How did whales get so big?

Millions of years ago, whales went from merely big to massive. Now, a group of researchers think they know how these gentle giants got so gigantic.

Nick Ut/AP/File
A blue whale, the largest creature to ever roam Earth, raises its tail above the water surface off the coast of Long Beach, Calif. Only a few million years ago the baleen whale family, which includes blue whales, averaged about 15 feet long. Now blue whales can be larger than 100 feet. A new study explains how an ice age triggered a relatively sudden evolution of huge body size in whales.

Scientists think they have answered a whale of a mystery: How the ocean creatures got so huge so quickly.

A few million years ago, the largest whales, averaged maybe 15 feet long. That’s big, but you could still hold a fossil skull in two hands.

Then seemingly overnight, one type of whale – the toothless baleens – became huge. Modern blue whales get as big as 100 feet, the largest creatures ever on Earth. Its skull is now bigger than a minivan and could probably fit more than five people inside, researchers said.

“We really are living in the time of giants,” said study co-author Nicholas Pyenson of the Smithsonian Natural History Museum. “Why is that?”

And it happened “in the blink of an evolutionary eye,” which makes it harder to figure out what happened, said Graham Slater at the University of Chicago, lead author of the study in Tuesday’s Proceedings of the Royal Society B.

Their study has proposed an answer: Ice ages in the last 3 to 5 million years started it, changing the oceans and food supply for whales.

The researchers used fossil records of the smaller whales to create a family tree for baleen whales – which include blue whales, humpbacks, and right whales. Using computer simulations and knowledge about how evolution works, they started filling in the gaps between the small whales and the modern super-sized version. They keyed in on a time period when the whales got huge and smaller whale species went extinct, somewhere between a few hundred thousand years ago and 4.5 million years ago.

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. Dr. Slater and Dr. Pyenson 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 said.

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, Pyenson 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.

Olivier Lambert at the Royal Belgian Institute of Natural Sciences, who wasn’t part of the study, calls it “a really convincing scenario.” But he said the lack of fossils in certain time periods is an issue.

As oceans warm from man-made climate change, the seas will be more like it was when the whales were smaller and they will have a more difficult time surviving, Slater and others said.

You've read  of  free articles. Subscribe to continue.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.