New Frogs With Teeth Changes Re-Evolution Theory

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"And now please show them your teeth Kermit!
Uh, Grover. Uh, Grover. I was going to say to you, you know how I'm a frog, you know, well frogs do not have teeth Grover, no teeth.
Open your mouth!" (YouTube/Sesame Workshop)

Almost everything you learn on Sesame Street is true. But on this one, Kermit's got it wrong. Of nearly six thousand known species of frogs, a new study out of Stony Brook University suggests there's actually one with a set of real-life chompers.

And that is spawning a conversation about evolution -- trait RE-evolution, to be exact. Take a look at all the species that don't have teeth. According to the 19th Century Dollo's Law, when a species loses a trait - like humans did tails - it never comes back. But these biologists say they've found a frog with teeth on both jaws - a trait not seen in some 200 million years. (Video from: National Geographic)

The tooth-frog species' name is Gastrotheca guentheri and lives primarily in the Andean forests of Colombia and Ecuador. Head scientist John tells the BBC, analyzing frog fossils and DNA sequences helped him prove his theory.

"Dr Wiens believes that this re-evolution can be considered a 'loophole' in Dollo's law. ... 'What G. guentheridid was to put teeth back on the lower jaw, rather than having to re-evolve all the mechanisms for making teeth 'from scratch'...'"

And The Frog Blog says the frog's set of teeth isn't the first example of re-evolution....

"...scientists have identified and debated several attributes that have apparently 're-evolved' over time including stick insect's wings ... and lost digits in lizards."

But as Wiens points out in his study - those examples have been subject to speculation. Wiens' research is considered a solid challenge to Dollo's Law - and a blogger for Science 2.0 says it's time to shake things up.

"...Dollo's law stated that complex traits lost cannot come back, evolution is irreversible - well, so what? It's been a long time since 1890 when paleontologist Louis Dollo asserted that and it was never a law anyway, it was just a hypothesis."

Wiens says the re-evolution of Gastrotheca guentheri's lower teeth took some 20 million years to come back, so Kermit might just have to wait awhile for that perfect smile.

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