More than two million years ago, the Earthlings with the biggest brains were dolphins, and certain whales, writes Robert Krulwich on his NPR blog Krulwich Wonders. Below is an excerpt from the post, which explores how the sizes of brains change during the course of evolution:
"Lori Marino, at Emory University in Atlanta, has been studying fossilized brains. And looking back, she sees sudden spurts of brain growth in different animals.
'"[T]he most dramatic increase in brain-to-body ratio in dolphins and toothed whales occurred 35 million years ago,' she tells Chris Impey, the astronomer and writer, in his book Talking About Life. Something happened to make their medium-sized brains bigger, Lori says, then bigger still. For 20 million years certain dolphin species kept their brains growing until — just as mysteriously as it started — about 15 million years ago, they stopped.
"Why? Had the dolphins answered some secret dolphin question? Figured out a puzzle? Adapted to an environmental change? Gotten tired? Hit a limit? What?
'"That's the $6 million question,' Lori tells Chris.
"We don't know. We do know, however, that dolphins aren't the only ones. The same thing happened to us."
Click here to read the whole Krulwich Wonders post.
Related:
Do dolphins deserve special status?
Hominid skull hints at later brain evolution
Photo by NASA
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