Isotope analysis and radiocarbon dating on human skeletons from medieval Sint-Truiden, Belgium

BackgroundProcesses shaping the formation of the present-day population structure in highly urbanized Northern Europe are still relatively 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.ResultsWe perform low-coverage sequencing of the genomes of 338 individuals spanning the 8th to the 18th 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.ConclusionsThis 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.塑造高度城市化北欧当前人群结构的背后过程目前仍相对缺乏深入认知。我们仍未明确当前可观测到的区域差异于何时、以何种方式形成，亦不清楚中世纪及之后的城市扩张、人口迁移与疾病大流行对这些过程产生了何种影响。 本研究对位于比利时北部法兰德斯（Flanders）地区圣特赖登（Sint-Truiden）市的8至18世纪338名个体的基因组开展了低覆盖度测序（low-coverage sequencing）。中世纪早期/盛期的圣特赖登人群结构更为多元，曾接收来自苏格兰或爱尔兰的移民，且彼时个体间的遗传亲缘关系较如今法兰德斯地区的当代人群更为淡薄。我们发现，携带高卢（Gaulish）或日耳曼（Germanic）血统的个体之间，与血液高维生素D水平相关的基因变异存在显著差异。尽管我们在58座中世纪晚期墓葬中的5座里检测到了鼠疫耶尔森菌（Yersinia pestis）感染的证据，但未能发现第二次鼠疫大流行（second plague pandemic）对人群遗传多样性或免疫基因的显著分化产生大规模群体层面的影响。 本研究揭示，低地国家（Low Countries）一座中世纪城市人群的遗传均质化过程绵延数个世纪。随着时间推移，圣特赖登人群逐渐与周边林堡省的当代人群愈发相似，这一现象大概率源于中世纪盛期之后长距离迁移的减少，以及日耳曼与高卢血统持续的本地混合过程——该过程塑造了如今低地国家可观测到的遗传梯度（genetic cline）。