A gap in the evolutionary history of the hippopotamus has finally been closed. New findings suggest that the now enormous hippopotamus that we see came from an ancestor a twentieth of its size.

Until now, the hippo was believed to be from the Suidae family of pigs, based on paleontological finds. Scientists now verify the hippo is actually closest in kin to the cetaceans, the group to which whales, dolphins and porpoises belong, according to ABC Science online.

The origin of the hippopotamus has been a mystery. But it is now confirmed the hippos came from anthracotheres, an extinct group of plant-eating, semi-aquatic mammals. They think that this ancestor may have spent much of its time immersed in water.

The oldest fossil of a hippo ancestor originally dated back to 20 million years ago. But remains of cetacean aged back to 53 million years. This gap left experts stumped. First they thought they never found ancestors of hippos. But really, they didn’t recognize them among the mammal fossils they already had. They are truly the kin of whales.

The key was a 28-million-year-old animal discovered in Kenya. The animal named Epirigenys lokonensis (‘epiri’ means hippo in the Turkana language and Lokone after the discovery site) was about the size of a sheep. Although it is not a direct forefather of today’s hippo, it lived much closer in time to the ancestor from which they both branched off.

The dental analysis helped the team to conclude that the E. lokonensis and the hippo both came from a forefather that migrated from Asia to Africa about 35 million years ago. This means the ancestors of the hippo were the first to hit the African continent before any of the large carnivores. Therefore, the modern-day hippo evolved in Africa, and is a creature truly prevalent to the continent.