Halle | Leipzig Team
PI Johannes Krause
Sampling of a petrous bone in a clean room facility using a dentist drill.
Further steps such as DNA extraction, library preparation, indexing and amplification are performed to prepare samples for sequencing.
HistoGenes – Role of archaeogenetics in the project
All skeletal elements for genetic investigations are processed in a clean room facility to avoid contamination with modern DNA. Bone powder is obtained from inside the petrous bones and the pulp chamber of teeth using a dentist drill. Subsequently, DNA is extracted and prepared for Next-Generation sequencing.Within recent years, methodological advances regarding the sequencing of genomic data and new approaches to model genetic components of different populations allowed the recovery and analysis of ancient DNA (aDNA) from various types of remains. This is opening up new perspectives to study the human past. In order to trace population history and migration in the Carpathian Basin during the Early Medieval period, petrous bones or teeth from more than 6000 individuals are being sampled. These elements usually contain a high amount of human endogenous DNA, i.e. DNA that belonged to the individual studied rather than for example DNA of the soil bacteria. In addition, teeth allow us to detect blood-borne pathogens and thus, to obtain a comprehensive picture about disease prevalence and spread throughout time.
Genetic ancestr and population structure
Looking at the genetic data of humans from individual cemeteries allows us to investigate levels of close biological relatedness as well as broader patterns of genetic ancestry and population structure. To account for the fact that genetic differences in most of Europe were already much smaller within the first millennium CE compared to prehistoric times, a high number of samples is required. This makes it also possible to disentangle relatedness on a very fine scale up to very low degrees of relatedness which provides important insights into population and family structure. In addition, IBD detection as well as shared SNPs (single nucleotide polymorphisms) across individuals are highly informative when aiming to find connections between individuals from different cemeteries and regions that span multiple centuries. We can thus study continuity and discontinuity on a population as well as community level.
In addition, all data is broadly screened for pathogens which provides valuable information on the impact of diseases and pandemics, such as the Justinianic plague on Early Medieval societies in Europe. A genetic screening is specifically useful to find pathogens, such as Yersinia pestis (causal agent of plague), that do not leave characteristic lesions on the skeleton and thus, can easily be dismissed by archaeological and anthropological investigations alone. The combination of pathogen analysis and complete human genomes might further provide clues to differing immunities in the various population groups.
Interpretation of the genetic findings from the large number of studied individuals in light of historical, archaeological, isotope and climatic data obtained by other researchers involved in this project allows us to generate a refined and complete picture of central eastern Europe during the Early Middle Ages.
Hypothesis on the Avar Origin and Genomic Evidence
Full study: doi:10.1016/j.cell.2022.03.007