For decades, the prevailing narrative in paleontology held that common hippos (Hippopotamus amphibius) vanished from central Europe at the conclusion of the last interglacial period, approximately 115,000 years ago. This assumption seemed logical given the substantial climatic shifts and environmental upheavals associated with the Ice Age. However, groundbreaking research has now upended this long-held belief, revealing that hippos not only survived but thrived in the Upper Rhine Graben region well into the last glacial period, between roughly 47,000 and 31,000 years ago, coinciding strikingly with the era of mammoths and woolly rhinos. This discovery offers a fascinating glimpse into the complex interplay of species adaptation and survival amid extreme climatic adversity during the Ice Age.
The international research team, orchestrated by experts from the University of Potsdam and the Reiss-Engelhorn-Museen Mannheim along with the Curt-Engelhorn-Zentrum Archäometrie, undertook a meticulous analysis of ancient hippopotamus remains excavated from gravel and sand deposits in southwestern Germany. These deposits, known to be exceptional continental climate archives, preserved bones sufficiently intact for advanced genetic and chronological studies. The project, part of the larger “Eiszeitfenster Oberrheingraben” initiative funded by the Klaus Tschira Stiftung Heidelberg, leveraged state-of-the-art paleogenomic sequencing alongside precision radiocarbon dating to reconstruct the lost narrative of these ice age giants.
Ancient DNA sequencing results unequivocally confirmed that these European ice age hippopotamuses were not a separate, now-extinct species, but in fact belonged to the same species as modern African hippos. This insight not only deepens our understanding of hippo evolution and migration but also challenges entrenched models that tied hippos exclusively to warm, interglacial climates. Contrary to prior assumptions, these semi-aquatic megafauna displayed remarkable resilience and adaptability, coexisting synchronously with cold-adapted megafauna like mammoths and woolly rhinoceroses during a middle Weichselian glacial phase characterized by fluctuating, often inhospitable environmental conditions.
The research revealed startlingly low genetic diversity within the Upper Rhine hippo population, suggesting that these animals existed as a relatively small and isolated group. Such genetic bottlenecking typically reflects restricted habitat ranges or population pressures, possibly linked to the fragmented landscapes and climatic volatility of glacial Europe. Despite these challenges, this isolated group evidently maintained a viable presence, illustrating the nuanced and often underestimated ecological complexity of Ice Age ecosystems, where pockets of suitable habitat persisted and allowed species considered heat-dependent to survive far beyond anticipated ranges.
One of the most compelling aspects of this discovery lies in the ecological implications it carries. Hippos require substantial water resources and relatively warm environments, yet their survival alongside cold-adapted megafauna like mammoths signals that regional microclimates and environmental refugia must have existed within the Upper Rhine Graben. This challenges the simplistic categorization of Ice Age Europe as a monolithic, frigid landscape and instead supports a paradigm of environmental heterogeneity, where diverse and shifting habitats formed mosaics supporting an array of species with contrasting climatic preferences.
Radiocarbon dating played an instrumental role in anchoring these findings within a precise temporal framework. By dating the bones to between approximately 47,000 and 31,000 years ago, the researchers aligned the hippos’ presence with a milder climatic interval amidst the Weichselian glaciation. This timing elucidates the dynamic environmental conditions of the last glacial period, where episodes of warming interspersed with cold phases permitted transient expansions of temperate habitats. Such climatic oscillations facilitated the temporary dispersal of thermophilic fauna like hippos into regions they were previously thought unable to colonize.
This reevaluation of the temporal range of hippos in central Europe also carries important methodological lessons for paleontological investigations. The authors strongly advocate for the reevaluation of other European hippo fossils traditionally assigned to interglacial periods. The prevailing dogma, based largely on stratigraphic assumptions and broader climatic reconstructions, may have led to misdated or misinterpreted fossil assemblages. Enhanced radiocarbon dating alongside genomic analyses can provide unprecedented resolution to better understand species’ evolutionary histories and interactions within changing Pleistocene environments.
Profoundly, this research underscores the power of interdisciplinary scientific approaches combining paleogenomics, geochronology, and paleoenvironmental reconstruction. Advances in ancient DNA technology allow researchers to unlock genetic information from fossilized bones that were once considered too degraded for analysis. Coupled with precise radiocarbon dating, these tools enable robust correlations between genetic data, species distributions, and climatic shifts, allowing a more nuanced reconstruction of Ice Age life and habitat use.
The presence of hippos in a region characterized by cold-adapted taxa also adds a rich layer to our understanding of Ice Age biodiversity and biogeographical dynamics. Hippos were not isolated anomalies but integral components of Pleistocene faunal assemblages in Europe, coexisting with megaherbivores like mammoths and woolly rhinos. This coexistence necessitates reconsideration of how paleoecological communities functioned, the role of species-specific physiological adaptations, and the extent to which climatic factors influenced their survival or extinction.
Intriguingly, scientists propose that localized environmental peculiarity, rather than broad Eurasian climatic trends, determined species survivorship and distribution. The Upper Rhine Graben appeared to offer a refugium—a haven of comparatively suitable climate and habitat—allowing warm-adapted megafauna like hippos to persist beyond their predicted extinction thresholds. Such refugia likely played critical roles throughout the Ice Age, preserving biodiversity and enabling successive waves of species migration and adaptation as climatic oscillations shaped the landscape over millennia.
Looking forward, researchers emphasize the potential to expand this line of inquiry to other heat-loving fauna whose presence in Europe has so far been confined to interglacial attributions. Systematic reanalysis of fossil records, integrating genomic and chronometric techniques, may yield further surprises about Ice Age animal distributions and their adaptive capacities. These studies not only deepen scientific understanding but also illuminate the intricate ecological legacies shaping modern biodiversity patterns today.
This pivotal research, recently published in the prestigious journal Current Biology, stands as a testament to the evolving understanding of Ice Age ecology. It highlights the necessity of revisiting assumptions about species’ climatic tolerances and dispersal timelines, particularly in light of novel methodological advancements. As Dr. Patrick Arnold aptly summarizes, the survival of hippos in central Europe during a pronounced ice age interval fundamentally transforms how paleontologists interpret species resilience and environmental complexity during the Pleistocene.
Ultimately, the discovery enriches the narrative of Ice Age Europe, revealing a dynamically structured landscape where heat-loving and cold-adapted species carved out niches within a patchwork of microclimates. It challenges reductive views of glaciations, illustrating that the last Ice Age presented not a singular extreme but a mosaic of environmental conditions fostering diverse biological communities. These insights promise to inspire new research avenues and stimulate broader discourse on how organisms adapt to and survive abrupt climatic shifts—a question with profound relevance for understanding current and future biodiversity challenges under ongoing global change.
Subject of Research: Not applicable
Article Title: Ancient DNA and dating evidence for the dispersal of hippos into central Europe during the last glacial
News Publication Date: 8-Oct-2025
Web References: DOI: 10.1016/j.cub.2025.09.035
References: Arnold et al., 2025, Current Biology 35, 1–9
Image Credits: Rebecca Kind, Reiss-Engelhorn-Museen Mannheim
