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A 10-century DNA study of Sint-Truiden reveals how medieval urbanization shaped genetic homogenization in the Low Countries.
Researchers sequenced 338 individuals from Sint-Truiden (8th-18th centuries). Early medieval residents were more genetically diverse, including migrants from Scotland or Ireland, and less related than present-day Flemish people. Gene variants for high vitamin D levels differed between those with Gaulish and Germanic ancestry. Despite Yersinia pestis in 5 of 58 late medieval burials, the second plague pandemic left no major population-scale genetic impact. Over centuries, the population became more similar to modern Limburg, likely due to reduced long-distance migration and local admixture of Germanic and Gaulish ancestries.
- Early/high medieval Sint-Truiden was more genetically heterogeneous and received migrants from Scotland or Ireland.
- Gene variants linked to high vitamin D blood levels differed between individuals of Gaulish and Germanic ancestry.
- The second plague pandemic (Yersinia pestis found in 5 of 58 late medieval burials) had no major population-scale impact on genetic diversity or immunity gene differentiation.
Sample interpretation
The site yielded 216 samples, with 99 Y-chromosome lineages resolved. Top Y haplogroups include R-P310 (n=4), I-M253 (n=3), and R-L151 (n=3), reflecting Germanic and Gaulish paternal lines. Mitochondrial DNA is diverse, with H1e1a, T2b, and K1a-T195C! each found in 4 individuals, plus T1a1, U6a1b1, and H1a1 (n=3 each). This mix supports the paper's finding of a heterogeneous early population that gradually homogenized.
For genealogy enthusiasts
For ancestry enthusiasts, this study shows that present-day genetic patterns in the Low Countries were shaped over centuries by migration, admixture, and urbanization. It highlights that medieval cities were melting pots, and that the genetic cline between Germanic and Gaulish ancestries formed gradually, not instantly.
Abstract
Background
Processes shaping the formation of the present-day population structure in highly urbanized Northern Europe are still poorly understood. Gaps remain in our understanding of when and how currently observable regional differences emerged and what impact city growth, migration, and disease pandemics during and after the Middle Ages had on these processes.
Results
We perform low-coverage sequencing of the genomes of 338 individuals spanning the eighth to the eighteenth centuries in the city of Sint-Truiden in Flanders, in the northern part of Belgium. The early/high medieval Sint-Truiden population was more heterogeneous, having received migrants from Scotland or Ireland, and displayed less genetic relatedness than observed today between individuals in present-day Flanders. We find differences in gene variants associated with high vitamin D blood levels between individuals with Gaulish or Germanic ancestry. Although we find evidence of a Yersinia pestis infection in 5 of the 58 late medieval burials, we were unable to detect a major population-scale impact of the second plague pandemic on genetic diversity or on the elevated differentiation of immunity genes.
Conclusions
This study reveals that the genetic homogenization process in a medieval city population in the Low Countries was protracted for centuries. Over time, the Sint-Truiden population became more similar to the current population of the surrounding Limburg province, likely as a result of reduced long-distance migration after the high medieval period, and the continuous process of local admixture of Germanic and Gaulish ancestries which formed the genetic cline observable today in the Low Countries.