Tracing Human Ancestral Migration from its Symbiotic Bacteria / Alexia Nguyen Trung

Tracing Human Ancestral Migration from its Symbiotic Bacteria / Alexia Nguyen Trung, in colloque "1st Virtual Conference for Women Archaeologists and Paleontologists. Nouveaux apports à l’étude des populations et environnements passés" organisé par le laboratoire Travaux et Recherches Archéologiques sur les Cultures, les Espaces et les Sociétés (TRACES) de l’Université Toulouse Jean Jaurès et le laboratoire Paléontologie Évolution Paléoécosystèmes (PALEVOPRIM) de l'Université de Poitiers, sous la responsabilité scientifique de Julie Bachellerie, Ana Belén Galán López (Traces), Émilie Berlioz et Margot Louail (Palevoprim). Université Toulouse Jean Jaurès, 8-9 mars 2021. Session 2 : Occupation of territories and population mobility. [Conférence enregistrée en distanciel].

Our understandingof the history of human migrations around the globe has greatly benefited fromthe development of human population genetics. It has revealed the routes ofcolonization and striking events of admixture of populations on the way. Manyspecies have accompanied humans on their journey, particularly microbes closelyassociated to their human host. H. pylori is present in the stomach of50% of humans. Its transmission is vertical, since it occurs particularlyduring childhood within the family, limiting the spread of a strain to itscarrier human group. Previous work has established that its presence in Homosapiens dates back to before the major human migrations and that H.pylori accompanied its host during the settlement process of continents, tothe point that the phylogeny traces in broad lines the history of humanmigrations since Out Of Africa. We have developed tools to reconstructthe history of bacterial genomes and particularly Horizontal Gene Transfer,which is the ability of bacteria to acquire genetic material from other strainsor species. We have shown the efficiency of these methods for retracing ancientcontacts and dating the history of free-living bacteria and we use the sameapproach to explore the history of H. pylori. By reconstructing thehistory of a sample of representative H. pylori strains, we use thesemethods to detail the historical contacts between strains and interpret theseevents in terms of contacts between ancestral human populations. We focus onthe complex history of European populations taking advantage of the ancientgenome of H. pylori extracted from Ötzi, the iceman, which dates back to around3000 BCA. Ötzi's H. pylori shows clear relationships with strains thatare found today in Asia. During this presentation we will detail the method anddiscuss our results on the history of human mobilities in Europe, through theprism of symbiotic bacteria.