You probably don't expect to see a hippopotamus attending a whale's family reunion. Although they look, in many ways, like polar opposites, these two groups of massive mammals actually are kin to each other. Bizarrely enough, hippopotamuses are believed by some to be whales' nearest extant family members.
The connection between hippopotamuses and whales is a distant one, dating back some 50 to 60 million years, according to researcher Jean-Renaud Boisserie and his team at the University of California at Berkeley. The common ancestor was a four-limbed, semiaquatic mammal known as a "walking whale" that branched off into two separate directions -- anthracotheres and cetaceans. Although the vast majority of anthracotheres went extinct more than 2 million years ago, sturdy hippopotamuses alone have remained alive and well.
Hairlessness and Glands
Although hippos and whales physically seem as different as night and day, they do display a few similarities. One notable similarity between the two groups is minimal hair -- both hippos and whales have barely any hair on their bodies. They also do not have sweat glands. These are both things that can assist them in their aquatic lifestyles.
Another tie between hippos and whales involves their underwater activities. Not only are hippos and whales able to nurse their juveniles while in the water, they also can both send handy vocal messages to each other while submerged.
Hippopotamuses' bodies, similarly to whales, are encased in dense fat that is reminiscent of whales' blubber, which is situated between their muscle and skin.
Hippos possess markedly thick bones, a trait whales also display. The thickness of their bones enables them to descend into the water both quickly and effortlessly.
Hippos, Peccaries and Pigs
Until the middle of the 1980s, hippopotamuses' closest family members were believed to be pigs and family Tayassuidae peccaries, the latter of which are New World pigs. Vincent Sarich, an anthropology professor, first brought up the notion of the hippo-whale tie. The idea of the tight familial relationship between these two groups of animals, when first brought into the public consciousness, was a highly contentious concept to many, and it still remains somewhat controversial.
- Understanding Evolution UC Berkeley: The Evolution of Whales
- UC Berkeley News: UC Berkeley, French Scientists Find Missing Link Between the Whale and its Closest Relative, the Hippo
- BBC News: Hippo is Whale's Cousin
- CBS News: Study - Hippos, Whales Related
- National Center for Science Education: A Tale of Two Entities - Whales and Hippos
- American Museum of Natural History: A Walking Whale - Ambulocetus
- The New York Times: Long Dismissed as Piglike, the Hippo Gains a Nobler Cousin, the Whale