Ribera i Lacomba, A. | Search bioRxiv

bioRxiv2024

Medieval genomes from eastern Iberia illuminate the role of Morisco mass deportations in dismantling a long-standing genetic bridge with North Africa

BackgroundThe Islamic influence on the Iberian Peninsula left an enduring legacy culturally and linguistically, however the demographic impact is less well understood. This study aims to explore the dynamics of gene flow and population structure in eastern Iberia from the early to late Medieval period through ancient DNA. ResultsOur comprehensive genomic analysis uncovered gene flow from various Mediterranean regions into Iberia before the Islamic period, supporting a pre-existing pan-Mediterranean homogenization phenomenon during the Roman Empire. North African ancestry is present but sporadic in late antiquity genomes but becomes consolidated during the Islamic period. We uncovered one of the earliest dated Islamic burials in Spain, which showed high levels of inbreeding. For the first time we also prove the persistence of North African ancestry in a Christian cemetery until the 17th century, in addition to evidence of slave traffick from the Maghreb. ConclusionsThis study reveals the complex interaction between political events and cultural shifts that influenced the population of eastern Iberia. It highlights the existence of a slave trade and underscores the lasting impact of historical events, such as the Expulsion of the Moriscos in 1609 CE, on the regions genetic and cultural landscape through mass population displacement and replacement.

evolutionary biology↗

bioRxiv2018

Ancient Yersinia pestis genomes from across Western Europe reveal early diversification during the First Pandemic (541-750)

The first historically documented pandemic caused by Yersinia pestis started as the Justinianic Plague in 541 within the Roman Empire and continued as the so-called First Pandemic until 750. Although palaeogenomic studies have previously identified the causative agent as Y. pestis, little is known about the bacteriums spread, diversity and genetic history over the course of the pandemic.\n\nTo elucidate the microevolution of the bacterium during this time period, we screened human remains from 20 sites in Austria, Britain, Germany, France and Spain for Y. pestis DNA and reconstructed six new genomes. We present a novel methodological approach assessing SNPs in ancient bacterial genomes, facilitating qualitative analyses of low coverage genomes from a metagenomic background. Phylogenetic analysis reveals the existence of previously undocumented Y. pestis diversity during the 6th-7th centuries, and provides evidence for the presence of multiple distinct Y. pestis strains in Europe. We offer genetic evidence for the presence of the Justinianic Plague in the British Isles, previously only hypothesized from ambiguous documentary accounts, as well as southern France and Spain, and that southern Germany seems to have been affected by at least two distinct Y. pestis strains. Four of the reported strains form a polytomy similar to others seen across the Y. pestis phylogeny, associated with the Second and Third Pandemics. We identified a deletion of a 45 kb genomic region in the most recent First Pandemic strain affecting two virulence factors, intriguingly overlapping with a deletion found in 17th-18th-century genomes of the Second Pandemic.\n\nSignificance StatementThe first historically reported pandemic attributed to Yersinia pestis started with the Justinianic Plague (541-544) and continued for around 200 years as the so-called First Pandemic. To date, only one Y. pestis strain from this pandemic has been reconstructed using ancient DNA. In this study, we present six new genomes from Britain, France, Germany and Spain, demonstrating the geographic range of plague during the First pandemic and showing microdiversity in the Early Medieval Period. Moreover, we detect similar genome decay during the First and Second Pandemic (17th to 18th century) that includes the same two virulence factors, thus providing an example of potential convergent evolution of Y. pestis during large scale epidemics.

evolutionary biology↗