Whales only became huge relatively recently
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They may be giants of the deep today, but blue whales only gained their huge size 2-3 million years ago.

Measuring up to 100ft in length and weighing in at more than 200 tons, the blue whale is the largest and heaviest living creature to have ever existed in the entire history of the world.

Now scientists have revealed that baleen whales - the group to which blue whales belong - were originally a lot smaller and only grew in size in response to changes to their food distribution.

"We think of [baleen whales] as being giants but if you consider this in the context of their 36m-year evolutionary history, they have only been giants for a 10th [of it]," said biologist Graham Slater.

This shift towards gigantism is thought to have occurred between 2 and 3 million years ago and is also believed to have arisen independently in multiple different branches of the whale family tree.

Rather than emerging in response to the evolution of bulk filter feeding or the appearance of large predators such as sharks however, this increase in size was most likely down to changes in the Earth's climate which caused the whales' prey to congregate in dense pockets.

"The bigger your mouth, the more you can take in and the less energy it costs you to do it," said Slater. "If you are big you can just store more energy - you have got a bigger fuel tank."

"If you are big your cost of transport is also lower so you get more miles to the gallon.