Mitochondrial DNA genetic diversity and LCT-13910 and deltaF508 CFTR alleles typing in the medieval sample from Poland

Searching for signals of recent natural selection in genes of the innate immune response - ancient DNA study

The last decade has seen sharp progress in the field of human evolutionary genetics and a great amount of genetic evidence of natural selection has been provided so far. Since host-pathogen co-evolution is difficult to trace due to the polygenic nature of human susceptibility to microbial diseases, of particular interest is any signal of natural selection in response to the strong selective pressure exerted by pathogens. Analysis of ancient DNA allows for the direct insight into changes of a gene pool content over time and enables monitoring allele frequency fluctuations. Among pathogenic agents, mycobacteria are proved to have remained in an intimate, long-lasting relation with humans, reflected by the current high level of host resistance. Therefore, we aimed to investigate the prevalence of several polymorphisms within innate immune response genes related to susceptibility to mycobacterial diseases (in SLC11A1, MBL2, TLR2, P2RX7, IL10, TNFA) in time series data from North and East Poland (1st-18th century AD, n = 207). The comparison of allele frequencies over time revealed a predominant role of genetic drift in shaping past gene pool of small, probably isolated groups, which was explained by the high level of population differentiation and limited gene flow. However, the trajectory of frequency fluctuations of two SNPs suggested the possibility of their non-neutral evolution and the results of applied forward simulations further strengthened the hypothesis of natural selection acting on those loci. However, we observed an unusual excess of homozygosity in the profile of several SNPs, which pinpoints to the necessity of further research on temporally and spatially diverse samples to support our inference on non-stochastic evolution, ideally employing pathway-based approaches. Nevertheless, our study confirms that time series data could help to decipher very recent human adaptation to life-threatening pathogens and assisting demographic events.

Analysis of medieval mtDNA from Napole cemetery provides new insights into the early history of Polish state

Contemporary historical anthropology and classical archaeology are concerned not only with such fundamental issues as the origins of ancient human populations and migration routes, but also with the formation and development of inter-population relations and the mixing of gene pools as a result of inter-breeding between individuals representing different cultural units. The contribution of immigrants to the analysed autochthonous population and their effect on the gene pool of that population has proven difficult to evaluate with classical morphological methods. The burial of one individual in the studied Napole cemetery located in central Poland had the form of a chamber grave, which is typical of Scandinavian culture from that period. However, this fact cannot be interpreted as absolute proof that the individual (in the biological sense) was allochtonous. This gives rise to the question as to who was actually buried in that cemetery. The ancient DNA results indicate that one of the individuals had an mtDNA haplotype typical of Iron Age northern Europe, which suggests that he could have arrived from that area at a later period. This seems to indirectly confirm the claims of many anthropologists that the development of the early medieval Polish state was significantly and directly influenced by the Scandinavians.