In "Frogs Evolve Teeth – Again: Mysterious re-evolution challenges evolutionary theory, scientists say", Christine Dell'Amore, (National Geographic News, February 10, 2011) tells us,
Lower-jaw teeth in frogs re-evolved after an absence of 200 million years, a new study says. The discovery challenges a "cornerstone" of evolutionary thinking, according to experts.
Of the more than 6,000 species of frogs, only one, a South American marsupial tree frog called Gastrotheca guentheri, has teeth on both its upper and lower jaws. Most frogs have only tiny upper-jaw teeth.
Apparently, G. guentheri has acted in violation of Dollo's law, according to which traits lost through evolution cannot be regained.
"It's a very clear case of reacquisition of a lost complex morphological structure, which, according to current thinking, should not be possible."
Well one thing for sure, that frog's gotta go. Worse:
"The fact that toothlike structures appear more often than real teeth means that tooth evolution doesn't automatically occur when the need arises, Yale's Wagner noted.
With that in mind, natural selection – the process by which favorable traits become more common over time within a species – is "not enough to explain" why the marsupial tree frog regained its lower teeth.
"I can confidently say that we don't know," Wagner said. "It's an extremely interesting question."
A friend wonders, "Did this guy get shot for saying this?"
I dunno. Anyone seen him around lately?
Texas Darwin lobby, please note. Another subject to cross off the list of what students can hear about.
Denyse O'Leary is co-author of The Spiritual Brain.