Even in the heart of the Ice Age, hippos clung to survival in central Europe, rubbing shoulders with woolly mammoths and rhinos.
Late Pleistocene hippos hung on in the region much longer than thought, sharing space with cold-adapted animals during a glacial period, researchers report in Current Biology. Genetic analysis and dating of fossils upends the idea that these water-loving giants vanished with the end of the warm Eemian interglacial around 115,000 years ago.
To unravel the mystery, the team studied hippo bones from gravel pits in Germany’s Upper Rhine Graben, a hotspot for Ice Age fossils. They sequenced the first paleogenome from one specimen and partial mitochondrial genomes from six others, while radiocarbon dating pinpointed ages for 28 hippo bones and nearby mammoth and rhino remains.
The DNA showed tight ties to today’s African common hippos. “European representatives were part of the same, once widespread species that is today restricted to sub-Saharan Africa,” the study authors note.
But the real shocker came from the dates. “Surprisingly, radiocarbon dating shows that hippos were present in central Europe during the middle Weichselian (a period spanning from earlier than 47 kya until ∼31 kya), i.e., well into the last glacial,” the researchers write. Mammoth and rhino fossils from the same spots dated to similar times, between about 47,000 and 31,000 years ago, hinting that warm-adapted hippos and icy giants either overlapped or took turns in the area during brief milder spells.
The genome hinted at hardship, too. “The low genome-wide diversity recovered suggests that it belonged to a small, isolated population,” according to the paper.
These hippos likely hunkered down in the Upper Rhine Graben as a refuge, where short warm phases kept rivers open and plants growing. “The Upper Rhine Graben offered a localized microclimate during several phases of MIS3 that was favorable for sheltering species that require more temperate conditions with relatively mild temperatures,” the authors explain.
As those warm blips faded, the hippos probably faded out.”Contrary to the traditionally accepted view, our newly dated bone remains reveal that hippos did not disappear in central Europe at the end of the Eemian as previously thought,” the study concludes. “A small population instead recolonized the central European Upper Rhine Graben during MIS3, likely from southern Europe.”
Citations: Current Biology. DOI: 10.1016/j.cub.2025.09.035
