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A marsupial frog from South America may not realize how special it is, but a team from Stony Brook University does.
Gastrotheca guentheri, one of a group of frogs known for carrying fertilized eggs in pouches, is the only ranine species known for sporting teeth on both upper and lower jaws. That trait is unusual because frogs are said to have been missing their lower teeth for some 200 million years.
For that reason, the quirk represents an apparent violation of Dollo’s Law, which states that traits that disappear in the course of evolution will never return. Study leader John Wiens explained, “The loss of mandibular teeth in the ancestor of modern frogs and their re-appearance in G. guentheri provides very strong evidence for the controversial idea that complex anatomical traits that are evolutionarily lost can re-evolve, even after being absent for hundreds of millions of years.”
the genetic information for producing teeth would have been preserved, and therefore the “flip” of a “simple” genetic switch-of-sorts—not an improbable increase in information—could explain this so-called “evolution,” which only changed a frog with teeth into (you guessed it) a frog with teeth.
Wiens’s team used a combination of fossil and genetic data to come to the conclusion that the lower jaw’s teeth disappeared approximately 230 million years ago, returning “within the past 20 million years.” The team has attempted to salvage Dollo’s Law by pointing out that the frog has always had teeth on its upper jaw, suggesting it was therefore less of a challenge for the teeth to re-appear on the lower jaw. And if we accepted the team’s story and timeline for the frog’s loss of teeth, we would agree: the genetic information for producing teeth would have been preserved, and therefore the “flip” of a “simple” genetic switch-of-sorts—not an improbable increase in information—could explain this so-called “evolution,” which only changed a frog with teeth into (you guessed it) a frog with teeth. And this still does not answer the question of how we got frogs from non-frogs or how we got frog experts from pond scum over millions of years.
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