Delving into the past, the international research team analyzed ancient DNA extracted from thirteen individuals interred in an Islamic cemetery dated between the tenth and twelfth centuries CE. The genetic data illuminate a complex mosaic of ancestries, ranging from predominantly European lineages to North African origins. This admixture traces back to the Muslim ascendancy of Ibiza in 902 CE, aligning closely with historical accounts documenting two primary waves of demographic change: firstly, the Umayyad expansion that inaugurated settlement on the island, and secondly, the Almoravid conquests that heralded fresh influxes in the early twelfth century.

The DNA sequences reveal not only European and North African connections but also compelling evidence of sub-Saharan African ancestry in two individuals. These findings resonate with medieval Arabic chronicles discussing trans-Saharan military expeditions and slave trade routes, but now provide direct biological proof of Ibiza’s entanglement in these expansive and sophisticated long-distance networks. One individual’s genome pointedly traces back to people from Senegambia, while the other exhibits genetic markers linked to southern Chad, affirming the breadth of cultural and demographic interactions mediated through the Sahel.

According to Ricardo Rodríguez-Varela, the study’s lead author and a researcher at Stockholm University’s Department of Archaeology and Classical Studies, these genomic revelations underpin a more nuanced understanding of Islamic Iberia’s demographic composition. “Our results demonstrate that communities in Islamic Iberia were not insular but part of an expansive network stretching into western and central Africa’s Sahel,” he explains. This biological connectivity corroborates written historical sources and paints a vivid picture of intersectional societies shaped by migration, trade, and cultural exchange across formidable geographical barriers.

Methodologically, the team employed cutting-edge genomic techniques including genotype imputation and haplotype-based local ancestry inference. These sophisticated statistical methods allowed them to reconstruct the timing and nature of gene flow events with remarkable precision. Their analyses suggest the primary North African genetic influx into Ibiza occurred merely two to seven generations prior to the individuals’ lifetimes, situating the main admixture episode in the late ninth century CE. This temporal estimate harmonizes with the historical timeline of Islamic incursions into the western Mediterranean, evidencing a relatively rapid genetic and cultural transformation.

Beyond population genetics, the researchers harnessed metagenomic approaches to screen for infectious pathogens within the ancient samples. Remarkably, one individual was identified as carrying Mycobacterium leprae, the causative agent of leprosy. This represents the first genetically confirmed case of leprosy from medieval Islamic Iberia. Intriguingly, this individual’s burial adhered to orthodox Islamic funerary rites without indications of social ostracism or differential treatment, paralleling patterns documented within contemporary Christian communities in the region.

Zoé Pochon, a co-author and metagenomics expert at Stockholm University, highlights the significance: “The integration of pathogen DNA analysis with ancient genomic data provides a dramatically expanded perspective on disease ecology and societal attitudes in the medieval Mediterranean world.” The discovery challenges assumptions about stigma surrounding leprosy during the period and suggests communal norms may have transcended religious divides.

Phylogenetic reconstruction situates the M. leprae genome near the root of a lineage prevalent across Europe from the seventh to thirteenth centuries. This lineage’s close relation to an early-diverging strain isolated in medieval Italy reinforces the hypothesis that Ibiza was a critical nexus within broader epidemiological and trade networks bridging the Mediterranean basin and continental Europe. These findings underscore how population movement facilitated not only human genetic flux but also the spread of infectious diseases, conveying profound implications for understanding the historical dynamics of disease transmission.

The study’s insights collectively illuminate how medieval Ibiza functioned as a genetic and cultural crossroads rather than an isolated periphery. Through integrating genomic data with archaeological and historical narratives, the research delineates a transformative epoch when Islamic and Christian spheres of influence in Iberia profoundly intermeshed. Anders Götherström, senior author and leader of the archaeogenetics group at the Centre for Palaeogenetics, asserts that “ancient DNA offers a unique lens into the lived realities underpinning epochal historical events, revealing the intimate biographies beneath geopolitical shifts.”

This comprehensive research advances the field of archaeogenetics by combining high-resolution genetic analyses with metagenomic pathogen screening, thereby forging a multidimensional reconstruction of medieval identities and health. It advances our understanding not only of demographic history but also of disease ecology and social interactions in regions where diverse cultures intersected. The findings herald a new era where genomic technologies decode the complexities of human history embedded within archaeological remains, challenging simplistic narratives and spotlighting the intertwined nature of migration, commerce, and health.

Collectively, these results compel a reassessment of the Mediterranean’s medieval past, portraying Ibiza as a microcosm of dynamic interactions spanning continents and cultures. The robust evidence for sub-Saharan African presence within Islamic Iberian populations affirms the Sahel’s crucial role in shaping medieval Mediterranean societies—a factor often marginalized in historical discourse. By integrating genetic evidence, historical documentation, and archaeological context, this study provides a compelling and nuanced account of how people, pathogens, and cultures converged at the crossroads of civilization.

In conclusion, the investigation of medieval burials from Ibiza opens vibrant new avenues for understanding the genetic and pathogenic diversity that characterized the Islamic Mediterranean world. Through meticulous genomic scrutiny and interdisciplinary collaboration, the study rewrites historical conceptions, revealing a richly interconnected world marked by migration, adaptation, and shared human experiences. As ancient DNA research continues to expand, studies like this exemplify the transformative power of genetics in unraveling the intricate tapestry of our collective past.

Subject of Research: Human tissue samples
Article Title: Analysis of medieval burials from Ibiza reveal genetic and pathogenic diversity during the Islamic period
News Publication Date: 26-Mar-2026
Web References: 10.1038/s41467-026-70615-9
References: Nature Communications
Keywords: ancient DNA, medieval Iberia, genetic diversity, Islam in Iberia, sub-Saharan ancestry, Mycobacterium leprae, leprosy, trade networks, archaeogenetics, Sahel, genomic admixture, pathogen genomics

The Centre for Palaeogenetics, a collaborative effort between Stockholm University and the Swedish Museum of Natural History, drew upon an extensive repository comprising 483 mammoth specimens, with 440 samples undergoing genetic sequencing for the first time. Among these materials was a remarkable steppe mammoth specimen dated to approximately 1.1 million years ago. Applying meticulous methods that differentiate between ancient host-associated microbes and modern contaminants, the researchers leveraged next-generation sequencing technologies and complex computational algorithms to tease apart the nuances embedded within this ancient DNA.

Lead author Benjamin Guinet eloquently describes the significance of their work: “Holding a million-year-old mammoth tooth and extracting microbial DNA that once existed in symbiotic association with the animal transcends previous temporal limits of ancient DNA studies. This pushes molecular paleontology into a new era where we can explore the co-evolution of microbes and their hosts far beyond anything previously achieved.” Such capabilities provide groundbreaking opportunities to investigate how microbial communities adapted, persisted, or contributed to the evolutionary trajectories of extinct species.

Crucially, the study identified six distinct microbial clades that demonstrated persistent associations with mammoth hosts across both temporal and geographic spectra. These groups include bacteria related to Actinobacillus, Pasteurella, Streptococcus, and Erysipelothrix, genera known to contain both symbiotic and pathogenic species. Notably, one Pasteurella-related bacterium closely aligns genetically with known pathogens responsible for fatal disease outbreaks in modern elephants. Since elephants are the closest extant relatives of mammoths, these results provoke provocative hypotheses about the disease ecology of prehistoric megafauna, raising questions about how microbial infections may have influenced mammoth health, population dynamics, and possibly even their extinction.

Perhaps the most extraordinary aspect of this research lies in the reconstruction of partial genomes from Erysipelothrix bacteria found in the 1.1-million-year-old steppe mammoth. This sample represents the oldest validated host-associated microbial DNA ever retrieved, pushing the boundaries of molecular preservation and analysis. The retrieval and assembly of such ancient genomes required extraordinary care to account for postmortem DNA damage, contamination controls, and the application of sophisticated phylogenetic tools to authenticate the ancient origin and biological relevance of the sequences.

Tom van der Valk, senior researcher and co-author, highlights the technical and interpretive challenges: “Microbial genomes evolve quickly and can be difficult to trace over vast time scales. Obtaining authentic DNA data spanning over a million years was akin to following an ever-changing trail. Our findings underscore that ancient remains can harbor rich biological information beyond the host genome, allowing us to piece together snapshots of ancient microbial ecosystems and their roles in adaptation, disease, and extinctions during the Pleistocene epoch.”

The research thereby expands the conceptual framework of paleogenetics by illuminating the microbiomes of extinct large mammals, providing a novel lens into prehistoric biology. While definitive conclusions on the health impacts of these microbes are constrained by DNA degradation and the paucity of direct comparative data, the persistent presence of certain microbial lineages over hundreds of thousands of years is suggestive of stable ecological relationships. This temporal longevity spans the broad geographic distribution of mammoths and includes the late survival of woolly mammoths on Wrangel Island until roughly 4,000 years ago, offering a rare glimpse into evolutionary continuity and microbial-host interactions over deep time.

Love Dalén, Professor of Evolutionary Genomics and co-investigator, emphasizes the transformative implications of the study: “Our work inaugurates a new chapter in the biological understanding of extinct species. In addition to decoding mammoth genomes, we can now begin to unravel the complex microbial communities that lived within and alongside these animals, offering profound insights into the co-evolution and ecological context of ancient life.”

Methodologically, the study exemplifies the integration of paleogenomics with cutting-edge bioinformatics, including metagenomic sequencing approaches and computational decontamination pipelines that discriminate between endogenous ancient DNAs and environmental or modern human contaminants. These techniques allowed the robust reconstruction of microbial genomes even in the face of typical challenges such as fragmentation, chemical modifications, and sparse molecule abundance.

Furthermore, this investigation sheds light on the potential co-adaptation of microbes and megafauna, possibly influencing host physiology, disease susceptibility, and evolutionary outcomes. Understanding such deep-time interactions holds relevance beyond paleontology, informing fields such as microbiome research, evolutionary medicine, and conservation biology by revealing ancient dynamics that may underpin present-day host-microbe relationships.

The find also provokes fresh questions about disease ecology in prehistoric times. Given the genetic similarity of some identified bacteria to known pathogens in modern elephants, ancient mammoths may have experienced similar infectious pressures, hinting at a complex web of microbial pathogenicity that could have shaped their survival and eventual extinction.

Finally, the team’s success illustrates the vast untapped potential of museum and fossil collections as reservoirs of ancient biological information. As sequencing technologies and analytical methods continue to advance, future studies are poised to delve deeper into the molecular fossil record, reconstructing broader aspects of life’s evolutionary history and microbial ecology across epochs.

This pioneering research not only enriches our understanding of mammoths and their microbial companions but also charts a roadmap for exploration into ancient host-microbe interactions, opening exciting frontiers in both evolutionary biology and genomics.

Subject of Research: Animals

Article Title: Ancient host-associated microbes obtained from mammoth remains

News Publication Date: 2-Sep-2025

Web References: 10.1016/j.cell.2025.08.003

Image Credits: Photo: Love Dalén

Keywords: Ancient DNA, Mammoth, Microbiome, Paleogenetics, Host-Associated Microbes, Pleistocene, Microbial Evolution, Pathogens, Steppe Mammoth, Genomic Sequencing