New analysis of ancient frozen Greenland rubbish heaps, called middens, has revealed new insights into several ancient societies that have passed through the country over the last five millennia. The findings include insights into ancient diseases and animals that the inhabitants kept but didn’t eat.

Although the team noted the potential risk that climate change could release dangerous ancient microbes into the modern environment, their analysis found little evidence that the pathogens they identified could pose a threat beyond the immediate area around the middens.

Ancient Middens Offer Historical Insights Beyond Traditional Artifacts

Archaeologists have often excavated items discarded by ancient societies from trash heaps to learn more about the people who lived there. Although such excavations often unearth things like animal bones and mollusk shells, offering insights into diet and hunting habits, these ancient rubbish heaps can also contain human artifacts, such as discarded blades and other tools.

In a country like Greenland, where different peoples have settled the region since 2,500 BCE, the ancient middens may also contain microbes that could offer researchers an entirely different type of historical data. For example, microbial data from middens could reveal which diseases ancient populations had to survive. The team notes that microbes could also help determine what ancient societies kept “but perhaps didn’t eat.”

Still, studies of ancient midden microbes are limited, leaving a gap in historical knowledge. The authors of the new paper also highlight that rapidly increasing Arctic warming could release infectious diseases to which humans have lost immunity over the ensuing generations.

Over One Thousand New Species Were Identified

To bridge the information gap, Dr Frank Møller Aarestrup, a professor at the National Food Institute of Denmark Technical University and corresponding author of the article detailing the team’s research, examined samples collected during 2020 and 2021 expeditions in West and South Greenland. During those expeditions, scientists collected samples from middens locked in time by permafrost, dating back as far as 4,500 years.

Among the middens sampled were the ancient Norse sites of Kapisilit and Narsarsuaq, where researchers collected soil samples from what the new paper’s authors termed “historic winter enclosures.” The site also contained evidence that it was a summer grazing ground for livestock.

After selecting several soil samples, Dr. Aarestrup’s team sequenced the DNA of ancient microbes found in the midden samples. Next, they compared the data, including entire bacterial communities, to 143 soil samples previously collected from areas of permafrost far away from any known historical human settlements.

According to the team’s statement, the sequencing revealed a total of 1,207 species and differing ranges of bacterial species per midden. In denser areas, the team identified as many as 202 species, whereas less microbe-dense middens had as few as nine.

The team’s analysis also found several species that had not been previously identified. This resulted in the team labeling the unidentified microbes using what they termed “broad taxonomic categories” above the genus and species level, such as family and order.

Preserving the ‘Biological Legacy’ of Human Activity

When comparing the microbial communities in the ancient middens with those from samples collected away from human settlements, the team found a significantly richer community of ancient bacteria preserved in the middens. The team notes that this discrepancy confirms that the middens “preserved the biological legacy of human activity.”

The most soil-like bacterial communities were identified within the oldest Paleo-Inuit middens. The researchers said the finding suggests that the microbial “imprint” left behind by humans and animals diminishes over time.

Bacterial communities were also associated with the types of waste discarded in each ancient midden. For example, although most middens contained bacteria associated with human and animal hosts, middens from colonial-era Nuuk contained decomposing seal skins. The middens from colonial-era sites were also rich in the bacterium Clostridium perfringens, which the team notes is “a major cause of food poisoning.”

Risk of Ancient Pathogens is Low

Although the team identified strains of bacteria that can cause botulism or other life-threatening conditions, such as toxic shock syndrome, sepsis, and gangrene, they also found a diversity of antimicrobial-resistance genes in the genomes of bacteria collected from the same middens.

According to the study authors, finding the two sets of genes in ancient and modern soil layers “signaled that microbes resistant to antimicrobials can linger in permafrost for centuries.”

Fortunately, the team’s analysis found that most of the identified microbes, including potentially dangerous pathogens, don’t spread far from middens, even those undergoing defrosting. As a result, the team said that these ancient microbes  “pose little risk to public health,” at least for the time being.

“Here we show that the risk of release of ancient pathogens from ancient middens in Greenland is currently low,” Dr. Aarestrup explained.

Instead, the researcher noted that Arctic middens appear to function like “long-term natural experiments,” in which both human- and animal-associated bacteria, including “opportunistic” species carrying resistance genes, remain detectable centuries later as a broader “legacy of human activity.”

The study “Microbial composition of archaeological middens: Tracing Human Footprints Through Centuries in Greenland’s Ancient Settlements” was published in Frontiers in Microbiology.

Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.

The Greenland Ice Sheet: An Unstoppable Catalyst of Global Sea-Level Rise

In the unfolding narrative of our planet’s climate crisis, the Greenland Ice Sheet stands as one of the most formidable agents of change. Since the dawn of satellite observations in 1992, this massive reservoir of ice has relinquished approximately 4,900 gigatons of ice, a staggering volume whose meltwater has contributed about 13 millimeters to the rise in global mean sea level. Such a figure, while already alarming, merely scratches the surface of potential long-term impacts. Even in a hypothetical future devoid of any additional warming, the Greenland Ice Sheet is effectively locked in to contribute an extra ~274 millimeters to global sea levels. This commitment underscores a sobering reality: the ice sheet’s decline is not simply a transient phenomenon but a geological-scale reordering, with the total potential of a 7-meter sea-level rise looming if complete melting ever unfolds.

To truly grasp the implications of the Greenland Ice Sheet’s evolution, scientists have undertaken comprehensive syntheses of its surface melt dynamics extending across centuries—from 1500 to projections as far ahead as 2200 CE. This historical and predictive vantage reveals a striking acceleration in surface melt beginning in the 1990s, characterized by a rapid increase of roughly 1 percent per year. This upsurge has not occurred in isolation. Rather, it is a direct consequence of amplified regional warming patterns coupled with notable alterations in atmospheric circulation dynamics. A phenomenon known as enhanced atmospheric blocking—where persistent high-pressure systems effectively stall weather patterns—has played a pivotal role in this rapid intensification of melt rates.

The consequences of these climate shifts manifest with increasing frequency and severity in extreme melt events. Since 2007, Greenland has experienced multiple unprecedented episodes where melting persists intensively over several consecutive days. These events reach apogees such as the extraordinary case of July 2012, during which almost the entirety of the ice sheet surface succumbed to thawing. Such extremes stress the limits of current predictive models and underscore the urgent need to understand the complex interplay of forcings driving these episodes.

Dominating the seasonal melt cycle is the absorption of shortwave solar radiation. Solar energy, pouring relentlessly onto the ice sheet’s surface during summer months, serves as the primary engine for surface melting. However, this process is far from straightforward or uniform. Turbulent heat fluxes—essentially the turbulent exchange of heat between the ice and atmosphere—alongside cloud cover dynamics and the critical feedback mechanism of albedo, significantly modulate the spatial and temporal variability of melt. Albedo effects refer to the reflectivity of the ice surface: as ice melts and dark patches or meltwater form, less sunlight is reflected back, and more is absorbed, accelerating melt rates in a self-reinforcing loop.

Yet, it is precisely the intricate and interlinked nature of these processes that confounds climate models. Even among today’s state-of-the-art regional climate models, there is a stark divergence in projections of Greenland’s surface melt and mass loss. When subjected to identical climate forcing scenarios, these models yield predictions differing by as much as a factor of two. This discrepancy highlights fundamental uncertainties inherent in simulating the nuanced physics of ice-atmosphere interactions, energy balance complexities, and meltwater behavior within the firn layers—densely packed snow that acts as a sponge holding meltwater before it refreezes or runs off.

A central challenge lies in the accurate representation and integration of these processes within numerical simulations. Extreme melt events, in particular, remain difficult to quantify and predict with confidence. The drivers behind these sporadic but increasingly frequent episodes are multifaceted, involving shifts in jet stream patterns, atmospheric blocking frequencies, and the enigmatic influence of cloud microphysics. Likewise, the fate of meltwater—whether it refreezes in the porous firn layers or contributes to runoff—critically influences the net mass balance of the ice sheet yet remains poorly constrained in many models.

Adding further layers of complexity, coupling between atmospheric forcing and the surface energy balance must accurately capture feedback loops and temporal variability. Discrepancies in these couplings propagate through simulations and exacerbate uncertainties in projections of future melt and associated sea-level rise contributions. Scientists recognize that overcoming these hurdles necessitates expanding observational networks across Greenland, leveraging advanced remote sensing methods combined with in situ monitoring to resolve fine-scale processes.

Furthermore, there is a burgeoning potential for integrating emerging data-driven approaches into this research frontier. Machine learning, artificial intelligence, and data assimilation techniques offer promising means to synthesize vast datasets, identify subtle patterns, and enhance the physical realism of model parameterizations. However, realizing these gains demands concerted efforts in model development, interdisciplinary collaboration, and continued investment in observational infrastructure.

The stakes could hardly be higher. Greenland’s meltwater contributions are a central element of global sea-level rise—one of the most significant threats to coastal communities worldwide. The unprecedented speed and scale of Greenland surface melt ask not only for scientific diligence but also for rapid climate mitigation and adaptation strategies. The Greenland Ice Sheet is both a harbinger and accelerator of change in Earth’s climate system, embodying losses that reverberate far beyond polar latitudes.

Looking to the centuries ahead, the trajectory of Greenland’s surface melt remains riddled with uncertainty but is unmistakably poised on an upward trend in response to continued warming. Understanding and predicting this trajectory with greater precision is not merely an academic endeavor; it is a prerequisite for global climate resilience planning. The Greenland Ice Sheet, with its vast store of frozen freshwater, is a sentinel of deep Earth system transformations, reminding humanity of the interconnectedness of climate, ice, and sea.

Our current epoch demands that we unravel the intricacies of ice sheet melting at a pace matching the climate forces reshaping our planet. The Greenland Ice Sheet’s story, as told from the past into the future, is both a cautionary tale and an invitation to innovate in climate science. Only through enhanced observational capabilities, refined models, and novel integrative approaches can we rise to this challenge. The fate of coastlines, ecosystems, and human settlements worldwide hinge on the answers we find in this colossal frozen archive.

As the Earth warms, the story of Greenland’s shrinking ice transforms from abstract projections into tangible realities. Extreme melt events once considered anomalies have become harbingers of a new normal, with implications cascading through global systems. The urgency of understanding this dynamic, the mechanisms underpinning it, and its future paths cannot be overstated. Greenland, in its ancient calm, increasingly pulses with restless change—bearing witness to and driving one of the most profound climate transformations of our era.

Subject of Research: Greenland Ice Sheet surface melt and its contributions to global sea-level rise.

Article Title: Past, present and future Greenland Ice Sheet surface melt, 1500–2200 CE.

Article References:
Hanna, E., Box, J.E., Fettweis, X. et al. Past, present and future Greenland Ice Sheet surface melt, 1500–2200 CE. Nat Rev Earth Environ (2026). https://doi.org/10.1038/s43017-026-00800-3

Image Credits: AI Generated

DOI: 10.1038/s43017-026-00800-3

Keywords: Greenland Ice Sheet, surface melt, sea-level rise, climate change, atmospheric circulation, atmospheric blocking, albedo feedback, turbulent heat fluxes, climate models, firn processes, meltwater retention, extreme melt events

Greenland, with its vast icy expanses and challenging environment, harbors a rich tapestry of human history etched into its landscape over millennia. The island’s archaeological record tells tales of successive human inhabitations that have left behind more than just stories and artefacts; it preserves complex biological legacies embedded within ancient refuse deposits known as middens. These middens, essentially ancient domestic rubbish heaps composed of animal bones, excrement, mollusk shells, and various artefacts, offer not only archaeologists but also microbiologists a unique window into the past. Their frozen state in Arctic permafrost has allowed microbial communities trapped over thousands of years to persist, raising compelling questions about the nature and dynamics of these ancient microbial populations.

The study of microbial life within these middens is far more than a niche query; it intersects with pressing concerns about human health, ecosystem integrity, and the potentially resurging threats posed by ancient pathogens. As the Arctic warms at an alarming rate—currently estimated to be three to four times faster than the global average—the thawing permafrost raises fears that dormant microbes, including pathogens from bygone eras, might be released back into the environment. The microbial fingerprints preserved in these deposits chronicle past human and animal interactions, environmental conditions, and disease ecology, providing invaluable data to reconstruct historical microbiomes and understand their evolution through millennia.

In groundbreaking research reported recently in Frontiers in Microbiology, scientists led by Dr. Frank Møller Aarestrup of the Technical University of Denmark embarked on an ambitious project to characterize the microbial composition of Greenland’s archaeological middens. Their experimental approach involved rigorous sampling of frozen middens from multiple chronological layers spanning approximately 4,500 years of human history—from the earliest Paleo-Inuit cultures to medieval Norse settlers and early Danish colonists. Employing advanced DNA sequencing techniques and bioinformatics, the team reconstructed diverse and complex bacterial communities present in these ancient deposits and compared them with microbes from surrounding pristine permafrost soils, unperturbed by human activity.

One of the striking revelations from this study was the extraordinary microbial richness residing within the middens. From as few as nine to as many as 202 bacterial species per midden, the researchers identified an aggregate of 1,207 distinct bacterial species across all samples. Intriguingly, many species could not be identified beyond broad taxonomic categories, underscoring the vast unknown microbial diversity in Arctic archaeological contexts and the general paucity of data on cold-environment microbiomes. This discovery shines a light on the hidden microbial world preserved under layers of ice and soil, aspects that have remained largely unexplored until now.

The middens invariably featured richer bacterial communities than adjacent soils, affirming their role as biological archives chronicling the legacy of human presence and activity. Among the deposits, middens linked to the Paleo-Inuit exhibited bacterial compositions closely resembling natural soil communities, suggesting a fading microbial imprint over thousands of years. Conversely, Norse and colonial middens revealed bacterial assemblages heavily influenced by human-related waste, livestock farming, and domestic activities, evidencing the intimate connection between past humans, their animals, and local microbes.

Practically, these midden microbiomes hosted a variety of bacteria associated with human and animal hosts. Notably, the researchers detected species such as Clostridium massilliamazoniense, innocuous but indicative of human fecal matter presence, alongside more pathogenic taxa like Clostridium baratii, which can lead to botulism, and Paeniclostridium sordellii, linked to severe human illnesses including toxic shock syndrome and gas gangrene. Such findings highlight how midden microbial communities serve as time capsules, preserving signatures of diseases that may have affected historic populations, which hold relevance to the emerging field of paleomicrobiology.

Furthermore, the microbial composition differed markedly depending on the nature of the organic waste constituting each midden. Middens from Greenland’s early colonial era, particularly those in Nuuk containing decomposing seal skins, harbored Clostridium perfringens, a bacterium notorious for causing food poisoning. Meanwhile, middens filled with animal carcasses were dominated by gut bacteria such as Romboutsia species and Paraclostridium sordellii. Early Norse deposits, rich in decomposing bones, exhibited an abundance of unknown species within the Proteobacteria and Clostridiaceae groups. This substrate-specific microbial differentiation provides new perspectives on historic dietary patterns, hunting practices, and animal domestication in Greenland.

An essential aspect of the team’s work was the investigation of antimicrobial resistance (AMR) genes within these ancient bacterial genomes. The researchers uncovered a diverse array of resistance genes, demonstrating that ancient permafrost soils and middens contained bacteria equipped with antimicrobial defense mechanisms. The persistence of these genes in both ancient and modern soil layers indicates the long-term stability and environmental retention of genetic elements conferring antibiotic resistance, a critical insight into the evolutionary history of AMR and its environmental reservoirs. Despite this, spatial analyses suggested that upon thawing, microbes from the middens do not tend to disperse widely, limiting the risk of pathogen spread under current conditions.

Importantly, the authors emphasized that the immediate threat to public health from ancient pathogens emerging from Greenland’s thawing middens is currently low. Dr. Saria Otani, co-author and associate professor, noted that the microbiome released from melting permafrost appears to be rapidly outcompeted or replaced by contemporary environmental microbes, reducing opportunities for ancient pathogens to proliferate. Nonetheless, this dynamic balance could shift with accelerating climate warming, necessitating vigilant monitoring.

To that end, the researchers advocate for the incorporation of microbiome characterization into routine archaeological protocols during future excavations at permafrost sites. The spatially and temporally resolved microbial data obtained could serve as early warning markers for pathogen emergence and inform conservation strategies during the rapidly unfolding Arctic environmental transition. This interdisciplinary study brilliantly exemplifies how combining microbiology, archaeology, and environmental science can unlock secrets buried in ice and soil, informing both our understanding of the past and preparations for an uncertain microbial future.

This pioneering research hence sets a precedent for microbiome-informed archaeology, where the “dustbins of history” are not merely relics of human culture but bearers of ancient microbial life, antimicrobial resistance, and metabolic potential. By resolving these ancient microbial ecosystems, scientists are better positioned to trace human-animal-environment interactions across centuries and to anticipate the potential consequences of microbial releases driven by climate change.

As global temperatures continue their inexorable rise, the Arctic remains a hotspot for uncovering hidden biogeochemical dynamics playing out beneath melting permafrost. Greenland’s middens now stand as invaluable archives that illuminate the intertwined narratives of human migration, settlement, livestock domestication, and the microbial world shaped by these processes. The revelations from these frozen repositories reinforce a broader vision of archaeology enriched by microbial ecology, where ancient microbial communities provide vital clues for understanding human history, health, and environmental change on a planetary scale.

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Subject of Research: Not applicable

Article Title: Microbial composition of archaeological middens: Tracing Human Footprints Through Centuries in Greenland’s Ancient Settlements

News Publication Date: 17-Jun-2026

Web References:
Frontiers in Microbiology Article

Image Credits: Louise Hindborg Mortensen

Keywords: Archaeology, Animal domestication, Anthropology, Archaeological sites, Prehistory, Microbial ecology, Infectious diseases, Gastrointestinal disorders, Health and medicine, Human biology, Public health, Land use, Iron Age

Satire piece on President Trump stopping all wars and bringing peace to the world. For that he should be given the Nobel peace prize.