WEBVTT - TEETH: Dental Evolution and Marching Molars 0:00:03.000 --> 0:00:04.840 Welcome to Stuff to Blow Your Mind, a production of 0:00:04.880 --> 0:00:13.760 I Heart Radio's How Stuff Works. Hey, you welcome to 0:00:13.760 --> 0:00:15.760 Stuff to Blow your Mind. My name is Robert Lamb 0:00:15.800 --> 0:00:18.279 and I'm Joe McCormick. And if you've been listening to 0:00:18.320 --> 0:00:21.000 the show, you know we just had our friend Katie 0:00:21.040 --> 0:00:23.840 Golden from Creature feature on. I think it was the 0:00:23.880 --> 0:00:27.280 episode right before this one where we talked about teeth 0:00:27.440 --> 0:00:29.240 with with Katie and that was a lot of fun. 0:00:29.280 --> 0:00:33.120 But Robert, I couldn't stop thinking about teeth. Oh yeah, 0:00:33.159 --> 0:00:37.040 I mean, teeth are weird. Teeth are wonderful and strange 0:00:37.120 --> 0:00:40.880 and grotesque. I was actually just at the dentist yesterday 0:00:40.920 --> 0:00:43.360 for a checkup, and I just kept thinking about just 0:00:43.520 --> 0:00:46.680 how weird it is that that I just regularly go 0:00:46.800 --> 0:00:49.680 to this place and pay another human being to reach 0:00:49.720 --> 0:00:53.320 into my mouth with special instruments and clean my weird 0:00:53.440 --> 0:00:59.080 bone like jaw protutions the outside bones, outside bones. Never forget, 0:00:59.120 --> 0:01:01.400 your teeth are outside bones. Their bones that you wash. 0:01:01.560 --> 0:01:04.800 Oh that's that's from Kimmy Schmidt, right. Yeah. Titus Syndromedon 0:01:04.959 --> 0:01:06.920 sings that song. I think he's auditioning for like a 0:01:07.000 --> 0:01:11.120 chewing gum commercial. But he's actually wrong. I'm sorry to say, 0:01:11.200 --> 0:01:13.520 despite how much I love that moment from the show, 0:01:13.680 --> 0:01:16.880 teeth are not outside bones. They are not bones at all. 0:01:16.920 --> 0:01:19.000 They're a totally different things. We can explain that in 0:01:19.000 --> 0:01:22.000 a minute. But yeah, yeah, I mean, well, let's go 0:01:22.000 --> 0:01:24.080 ahead and get into it. So, yeah, our teeth are 0:01:24.120 --> 0:01:27.080 bone like in many respects. Uh yeah, but they are 0:01:27.160 --> 0:01:30.080 not bones. So just for an example, bones are composed 0:01:30.120 --> 0:01:33.959 of calcium, phosphorus, sodium, and other minerals. Uh And but 0:01:34.040 --> 0:01:37.600 mostly it's the protein collagen that forms the living, growing 0:01:37.840 --> 0:01:43.080 collagen framework in bones. Bones have impressive regenerative powers. You 0:01:43.160 --> 0:01:46.560 break a bone, it can even like a really vicious 0:01:46.600 --> 0:01:50.080 break of a bone, and it can heal back. Also, 0:01:50.280 --> 0:01:53.920 bone marrow produces red and white blood cells. Teeth do 0:01:54.000 --> 0:01:58.120 not have bone marrow. Instead, they have dental pulp. So teeth, 0:01:58.120 --> 0:02:00.720 on the other hand, are you know, they're composed of calcium, 0:02:00.760 --> 0:02:04.120 phosphorus and other minerals. They're harder than any bone that 0:02:04.160 --> 0:02:06.760 we have in the body. Yeah, but they also lack 0:02:06.840 --> 0:02:09.720 the regenerative powers of bones. So if you crack or 0:02:09.720 --> 0:02:12.600 break a tooth, you're gonna need at least a root canal, 0:02:12.720 --> 0:02:15.960 if not a total extraction. That is kind of strange, 0:02:16.320 --> 0:02:20.720 that seems. I wonder what the the evolutionary reason for 0:02:20.760 --> 0:02:23.040 that is. I would expect, you know, there would be 0:02:23.040 --> 0:02:26.560 a strong pressure on the ability to regenerate teeth. Well, 0:02:26.600 --> 0:02:29.000 it depends on how this really gets into like the 0:02:29.000 --> 0:02:33.440 bigger questions of of biological mortality, right, like what do 0:02:33.440 --> 0:02:36.600 you need your teeth for? How long are you going 0:02:36.639 --> 0:02:38.720 to be a viable organism? How long do you need 0:02:38.760 --> 0:02:41.480 to live, you know, in order to accomplish your genetic 0:02:41.520 --> 0:02:45.160 mission of you know, reproduction, uh and so forth, and 0:02:45.160 --> 0:02:48.000 and you know, the evolution isn't really concerned with long 0:02:48.080 --> 0:02:50.760 term dental health beyond that point. Well maybe yeah, maybe 0:02:50.840 --> 0:02:54.760 we don't need teeth because um, well for one thing, 0:02:54.800 --> 0:02:57.959 we're not like sharks, right, we're not just like biting 0:02:58.240 --> 0:03:03.000 indiscriminately into whole organisms and you know, cross bones and 0:03:03.040 --> 0:03:05.519 stuff like that. We we tend to if we're eating 0:03:05.680 --> 0:03:09.560 an animal, we kill it before we start biting into it. Uh, 0:03:09.600 --> 0:03:11.680 So you know, you you would be able to have 0:03:11.800 --> 0:03:14.320 the time to seek out the soft parts to bite into, 0:03:15.160 --> 0:03:18.119 and so you're not using your teeth in a kind 0:03:18.120 --> 0:03:21.080 of like violent, fast moving kind of way like a 0:03:21.080 --> 0:03:23.840 lot of other organisms would yeah, and and it really 0:03:23.960 --> 0:03:25.960 drives home one of the key and I guess kind 0:03:26.000 --> 0:03:27.760 of obvious things that we're gonna we're gonna touch on 0:03:27.800 --> 0:03:32.560 here and there is that as as organisms evolve, their 0:03:32.639 --> 0:03:35.440 teeth are going to change to meet the demands of 0:03:35.520 --> 0:03:38.320 their diet. And if if you're if you do not 0:03:38.520 --> 0:03:42.320 need your robust teeth of old anymore, well, those those 0:03:42.320 --> 0:03:45.000 teeth are going to change, and you're gonna end up 0:03:45.040 --> 0:03:47.480 with a dental model that is going to be more 0:03:47.520 --> 0:03:50.000 in keeping with what you're actually going to use your 0:03:50.040 --> 0:03:53.080 choppers for. It's funny. You could think of teeth in 0:03:53.120 --> 0:03:56.960 a way as a form of convergent evolution. So like 0:03:57.040 --> 0:04:02.360 the same way that you see uh wings evolving independently 0:04:02.440 --> 0:04:05.880 in different lines of animals. It's not that everything on 0:04:06.040 --> 0:04:10.080 Earth that has wings evolved from a common winged ancestor. 0:04:10.480 --> 0:04:13.680 So wings arose in one case in insects, and then 0:04:13.720 --> 0:04:18.039 they separately arose in you know, mammals, They rose in 0:04:18.120 --> 0:04:20.640 bats and stuff, and then they separately arose in the 0:04:20.640 --> 0:04:23.800 dinosaurs that became birds, and then also in the other 0:04:23.960 --> 0:04:27.600 the flying reptiles, right, which are not dinosaurs, but also 0:04:27.640 --> 0:04:32.000 independently evolved wings. Uh. So, so you see winged flight 0:04:32.120 --> 0:04:34.960 evolving over and over despite the fact that all these 0:04:35.080 --> 0:04:39.000 organisms don't come from wings of a common ancestor organism 0:04:39.000 --> 0:04:40.960 that I mean, I guess if you go far back enough, 0:04:41.000 --> 0:04:42.880 they all do have a common ancestor, but it didn't 0:04:42.920 --> 0:04:45.719 have wings. Um. And you can see a kind of 0:04:45.760 --> 0:04:49.560 similar thing in different things we call teeth. That you know, 0:04:49.760 --> 0:04:53.240 lots of organisms have an opening of the alimentary track, 0:04:53.360 --> 0:04:56.120 They've got a mouth of some kind or another, and 0:04:56.279 --> 0:04:58.920 it it just often happens to be the case that 0:04:59.080 --> 0:05:02.880 organisms evolved of a need to mash and crush and 0:05:02.920 --> 0:05:05.880 cut things that are going into the front of the 0:05:05.920 --> 0:05:09.080 elementary tract. And that's how you get these different evolutions 0:05:09.080 --> 0:05:12.200 of things that are like teeth. Uh. And there there 0:05:12.200 --> 0:05:13.960 are a lot of different things you might call teeth, 0:05:14.240 --> 0:05:18.080 and not all are evolutionarily related to the calcified structures 0:05:18.120 --> 0:05:21.839 we see in animals like ourselves. In fact, one great 0:05:21.880 --> 0:05:24.680 example of of a whole different kind of of tooth 0:05:24.760 --> 0:05:28.360 world that I was thinking about just recently is uh. 0:05:28.400 --> 0:05:31.839 It reminds me of this controversy over the mouth of 0:05:32.240 --> 0:05:36.680 a Cambrian predator that I I have been calling Anomala 0:05:36.760 --> 0:05:40.360 carus or Anomala carress. I just found out that some 0:05:40.400 --> 0:05:43.760 people pronounce it anomalacrous, and now now I feel like 0:05:43.800 --> 0:05:45.919 my whole world has been turned on its head. I 0:05:45.960 --> 0:05:47.680 don't know which to say, but I think I'm gonna 0:05:47.760 --> 0:05:50.560 keep saying Anomala carress even if that's wrong, for the 0:05:50.600 --> 0:05:54.200 sake of consistency. This is this is basically, if you've 0:05:54.240 --> 0:05:56.560 ever been to a natural history museum, you've probably seen 0:05:56.560 --> 0:06:01.160 a representation of this. Uh this this pretty historic fish. Yeah, 0:06:01.160 --> 0:06:04.320 I mean, well not a fish, well organism and the 0:06:04.520 --> 0:06:08.760 this long predating fish. So the Cambrian period, of course, 0:06:08.800 --> 0:06:11.840 you know, it's roughly five hundred million years ago. It's 0:06:11.920 --> 0:06:14.799 the first time in the history and the fossil record 0:06:14.839 --> 0:06:18.479 of Earth where we suddenly see this explosion and diversity 0:06:18.520 --> 0:06:22.000 of animal body forms. You know, before this, there were animals, 0:06:22.080 --> 0:06:24.880 and most of them had soft bodies and leave very 0:06:24.880 --> 0:06:27.919 little records. But there were things like worms of various 0:06:28.000 --> 0:06:32.640 kinds um. But but then suddenly around the Cambrian period, 0:06:32.880 --> 0:06:35.039 you see all these different life forms emerging, and a 0:06:35.040 --> 0:06:37.880 lot of the life forms have hard shells. This is 0:06:37.920 --> 0:06:40.880 where you see the explosion of trialobytes. It sometimes thought 0:06:40.880 --> 0:06:44.360 of as the age of trialobytes, which are these scuttling 0:06:44.440 --> 0:06:46.920 you know, almost like insect or crab like creatures that 0:06:46.960 --> 0:06:48.960 would move along the bottom of ocean floors and have 0:06:49.040 --> 0:06:52.120 these hard shells on their backs. But Anomala keras or 0:06:52.160 --> 0:06:56.040 anomal ochrous appears to have been the top predator or 0:06:56.120 --> 0:06:59.960 one of the top predators of the Cambrian period, which 0:07:00.160 --> 0:07:03.480 was and it was this lobed swimming predator that grew 0:07:03.560 --> 0:07:07.240 up to about six ft long. And when the fossils 0:07:07.320 --> 0:07:12.200 of Anomala Carras were first discovered, paleontologists thought that they 0:07:12.200 --> 0:07:16.640 were actually looking at two different species because it's a 0:07:16.720 --> 0:07:20.880 mostly soft bodied organism, so its entire body usually doesn't 0:07:20.920 --> 0:07:24.600 get preserved or doesn't get preserved very well. And since 0:07:24.640 --> 0:07:26.960 most of their bodies are these soft parts that don't 0:07:27.000 --> 0:07:30.720 get fossilized, usually there were really only two parts of 0:07:30.720 --> 0:07:34.880 the body that paleontologists kept finding. These two parts were, 0:07:34.960 --> 0:07:39.320 first of all, these little pairs of shrimp looking things 0:07:39.360 --> 0:07:41.120 that they would come in pairs, and they would kind 0:07:41.120 --> 0:07:43.920 of have these curved shapes and they, I mean, they 0:07:43.920 --> 0:07:46.080 looked like shrimp shells, that's the best way to put it. 0:07:46.760 --> 0:07:50.280 And that's actually where the name of Anomala carus comes from. 0:07:50.760 --> 0:07:53.560 Uh Anomla carus. I mean, you know, anomaly in cars 0:07:53.600 --> 0:07:57.160 means weird shrimp, usual unusual shrimp. So you have these 0:07:57.160 --> 0:07:59.680 pairs of shrimps, and then the other part that they 0:07:59.720 --> 0:08:03.679 would often find would be these circular rings of hard 0:08:03.800 --> 0:08:07.880 looking plates. Now the shrimp looking things, we actually we 0:08:07.880 --> 0:08:11.160 actually figured out that these two different things actually were 0:08:11.200 --> 0:08:15.080 different parts of the same organism, this Cambrian predator, and 0:08:15.120 --> 0:08:18.400 so the shrimp looking things, it turned out, were curly 0:08:18.840 --> 0:08:22.160 we think, feeding tentacles that were on the underside of 0:08:22.200 --> 0:08:24.760 the head. So you'd see this thing swimming along. It's 0:08:24.760 --> 0:08:26.600 got the eyes in the front, and then sort of 0:08:26.640 --> 0:08:29.040 as a mouth, it's got this like, you know, two 0:08:29.120 --> 0:08:33.480 lobed mustache of shrimp tentacles that we think probably could 0:08:33.520 --> 0:08:35.720 kind of like grab things and push them toward the 0:08:35.760 --> 0:08:38.160 mouth parts. And then the mouth parts would be the 0:08:38.240 --> 0:08:41.920 other part that gets fossilized. That ring of plates. That's 0:08:41.960 --> 0:08:45.800 the mouth that's sort of halo of teeth, like a 0:08:45.880 --> 0:08:49.200 tooth lined sphincter of death. I mean, really, that's all 0:08:49.200 --> 0:08:51.880 a mouth is, is that it is the it is 0:08:51.920 --> 0:08:54.160 the anti aanus it's the other the other side of 0:08:54.160 --> 0:08:57.560 the organism. Yeah, just imagine like like an anus that's 0:08:57.600 --> 0:09:00.840 just surrounded by a circle of teeth that moved in word. Right, 0:09:00.880 --> 0:09:03.079 And as we've discussed, we had we did a whole 0:09:03.120 --> 0:09:05.520 at least one whole episode on the evolution of the anus, 0:09:05.960 --> 0:09:08.840 and of course you didn't always have two openings in organisms. 0:09:08.840 --> 0:09:11.480 You had organisms that had to depend on one um 0:09:11.600 --> 0:09:15.319 orifice for both functions. Which is amazing that that we're 0:09:15.320 --> 0:09:17.160 not saying that's the case with no, no, not at all. 0:09:17.240 --> 0:09:19.640 We're just sort of demystifying the difference between the anus 0:09:19.640 --> 0:09:22.679 and the mount. Actually, I don't know for sure whether 0:09:22.720 --> 0:09:24.840 an Almala cars had an anus or not, but I'm 0:09:24.880 --> 0:09:27.480 pretty sure it had an anus. I had to get 0:09:27.559 --> 0:09:30.559 had some form of venus, right it had. I would 0:09:30.559 --> 0:09:32.840 have to guess it had a one way digestive system, right, 0:09:32.880 --> 0:09:34.920 I mean those we discussed in those episodes. There are 0:09:35.000 --> 0:09:38.000 organisms that do not or come to not have an anus. 0:09:38.240 --> 0:09:42.240 You know, sometimes an organism in a certain phase of 0:09:42.240 --> 0:09:46.360 its life no longer has to worry with defecating, or 0:09:46.760 --> 0:09:50.000 has come to a situation where it cannot defecate anymore, 0:09:50.080 --> 0:09:52.280 and we'll just have to live with it. Yeah, certain 0:09:52.360 --> 0:09:55.319 varieties of scorpion that have lost their anus because their 0:09:55.320 --> 0:09:57.920 anus was on what like a third or fourth segment 0:09:57.960 --> 0:10:00.960 of their tail, which they jettison to escape a predict. 0:10:01.040 --> 0:10:04.720 It's a very sad scorpion story. But to the Anomala 0:10:04.760 --> 0:10:07.760 carus mouth, So from what I can tell, there's actually 0:10:07.800 --> 0:10:11.960 still scientific disagreement about those mouth parts, about that sphincter 0:10:12.040 --> 0:10:15.360 of death, about that ring of teeth pointing inward. So 0:10:15.559 --> 0:10:19.880 it has long been assumed that Anomala Carus preyed on 0:10:20.040 --> 0:10:23.040 trial bytes in one way or another. But how right? 0:10:23.080 --> 0:10:27.400 Trial bytes have these really hard protective shells on their backs, 0:10:28.000 --> 0:10:32.959 and some paleontologists thought, well, maybe the Anomala Carus would 0:10:33.520 --> 0:10:36.320 eat them by attacking them right after molting when their 0:10:36.320 --> 0:10:39.400 shells would have been soft, or maybe it would attack 0:10:39.440 --> 0:10:42.280 them by like scooping them up with its little feeding shrimps, 0:10:42.320 --> 0:10:45.760 the feeding tentacles, and then cracking or prying off the 0:10:45.800 --> 0:10:48.520 shell somehow with those rings of plate like teeth in 0:10:48.559 --> 0:10:52.000 the mouth. But I've read criticisms of this model coming 0:10:52.040 --> 0:10:54.480 from the last decade or so, basically saying that some 0:10:55.200 --> 0:10:58.760 current models of the Anomala carus mouth show that it 0:10:58.800 --> 0:11:01.480 just would not have been wrong enough to crack through 0:11:01.600 --> 0:11:04.840 trialobyte shells, and maybe maybe it had to feed on 0:11:04.920 --> 0:11:08.520 soft bodied organisms like jellyfish or worms instead. I don't 0:11:08.520 --> 0:11:10.960 know if the idea of eating trio bytes right after 0:11:11.040 --> 0:11:13.200 molting would get around this problem. It might or it 0:11:13.280 --> 0:11:17.280 might not. Um So, did the Anomala cars actually have 0:11:17.520 --> 0:11:20.920 this this crushing sphincter of deadly teeth or not? I don't. 0:11:20.960 --> 0:11:22.440 I don't know if we know the answer to this 0:11:22.559 --> 0:11:25.559 right now. This seems like a still open question. I mean, 0:11:25.600 --> 0:11:27.840 obviously it did have these plates, it did have these 0:11:27.840 --> 0:11:32.040 mouth parts, but we don't know how strong its mouth was. Yeah, 0:11:32.080 --> 0:11:34.040 it is just so weird to look at a representation 0:11:34.080 --> 0:11:36.280 of these because it's like it's it's the it's the 0:11:36.400 --> 0:11:38.800 sphincter of death, like you said, but it's also this feeling. 0:11:38.800 --> 0:11:41.400 It's that it's like a teeth. It's like teeth made 0:11:41.400 --> 0:11:45.840 of broken glass. Uh, It's it's very strange to to 0:11:45.920 --> 0:11:48.840 look at. Yeah, it was originally thought when people found 0:11:49.280 --> 0:11:51.480 the mouth parts in isolation, so you'd just be this 0:11:51.679 --> 0:11:53.480 ring of plates and they didn't know it was the 0:11:53.480 --> 0:11:57.040 same organism as the pair of weird shrimps. They I 0:11:57.080 --> 0:11:59.760 think originally thought this might have been some part of 0:11:59.800 --> 0:12:03.120 a like weird old jellyfish. All right, on that note, 0:12:03.120 --> 0:12:04.440 we're going to take a quick break, but when we 0:12:04.520 --> 0:12:07.080 come back, we will continue to explore, to explore the 0:12:07.120 --> 0:12:16.360 weird wide world of teeth. So another thing, uh, you know, 0:12:16.400 --> 0:12:18.560 we were saying, of course again that teeth are not 0:12:18.640 --> 0:12:21.320 outside bones. As great as the song is, they're not 0:12:21.400 --> 0:12:25.320 bones at all. They're these hardened structures. And one question 0:12:25.400 --> 0:12:29.240 is where do teeth come from? Like what is their 0:12:29.280 --> 0:12:34.000 evolutionary history as we know them? And the current evidence 0:12:34.040 --> 0:12:38.200 indicates that the earliest known teeth evolved and I guess 0:12:38.200 --> 0:12:40.920 this would be different than like the Cambrian sort of mouthplates. 0:12:41.040 --> 0:12:45.480 This would be like teeth in jawed animals. You know, Uh, 0:12:45.520 --> 0:12:50.040 the earliest known teeth evolved not as adapted bones, because 0:12:50.040 --> 0:12:52.320 that's where you sort of think, right, you think, well, 0:12:52.640 --> 0:12:54.840 you know, you had some bone structures and over time 0:12:54.920 --> 0:12:57.640 those evolved into tooth like shapes, so rights of the 0:12:57.679 --> 0:12:59.760 bones would be coming out of the jaw and doing that. 0:13:00.200 --> 0:13:02.959 But actually it looks like the earliest teeth evolved and 0:13:03.040 --> 0:13:07.840 not as adapted bones, but as adapted fish scales. I 0:13:07.920 --> 0:13:11.520 was looking at a paper from Biology Letters in by 0:13:11.559 --> 0:13:16.480 Martin Rookline and Philip C. J. Donohue called roman Dina 0:13:16.559 --> 0:13:20.840 and the Evolutionary Origin of Teeth basically finds evidence from 0:13:20.880 --> 0:13:25.200 a species called roman Dina stalina, which is an extinct plaqueoderm, 0:13:25.320 --> 0:13:28.920 and a plaque aderm is a type of armor plated 0:13:29.040 --> 0:13:32.280 ancestral fish from more than four hundred million years ago. 0:13:32.520 --> 0:13:35.560 One plaque aderm you've probably seen fossils of before, is 0:13:35.640 --> 0:13:40.600 the awesome, the terrifying dunkle Osteus. This is another superstar 0:13:40.760 --> 0:13:45.360 of a sort of a prehistoric creature exhibits and museums. Yeah, 0:13:45.559 --> 0:13:48.720 you look up a dunkle osteous cast or a dunkle 0:13:48.840 --> 0:13:53.160 Osteus skull. I mean it's chomp city just unbelievable, and 0:13:53.200 --> 0:13:57.160 they got huge. Imagine this gigantic fish with this chomp 0:13:57.200 --> 0:13:59.960 city head. It is definitely something out of a movie. 0:14:00.200 --> 0:14:02.200 Oh yeah, well, like why we keep making all these 0:14:02.200 --> 0:14:05.120 shark tack movies. They need to make a movie about this. 0:14:05.160 --> 0:14:08.040 You can caught Dunkles, like a monster would be just 0:14:08.120 --> 0:14:11.359 named Dunkles, I like it, or just dunks dunks Dunks 0:14:12.320 --> 0:14:19.360 dunk Dunks, dunk Dunks dunk dunks I'm sorry, okay, but anyway, 0:14:19.400 --> 0:14:23.360 in the study X ray analysis of fossil remains of 0:14:23.360 --> 0:14:26.440 this fish, again, this is not dunkle Osteus, this is 0:14:26.440 --> 0:14:30.760 a different plaque. DRM Roman Dina Stalina showed that scales 0:14:31.000 --> 0:14:34.280 evolved first the fish. Scales evolved first, and then teeth 0:14:34.440 --> 0:14:38.440 evolved in this line of fish as an adapted type 0:14:38.440 --> 0:14:42.440 of scale cell along a structure called the toothplate. And 0:14:42.760 --> 0:14:47.240 isn't it weird how scales became so many different things 0:14:47.280 --> 0:14:53.360 like bird feathers evolutionarily are adapted from ancestral reptile scales. 0:14:53.640 --> 0:14:57.320 Scales over time grew into these these filaments and things 0:14:57.360 --> 0:15:01.160 that eventually became feathers. But it's also thought that mammal 0:15:01.240 --> 0:15:04.400 fur and mammal hair are adapted from scales of a 0:15:04.440 --> 0:15:07.520 common ancestor. Well, I mean they've they've had time, right, 0:15:07.800 --> 0:15:09.320 That's that's one way to look at it. And it 0:15:09.360 --> 0:15:12.120 seems like teeth or another example here in these fish 0:15:12.160 --> 0:15:14.760 from four million years ago, it looks like teeth are 0:15:14.760 --> 0:15:17.840 coming out of the adaptation of scale cells. Now as 0:15:17.840 --> 0:15:20.000 we uh, you know, we're gonna go ahead and jump 0:15:20.080 --> 0:15:23.280 the time machine and go, you know, go go go 0:15:23.360 --> 0:15:25.800 forward in time here, and you know, it's easy to 0:15:25.840 --> 0:15:28.600 sort of fall into the trap of thinking, okay, certainly, 0:15:28.880 --> 0:15:31.960 especially when we get into mammal teeth, we're basically talking 0:15:32.000 --> 0:15:35.720 about the same scenario in any given organism, right, I mean, yes, 0:15:35.800 --> 0:15:38.800 you're your dog's teeth don't look quite like human teeth, 0:15:38.840 --> 0:15:41.560 but there are a lot of parallels. A cow's teeth 0:15:41.840 --> 0:15:44.120 don't look exactly like a dog's teeth, but there are 0:15:44.120 --> 0:15:46.720 a lot of parallels, you know. But then again, as 0:15:46.720 --> 0:15:48.920 we know from our conversation with Katie, I mean, beaver 0:15:49.000 --> 0:15:51.920 teeth just chuck the boat over, right, And another one 0:15:51.960 --> 0:15:55.600 that really checks the boat over are the are the 0:15:56.120 --> 0:16:00.960 teeth of elephants. And they're extinct ken um, because when 0:16:01.000 --> 0:16:03.320 when you look at an elephant or a mastodon or 0:16:03.360 --> 0:16:08.640 a mammoth, first of all, they're polyphiodonts rather than uh, diffidants, 0:16:08.840 --> 0:16:11.880 meaning that they're psych They cycle through teeth their entire 0:16:12.000 --> 0:16:15.200 life rather than depending on a mere two sets of teeth, 0:16:15.880 --> 0:16:20.320 So more kind of like sharks to an extent. Basically, 0:16:20.400 --> 0:16:22.680 like with a human, you have you have two sets. 0:16:22.720 --> 0:16:24.400 You got that first set, those baby teeth, and you 0:16:24.400 --> 0:16:27.520 get those adults set. Uh, the adult teeth, and you've 0:16:27.520 --> 0:16:30.040 got to make that adult set last because those are 0:16:30.040 --> 0:16:33.480 the ones that are supposed to take you to the grave. Uh. 0:16:33.520 --> 0:16:36.600 With the elephant is a different scenario. There's still a 0:16:36.640 --> 0:16:40.560 limited number of teeth. It's not just teeth forever, but 0:16:40.600 --> 0:16:43.560 it's it's but it's also just a totally different um 0:16:43.720 --> 0:16:46.400 like way that they grow. So you have long ridges 0:16:46.440 --> 0:16:50.200 of teeth that move not from bottom to top, you know, 0:16:50.280 --> 0:16:52.840 like when when you think of like a a child, 0:16:52.880 --> 0:16:55.240 a young child about their their their they lose their 0:16:55.240 --> 0:16:58.160 baby teeth and than those adult teeth grow up out 0:16:58.160 --> 0:17:00.480 of the job like down down in the jaw and 0:17:00.480 --> 0:17:02.960 then they load up to the yeah or or down 0:17:03.040 --> 0:17:04.600 or you know, they come down and they come up 0:17:04.600 --> 0:17:07.120 out of the jaw right. Well, it's great to see 0:17:07.119 --> 0:17:09.560 those like cross sections of the jawbone that the baby 0:17:09.560 --> 0:17:12.560 teeth still in there is disgusting. It's like, how could 0:17:12.560 --> 0:17:14.359 you ever look at a child the same way again? 0:17:14.920 --> 0:17:18.280 But with elephants, you have long ridges of teeth that 0:17:18.440 --> 0:17:24.120 move from back to front along upper and lower in jaws, lowly, 0:17:24.520 --> 0:17:27.639 slowly wearing into a shelf at the front as the 0:17:27.720 --> 0:17:31.960 roots are absorbed. So segments of the warranteeth in these 0:17:32.000 --> 0:17:36.960 teeth are are oblong looking things too, So basically they 0:17:37.080 --> 0:17:39.240 just move out of the back of the jaw along 0:17:39.240 --> 0:17:41.240 to the front of the jaw and then they break 0:17:41.280 --> 0:17:44.840 off in sections, sort of like a pez dispenser or 0:17:45.000 --> 0:17:46.239 one way I like to think of it. It's it's 0:17:46.280 --> 0:17:49.560 kind of like a toblarown bar. Each elephant tooth or 0:17:49.640 --> 0:17:52.720 masted on tooth is a tobleroom bar that gets worn 0:17:52.840 --> 0:17:55.600 down and as it reaches the front, segments of that 0:17:55.640 --> 0:17:58.600 toblar room bar just fall out, and then in the 0:17:58.600 --> 0:18:02.879 back of the jaw, fresh teeth are growing out, uh, 0:18:02.960 --> 0:18:04.960 you know, growing out of roughly the same place you know, 0:18:05.040 --> 0:18:08.080 where your wisdom teeth would be located. So this alone 0:18:08.119 --> 0:18:11.480 is crazy. You know, most animals have vertically grown choppers, 0:18:12.200 --> 0:18:15.840 but elephants and the kin of elephants essentially have six 0:18:15.920 --> 0:18:21.080 sets of molars that that replace over time. So basically 0:18:21.160 --> 0:18:24.199 the way the cycle goes is that, uh, they have 0:18:24.520 --> 0:18:27.359 you know, one set of molars at birth um and 0:18:27.400 --> 0:18:30.520 they keep those for about they lose those after two years, 0:18:30.760 --> 0:18:34.000 then they get a second set, lose those at six years, 0:18:34.280 --> 0:18:35.879 and they get a third set of fourth set of 0:18:35.920 --> 0:18:38.119 fifth set in a sixth set, and then the in 0:18:38.280 --> 0:18:41.440 rare circumstances they will get a seventh set of molars 0:18:41.480 --> 0:18:43.919 that come out of the back. But then that's how 0:18:43.920 --> 0:18:45.720 you know you're dealing with like a real silver back. 0:18:45.800 --> 0:18:49.239 Like well, it's actually one way that the scientists are 0:18:49.240 --> 0:18:52.320 able to age the remains of elephants, Like you find 0:18:52.600 --> 0:18:55.359 the remains of the jaw, and you can look and 0:18:55.400 --> 0:18:57.200 you can see you can learn a lot from it. 0:18:57.240 --> 0:18:59.639 If it's a different type of elephant ken you know 0:18:59.720 --> 0:19:02.880 it's amathur massed on, you can you can study exactly 0:19:02.880 --> 0:19:04.760 what kind of foods it was eating based on what 0:19:04.800 --> 0:19:07.680 those teeth looked like. But then if it's a particularly 0:19:07.680 --> 0:19:11.160 old elephant, um, well, look, I'll say first let's say 0:19:11.320 --> 0:19:14.399 it was a you know, an adult elephant that wasn't 0:19:14.440 --> 0:19:17.399 too old. Then you would see like the worn teeth, 0:19:17.600 --> 0:19:19.399 and then you would see in the back where fresh 0:19:19.400 --> 0:19:22.600 teeth were growing out. But then in the an older 0:19:23.280 --> 0:19:26.760 adult elephant, it's on its last set, the hole in 0:19:26.800 --> 0:19:30.080 the back of the jaw, back on each side of 0:19:30.080 --> 0:19:32.359 the jaw would be closed. It has just become solid 0:19:32.359 --> 0:19:35.280 bone again because it is on its last set of teeth, 0:19:35.480 --> 0:19:37.959 and those are the teeth that are going to take 0:19:38.000 --> 0:19:39.840 it to the grave. I can't remember if you already 0:19:39.840 --> 0:19:42.640 said this or the teeth. Is it born with all 0:19:42.760 --> 0:19:46.080 these teeth already there? Or do the teeth like generate 0:19:46.200 --> 0:19:48.960 over time they generate? Okay, yeah, they're not already loaded 0:19:49.000 --> 0:19:52.199 back there? Um, so these are also these are known 0:19:52.240 --> 0:19:55.200 as high it's known as hind molar progression, also known 0:19:55.240 --> 0:19:57.920 as marching molars, which I particularly like that one because 0:19:57.920 --> 0:20:00.359 there's this idea that they're marching from the back of 0:20:00.359 --> 0:20:05.120 the jaw towards the front and the main other extent 0:20:05.280 --> 0:20:08.800 creatures that have these are the manatees, which I'll get 0:20:08.840 --> 0:20:11.440 back to in a bed. And interestingly enough, the manatees 0:20:11.520 --> 0:20:14.560 have them, but the doo gong, the relative of the manatee, 0:20:14.920 --> 0:20:20.160 does not. Kangaroo molars also apparently work in this fashion. Um. 0:20:20.240 --> 0:20:22.920 But but then other creatures like you. You might look 0:20:22.920 --> 0:20:26.399 to the rock higher ax, which is the elephants rodent 0:20:26.480 --> 0:20:29.919 like relative. But even though it has some elephant like 0:20:30.040 --> 0:20:33.760 qualities to its uh to its teeth, including two rodent 0:20:33.840 --> 0:20:36.800 like front teeth, are actually tiny tusks, it doesn't have 0:20:36.880 --> 0:20:40.879 marching molars. Um. But uh I mentioned already how the 0:20:40.920 --> 0:20:45.200 elephant molars are also elongated. Uh they they They're really 0:20:45.200 --> 0:20:48.040 crazy to look at because it looks like fused teeth 0:20:48.480 --> 0:20:51.480 in a sense. It's it's like a big long chunk 0:20:51.680 --> 0:20:55.960 of teeth and it's essentially it has enamel loops for 0:20:56.080 --> 0:20:59.440 grinding plant matter. So that's what the elephants using these for. 0:20:59.520 --> 0:21:03.240 It's just minding top to molars against bottom molars and 0:21:03.600 --> 0:21:05.720 uh and that is of course wearing the teeth down 0:21:05.800 --> 0:21:09.320 as well, thus the need to continually replace them. Right, 0:21:09.359 --> 0:21:12.320 the elephant is herbivore. It's gonna be eating rough plant matters, 0:21:12.320 --> 0:21:14.320 so it needs sort of a mortal mortar and pestle 0:21:14.400 --> 0:21:16.960 in the mouth to to mash it up real good. Yeah. 0:21:17.560 --> 0:21:19.960 But again, when the when the teeth are done, that's it. 0:21:20.080 --> 0:21:22.080 And this is going to lead in the wild especially, 0:21:22.160 --> 0:21:24.879 is going to lead to malnutrition and or starvation. So 0:21:25.000 --> 0:21:27.680 I encourage everyone to think about elephant teeth the next 0:21:27.720 --> 0:21:30.879 time you see an elephant. Certainly if you have the 0:21:30.960 --> 0:21:32.240 chance to see one in the wild, but if you 0:21:32.240 --> 0:21:34.719 see one in a zoo or what have you, like 0:21:34.800 --> 0:21:38.120 it's teeth or just or as amazing as any other 0:21:38.520 --> 0:21:41.320 amazing quality of the elephant, like yes, it's trunk is 0:21:41.359 --> 0:21:44.159 a is a is a marvel of the natural world. 0:21:44.160 --> 0:21:47.080 But also its teeth are just so super weird. Yeah, 0:21:47.080 --> 0:21:50.040