Stone Age Yersinia pestis genomes shed light on the early evolution, diversity, and ecology of plague

The bacterial pathogenYersinia pestisgave rise to devastating outbreaks throughouthuman history, and ancient DNA evidence has shown it afflicted human populations asfar back as the Neolithic.Y. pestisgenomes recovered from the Eurasian Late Neolithic/Early Bronze Age (LNBA) period have uncovered key evolutionary steps that led to itsemergence from aYersinia pseudotuberculosis-like progenitor; however, the number ofreconstructed LNBA genomes are too few to explore its diversity during this criticalperiod of development. Here, we present 17Y. pestisgenomes dating to 5,000 to 2,500y BP from a wide geographic expanse across Eurasia. This increased dataset enabled usto explore correlations between temporal, geographical, and genetic distance. Ourresults suggest a nonflea-adapted and potentially extinct single lineage that persistedover millennia without significant parallel diversification, accompanied by rapid dis-persal across continents throughout this period, a trend not observed in other pathogensfor which ancient genomes are available. A stepwise pattern of gene loss provides fur-ther clues on its early evolution and potential adaptation. We also discover the presenceof theflea-adapted form ofY. pestisin Bronze Age Iberia, previously only identified inin the Caucasus and the Volga regions, suggesting a much wider geographic spread ofthis form ofY. pestis. Together, these data reveal the dynamic nature of plague’s forma-tive years in terms of its early evolution and ecology

The postearthquake stress state on the Tohoku megathrust as constrained by reanalysis of the JFAST breakout data

International audienceThe Japan Trench Fast Drilling Project (JFAST) endeavored to establish the stress state on theshallow subduction megathrust that slipped during theM9 Tohoku earthquake. Borehole breakout datafrom the drill hole can constrain both the orientation and magnitude of the principal stresses. Here wereanalyze those data to refine our understanding of the stress state on the fault. In particular, we (1) improvethe identification of breakouts, (2) consider a fuller range of stress states consistent with the data, and (3)incorporate new and more robust laboratory constraints on rock strength. The original conclusion that theregion is in a normal faulting regime after the earthquake is strengthened by the new analysis. The combinedanalysis suggests that the earthquake released sufficient elastic strain energy to reset the local stressfield