I am biased, but two sets of teeth has always felt like the proper number of sets of teeth for one lifetime—one smaller trial run and then a final set of chompers once our faces are big enough to accommodate them, the possibility of veneers notwithstanding. We start toothless to drink milk and then our baby teeth help us learn to chew in our baby-sized jaw, only to be later pushed out by our larger adult teeth that fit our adult-sized jaws and remain with us for the end of our lives. This is true of cats and dogs and most other mammals, with some notable exceptions—manatees, elephants, and kangaroos all replace their teeth multiple times in their lifetimes, and echidnas never grow any teeth at all.
Now, Menna Jones, a vertebrate ecologist at the University of Tasmania, has confirmed another exception to the mammalian two-sets rule. Tasmanian devils, which are the largest surviving carnivorous marsupial, have only one set of teeth throughout their whole life. In a new paper in the journal Proceedings of the Royal Society B, Jones explains that the devil's single set of teeth gradually erupts from the gums, poking out more and more as the animal ages to fill the mouth of the adult animal. "This is a very cool fact about a very cool species, and it shows a completely different evolutionary solution to having teeth in growing animals than what we’re familiar with," Jones said in a press release.
I have to admit I'd never thought of "having teeth" as a condition that necessitated a solution. But I'd also never questioned if the solution evolution has passed on to me was the one I would choose, if that were an option. Normally I would advocate against bothsidesism, but I'll make an exception here to consider the pros and cons of the Tasmanian devil's solution to the eternal dilemma of having teeth as compared to our arguably wasteful human one. (Sharks and other creatures with conveyor belts full of replaceable teeth are exempt from this discussion.)
The Case For Two Sets Of Teeth
When I was a kid, I remember opening the book In a Dark, Dark Room and Other Scary Stories—the book with the green ribbon story—in a quiet corner of a library and becoming unspeakably horrified. The first story is about a boy who, for some reason, is running around a series of seedy alleys at night. He turns a corner to find a man, who smiles at him, revealing an unusually large set of teeth. The boy runs away until he sees another man, who smiles and reveals an even larger set of teeth. This—spoiler!—is the narrative arc of the story. The boy sees another man with even bigger teeth, and then he runs home. One might think that the story of the girl whose head—spoiler!—falls off after she removes the green ribbon around her neck would be more scarring for a young reader, but I remember thinking the green ribbon story was pretty clever. The story that really horrified me was "The Teeth," how big and long and tall they were.
Teeth, at least as they befit humans, should not be overly long and tall. Can you imagine a baby with adult-sized teeth? The strategy of gradual, continuous eruption really only works if you have nicely pointy teeth like the Tasmanian devil. This way, permanent adult teeth can look somewhat normal emerging from the gums of a baby because just the tiny tip is poking out. Our human teeth are largely more rectangular and block-like than the devil's, and are thusly denied the privilege of subtle eruption.
Sure, it's a little strange to think about the fact that we grow an entire set of teeth that we lose over the course of years, embedded in PB&J sandwiches and plucked by hand from their tender roots. But there are a limited number of socially acceptable keepsakes for sentimental parents to store in little boxes, only to be discovered and sometimes regifted back to their original owner. Let them have their teeth!
The Case For Big Baby Teeth Forever
I'll admit it's pretty convenient for us to have a trial run of tiny, nubby, silly teeth that fit our tiny baby jaws, holding space for a more mature and refined set. But it's also a lot of trouble! Wouldn't it be nice to never worry about tying a wiggly tooth to a string attached to a doorknob and slamming the door to knock it out? (Absolutely do not do this.) Would we all have the same recurring dream of our teeth falling out if we weren't all subjected to this very experience at such a tender age?
The thing about having baby teeth is that you don't just have the baby teeth. Although teeth begin developing in the fetus, our 20 baby teeth, perfectly sized to our baby jaw, usually erupt from our gums when we are between six months and a year old. But our adult teeth also start growing before we are born. They do not appear in our gums until they are large enough to push out our baby teeth, where they ideally remain until the end of our lives, with the exception of wisdom teeth that erupt in our late teens or early twenties. But before that time, our adult teeth are still there, lurking beneath the baby teeth in hidden chambers. Of course, you can only see this in X-rays. But as far as solutions go, is this really better? Sometimes when I see a child smile, I think about how all their adult teeth are lurking behind their pearly chiclets, waiting to descend.
If I were to write a sequel to In a Dark, Dark Room and Other Scary Stories, maybe In a Darker, Darker Room: 2 Scary, 2 Stories, I would write a story about an adult who wanders around a beautiful park on a bright and sunny day. This adult would not encounter any spooky men with too-large teeth, but only a series of young and smiling children. Each child has a brighter and more beautiful smile. But as the adult gets closer, they will see all of the child's hidden, secret, soon-to-be adult teeth. The last line of the story would be: By way, this is all 100 percent real, just ask your dentist.
