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Do Fish Have Fingers?

DAVID GREENE, HOST:

I'm David Greene with a story about fish fingers. No, this is not a cooking segment. NPR's Joe Palca doesn't do cooking stories for his series Joe's Big Idea, but he does do stories about genetics and evolution. And today Joe tells about research unveiling the evolutionary similarity between fish fins and mouse fingers.

JOE PALCA, BYLINE: You can get kind of specialized in science, take for example Neil Shubin's work at the University of Chicago. Andrew Gherke is one of Shubin's graduate students.

ANDREW GHERKE: In the Shubin lab we're generally interested in the fin to limb transition.

PALCA: It may sound esoteric, but understanding the fin to limb transition is critical to understanding how life crawled out of the ocean and onto land. Gherke says they've found fish fossils that have bones that clearly show a transition to a land animal's wrist bones.

GHERKE: But the question is do living fish have an equivalent of those structures?

PALCA: At first blush, it doesn't look like it.

GHERKE: Well, if you just look at the bones, it's really hard to say, oh, this looks like a wrist or, oh, these look like digits.

PALCA: Gherke decided instead of looking at fish anatomy, let's look at genetics. So he compared the genome of a fish called a gar with a genome of a mouse. In particular, he wanted to see if gar had the genetic elements that were responsible for development of wrists and fingers in the mouse.

GHERKE: Our data is suggestive that they do.

PALCA: In other words, even though they don't have bones that look like wrists or fingers, gar have the genetic sequences that are needed to make wrists and fingers. Gherke's research appears in the journal PNAS. If Gherke sounds a bit cautious about his claims, it's because there may be other reasons those genes are present in gar that have nothing to do with the development of wrists or fingers. Gherke says finding these genetic similarities between fish and a mammal is remarkable. Because if you just look at the bones of a fish fin or a mouse or human hand, you'd say...

GHERKE: ...We're not closely related at all. This is very, very different.

PALCA: But you get a different story when you look at the genomes.

GHERKE: We're so similar to other animals and fish when you look at it at this sort of developmental and genomic level.

PALCA: As Gherke's advisor Neil Shubin likes to say, we all have our inner fish. Joe Palca, NPR News. Transcript provided by NPR, Copyright NPR.