New evidence from ancient bones has overturned the long-held assumption that hippopotamuses vanished from central Europe as the glaciers of the last ice age advanced. Research published in the journal Current Biology reveals that these megafauna, typically associated with warm African rivers, successfully survived in what is now southwestern Germany deep into the glacial period, tens of thousands of years later than previously believed. The discovery paints a more complex picture of Europe’s ice age ecosystems, suggesting a mosaic of climates where both cold-adapted and heat-loving species could find refuge and coexist.
An international team of scientists has demonstrated that the common hippopotamus, Hippopotamus amphibius, inhabited the Upper Rhine Graben between 47,000 and 31,000 years ago. For decades, the paleontological consensus was that hippos disappeared from this region with the end of the last major warm period, approximately 115,000 years ago. By using advanced dating and genetic analysis on remarkably well-preserved fossils, researchers from the University of Potsdam and the Reiss-Engelhorn-Museen Mannheim have definitively shown that a resilient population persisted through a milder phase of the Weichselian glaciation. This finding not only rewrites the timeline of European megafauna but also challenges traditional views of the ice age environment, indicating that pockets of habitable territory allowed for unexpected ecological diversity.
A Surprising Coexistence
The updated timeline places hippos in a landscape they shared with iconic ice age animals. Fossil evidence confirms that these semi-aquatic mammals lived alongside species adapted to harsh, cold climates, including the woolly mammoth and the woolly rhino. This surprising assemblage of fauna suggests that the European climate during the glacial period was not a monolithic deep freeze but was instead characterized by significant regional and temporal variations. The Upper Rhine Graben, a rich continental climate archive, appears to have served as a crucial refugium, offering conditions suitable for a diverse range of large animals.
The survival of hippos depended on intermittent warmer climatic phases within the broader ice age. These intervals, though transient, were significant enough to maintain unfrozen rivers and support the grassland vegetation upon which the animals fed. The presence of a species so heavily dependent on liquid water provides definitive proof that certain river valleys remained hospitable even as ice sheets dominated landscapes further north. This evidence forces a reevaluation of the environmental carrying capacity of glacial Europe and the complex interplay between climate oscillations and biodiversity.
Advanced Techniques Provide Clarity
The breakthrough was made possible by applying modern analytical methods to fossils that had been housed in museum collections. The research team combined two powerful techniques: radiocarbon dating and paleogenomic analysis, to unlock the secrets held within the ancient bones.
Precision Radiocarbon Dating
Directly dating the fossilized bones was a critical step in overturning the old timeline, which was largely based on the assumed age of the geological layers where fossils were found. Dr. Ronny Friedrich of the Curt-Engelhorn-Zentrum Archäometrie, an expert in age determination, noted the exceptional quality of the material. “It’s amazing how well the bones have been preserved,” he stated, explaining that many skeletal remains were suitable for sampling, which is not a given after such a long time. The radiocarbon results conclusively placed multiple hippo specimens within a timeframe from 47,000 to 31,000 years ago, firmly within the last glacial period. This precise chronology provides an anchor for understanding the environmental conditions that prevailed at the time.
Ancient DNA Sequencing
To confirm the species identity and understand its population dynamics, the scientists sequenced ancient DNA extracted from the fossils. The paleogenomic analysis yielded two key insights. First, it confirmed that the ice age animals were not a distinct, extinct European species but belonged to Hippopotamus amphibius, the same species found in Africa today. This direct genetic link underscores the animals’ adaptability. Second, the genetic data revealed remarkably low genetic diversity within the Upper Rhine population. This finding suggests that the group of hippos that survived in this European refuge was likely small and isolated, cut off from larger populations in the south. This genetic bottleneck highlights their precarious existence in a fluctuating, challenging environment.
Revising the Ice Age Landscape
This discovery has profound implications for how scientists understand the Pleistocene epoch in Europe. The long-held image of a vast, homogenous tundra-steppe is being replaced by a more nuanced model of environmental heterogeneity. The survival of a heat-loving species like the hippopotamus demonstrates that the continent was a patchwork of different habitats, where localized conditions could diverge significantly from the regional average. These findings are part of a larger initiative, the “Eiszeitfenster Oberrheingraben” project, which explores how ancient climates shaped the species that lived through them by studying thousands of bones stored at the Reiss-Engelhorn-Museen.
The study also serves as a methodological call to action for paleontologists. The researchers urge for a reevaluation of other European hippo fossils that have been traditionally assigned to warmer interglacial periods based on stratigraphy alone. Direct dating, they argue, is essential for building an accurate timeline of species presence and extinction. As first author Dr. Patrick Arnold summarized, “The results demonstrate that hippos did not vanish from middle Europe at the end of the last interglacial, as previously assumed.” This approach could reveal other instances of unexpected species survival, further refining our knowledge of life during the ice ages.
A Tale of Resilience and Extinction
The story of Europe’s last hippos is ultimately one of temporary success and eventual disappearance. While the population in the Upper Rhine Graben demonstrated remarkable resilience by adapting to life in a fluctuating glacial-era climate, they were unable to hold on indefinitely. The conditions that allowed their survival—the brief warm intervals—eventually gave way to the much colder conditions of the Last Glacial Maximum, the peak of the ice age around 25,000 years ago. This final, intense period of glaciation likely eliminated the remaining habitats capable of supporting them in central Europe.
Their eventual extinction from the region underscores the immense pressure that dramatic climate shifts place on even the most adaptable species. The low genetic diversity of the population may have also limited its ability to respond to this final challenge. By studying the factors that allowed these hippos to survive for thousands of years in an unlikely environment, as well as the forces that led to their ultimate demise, scientists can gain valuable insights into the complex dynamics of megafauna extinction and the profound impact of climate change on biodiversity.
