Life began in the oceans, and for hundreds of millions of years, that’s where it stayed. It took our deep ancestors eons to crawl, flop and gasp their way onto land. It turned out to be a pretty good decision, all told, as those creatures found a brand new world to inhabit. The ancient pioneers eventually led to mammals, including us — children of the land through and through.
So, it’s a bit surprising that some of us decided to go back. Around 50 million years ago during a time known as the Eocene, a select few species of mammals decided to re-submerge themselves. The largest group of these aquatic fundamentalists would become the cetaceans, which we know today as whales, dolphins and porpoises.
