Preprint Genetic Study on Galicia

[Grace O'Malley]

Has anyone looked at this yet? It's quite interesting. This is an AI summary. So it looks like the North African ancestry is pre-islamic. Also a relatively high amount of 21.2% of ydna E1b.


Finally, the analysis of mtDNA haplogroups in the GAL dataset reveals that only 1.1% of the samples belong to North African lineages (U6 haplogroups), withno Sub-Saharan lineages (L haplogroups) detected. In sharp contrast, an analysis of the Y-chromosomes of GAL males (n = 33) indicates that 21.2% (E1b1b1 haplogroups) show a contribution from North African/Middle Eastern lineages.

AI Overview
Whole-genome sequencing in Galicia has uncovered evidence of male-biased, pre-Islamic North African ancestry, along with subtle population structure and micro-geographic patterns of disease risk DNA. The study reveals a signal of ancestry related to trans-Mediterranean contacts preceding Islamic rule, with a higher concentration in southern regions of Galicia and a decline towards the north. Y-chromosome analysis suggests a predominantly male influx, indicating a larger paternal contribution from North Africa. The research also highlights variations in polygenic risk scores for common diseases across different genetic clusters within Galicia, suggesting a link between ancestry and disease susceptibility.
Key Findings:
Pre-Islamic North African Ancestry:
The study identified a significant North African/Middle Eastern autosomal ancestry component, estimated to be around 13.5% to 16.5%.
Male-Biased Admixture:
Y-chromosome and mitochondrial DNA analyses indicated that the North African ancestry was introduced primarily through a male-biased influx, suggesting a predominantly paternal contribution.
Admixture Timing:
Genomic analyses suggest that the admixture event occurred around 620-670 CE, predating the Islamic incursion of 711 CE and the Reconquista.
Population Structure:
The study also revealed a subtle South-to-North decline in North African ancestry, indicating a potential southern entry route.
Micro-Geographic Disease Risk:
Analysis of polygenic risk scores for common diseases (e.g., breast and ovarian cancer, Alzheimer's, schizophrenia, and type 2 diabetes) showed distinct disease risk patterns across different genetic clusters within Galicia.
Impact on Public Health:
The findings underscore the need to consider genetic ancestry when assessing disease risk and developing public health strategies.
Significance:
This research challenges the prevailing assumption that North African ancestry in Iberia is solely attributable to Islamic rule. The findings emphasize the importance of considering historical population movements and interactions, even those predating major historical events, when analyzing genetic heritage. The identification of micro-geographic patterns of disease risk highlights the potential for personalized medicine approaches that take into account individual genetic backgrounds and ancestry.

https://www.biorxiv.org/content/10.1101/2025.06.27.662083v1.full.pdf

https://www.biorxiv.org/content/10.1101/2025.06.27.662083v1.full

[Grace O'Malley]

https://www.biorxiv.org/content/biorxiv/early/2025/07/01/2025.06.27.662083/F1.large.jpg?width=800&height=600&carousel=1

Figure 1.
(A) Map illustrating the datasets used in this study, with a zoomed-in section providing details on the Galician (GAL) dataset sampling locations (indicating also the four provinces of the region: A Coruña, Lugo, Ourense and Pontevedra). (B) Kinship analysis of the GAL dataset, showing that after filtering out closely related individuals (removed from the plot), the remaining samples used in this study exhibit no close familial relationships. (C) MDS analysis comparing the GAL dataset to major continental populations. The left MDS plot includes a zoomed-in view of the European genomes, highlighting the centroids of the population datasets. See Table 1 for population code details.

https://www.biorxiv.org/content/biorxiv/early/2025/07/01/2025.06.27.662083/F2.large.jpg?width=800&height=600&carousel=1
Figure 2.
(A) Bar plot depicting individual ancestry proportions estimated using ADMIXTURE with both unsupervised (left) and supervised (right) clustering approaches, considering K values from 4 to 5. (B) Interpolated frequency map of the Middle East and North African component among GAL donors across the Galician region, based on the ancestry component identified in (A) (see indications for Fig. 2_1; Fig.2_2, and Fig.2_3). (C) f₃-statistics in the form f₃(XEUR, XNAF/SSH; GAL), measuring shared genetic drift. Each dot represents an f₃ value calculated for a pair of source populations with GAL as the target population. Blue dots correspond to combinations involving sub-Saharan African populations, red dots indicate combinations with North African or Middle East populations, and filled red dots highlight statistically significant results (Z-score ≥ 3), suggestive of admixture events contributing to the genetic makeup of the GAL population. Negative f₃ values indicate potential evidence of admixture, while positive values reflect shared genetic drift. See Table 1 for population code details.

[Friends of Oliver Society]

That makes much more sense than it came from the Moorish invasion in 711. The only mention of a Moorish community in the historical record was a Berber community in Galicia that within a couple of decades left to take a part in an ethnic civil war against the Arab elite in the south. The Arabs took the best land and the Berbers were hella mad for being treated like second class citizens despite being the majority and doing all the fighting.

[Opie]

What about Asturias? It was the only the kingdom that Moors didn't conquer.

[Grace O'Malley]

https://www.biorxiv.org/content/biorxiv/early/2025/07/01/2025.06.27.662083/F4.large.jpg?width=800&height=600&carousel=1
(A) Map illustrating the sampling locations of the NDNAB dataset, which includes Iberian donors whose grandparents were born in the same provinces. Circle sizes are proportional to sample sizes and are centered on the main provincial capital cities. (B) Circular phylogeny (top-left) of the NDNAB dataset (fully expanded in Figure S3 – Supplementary File) and a dendrogram (right), where terminal branches are collapsed into nodes representing major geographic regions in Iberia (except Galicia), corresponding to the main autochthonous populations. Unlike other regions, the three Galician clusters were kept separate to facilitate direct comparisons with those observed in the GAL dataset. The proportions indicated to the right of the regional names represent the percentage of samples in each cluster originating from the corresponding autochthonous region, acknowledging that some individuals were sampled in other (often neighboring) regions. Additionally, the total sample size, the number of terminal branches (quantities separated by hyphens), and their respective sample sizes are provided (e.g. fineSTRUCTURE detected three clusters in Cantabria, with sizes 14, 8, and 3 individuals). Symbols in the collapsed nodes of the dendogram correspond to those used in panels C and D. (C) PCA of NDNAB donors, illustrating the clustering pattern observed in (B). (D) Interpolated frequency maps of the continental Spanish territory, depicting the geographic distribution of clusters identified in (B); the numbers following the region names indicate the maximum number of fineSTRUCTURE clusters represented in the maps. For the specific case of the Andalusia/Central region, we show the distribution of the three main clusters in this area (bottom maps), with sample sizes of 128, 35, and 32, each displaying slightly different geographic distributions.

[Opie]

That makes much more sense than it came from the Moorish invasion in 711. The only mention of a Moorish community in the historical record was a Berber community in Galicia that within a couple of decades left to take a part in an ethnic civil war against the Arab elite in the south. The Arabs took the best land and the Berbers were hella mad for being treated like second class citizens despite being the majority and doing all the fighting.

Galicia was a part of Al-Andalus. Asturias was the only Kingdom that Moors couldn't conquer. If OP wants to see whether Muslim conquest had a genetic impact on Iberians or not. She should look into Asturian genetics and compare it to rest of the Iberians. Asturians are the best baseline for that.

[Grace O'Malley]

From the study this tends to suggest that Galicia is less genetically distinct than Cantabria, Basque Country, Asturias and is more similar to other Iberian regions. While northern regions (Basque Country, Cantabria, Asturias) remain distinct, Galicia appears more integrated into broader Iberian genetic variation, clustering recently with central/southern populations.


In light of the sharp contrast in clustering patterns, we performed a fineSTRUCTURE analysis on the NDNAB dataset (n = 453, with 474,761 SNPs after applying the same filters as for the whole-genome data). This dataset includes independent Galician samples alongside donors from various Spanish regions, enabling a detailed assessment of Galicia’s population structure within a national context. This dataset encompasses individuals from Galicia, Asturias, Navarra, Cantabria, the Basque Country, Catalonia, Andalusia, Castilla-La Mancha, and Castilla y León, all regions also examined in Bycroft et al.’s study (2019); Figure 4A. Consistent with our findings in the GAL dataset, fineSTRUCTURE identified only three clusters among Galician donors in the NDNAB dataset. Similarly, one cluster contained most of the Galician samples (n = 46), mirroring the ‘Main’ GAL cluster, while the remaining two minor clusters comprised 7 and 3 individuals, respectively. In the broader NDNAB Iberian dataset, a total of 23 clusters were detected (including the Galician ones), each closely reflecting the geographic origin of the donors (Figure 4B; Figure S3 – Supplementary File). Unlike Bycroft et al., (2019) the first major split in the phylogenetic tree of our NDNAB Spanish dataset separates clusters exclusively found in the northern and geographically adjacent region of Cantabria (three clusters) and the Basque Country/Navarra (two clusters) from the rest of the Iberian Peninsula. The next phylogenetic subdivision separates Asturias (six clusters, with one dominant cluster dominating most individuals in the region [n = 36]), followed by Catalonia (with a unique and well-differentiated cluster; n = 94). Galician genomes emerge at the most recent branching point of the phylogeny, clustering alongside a mixed group of individuals from Andalusia and Central Iberia. This group comprises seven clusters, with three major ones including 128, 35, and 32 individuals, respectively. This clustering pattern differs markedly from that reported by Bycroft et al. (2019), where Galicians from Pontevedra, their hyper-highly stratified Galician province, exhibited the earliest genetic differentiation and accounted for about half of the total clusters found in Iberia. In their analysis, the next major split separated the Basque Country individuals from the rest of the Iberian Peninsula, followed by a division isolating the remaining Galician samples in their dataset.

The PCA analysis of the fineSTRUCTURE clusters found in the NDNAB database (Figure 4C) further supports the phylogenetic structure observed in the dendrogram (Figure 4B). The primary separation in PC1 (8.3%) distinguishes the Cantabria/Basque Country/Navarra clusters from the rest of the dataset. PC2 (4.1%) further differentiates the Basque Country/Navarra from the remaining regions. PC3 (2.7%) highlights the genetic distinction between Asturias and Cantabria, while PC4 (2.1%) again emphasizes the differences among these northern Iberian regions. Notably, all four principal components successfully capture and distinguish the clusters identified in the dendrogram, reinforcing the observed population structure.

[Friends of Oliver Society]

Galicia was a part of Al-Andalus. Asturias was the only Kingdom that Moors couldn't conquer. If OP wants to see whether Muslim conquest had a genetic impact on Iberians or not. She should look into Asturian genetics and compare it to rest of the Iberians. Asturians are the best baseline for that.

Galicia was never part of al-andalus except when a small community of Berbets lived in southern Galicia (a small area) that left to take part in a rebellion within a couple of decades.

In maps they show all of Iberia exceot Asturias as part of Al-Andalus but the Moors left the Atlantic strip alone because it's too mountainous. In these maps even the Basques are included, which is absurd. The Basques didn't form their own kingdom from a rebellion against the Moors.

Claiming you control territory doesn't mean you do. There were no known Moorish communities in the Atlantic strip except what I mentioned and no political control over them land.

When Asturias absorbed Galicia they didn't fight Moors. They fought Christians. They made alliances with local leaders and fought Galicians who would not submit to Asturian authority. No mention of Muslims.

[Beowulf]

Galicia was never part of al-andalus except when a small community of Berbets lived in southern Galicia (a small area) that left to take part in a rebellion within a couple of decades.

In maps they show all of Iberia exceot Asturias as part of Al-Andalus but the Moors left the Atlantic strip alone because it's too mountainous. In these maps even the Basques are included, which is absurd. The Basques didn't form their own kingdom from a rebellion against the Moors.

Claiming you control territory doesn't mean you do. There were no known Moorish communities in the Atlantic strip except what I mentioned and no political control over them land.

When Asturias absorbed Galicia they didn't fight Moors. They fought Christians. They made alliances with local leaders and fought Galicians who would not submit to Asturian authority. No mention of Muslims.



https://www.youtube.com/watch?v=Q0DyCuxBwvs

This is a video that i liked a lot which kinda explains that situation.

[Grace O'Malley]

Summary below.

This evidence collectively disputes the conventional assumption that North African and Middle Eastern genetic impact in northern Iberia stemmed exclusively from south-to-north diffusion during Islamic rule and the Reconquista (contra Bycroft et al., 2019). Instead, it points to earlier, independent episodes of gene flow as significant contributors to this genetic legacy. Possible drivers include:

Prehistoric contacts and Roman-era migrations,
Post-Phoenician trade networks,
Trans-Mediterranean interactions predating the 8th-century Islamic conquest, such as the trafficking of enslaved individuals.
Religious institutions—especially monasteries—may have been pivotal in this process, serving as hubs for the reception and management of enslaved labor, thereby shaping regional demography over centuries.

The Riddle of African Ancestry in Galicia
Genetic studies—primarily focusing on uniparental markers—have consistently identified a notable proportion of North African ancestry in Galicia, which is comparable to or even surpasses that of other Iberian regions (Supplementary Text). High-resolution whole-genome sequencing (WGS) data reveals that the North African/Middle Eastern genomic component in Galicians (GAL) ranges from 13.5% to 16.1%, exceeding estimates for other Iberian populations (IBS: 7.8%–12.6%; BAS: 5.1%–7.8%). Approximately half of this component aligns with Mozabite-like ancestry (Berbers from Algeria’s M’Zab Valley), while the remaining portion corresponds to Middle Eastern ancestry, primarily linked to Bedouin (BED) populations—nomadic Arab groups historically associated with the Levant and Arabia, whose expansion intensified after the 7th-century Islamic conquests.

Spatially, this ancestry is ubiquitous across Galicia, indicating long-term, widespread gene flow rather than isolated events. A subtle south-to-north gradient suggests entry via maritime or overland routes from the southwest, though further studies with expanded sampling are needed to clarify migration dynamics.

Sex-Biased Admixture Patterns
A striking discrepancy exists between genetic systems:

Y-chromosome: 21.2% North African ancestry (high paternal contribution).
Autosomal genome: 13.5%–16.5%.
Mitochondrial DNA (mtDNA): Only 1.0%.
This male-skewed admixture aligns with broader Iberian trends, likely reflecting historical male-dominated migrations—whether pre-Islamic, Islamic-era, or post-Reconquista.

Sub-Saharan Ancestry: A Further Complexity
A low but statistically significant sub-Saharan African component appears in:

GAL: 1.0%–2.8% (mean: 1.9%).
IBS: 0.3%–1.2% (mean: 0.75%).
BAS: Absent.
This signal is undetectable in unadmixed North African/sub-Saharan reference populations, complicating its interpretation. Possible explanations include:

Direct sub-Saharan gene flow (e.g., via trans-Saharan or Atlantic slave trade routes).
Model misattribution due to shared genetic drift between Mozabite-like and sub-Saharan groups (e.g., Yoruba [YRI]).
Historical and Phylogeographic Context
Uniparental marker studies (e.g., Barral-Arca et al. 2016) report sub-Saharan mtDNA in Iberia (0–5%), with elevated frequencies in regions like La Rioja (5.0%), Asturias (3.6%), and Galicia (2.9%; mean: 1.4% in mainland Spain).
Cerezo et al. (2012) suggest ~65% of European L-lineages (sub-Saharan mtDNA) arrived during Roman, Islamic, or transatlantic slave trade periods, while 35% may derive from earlier gene flow (~11,000 years ago).
Romani populations in Iberia also carry sub-Saharan mtDNA (Gómez-Carballa et al., 2013).
Ancient DNA supports prehistoric African-Iberian gene flow, possibly via the Strait of Gibraltar (González-Fortes et al., 2019).

Conclusions
Galicia’s unexpectedly high North African/Middle Eastern ancestry—coupled with sub-Saharan traces—points to multilayered demographic processes beyond Islamic-era migrations. Key contributors include:

Prehistoric trans-Mediterranean contacts.
Roman and post-Phoenician networks.
Sex-biased medieval migrations.
Early sub-Saharan introgression.
Limitations in existing African genomic datasets hinder precise resolution, urging future studies with expanded WGS data and ancient DNA to disentangle these complexities.


The study is suggesting that the North African and Middle Eastern in Galicia was not just one event or due to the Islamic period but could have occurred at earlier periods such as Roman military postings, Late Antique slave trade, and Mediterranean commerce so not just one period.

Here are the conclusions from the study.



This study represents the first comprehensive analysis of WGS variation in the Galician population. Despite Galicia’s historical reputation as a genetically isolated region within the Iberian Peninsula, our results reveal no strong signatures of long-term isolation. On the contrary, we observed low levels of fine-scale population structure, challenging previous claims of extreme substructure in the area.

Importantly, we identified a significantly higher North African and Middle Eastern genetic component in Galician genomes than previously reported. This ancestry is distributed across the entire Galician territory, suggesting widespread historical admixture and sustained gene flow within the region. Such connectivity may have reduced levels of inbreeding that might otherwise be expected in a small, demographically scattered population, particularly when contrasted with other Iberian groups with larger effective population sizes. We detected a male-biased contribution to this African component, along with a subtle South-to-North frequency gradient. This geographic pattern may reflect a southern entry point into Galicia, possibly via maritime or overland routes, though further investigation is needed to confirm this hypothesis. Most notably, the timing of admixture predates Islamic rule in the Iberian Peninsula, challenging the traditional assumption that the observed African component in Galicia is primarily the result of Arab-Berber expansion and the subsequent Reconquista.

In addition, our analyses show that PRS vary modestly across Galicia, with evidence of microgeographic stratification both regionally and among fine-scale genetic clusters. However, we also found that WGS provides limited additional resolution over exome sequencing for the characterization of common, clinically relevant variants in this population. This highlights the importance of matching sequencing strategies to specific research goals. In many cases, targeted approaches such as exome or gene panel sequencing may offer a more cost-effective means of maximizing clinically actionable insights.

So one thing I take away from this study among the earlier North African input is that Galicia is not particularly isolated or different from the rest of Spain.

Any other opinions? I hope more studies come out like this from different areas of Europe.

[Opie]

What about this map? Is it accurate?

141941

[Abaddon]

What i don't understand is why they mixed both NA and ME (Druze) components, that's the first time i see it.


What about this map? Is it accurate?

141941

Why does that interest you?

[Friends of Oliver Society]

What about this map? Is it accurate?

141941

I don't see anything wrong with it. The study said Asturias is more isolated than Galicia but not as isolated as the Basque lands, which implirs some NA admixture. I remember from Dienekes project people from Asturias and Cantabria had some NA (there is a community of shepherds in Cantabria that have NA papa y).

This can be explained by people captured in battle and slave raids that took people that were mixed with NA being brought north.

Most of Galicia's NA admixture is probably from this pre-Islamic incursion but that doesn't mean all of it is. Im sure much is from people who were captured.

Anyway, there was a previous study of an individual Galician bishop that had NA ancestry. This was a big clue that NA in Galicia predated the Moorish invasion because you don't become a bishop unless you're from an important noble family.
Muslim nobility wouldn't hand over their daughter to a Christian because it meant the daughter would have to convert to Christianity, which in Islam means death. On the other side, Christian kings in the early centuries when Christian kingdoms were weak made alliances (or as vassals) with the Moors by handing over their daughters to seal the deal. It's not a death sentence if a Christian converts to Islam.

[LamarckAndHisGiraffe]

I don't see anything wrong with it. The study said Asturias is more isolated than Galicia but not as isolated as the Basque lands, which implirs some NA admixture. I remember from Dienekes project people from Asturias and Cantabria had some NA (there is a community of shepherds in Cantabria that have NA papa y).

This can be explained by people captured in battle and slave raids that took people that were mixed with NA being brought north.

Most of Galicia's NA admixture is probably from this pre-Islamic incursion but that doesn't mean all of it is. Im sure much is from people who were captured.

Anyway, there was a previous study of an individual Galician bishop that had NA ancestry. This was a big clue that NA in Galicia predated the Moorish invasion because you don't become a bishop unless you're from an important noble family.
Muslim nobility wouldn't hand over their daughter to a Christian because it meant the daughter would have to convert to Christianity, which in Islam means death. On the other side, Christian kings in the early centuries when Christian kingdoms were weak made alliances (or as vassals) with the Moors by handing over their daughters to seal the deal. It's not a death sentence if a Christian converts to Islam.

Galicians have a pre-islamic minor berber input that is also found in Southern-Central Portugal.

[Flashball]

The most non-European region of Spain.

Many members of Apricity have their ancestors from this region.

[Friends of Oliver Society]

The most non-European region of Spain.

Many members of Apricity have their ancestors from this region.

Only one and he - which is actually me - can pass better in northern France than you (we've all seen your photos a million times because you're mentally ill over looking obviously foreign in northern France and lying about your ancestry in the past).