Here's how whales became the biggest animals on the planet

Blue whales can expand their throat pleats to accommodate a giant mouthful of krill and water.

Washington: Blue whales are the most massive animals to exist in the history of animals. Dreadnoughtus and those other thundering, 60-ton dinosaurs? Bantamweights next to one of today's 100-ton Balaenoptera musculus.

"We truly live in an age of giants," said Nicholas D Pyenson, an expert in the paleobiology of marine mammals at the Smithsonian's National Museum of Natural History. Blue whales, he said, can grow as long as three city buses parked end to end. Living blue whales would be even bigger, too, if it weren't for the sailors who killed most of the 110-foot, quarter-of-a-million-pounders 100 years ago.

Yet evolutionarily speaking, whales are recent leviathans. After the largest dinosaurs died off, land mammals bulked up, leading to elephant-size rhinoceroses, sloths and armadillos about 35 million years ago. The ancestors of today's giant whales, meanwhile, stayed curiously small.

In the new study, Pyenson and his co-authors note that shoreline ecosystems changed about 3 million years ago, around the same time that baleen whales got huge. First, seasonal windy upwellings began to kick up nutrients along the coast; later, glacial runoff added to the richness of these pockets. The net results were souped-up marine ecosystems where whales could feast.