A new study has finally provided an answer relating to the evolution of gigantism of Whales. Fossil records show that ancient whales were much smaller than the currently living enormous creatures.
A few million years ago, the largest whales, averaged maybe 15 feet long. Then one type of whale - the toothless baleens - became huge. Modern blue whales get as big as 100 feet, the largest creatures ever on Earth.
Researchers suggest that the reason might be due to changes in climate that affected the food that some whales eat: krill and small fish. They concluded that when the size changes started, the poles got colder, ice expanded and the water circulation in the oceans changed and winds shifted.
Instead of being spread throughout the ocean, lots of krill started being packed into a small area. Bigger whales were simply more efficient at eating the dense pockets of krill as compared to theor smaller counterparts.
Graham Slater at the University of Chicago, lead author of the study said, "Cold water went deep and moved closer to the equator and then eventually bubbled back up in patches rich with the small fish and other small critters that whales eat."
"Before that, whale food was spread out, relatively easy to get at. Now, they are giant buffets amid hundreds of miles of whale food deserts. That's why you can see lots of whales in the summer in California's Monterey Bay", Slater added.
"Baleen whales, which have no teeth, feed by gulping tremendous amount of ocean, filtering out the water and eating the critters they capture. Toothed whales, like sperm whales, hunt individual fish or squid, so the ocean changes that made food less evenly spread out didn't affect them as much. But baleen whales hunt schools of fish or swarms of krill", co-author Nicholas Pyenson of the Smithsonian Natural History Museum said.
"If you are a whale, the easiest way to take advantage of dense but sparsely available resources is to get big", Slater said. "If you are big, you basically can get more miles to the gallon."
Baleen whales went from 15 to 100 feet in about the same time as humans evolved, he said.