Eli5 How did mammals end up in the ocean?

Question

I’m watching dolphins pop out of the water to breathe, and it just seems absurd that animals that live in water need to breathe air.

In: 9

Answer 1

Dolphins are descended from Pakicetus, a terrestrial wolf-like mammal that lived near the water. Over time, this creature and its descendants adapted more and more to life in the water until legs were no longer an advantage and they became fully aquatic.