Archaeogenetic Perspectives on Population History and Health in Northeastern Fennoscandia

Abstract

According to recent ancient DNA studies, European populations mainly carry a combination of ancestry components from Palaeolithic to the early Bronze Age hunter-gatherers, the farming-associated populations from the Neolithic on, and the Eurasian steppe pastoralists from the Bronze Age, albeit in various proportions. Additionally, prehistoric Siberians from the modern-day northern Russia are assumed to have genetically contributed to Northeast-European populations. In this thesis, genetic changes in the Fennoscandian population, especially concerning the Finns, situated at the crossroads of east and west, are inspected through ancient DNA. The region corresponding to modern-day Finland was a long-time home to groups sustained by foraging, hunting and fishing, whereas agricultural communities emerged in the area only gradually and relatively late, approximately from ~2000BCE onwards. The low population size throughout Finland’s history is partly responsible for a reduced genetic diversity. The sparsity of the early settlements has likely spared the region from some of the large European epidemics of infectious diseases. Increase in the population growth from medieval to early modern period paved way for new trading networks and introduced further genetic admixture to the local gene pool. However, notable genetic segregations both within Finland, and between its modern population and other Europeans still exist. In addition to human migrations, the urbanization over historical time periods also facilitated the spread of infectious agents from elsewhere in Europe, affecting the health conditions of the northern peripheries.

In this dissertation, a previously undescribed Siberian ancestry source is detected in prehistoric Fennoscandia, illuminating the arrival of an excess eastern ancestry in the local gene pool today. Furthermore, genetic signals from the hunter-gatherer and agriculture-associated ancestors of Finns and Sámi, and genetic dichotomy between southwestern and northeastern Finland are investigated through maternal lineages from the Roman Iron Age (300- 800 CE) to the early modern period (1500-1800 CE). Finally, the aspect of health in the historical northern communities is addressed, and the causative agent of syphilis and other treponemal diseases, Treponema pallidum, is reconstructed genome-wide from archaeologically studied human remains from Finland, Estonia and the Netherlands. This ancient pathogen genomics based study showcases the relationships between modern and historical forms of treponemal bacteria and reveals the high diversity of pathogenic Treponema pallidum strains in early modern Europe.