Hippos once roamed frozen Germany with mammoths

Extinction Timeline Rewritten

Until recently, scientists thought the common hippopotamus (Hippopotamus amphibius) disappeared from central Europe roughly 115,000 years ago, when the last interglacial period ended. However, the new study -- conducted by researchers from the University of Potsdam, the Reiss-Engelhorn-Museen Mannheim, the Curt-Engelhorn-Zentrum Archäometrie Mannheim, ETH Zurich, and several international partners -- reveals that hippos actually persisted in the Upper Rhine Graben of southwestern Germany tens of thousands of years later, well into the middle of the last ice age.

The Upper Rhine Graben serves as a vital record of ancient climate conditions. Animal bones buried for millennia in layers of gravel and sand offer rare windows into the past. "It's amazing how well the bones have been preserved. At many skeletal remains it was possible to take samples suitable for analysis -- that is not a given after such a long time," said Dr. Ronny Friedrich, a specialist in age determination at the Curt-Engelhorn-Zentrum Archäometrie.

Genetic and Radiocarbon Clues

Researchers examined numerous hippopotamus fossils using both genetic and radiocarbon dating methods. Ancient DNA sequencing revealed that these Ice Age hippos were closely related to modern African populations and were part of the same species. Radiocarbon dating confirmed their presence during a warmer phase of the middle Weichselian glaciation, when conditions temporarily allowed the animals to survive in central Europe.

Further genome-wide analysis showed that the European hippo population had extremely low genetic diversity, suggesting it was both small and geographically isolated. Fossil evidence also revealed that these warm-adapted hippos lived alongside cold-climate animals such as mammoths and woolly rhinoceroses -- an unusual ecological mix that highlights the complexity of Ice Age environments.

Rethinking Europe's Ice Age Ecosystem

"The results demonstrate that hippos did not vanish from middle Europe at the end of the last interglacial, as previously assumed," summarizes first author Dr. Patrick Arnold. "Therefore, we should re-analyze other continental European hippo fossils traditionally attributed to the last interglacial period."

Prof. Dr. Wilfried Rosendahl, general director of the Reiss-Engelhorn-Museen Mannheim and project leader of "Eiszeitfenster Oberrheingraben" is convinced that ice age research still holds many exciting questions: "The current study provides important new insights which impressively prove that ice age was not the same everywhere, but local peculiarities taken together form a complex overall picture -- similar to a puzzle. It would now be interesting and important to further examine other heat-loving animal species, attributed so far to the last interglacial."

The research was carried out as part of the "Eiszeitfenster Oberrheingraben" project, supported by the Klaus Tschira Stiftung Heidelberg. This interdisciplinary effort aims to shed light on climate and environmental evolution in the Upper Rhine Graben and southwestern Germany over the past 400,000 years. The study focused on Ice Age bones from the Reis collection, housed at the Reiss-Engelhorn-Museen, which continue to reveal remarkable insights into Europe's dynamic prehistoric world.