBE: CSIC-Pompeu Fabra University) and professor/researcher at the Department of Medicine and Life Sciences (MELIS) at UPF, who co-led the study.

Tracing the Iberian Peninsula’s imprint on genomes

In the GCAT genomes, geneticists looked for deviations from an average Iberian genomic profile. "This profile is characterized by 5–10% hunter-gatherer ancestry from over 6,000 years ago, 55–60% Anatolian farmer ancestry, and 35–40% from the migration of Steppe nomads about 4,000 years ago, known as Yamnaya," explains Elena Bosch, principal investigator at the Institute of Evolutionary Biology (IBE: CSIC-University of Pompeu Fabra) and full professor and researcher at MELIS (UPF), co-leader of the study.

Differences from the average genome may hide potential adaptive variants that could have provided survival advantages on the Iberian Peninsula. However, the results reveal a large number of adaptations shared with the rest of Europe.

Catalans: as Spanish, as French, and European

GCAT participants exhibit a typical European genetic profile, with a small proportion of North African ancestry, found only in the Iberian Peninsula, southeastern France, and Sicily. "Migrations that have shaped European history favored genomic admixture among local populations," notes Calafell. The results align with previous findings using genomes across Spain.

The team also analyzed the 16th-century French diaspora resulting from the Wars of Religion. Although these immigrants came to represent a quarter of the Catalan population, the study detected no specific genomic footprint. "The similarity with the French is already explained by centuries of previous admixture and borders that did not limit population interactions," adds Calafell.

Signatures of selection: from fat metabolism to preference for spicy food

The team discovered new genetic variants with adaptive signatures in contemporary Europeans, including the gene SMYD1, potentially increasing resistance to influença, the gene FDFT1, related to cholesterol metabolism, the gene UBL7, linked to immune response, and the trs55852693 polymorphism, associated with a greater preference for spicy food.

 Spicy food. Source: Pexels.

Additionally, the study confirms previously characterized functional adaptations in GCAT data, known in European populations, such as light skin, lactose tolerance, and immune response traits. "These are genetic signatures shared across non-African populations, likely the result of similar environmental pressures following the migration of Homo sapiens Out of Africa," notes Jorge Garcia Calleja, predoctoral researcher in Bosch’s Population Evolutionary Genetics group at IBE (CSIC-UPF).

Future work will include functional studies of the newly identified genetic traits to understand their mechanisms of action. "Understanding a gene variant’s function is not the same as understanding the cause of adaptation, which is usually linked to past selective pressures that are not always known," Bosch points out.

Catalan genetics as a reflection of Europe’s migratory crossroads

Human history is a story of ongoing migrations. Population studies use reference profiles from individuals with diverse local surnames to better represent regional origins. However, global admixture makes being Catalan, Spanish, or European a blurred concept. "Genetically, we all share more than 99.9% of DNA, and population differences exist, but they are minimal," comments Garcia-Calleja.

Globalization will increase genetic mixing, and in an environment with universal medicine and nutrition, selective pressure may decrease, making some traits less common. "In the future, the question of what it means genetically to be Catalan, Spanish, or European may no longer make sense beyond being human," concludes Calafell.

Reference article: J. Garcia-Calleja, S.A. Biagini, R. de Cid, F. Calafell, E. Bosch; “Inferring past demography and genetic adaptation in Spain using the GCAT cohort”; Scientific Reports (2025). DOI: https://doi.org/10.1038/s41598-025-98272-w

The original research article is open-access in Catalan and can be consulted here: https://zenodo.org/records/15261991