The genetics of kinship in remote human groups.

For fifteen years, part of the work of our research team has been focused on the study of parental links between individuals living hundreds or thousands of years ago, whose remains have been found in single graves or large funerary complexes. These studies have been undertaken using methods developed by forensic genetics to identify individuals, mainly based on the genotyping of autosomal STR (Short Tandem Repeats). Issues arose from this work, namely the limits of studying small numbers of subjects, originating from groups of finite sizes where kinships cannot be inferred a priori and for which reference allelic frequencies do not exist. Although ideal human populations are rare when undertaking such studies, the Yakuts of Eastern Siberia constitute a very advantageous model, with large numbers of small pastoral communities and well-preserved archaeological material. The study of kinship in the ancient Yakuts allowed us to highlight the difficulties in analysing genetic data from small ancient human groups and to develop a strategy to improve the accuracy of statistical computations. This work describes this strategy and possible solutions to the study of populations outside of the frame of reference of global meta-populations, due either to isolation, remoteness or antiquity.

Tuberculosis epidemiology and selection in an autochthonous Siberian population from the 16th-19th century.

Tuberculosis is one of most ancient diseases affecting human populations. Although numerous studies have tried to detect pathogenic DNA in ancient skeletons, the successful identification of ancient tuberculosis strains remains rare. Here, we describe a study of 140 ancient subjects inhumed in Yakutia (Eastern Siberia) during a tuberculosis outbreak, dating from the 16(th)-19(th) century. For a long time, Yakut populations had remained isolated from European populations, and it was not until the beginning of the 17(th) century that first contacts were made with European settlers. Subsequently, tuberculosis spread throughout Yakutia, and the evolution of tuberculosis frequencies can be tracked until the 19(th) century. This study took a multidisciplinary approach, examining historical and paleo-epidemiological data to understand the impact of tuberculosis on ancient Yakut population. In addition, molecular identification of the ancient tuberculosis strain was realized to elucidate the natural history and host-pathogen co-evolution of human tuberculosis that was present in this population. This was achieved by the molecular detection of the IS6110 sequence and SNP genotyping by the SNaPshot technique. Results demonstrated that the strain belongs to cluster PGG2-SCG-5, evocating a European origin. Our study suggests that the Yakut population may have been shaped by selection pressures, exerted by several illnesses, including tuberculosis, over several centuries. This confirms the validity and necessity of using a multidisciplinary approach to understand the natural history of Mycobacterium tuberculosis infection and disease.