Evolution of the Whale

Indohyus was not the ancestor of whales, but was almost certainly its cousin. But if we go back four million more years, to fifty-two million years ago, we see what might well be that ancestor. It is a fossil skull from a wolf-sized creature called Pakicetus, which is a bit more whale-like than Indohyus, having simpler teeth and more whale-like ears. Pakicetus still looked nothing like a modern whale, so if you had been around to see it, you wouldn’t have guessed that it or its close relati...

 Hippopotamus as Closest Relative to the Whale

good candidate is the hippopotamus, which, although closely related to terrestrial mammals, is about as aquatic as a land mammal can get. (There are two species, the pygmy hippo and the “regular” hippo, whose scientific name is, appropriately, Hippopotamus amphibius.) Hippos spend most of their time submerged in tropical rivers and swamps, surveying their domain with eyes, noses, and ears that sit atop their head, all of which can be tightly closed underwater. Hippos mate in the water, an...