Whales Were Not Always As Big As They Are Today, Study Says

Posted: May 25 2017, 6:10am CDT | by , Updated: May 25 2017, 6:15am CDT, in News | Latest Science News

 
Whales were Not Always as Big as They are Today, Study Says
Credit: Silverback Films/BBC

We may have finally know why blue whales are so enormous

Blue whales are the largest animals ever known to have lived on Earth. These marine giants can grow up to 100 feet long and weigh around 200 tons. Their tongues alone can be as massive as an elephant. But blue whales were not always like this. According to a new research, it was only recently that they evolved to their massive size and it took them 3 million years to transform themselves into the enormous creatures as we know them today. That may sound a long time but in geological terms it is a very short period.

“We might imagine that whales just gradually got bigger over time, as if by chance, and perhaps that could explain how these whales became so massive,” said co-researcher Graham Slater from University of Chicago. "But our analyses show that this idea doesn't hold up – the only way that you can explain baleen whales becoming the giants they are today is if something changed in the recent past that created an incentive to be a giant and made it disadvantageous to be small.”

How and why whales got so big has remained a mystery until now. The lack of fossil record is one of the biggest problems in understanding their evolutionary history.

“We haven’t had the right data. How do you measure the total length of a whale that’s represented by a chunk of fossil?” Nicholas Pyenson, the curator of fossil marine mammals at Smithsonian’s National Museum of Natural History said.

If proper fossil record is not available, there would be no way for researchers to ever learn the changes occurring in the species. But researchers believe that the skull of the whale can represent the overall size of the body.

For the study, researchers used the fossilized skulls of the whales found in the Smithsonian museum. The museum contains the largest skull collection for both living and extinct baleen whales, including blue whale and is an ideal place to examine the evolutionary relationships between whales of different sizes. Using this collection, researchers estimated the length of 63 extinct whale species (more than 30 million years old) and 13 species of modern whales. The data clearly showed that the large whales that exist today were not present in the whales' early history while the shift in the size of whale body occurred about 4.5 million years ago. That is fairly recent. Not only did whales with bodies longer than 33 feet begin to evolve around this time, but smaller species of whales also began to disappear.

This evolutionary shift took place at the beginning of the Ice Ages and corresponds to the climate change. Researchers suggest that the climate change filled the oceans with massive food supplies. With easy excess to food, the whales became so enormous and their foraging behavior got even more efficient as their body size increased.

“An animal's size determines so much about its ecological role," said Pyenson. "Our research sheds light on why today's oceans and climate can support Earth's most massive vertebrates. But today's oceans and climate are changing at geological scales in the course of human lifetimes. With these rapid changes, does the ocean have the capacity to sustain several billion people and the world's largest whales? The clues to answer this question lie in our ability to learn from Earth's deep past – the crucible of our present world – embedded in the fossil record."

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Hira Bashir covers daily affairs around the world.

 

 

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