Today’s hippos are the last two species of a once widespread and diverse family. Their prehistoric relatives roamed Africa, Europe, and Asia, exhibiting a wide range of sizes and forms now known only from the fossil record. The evolutionary history of these extinct animals reveals a journey of adaptation, diversification, and eventual decline.
The Hippo Family Tree
The earliest ancestors of hippos appear in the fossil record during the Miocene Epoch, which began about 23 million years ago. Scientists once believed hippos were related to pigs based on molar similarities. However, genetic evidence revealed their closest living relatives are cetaceans, the group including whales and dolphins.
This understanding places hippos and whales with a common semi-aquatic ancestor that diverged from other even-toed ungulates around 60 million years ago. The hippo line is thought to have descended from land-dwelling mammals called anthracotheres. Fossils like the 28-million-year-old Epirigenys lokonensis from Kenya support the genetic link to cetaceans and confirm the anthracothere lineage.
Giants of the Past: Significant Ancient Hippo Species
One notable prehistoric hippo is Hippopotamus gorgops, which inhabited Africa during the late Pliocene and Pleistocene. A feature of H. gorgops was its periscopic eye sockets, set higher on its skull than in modern hippos. This adaptation allowed it to see above water while almost completely submerged, suggesting a highly aquatic lifestyle. It was also larger than its modern counterpart, reaching lengths of over 4 meters.
Another species was Hippopotamus antiquus, which was widespread across Europe during the Pleistocene. This giant hippo was larger and more robust than the living common hippo, with fossil remains found from the Iberian Peninsula to the British Isles and Germany. Its dental structure and massive frame indicate it was a powerful grazer, thriving in the warmer interglacial periods when Europe’s climate supported lush riverine habitats.
The fossil record also reveals a trend of dwarfism on islands. On Mediterranean islands like Cyprus and Crete, as well as on Madagascar, several species of pygmy hippos evolved. The Cypriot dwarf hippo, Hippopotamus minor, was one of the smallest known hippos, a result of adapting to an island environment with limited resources and fewer predators, a phenomenon known as insular dwarfism. These small hippos survived until the end of the Pleistocene or early Holocene.
Ancient vs. Modern Hippos
Comparing ancient hippos to the two living species—the common hippo (Hippopotamus amphibius) and the pygmy hippo (Choeropsis liberiensis)—reveals differences in anatomy and scale. Many prehistoric species like H. antiquus were larger than the modern common hippo. In contrast, island species like H. minor were smaller than the modern pygmy hippo, showcasing the family’s adaptive flexibility.
Skull morphology shows variation, particularly in eye placement, with some extinct forms having more elevated eye sockets than modern hippos. This suggests some extinct species may have spent more time in the water. Dental features also varied, with differences in tusk size and molar shape likely reflecting diverse diets and environmental pressures.
The general body plan remained consistent, with a barrel-shaped torso, stout legs, and a large head. This robust build has been a successful formula for millions of years. The existence of both giant and dwarf species highlights a past ecological diversity not seen in the two surviving hippo species.
Fossil Discoveries and Extinction
The fossil record provides all our direct evidence of ancient hippos. The locations of discovered bones, teeth, and skulls map out the family’s once-vast distribution across multiple continents. These remains are often found in ancient riverbeds and lake deposits, consistent with the semi-aquatic nature of these animals.
The decline of the diverse hippo lineages occurred towards the end of the Pleistocene Epoch. The widespread extinction of species like H. antiquus in Europe and other giant forms coincided with major climate shifts associated with the ice ages, which altered their habitats.
The pygmy hippos on islands like Cyprus and Madagascar became extinct much more recently, potentially overlapping with the arrival of early humans. A combination of environmental change and human hunting pressures likely contributed to their disappearance. This pattern mirrors the extinction of other megafauna during the same period.