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Imagine That! - Dolphin and Human Brain Size

Imagine That!
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Imagine That! - Dolphin and Human Brain Size

Credit: NSF/Finger Lakes Productions International

Audio Transcript:

Humans are the brainiest animals on earth -- that's why we rule the animal kingdom. But there's a close runner-up...

Imagine that!

(SOUND: waves, porpoise vocalizations)

You might think a chimpanzee would be closest to humans on the intellectual ladder. But actually, porpoises and dolphins -- a class of animals called toothed whales -- have brains that are almost as large as ours...

(SOUND: chimp talk)

...larger in relation to their body size than other primates like chimps and gorillas. That's why we study their behavior, and are trying to figure out how to talk to them.

Dr. Lori Marino of Emory University has been comparing how we got our big brains with how dolphins and porpoises got theirs. She's tracking two different paths through evolution.

What she found is that for porpoises and their cousins, the amazing turning point toward a large brain came forty-seven million years ago...much sooner than for humans.

Marino: "Human brain size didn't increase dramatically until about 2 million years ago. And if you go back two million years, the dolphins and whales swimming around actually had a larger relative brain size than humans. So it's only very recently that we've been the brainiest on the planet."

A tiny twist of fate two million years ago -- and we might not be the animals going to college! I'm Eric Phillips.

"Imagine That!" covers projects funded in part by the U.S. government's National Science Foundation. Federally supported research -- brought to you by you! Learn more at

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