Frogs Evolve Teeth—Again

[sparkchaser]

Interesting article.

Frogs Evolve Teeth—Again

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.

A new analysis of the frog family tree reveals that the common ancestor of frogs, which long had lower-jaw teeth, lost them more than 230 million years ago before eventually going extinct.

The marsupial frog G. guentheri didn't have lower teeth, then "boom, around 5 to 15 million years ago, it got them ... ," said John Wiens, who authored a recent study on the phenomenon.

The discovery runs counter to a principle called Dollo's law, which states that physical structures lost during evolution are never regained, according to Wiens, an evolutionary biologist at Stony Brook University in New York State.

In fact, the teeth's reappearance may have exposed the law's loophole: That it's "much easier to re-evolve things if you're already making them somewhere else," Wiens said.

In other words, the frog "didn't have to make teeth on the lower jaw from scratch, because they're already making them on the upper jaw."

 

[beer good]

It's interesting, but I'm not sure it's as radical as the article makes it sound. I checked with a friend who's a doctor of biology, who said it's a) not exactly news (wikipedia already lists several other exceptions) and b) not all that big a surprise; most of the time when a trait is "lost", it remains part of the genetic code but is for the most part inactive (whale fetuses have hind legs; humans are occasionally born with a tail; etc), so just as the article says, it's not like the frog has needed to repeat the entire evolution of teeth from scratch. They always had the theoretical ability for teeth, in both jaws; the odd thing is that that gene was "activated" again after such a long time. That's very statistically unlikely and depends on a lot of things going right, but it's not quite revolutionary.

That said, frogs with teeth? Sounds like a Stephen King story, but seriously oh my god it's TRUUUUUUUUUUE GET THEM AWAY FROM ME







*ribbit*