The evolution of whales

We know that living things change over time. It is called evolution. For example, some dinosaurs evolved into birds. Another example is that before whales were in water, they were walking on land. Today we’re going to talk about whales. 

So, before whales were swimming 50 million years ago there was a small animal with four legs called Pakicetus in Pakistan and India. It was an amphibious mammal and swam in freshwater and ate on land which is not what modern whales do.  Then Ambulocetus came 49 million years ago in the same place, and it is at that time that whales first started to live in seawater. Then, 45 million years ago, another animal Remingtonocetus evolved in an ocean called Tethys and it was in water almost the whole time.  Protocetus came at the same time as the Remingtonocetus and it had nostrils that were in the middle of its skull. Basilosaurus came 35 million years ago and it was huge (about 60 feet). Dorudon was like Basilosaurus except it was smaller.  

So, over millions of years, from mammals that were small like dogs, whales became large animals. Today, there are two categories of whales. Baleen whales (blue whales for example) can eat krill and microscopic things and can only swallow them because they have no teeth. The other is called Toothed whales (dolphins for example) that can eat fish and squid with their teeth, and these came about 30 million years ago. 

Whales have a big heart depending on their size. Modern whales have noses called blowholes which is where they breathe from and water comes out. Blue whales can hold their breath for 90 minutes. 

The humpback whale is a modern whale that also lived about 35 million years ago. It has a hump near its dorsal fin and that’s why it’s named the humpback whale. 

The blue whale came two million years ago. It is the largest animal in the world. It is larger than the largest shark Megalodon which could eat anything in the water (except for this whale because it was bigger).