Evolution of Biggest Whales Linked With Ocean Productivity

By Becky Oskin

Starting out the size of a hippo some 50 million years ago, whales have since evolved into the largest animals on Earth. But their growth wasn’t steady over the millennia; instead, filter-feeding whales like the blue whale only ballooned in size starting about 2.5 million years ago. Whales’ grass-gobbling relatives, such as sea cows, also expanded in size during this time.

Blue whale

A blue whale off the coast of Southern California. Photo by D Ramey Logan, via Wikipedia.