Scientists think they’ve figured out why the largest whales—that are of the baleen variety, including the blue whale—was so great. As they explain in a study in the Proceedings of the Royal Society B, the researchers found that those giants are not really in the colossi to about 4.5 million years ago.
Their theory is that changes in the climate around that time created the perfect food in the ocean for them to thrive. Specifically, glacial sheets in the northern hemisphere led to nutrient-rich expire in coastal waters, reports NPR.
In addition, upwelling currents were still more nutrients from depth, resulting in large patches of krill and fish (whale prey) gorging on them, and points to the Atlantic ocean.
One other factor has played a role: the Whales had to travel great distances to feed with this easy-to-prepare meals and larger baleen whales, those had an advantage over their smaller cousins.
“All of a sudden—boom—we see them get very big, like the blue whale,” Nick Pyenson of the Smithsonian Institution’s National Museum of Natural History tells the New York Times.
“It’s like going from whales the size of minivans to more than two school buses.” Blue whales and their congeners, had still more to go for them.
Because of their ribs—mouth filters made of the same material as human fingernails—the whales were able to take large mouthfuls and spit the water back out, without losing fish in the process.
Researchers believe that this is the reason why the fossils show whales of about 30 metres in length, began to balloon in size around this time, while the smaller whales disappeared.
Over a few million years, large whales increased from 10 tonnes in mass up to 100 tons. (Humpback whales are surprisingly researchers.)
This article originally appeared on Newser: There is a Simple Reason that the Blue whale is So Big