Why our teeth don’t grow back after a certain age?
In: 5
Keep in mind that humans evolved over the course of millions of years, not the last 50, so any traits we have are more adapted to the average experience over that time than to the current environment (though there’s a lot of genetic traits that allow flexibility triggered by different environments). So the answer is complicated but can be boiled down to a number of points:
1: They kind of do. When you outgrow your baby teeth, you get adult teeth. Then you get extra wisdom teeth later to help replace any molars you might have lost (which can cause a lot of crowding if for some strange reason like dental hygiene you don’t have a mouth filled with rotting teeth by your late teens).
2: There’s tradeoffs. More teeth means more complicated mouth trauma, you either need loose fragile teeth that can be pushed out of the way when new teeth come in (like baby teeth), which are thus inferior for biting and chewing, or you need a lot of force to push the new ones in which can make your mouth crooked and damage your gums and whatnot. Additionally, continuously generating new teeth like a shark requires mouth infrastructure to build them and resources to use. Keep in mind that human head space is at a premium, our heads are already so massive from our brains that they cause trauma and possible death during births, especially before modern medicine, so anything else taking space in your head needs to increase survival rates more than death rates or it isn’t worth it.
3: Evolution doesn’t really care about comfort or old people. Once you’ve had as many babies as you’re going to have, the only thing evolution cares about is you supporting them as much as possible so they can have their own. You already get extra teeth in your late teens, early 20s, they just need to survive another decade for you to have the last of your kids, and then you can gum food or use dentures or something for another decade until you die of dysentery. If it doesn’t kill you before you have kids, and it doesn’t make other people hate you enough to refuse to have kids with you, then evolution doesn’t care: there are bigger priorities.
4: Evolution doesn’t actually literally care. It doesn’t optimize for “the best”, it just goes with “good enough”. If your ancestors had trait X, and they survived long enough to have kids, then you exist and you have trait X. If trait Y might have been better but didn’t happen to mutate into existence, or if it did but by sheer luck the person who had it died for a completely unrelated reason, then you don’t have trait Y. Oh well. Your parents didn’t have teeth that grew back, and they survived, so here you are. Hopefully you’ll survive too.
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