Zimmer has a summary of the latest discoveries in the evolution of the baleen whales. It’s beautiful stuff, with the lineage showing their origin from toothed whales, through a phase where they had both teeth and baleen, to their current condition lacking teeth and having only baleen.
Pharyngula
Evolution, development, and random biological ejaculations from a godless liberal
That’s the good stuff!!! Oh redundancy
Random thought about teeth: if they aren’t needed–as in, absolutely critical for the animal in question to be able to eat its food–they go away. Platypuses (platypi?) have no teeth, even though it looks like they could use them. No surviving whale has both teeth and baleen. So are teeth in general a bad adaptation, something to be jettisoned if at all possible? The number of dentists needed to keep human teeth healthy suggests that it might be so.
I love Carl Zimmer.
Dianne:
By analogy with antipus (antipodes) and octopus (octopodes), the pedantically-correct plural of “platypus” is “platypodes,” with the stress on the second syllable.
To answer your question, I would imagine that in quite a few environmental niches, teeth are indeed maladaptive. We certainly can’t make a blanket statement to that effect, though, because obviously not all environmental niches are equivalent. But the fact that our teeth are trivially easy to destroy (and believe, you, me, I know that all too well) is not indicative that they are not ecologically necessary or maladaptive, at least not for our location in the food chain.
Ugh. That last sentence of mine was a bit tortured, grammatically speaking, but I think you can get the idea.
I’m definitely out of my depth here, but don’t most sharks replace their teeth with great frequency–about every 7-8 days? It would seem that permanent teeth can be maladaptive, but the continuous production of new teeth would be advantageous indeed. (And of course, the shark is not a mammal that returned to the sea.)
I totally want that.
Yeah, sharks do replace their teeth relatively frequently. The other interesting thing about shark teeth, at least in large predatory ones like the Great White (I don’t know about others), is that the teeth are highly sensitive touch organs. A great white will scope out potential prey by giving it a light probe bite. If it’s tasty, down the gullet it goes, but if not, the shark looks for something else. Sharks scare the fuck out of me, but that’s super-neat.
I don’t know what kind of timeframe we’re talking about with the replacement, but I’d imagine that it varies pretty dramatically from species to species.
By analogy with antipus (antipodes) and octopus (octopodes), the pedantically-correct plural of “platypus” is “platypodes,” with the stress on the second syllable.
Ok, but don’t tell anyone whose first language is German that or you’ll never get to make fun of their pluralization rules again.
I didn’t mean to suggest that teeth were always maladaptive–certainly a large number of animals have and need them, including humans–but that in situations where they aren’t absolutely necessary (ie if the animal in question has baleen or can chew its food with bony plates in its jaw like the platypus) then the teeth become a detriment to survival rather than an advantage quite quickly. Hence, my claim that teeth are a “good enough” adaptation in some circumstances but aren’t really optimized, that they’re more like the panda’s thumb than the eye. At least primate-type teeth. Rodent teeth seem much better formed. Then again, they have to be. A rodent with a missing front tooth is a dead rodent.