Ancient Fossil Ancestor Reveals that Hippos and Whales are Evolutionary Cousins

Fossils discovered in Kenya may tell researchers a bit more about the evolution of hippos. Scientists have discovered a new fossil ancestor of today's hippo family that bridges a gap that separates these animals from their closest modern-day cousins, the cetaceans.

The ancestry of hippopotamuses has remained a bit of a mystery for years. These semi-aquatic animals, with their unusual morphology and primitive skulls were thought to be related to the Suidae family, which includes pigs and peccaries. But in the 1990s and 2000s, DNA comparisons showed that the hippo's closest living relatives were the cetaceans, which include whales and dolphins. This disagreed with most paleontological interpretations at the time, and a lack of fossil evidence hindered attempts to uncover the truth about hippo evolution.

Now, researchers have found the missing link between hippos and whales. The scientists analyzed a half-jaw and several teeth discovered in the Lake Turkana basin in Kenya. The new fossil species dates back about 20 million years and shows the whole history of African fauna in a new light.

Africa was an isolated continent from about 110 to 18 million years ago. In fact, most of the iconic African fauna are relatively recent arrivals on the continent, and the same was thought to be true of hippos. This latest fossil, though, reveals that hippo ancestors migrated from Asia to Africa about 35 million years ago.

The findings reveal a bit more about the lineage of hippos. More specifically, it shows how these animals are indeed related to cetaceans.

The findings are published in the journal Nature Communications.

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