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Scientists use teeth to analyze evolution of whales walking on land to swimming in ocean

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Posted at 2:17 PM, Jun 15, 2021
and last updated 2021-06-15 14:17:08-04

SAN DIEGO, Calif. — The ancestors of whales used to walk on land, and San Diego scientists are working to uncover mysteries about how the evolution from land to sea took place. They’re turning to whales’ teeth to find answers.

More than 50 million years ago, whales’ ancestors walked on land. Now, they still have features that link the land tendencies.

“They’re air-breathing mammals that are fully aquatic today but their ancestors walked on land with four legs. That transition from a four-legged terrestrial mammal to a fully aquatic marine animal that swims with a tail is an amazing transition and the fossil record preserves the details of that land to sea transition,” said Eric Ekdale, a lecturer of Biology at San Diego State University.

Ekdale and fellow scientist Tom Demere, who is the Curator of Paleontology at the San Diego Natural History Museum, decided to dig deeper into this transition.

Fossil records show that millions of years ago, whales had teeth. Now, whale fetuses have teeth, but those teeth disappear by birth and are replaced with something called baleen, which is the same substance that makes up human hair and nails.

But what happened in between? And when?

Using CT scans, Ekdale and Demere analyzed fossils from the middle of those two time frames and discovered that those whales had both teeth and baleen. This tells them that there was a gradual overlap before whales lost teeth.

“What’s really intriguing though is we’re able to use this modern technology to investigate a fossil. We couldn’t have done this 25 years ago,” said Demere.

The two say that it might seem like an insignificant thing to analyze, but it’s an important piece of the puzzle when looking at a big-picture transition. It’s also rare for mammals to lose teeth the way whales have.

“To lose teeth is kind of a big deal. Most mammals have teeth but the animals that don’t have teeth, they’ve done something different. We view this in an evolutionary perspective as an adaptation,” said Demere.

Baleen whales are the largest animal to have ever lived on this planet. They include blue whales, humpback whales, gray whales, and more.

There is currently a display of this research on the third floor of the San Diego Natural History Museum.

This story was originally published by Leah Pezzetti at KGTV.

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