Background Hansen’s disease (leprosy), widespread in medieval Europe, is today mainly prevalent in tropical and subtropical regions with around 200,000 new cases reported annually. Despite its long history and appearance in historical records, its origins and past dissemination patterns are still widely unknown. Applying ancient DNA approaches to its major causative agent, Mycobacterium leprae, can significantly improve our understanding of the disease’s complex history. Previous studies have identified a high genetic continuity of the pathogen over the last 1500 years and the existence of at least four M. leprae lineages in some parts of Europe since the Early Medieval period. Results Here, we reconstructed 19 ancient M. leprae genomes to further investigate M. leprae’s genetic variation in Europe, with a dedicated focus on bacterial genomes from previously unstudied regions (Belarus, Iberia, Russia, Scotland), from multiple sites in a single region (Cambridgeshire, England), and from two Iberian leprosaria. Overall, our data confirm the existence of similar phylogeographic patterns across Europe, including high diversity in leprosaria. Further, we identified a new genotype in Belarus. By doubling the number of complete ancient M. leprae genomes, our results improve our knowledge of the past phylogeography of M. leprae and reveal a particularly high M. leprae diversity in European medieval leprosaria. Conclusions Our findings allow us to detect similar patterns of strain diversity across Europe with branch 3 as the most common branch and the leprosaria as centers for high diversity. The higher resolution of our phylogeny tree also refined our understanding of the interspecies transfer between red squirrels and humans pointing to a late antique/early medieval transmission. Furthermore, with our new estimates on the past population diversity of M. leprae, we gained first insights into the disease’s global history in relation to major historic events such as the Roman expansion or the beginning of the regular transatlantic long distance trade. In summary, our findings highlight how studying ancient M. leprae genomes worldwide improves our understanding of leprosy’s global history and can contribute to current models of M. leprae’s worldwide dissemination, including interspecies transmissions.

Link to this article: http://journals.cambridge.org/abstract_S0003598X00049887How to cite this article: Dmitry S. Korobov and Alexander V. Borisov (2013). The origins of terraced eld agriculture in the Caucasus: new discoveries in the Kislovodsk basin. Kislovodsk basin 0 km 400 N Turkey Iran Iraq G eo rg ia Azerbaijan A Ukraine Kazakhstan n Russia A r m e n ia n i n ia Terraced field systems are a feature of many regions of the world and have been dated as early as 6000 cal BC in the Levant (Kuijt et al. in Antiquity 81 (2007: 106-18)). The discovery of agricultural terraces in the northern Caucasus, reported here, extends their distribution into a new area. Relatively low population levels in the late medieval and early modern periods have preserved several blocks of terraced fields, some of them created at the beginning of the first millennium BC, others in the mid first millennium AD. The earlier terraced fields, associated with material and settlements of the Koban culture, culminated in over-exploitation of the land and exacerbated erosion during environmental change in the mid first millennium BC. The later series of terraced fields are of different form and are associated with the settlement in the area of communities of Alans in the first millennium AD. They largely avoided the areas rendered infertile by Koban period overexploitation. The morphology and chronology of the terraced field systems are explored using a combination of aerial photography, GIS analysis and field investigations.

No abstract

No abstract

No abstract