It might seem surprising, but both whales and hippos share a common ancestor that lived over 50 million years ago. While whales evolved to live in the ocean, hippos stayed on land.
Here's how we know they're related:
* Fossil evidence: Scientists have found fossils of early whale ancestors that show features similar to hippos, like their large bodies and the shape of their teeth.
* Genetic analysis: Modern genetic analysis confirms the close evolutionary relationship between whales and hippos.