A species of frog that resides in the forests of Colombia and Ecuador has disregarded the conventional theory of evolution by ‘re-evolving’ teeth on the lower jaw after more than 200 million years.
The tree-dwelling Gastrotheca guentheri are the only frogs known to have teeth on both their upper and lower jaws, although it was not always this way.
“I combined data from fossils and DNA sequences with new statistical methods and showed that frogs lost their teeth on the lower jaw more than 230 million years ago, but that they reappeared in G. guentheri within the last 20 million years,” explains scientist Dr. John Wiens to the BBC Monday.
The discovery fuels a long-running debate among scientists over the possibility of re-evolving “lost” traits, where in the past scientists have argued that “lost” traits cannot return.
Dr. Wiens believes that the new evidence provides a “loophole” to this assertion, providing “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.”
He suggests that the presence of teeth on the upper mouth provided the “mechanisms for developing teeth” on the lower jaw, as opposed to re-evolving these mechanisms “from scratch.”
Scientists have considered the same phenomenon with regard to several other organisms such as a stick insect’s wings and the return of lost digits in lizards, which are also believed to have re-evolved.
The G. guentheri frog species live primarily in the Andean forests of Colombia and Ecuador, although conservation specialists have listed them as vulnerable due to their “extremely fragmented” habitat.