Urbanization and genetic homogenization in the medieval Low Countries revealed through a ten-century paleogenomic study of the city of Sint-Truiden - Genome Biology

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.

BioMed CentralOwyn Beneker

Unveiling Medieval Genetic Mysteries through Palaeogenomics

In an archaeological feat blending the intrigue of human history with cutting-edge genetics, researchers have uncovered new dimensions about medieval urbanization and genetic shifts through a comprehensive study of the city of Sint-Truiden. Situated in modern-day Flanders, Belgium, this remarkable study spans over a thousand years.

A Thousand-Year-Old Cemetery: A Portal to the Past

An excavation at Sint-Truiden unearthed a cemetery which had been in use for centuries, from as early as the seventh century. Within this space, known as Trudoplein and Groenmarkt, more than 3000 burials were discovered. The study scrutinized the genetic makeup of these individuals, offering a rare glimpse into the ancestral narratives of the medieval population.

The Early Medieval Mosaic

The early inhabitants of Sint-Truiden were found to display a remarkable genetic heterogeneity. The population favored a blend of Gaulish and Germanic ancestries, painting a picture of ongoing and complex interactions. Visitors and migrants from places like Scotland or Ireland added layers to this rich tapestry, intertwining destinies across the seas.

Grave Goods and Ancestral Connections

The findings revealed that individuals buried in proximity to the abbey at Trudoplein were likely more Gaulish in ancestry. It hints at how social and perhaps religious affiliations were reflected in burial practices, underscoring the city's vibrant socio-cultural milieu.

Migration in Medieval Low Countries

The medieval history of the Low Countries, particularly in northern Belgium's Flanders region, is a captivating tale of socio-political and economic transformation. A shining example of this transformation is the city of Sint-Truiden. This city, strategically located along significant Roman roads, became a bustling center of growth and trade over the centuries.

The Excavation and Its Palimpsest of Time

Recent archaeological excavations in the heart of Sint-Truiden revealed a cemetery in use from the seventh to the eighteenth century. Unearthed from the city squares of Trudoplein and Groenmarkt, over 3,000 burials offer a vibrant tapestry of demographic shifts and regional ancestry.

Illuminating Ancient Genomes

Through paleogenomic analysis, the study sequenced the genomes of 338 individuals, uncovering detailed patterns of migration and genetic admixture. The early medieval population of Sint-Truiden was notably diverse, incorporating migrants from Scotland or Ireland, evidencing a broader pattern of regional connectivity.

Exploring Genetic Ancestry and Homogenization

The medieval town of Sint-Truiden, located in what is now the Belgian province of Limburg, has proven to be a treasure trove for understanding genetic ancestry and homogenization in Europe. This vibrant archaeological site spans from the eighth to the eighteenth century, providing a ten-century paleogenomic window into the past.

Unearthing Diversity: Dig Sites and Findings

Within Sint-Truiden, two key burial sites were excavated: Trudoplein and Groenmarkt. These sites revealed over 3,000 burials, with artifacts and human remains that tell stories of migration and local ancestry.

The Genetic Tale of Two Populations

Analyzing ancient genomes, researchers discovered a fascinating split between Gaulish and Germanic ancestries. The Trudoplein burials revealed higher Gaulish influence, possibly due to the abbey's connections to the region of Metz, France. Meanwhile, the Groenmarkt site illustrated a more mixed ancestry, showing the varied origins of settlers in medieval Sint-Truiden.

Pandemics and Genetic Stability

Intriguingly, while there were signs of a Yersinia pestis infection, otherwise known as the plague, in some burials, there appeared to be little impact on the genetic diversity or immunity genes of the population at large. This poses poignant questions about the resilience and adaptability of medieval societies amidst catastrophic pandemics.

Impact of Plague on Medieval Populations

The research on the genetic and archaeological findings from Sint-Truiden offers profound insights into the impact of the plague on medieval populations. Among the 404 samples analyzed, a subset included individuals who were likely victims of the Black Death, providing the first genetic evidence of Yersinia pestis in this region.

DNA Discoveries: Individuals and the Plague

The rich genetic data harvested revealed fascinating stories about the people interred there. The team found evidence of Yersinia pestis from the fourteenth century in five individuals. The DNA signatures of the bacterium echo the pandemic's silent yet impactful outreach to medieval cities, providing scientific proof that the Black Death impacted Sint-Truiden, despite historical records failing to mention it.

A Continuity Captured over Centuries

As centuries rolled on, Sint-Truiden's genetic profile became more homogenous, aligning closely with what we observe in the present-day people of Limburg. This gradual cline of genetic mixing reflects reduced long-distance travel and highlights localized interactions within the medieval Low Countries.

From Ancestral Stories to Present-Day Populations

Over the centuries, the genetic lines visibly tightened into the pattern seen today, mirroring the demographic landscape of modern Limburg. Yet the enduring question remains—how did remarkable events like the Black Death shape not just genetic lines, but human lives and history?

A Living Document of History

With history etched in bones and DNA, Sint-Truiden provides a narrative of continuity and change, weaving together the dynamics of migration, socio-economic shifts, and epidemiological pressures. This study not only deciphers the genetic story of a past city but also brings into focus the intricacies of human existence through the ages.

As technological advancements continue to decode the past linguistically encrypted within our genes, studies like these keep slicing through the mist of time, bringing to light the lived experiences of those who walked long before us. Sint-Truiden stands as a beacon today, not just of ancient struggle, but also as a testament to human resilience and adaptation in the face of crisis.

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