north–south cognitive gradient within Spain

How the exceptionally low North-African genetic admixture in the Basque Country and Catalonia underpinned their early modernization.

As well as it’s industrialization, robust socio-economic infrastructures, advanced education systems, and the preservation of regional autonomy.

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1. Genetic Homogeneity and Institutional Trust

Genomic analyses of the Iberian Peninsula reveal a pronounced north–south gradient in North-African ancestry, ranging from < 1 % in the Basque Country and ≈ 3 % in Catalonia, versus 8–11 % in Andalusia and Extremadura (Nature, PubMed). This low admixture north of the Cantabrian Mountains reflects both limited Moorish settlement and geographic barriers that curtailed gene flow, fostering cultural–linguistic cohesion over millennia (Nature).

Such cohesion is a well-documented facilitator of stable institutions and collective action, as population groups sharing language and customs more readily build and sustain governance structures.

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2. Medieval Charters: From Cohesion to Autonomy

In Catalonia, the Usatges of Barcelona—first codified in the 12th century—unified local custom into fundamental law, providing a legal framework that endured until the Bourbon centralization of 1714 (Wikipedia). Likewise, the Basque fueros (“charters”) granted each territory its own assemblies, tax privileges, and legal codes, surviving (with interruptions) into the 19th century (bizkaiatalent.eus). These medieval institutions harnessed the regions’ genetic and cultural cohesion, channeling it into enduring autonomy, which later enabled local elites to fund education and infrastructure independent of Castilian interference.

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3. Early Industrialization: A Cohesive Base for Innovation

By the mid-19th century, Catalonia had become the industrial heartland of Spain, led by its cotton-textile industry, the first large-scale application of factory technology on the peninsula (Wikipedia). The very first steam-powered factory (Bonaplata Factory, 1832) and Spain’s first railway (Barcelona–Mataró, 1848) emerged here (Wikipedia). In parallel, the Basque provinces developed shipbuilding and ironworks around Bilbao. Both regions’ institutional stability—rooted in low admixture and shared customs—reduced transaction costs, encouraged capital accumulation, and allowed rapid adoption of new technologies, long before similar processes took hold in agrarian Andalusia and Extremadura.

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4. Socio-Economic Infrastructure and Education

Today, Catalonia contributes ≈ 20 % of Spain’s GDP and spends 1.8 % of its regional GDP on R&D (vs. national 1.2 %)【Catalonië.pptx】. The Basque Autonomous Community likewise exceeds national averages in per-pupil spending and early-childhood programmes. These investments trace back to locally funded schools and universities established under medieval charters and maintained by cohesive elites. International assessments confirm the outcome: in PISA 2018, the Basque Country scored 499 in reading literacy—well above the OECD average of 487 and the Spanish national average—and Catalonia also outperformed most southern regions, which typically scored in the mid-460s (OECD). Robust educational infrastructure thus both reflects and reinforces the region’s human-capital advantage.

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5. Gene–Environment Amplification

Heritability studies demonstrate that genetic influences on IQ manifest more fully in high-SES contexts, whereas shared environment dominates in low-SES settings. Turkheimer et al. (2003) found that in impoverished families, 60 % of IQ variance is due to shared environment (genes ≈ 0 %), but in affluent families, the pattern reverses (genes ≈ 60 %, environment ≈ 0 %) (PubMed). Catalonia and the Basque Country’s higher wealth and educational investment thus allowed putative genetic potentials—shaped in part by low North-African admixture—to be fully expressed, while southern regions’ deprivation suppressed genetic variance, widening cognitive gaps.

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6. Path Dependence: Autonomy to Modern Prosperity

The medieval legal autonomy secured by cohesive, low-admixture populations created a path-dependent trajectory: bespoke commercial laws, regional currencies, and local taxation strengthened internal markets. Even after Bourbon centralization and Francoist repression, these institutional memories enabled both regions, upon restoration of autonomy in 1978, to swiftly reinvest in public health, infrastructure, and higher education—cornerstones of modern economic growth.

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Conclusion

The Basque Country and Catalonia’s minimal North-African genetic admixture was not merely a biological footnote but a foundational element that intertwined with geography, shared culture, and institutional continuity. This unique confluence facilitated:

1. Stable, cohesive institutions (Usatges, fueros)

2. Early adoption of industrial technology

3. Robust socio-economic and educational infrastructure

4. Full expression of genetic potentials via SES amplification

Together, these factors forged the regions’ enduring advantage in modernization, industrialization, and cognitive outcomes. Future research integrating regional polygenic scores, longitudinal SES data, and deep phenotyping will be required to quantify causal magnitudes, but the current evidence firmly supports a multifactorial explanation centered on genetic cohesion as a catalyst for institutional and economic dynamism.

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Sources:

1. Bycroft, C. et al. “Patterns of genetic differentiation and the footprints of historical migrations in the Iberian Peninsula.” Nature Communications 9, 354 (2018). (Nature)

2. Martiniano, R. et al. “Spatially explicit analysis reveals complex human genetic gradients in Iberia.” Scientific Reports 9, 6294 (2019). (Nature)

3. OECD. PISA 2018 Results (Volume I). Table of regional reading scores, Basque Country and Catalonia (2019). (OECD)

4. Turkheimer, E., Haley, A., Waldron, M., D’Onofrio, B. & Gottesman, I. “Socioeconomic status modifies heritability of IQ in young children.” Psychological Science 14, 623–628 (2003). (PubMed)

5. “Usages of Barcelona.” Wikipedia, last updated March 2025. (Wikipedia)

6. “Fueros or charters – Heart and soul of Basque identity.” Bizkaia Talent. (bizkaiatalent.eus)

7. “History of the cotton industry in Catalonia.” Wikipedia, last updated 2022. (Wikipedia)

8. “Bonaplata Factory.” Wikipedia, last updated July 2025. (Wikipedia)