Hippos in the Ice Age? DNA reveals a survival story

Europe during the Ice Age wasn’t always the frozen wasteland we imagine. Between glaciers and tundra, rivers still flowed, and the land breathed in warm intervals. In those moments, something remarkable happened – hippos lived there.

A new study published in the journal Current Biology shows that these tropical giants survived in central Europe much longer than anyone thought possible. The discovery changes how we see the past and the creatures that endured it.

Hippos survived the Ice Age

Scientists once believed hippos vanished from Europe about 115,000 years ago, when the last warm period ended.

But researchers from the University of Potsdam, Reiss-Engelhorn-Museen Mannheim, and the Curt-Engelhorn-Zentrum Archäometrie uncovered a different story. Their analysis of ancient bones shows hippos lived in the Upper Rhine Graben between 47,000 and 31,000 years ago – deep into the Ice Age.

That means hippos walked beside mammoths and woolly rhinos in a world far colder than their African home. They managed to hold on during brief warmer phases when rivers thawed and plants returned.

These warm windows didn’t last long, but long enough for life to adapt, even if only for a few thousand years.

Clues hidden in bones

The Upper Rhine Graben hides its history in layers of gravel and sand. Among those sediments, researchers found bones that told stories of survival.

“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 from the Curt-Engelhorn-Zentrum Archäometrie.

His team studied isotopes in the remains to understand the environment. The results showed that these hippos lived near open rivers, surrounded by grasslands and mild weather.

Even during the Ice Age, some valleys stayed unfrozen, giving them enough warmth and water to survive. These places became small sanctuaries in an otherwise freezing world.

Genetic threads across time

Ancient DNA pulled from the bones linked these hippos to the same species living in Africa today.

The genetic data showed close relations but revealed something else too – a loss of diversity. That meant the group in Germany was small and isolated, cut off from others.

Radiocarbon dating placed the bones in a short warm period during the middle of the Weichselian glaciation. It was a time when mammoths, reindeer, and woolly rhinos still roamed.

Warmth-loving and cold-adapted species shared the same lands for a while, surviving side by side. The climate didn’t freeze everything at once; it shifted, giving species room to move, retreat, and reappear.

Hippos in uneven climate

The study makes one thing clear: the Ice Age didn’t hit every place equally. It was a patchwork of climates, where one valley might be green while another froze solid.

“The results demonstrate that hippos did not vanish from middle Europe at the end of the last interglacial, as previously assumed,” said study co-author Dr. Patrick Arnold.

His words urge scientists to look again at European fossils and rethink which bones belong to which period.

“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,” noted Professor Wilfried Rosendahl, who leads the “Eiszeitfenster Oberrheingraben” project.

His team wants to understand how regional climate quirks shaped life’s persistence.

Windows of survival

Small changes in temperature once created new possibilities. When the air warmed for a few centuries, rivers opened, grass grew, and species like hippos took advantage.

When the cold returned, they disappeared again. The rhythm of climate was their fate. Researchers believe these short warm intervals helped not just hippos but other warm-weather animals too.

Some elephants, lions, and giant deer might have survived in similar refuges. The same forces that shaped their survival also influence species today—those already facing changing climates and vanishing habitats.

Hippos adapted and endured

The “Eiszeitfenster Oberrheingraben” project, funded by the Klaus Tschira Stiftung Heidelberg, explores how ancient climates shaped the species that lived through them.

The team studies thousands of bones stored at the Reiss-Engelhorn-Museen to trace 400,000 years of environmental shifts.

The European hippo’s story is one of endurance. It reminds us that even during the most hostile times, life adapts in unexpected ways.

For a while, the cold rivers of Europe carried more than ice – they carried hippos. And their bones, buried for millennia, still whisper that survival is rarely simple.

The study is published in the journal Current Biology.

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