I searched for “baby teeth” and got a vast number of threads, none of which seemed to have any relevancy to the subject.
Anyhow, what is the reason humans and some animals have baby teeth, which eventually have to be replaced by “adult teeth”?
Do we get these for the same reason sharks… Never mind.
Any thoughts?
It has to do with how the jaw changes shape, IIRC. Let me see if I can find a link.
ETA: From here:
-XT
Yep, size of the skull and jawbone. The baby mouth is too small to fit the full array of adult teeth, so they get a junior set, smaller in size and number, which are replaced by the larger adult teeth (and more of 'em) as they grow.
Now your next question will be, “but why don’t they just have fewer full sized teeth as babies and grow in more when they get bigger?” The answer, unsatisfying as it is, is that they just don’t. No predecessor pre-human animal developed that particular mutation, or if they did, it wasn’t any better for their reproduction or survival than the more common primary/secondary teeth procedure, so it didn’t persist in the species.
So why don’t the teeth simply wait until the skull is big enough for real teeth?
Possibility; to get kids off the teat earlier. 
Peace,
mangeorge
lol, mangeorge! Yeah, my kid bit me once. I wasn’t thinking, and I slapped his little face. He cried for about 2 minutes; I cried for hours. 
But the little bastard never bit me again! 
Seriously, though, if we look at hunter-gatherer societies as the “natural” way of human animal behavior, kids probably nurse naturally for 4 or 5 years, but start eating some solids after a year, when they have some teeth. If you consider the “natural” diet of humans, they do need some teeth to process vegetation and meat, and the sooner they can do it on their own, the fewer calories and natural resources Mom loses in making purees and gruel for them to eat.
My ex would sympathize with you, WhyNot.
I can tell you from experience, if something tastes good, but is too much trouble to chew, the hid will simply swallow. No matter the size of the tidbit. My oldest daughter scared the crap out of me by doing just that. Blue babies are not pretty.
Always cut hot dogs into pieces small enough for the child to easily swallow whole. :eek:
Man, can you imagine a baby with full-sized adult teeth? That’d be more disturbing than the “doggie dentures” commercials.
Yeah, smooshy processed foods that don’t actually require much chewing, like hot dogs and McDonald’s burgers, are the worst. Hot dogs are notorious kid chokers, along with popcorn and jelly beans. Even sliced into rounds, hot dogs are just the perfect diameter to lodge in the trachea like a drain stopper. Parent tip: cut them lengthwise, at least once (I quarter them lengthwise, just to be sure) *then *slice 'em up.
When my son was about 2 or 3 years old, we gave him a sliced-up hot dog. We didn’t realize that he wasn’t chewing them until he abruptly threw them all up whole. They looked like they hadn’t been chewed at all.
(This ended up being so traumatic for him that he refused to eat a hot dog again until he was a teen-ager.)
I can’t see your alternative (having fewer teeth as babies, and then having more grow in as they get older) working very well.
Remember that the teeth are rooted in the jawbone, and not very moveable. So when they have fewer teeth as a baby, there would have to be gaps between the teeth for the later ones to grow into. Seems like these gaps would make it harder for chewing, and would be obvious places for food pieces to get stuck and promote tooth decay. Plus when the later teeth grew in, they would have to be perfectly centered between the existing teeth – a little bit too far in either direction and you would end up with teeth too tightly together on one side, and a small gap on the other side. (And it’s fairly common or dentists to deal with teeth coming in out of place already; that can require major dental work to fix.)
Also, I would wonder about the effect of wear on the teeth. You would have 1 set of teeth that has been in use for several years longer than the teeth in between them. Would those older teeth have excessive wear compared to the in-between ones? Would they tend to have more cavities, having been exposed longer? Starting over with a completely new set of teeth, discarding your baby teeth works well.
Seems like a lot more possible ways for things to go wrong under your alternative. The one evolution has settled on seems to work pretty well.
Teeth could always grow in from one side of the jaw - all the new ones come in at the back, for example. For mammals with specialized teeth (like us humans) that could be a real problem, but we’d make it.
Another reason for baby teeth: In a world without oral hygiene, your first set can rot out and then be replaced by a good, adult set. The adult set don’t rot out until you’ve had time to get pregnant and give birth to someone with a new baby set.
Well, assuming i got all my adult teeth by 10 (I can’t remember when that happened), my teeth are now around 73 years old. I have had several fillings since, and only three extractions, otherwise still got them all.
Considering all the work they have done during that time, it seems them thar suckers are pretty tough.
Actually, Paleolithic and Mesolithic skulls tend to sport unrotted, cavity-free teeth. It’s only after the switch to agriculture, very recently in evolutionary terms, that human teeth began rotting away.*
*Some Mesolithic societies relying heavily on sugary fruit did have caries problems, but things really took off with the starchy, carb-rich agricultural produce, and only got worse with the invention of white flour and sugar.
I know that continual tooth replacement is the norm in sharks, but I don’t know about other lower orders of vertebrates. So maybe a better question to ask is why mammals replace their teeth only once in their lives, instead of several times, or continuously.
All mammals develop two sets of teeth (excepting some toothless variations). The genetic structure that controls this is very deeply embedded in the common ancestor of all mammals. Human teeth are just conforming to the same pattern as all other mammals.
Nobody knows why mammals developed the two sets of teeth mode, instead of the more practical system of endlessly replacing teeth like sharks. I would suspect it’s tied to the unique feature of mammals, feeding their young. It wouldn’t seem that mothers nursing their young until they reached maturity would be the most practical system. So a set of teeth to cover the period between weaning and adulthood might have been advantageous for survival. The tooth patterns of mammals have adapted widely since it all started, so looking at details of teeth in modern mammals might never reveal how it began.
Another term for baby teeth is milk teeth, so you may be on to something there.
As for whether it would be better if we hadn’t lost the ability to endlessly replace teeth, I think probably not. Mammal teeth have evolved to meet the “expectation” of lifetime duration under normal conditions (for humans, that only includes pre-ag hunter-gatherers). While I’m not an expert on teeth, I’d feel safe in betting that a human adult tooth, generally speaking, is better than any shark’s tooth in terms of its structural and functional qualities. IOW, presumably mammals evolved towards fewer and better teeth.
That’s a reasonable conclusion. There are shark’s teeth that are around 400 million years old. Mammal’s teeth go back around 200 million years, and form the basis for dating the origin of mammals. It sounds like teeth in general are pretty tough. I don’t think I could make solid argument for either one to be funtionally or structurally better.
At least in mammals, teeth begin to form from stem cells early in embrionic development. I’m not sure of the process for generation of the second set of teeth, but I think in humans they are already developing when a baby is born. Mammal’s teeth might actually be a simpler and more practical system because new teeth don’t have to form later in life. Sharks don’t lactate, at least some are born with a full set of teeth, and start their lives as predators, needing teeth to catch and eat food. Mammals don’t need teeth for a while after they are born, and they be disadvantageous at an early age for teeth that may have to last a while (they may not fit in the newborns mouth, they may require too much energy in pre-natal development, as a couple of possible reasons). So having two sets of teeth like mammals may be a simpler system that allows a scheduled set of stages in a mammal’s life, toothless, baby teeth, permanent teeth (and for some, toothless again). That system is probably interwined with associated mammalian characteristics such as lactation, and a long infancy.
So I don’t think mammals would be better off with the shark system. But dinosaurs did pretty well with the endless supply system. That might have been the only way for the really big ones to get that way. So I solidly conclude that I have no idea which system is better. But without the mammalian system, mammals would be very different.
Then again, the only dinosaurs left are toothless feathered ones, so they’re doing better without it.
Um, shouldn’t the parent tip be, “Don’t feed your kids McDonald’s burgers.”?
lol. Honestly? No. There’s nothing wrong with a burger, be it McDonald’s or homemade, once in a while. Of course, it’s easy to overdo it, but in moderation, the human body can handle a sixth of a pound of ground beef, a ton of salt and two servings of bread, extra sugar, even a small body.
But watch 'em and make sure they’re *chewing *it, or cut it up into itty bitty pieces.