Why are whales so big?

Earlier this month, people around the world gawked at viral photos of a massive sea monster that had washed up on an Indonesian beach. Aside from looking like a grotesque, melting, Dalí-worthy nightmare, part of what was so strange and horrifying about the carcass was the size — the beast from the deep stretched nearly 50 feet in length.

Unfortunately, reality is always a little disappointing: The remains belonged to a baleen whale. But there is certainly something rather mythical and monstrous about cetaceans, and how exactly they became so colossal compared to everything else on Earth. The blue whale, for example, can stretch over 80 feet and weigh 380,000 pounds.

A study published Tuesday might have the answers. Whales, as it turns out, only became enormous in the past 4.5 million years or so: "All of a sudden — 'boom' — we see them get very big, like blue whales," the author of the paper, Smithsonian Institution marine mammal fossil curator Nick Pyenson, told The New York Times. "It's like going from whales the size of minivans to longer than two school buses."

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Around the time whales bloated up to the size of, uh, whales, large ice sheets were beginning to cover swaths of the Northern Hemisphere:

In other words, whales were able to gorge themselves on zooplankton and krill to their car-sized-heart's content. In order to migrate and follow the food sources with the seasons, too, larger aquatic mammals were also more likely to survive the transoceanic journeys.

"A blue whale is able to move so much further using so much less energy than a small-bodied whale," explained evolutionary biologist Dr. Graham Slater said. "It became really advantageous if you're going to move long distances if you're big."