Whole‐Genome Sequencing in Galicia Reveals Male‐Biased Pre‐Islamic North African Ancestry, Subtle Population Structure, and Microgeographic Patterns of Disease Risk
Pardo‐Seco et al. · doi:10.1096/fj.202502634r
What the study found
Galicia sits at the westernmost edge of Europe. Researchers sequenced the whole genomes of 91 people from there and compared them with 1,078 genomes from other Spanish and continental populations. Galicia turned out to be less unusual than recent claims had suggested: one major genetic cluster and four smaller, localised ones, a pattern the authors say fits broader Iberian structure. Data from the Spanish National DNA Bank, 453 people, showed the same shape.
The clearest ancestry result is a North African and Middle Eastern component making up 13.5% to 16.5% of Galician genomes. It is strongly male-biased: 21.2% on the Y chromosome, which passes father to son, against 1.1% in mitochondrial DNA, which passes mother to child. The authors say it was likely introduced by trans-Mediterranean contact around 620 to 670 CE, before the Islamic conquest of 711 CE, and that this calls for re-examining assumptions about Islamic-era ancestry. The signal has a subtle south-to-north gradient.
Phylogenetic analysis places the Galician clusters on terminal, recently diverged branches, which argues against earlier models of ancient separation. Slightly raised homozygosity, driven by one cluster from Porto do Son, suggests mild regional inbreeding. Polygenic risk scores for common diseases also vary geographically in line with this structure.
Key points
Whole-genome sequencing of 91 people from Galicia, compared with 1,078 genomes from other Spanish and continental populations.
A North African and Middle Eastern ancestry component makes up 13.5% to 16.5% of Galician genomes.
The signal is male-biased: 21.2% of Y-chromosome ancestry against 1.1% of mitochondrial ancestry.
The authors suggest trans-Mediterranean contact around 620 to 670 CE, before the Islamic conquest of 711 CE.
Relevance to this lineage
This sits in the medieval layer of the story told here, North Africa moving north. It adds Galicia, at the western edge of Europe, to the places where North African ancestry shows up before the Islamic conquest, alongside Sicily and Ibiza. The male bias is the striking part: the North African input came through men far more than through women.
It says nothing directly about the Chtouka family. The study names no haplogroup branch, no E-PF2546, no H1-T16189C!, and no part of Morocco. What it does show is the same asymmetry running in the opposite direction: here a father's line carries North African ancestry into Iberia, while this family's mother's line traces back to a lineage that crossed from Iberia into North Africa thousands of years earlier.
This is a summary, not the paper
Written here as an aid to reading, from the paper’s published abstract. Where this page and the study disagree, the study is right — read it. Full citation: Pardo‐Seco, J. et al. (2025). The FASEB Journal, 39, e71253. All fifteen summaries are listed on the research page.
Last updated: 16 September 2026