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How are hippopotamuses related to whales and dolphins?
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hippopotamus
The word hippopotamus is Greek for “river horse,” which reflects their behavior: they are often seen basking on the banks or sleeping in the waters of rivers, lakes, and swamps across Africa. They favor shallow areas where they can sleep half-submerged, though these places can become quite crowded—as many as 150 hippos may use one pool in the dry season.
While hippopotamuses were historically linked to pigs and peccaries based on physical characteristics, modern molecular studies indicate that they are more closely related to cetaceans—the group that includes whales and dolphins.1
These two groups share an earlier common ancestor than previously thought. This evolutionary connection is significant because it challenges older classifications that relied solely on morphological (anatomic) comparisons. While scientists continue to refine the evolutionary history of these animals through techniques like DNA sequencing, the evidence suggests that hippos and cetaceans represent a distinct lineage within the order Artiodactyla.12