Hey, ever you wanted, it's me Josh, And for this week's s Y s K Selecta, I've chosen How Fossils Work, which actually is one of the most scientifically interesting, amazing, mind bending episodes that we've ever done. And I just listened to it and it still holds up. So I hope that you enjoy it. And as they say on with the show, welcome to Stuff you should Know from house Stuff Works dot com. Hey, and welcome to the podcast. I'm Josh Clark with me as always as the intrepid paleontologist Charles W. Chuck Bryant. It's terrible' no I like it. Okay, I wish I was a paleontologist. Let your new nickname or intrepid at least, let's just go with paleontologists. That'd be great. Okay, we're talking fossils today, Dude, this isn't really interesting stuff. It really is. And um, you can tell that Tracy Wilson are esteemed head of the writing editor. I think she's site director director, right. Um you can tell that she was very, very excited. She took her time and really doled this one out. I think um savor is the right word. You can feel it her smiling through the keyboard. Yeah, she's very happy to write how fossils work. And um, we're happy to do it because it's one of those very comprehensive articles on the site that you just has everything you need. Sedimentary rock, flat bones versus round bones, leaf impressions, has it all. Unless you're an intrepid paleontologist. Then we'll get an email saying it actually wasn't very comprehensive. You guys royally screwed this up. We just wait until we get into punctuated versus gradual evolution. Chuck. Um, you've heard of Lucy right, the Australia Kiss. Yeah, okay, Well, um, she was I think three point two million years old. That's one old lady. It really is the earliest hominid we've found as far as I know. Um. But there is a part of her foot missing. It's always been missing that we've never found before. So this thing, this bone, was so essential and we couldn't tell how she walked until recently. Why because the missing bone, we couldn't tell how she walked exactly. We we we can tell so much from bones that when we don't have the right bones we can't tell anything. So she may have been in a knuckle dragger, she may have hopped. We didn't know. Well. Recently, UM, some people from the University of Missouri or Missouri, depending on whether or not you live in the state. UM found the Uh, the group of foot bones needed to show what kind of walker Lucy was. And she walked up right? How was her gate? Upright? Upright? Just like a human. She had a hitch and her get along, she had a pepper and her step. Possibly she knew she'd be famous one day. She was loved with duc But but consider this, right, Okay, three point two million year old footbones were found, and we could tell from them how she walked. This is the state of the field that you remember paleontology. Pretty cool. This is how advanced it is. And yet it's really just kind of using common sense to figure out what old bones mean. Common sense and science. Fossils go, let's talk about it, Chuck, what are some of the different kinds of fossils. Uh, well, one of my favorite kinds of trace fossil. Yeah, that's actually one of my favorites too. It's like, um, that Jesus footprint thing. Footprints in the sand. Yeah, sort of is josh um. That is when it's actually not part of the organism at all, but it's um like tooth marks in a chunk of wood from a saber tooth tiger. Or footprints or footprints or track ways as Tracy calls them. Yes, footprints tracks. It's just unnecessary, but it has a pleasant tone, you know science. Yeah, like they're not footprints, they're track ways. I'm bored in Ethiopia, let's call him track ways. So trace fossils is one. Of course, there's bone fossils, right, the most famous fossils. Yeah, those are great too. They got nothing on trace fossils. So actually, bone fossils, that's that's what you really want. If you're going to reconstruct the dinosaur for your museum. You can't deal it with footprints, No, you can't. You need the bones, you do. And the bones are of course the most famous ones in the dinosaur. Bones are the most famous of all the bone types. Right. So there's something that I think um is often missed by lay people such as myself, um and in that when you find a bone, right, so you find like a big old dinosaur bone, it's really geologically speaking, it's not a bone any longer. It's not like you find a bone buried in your yard that was an animal from like, you know, thirty five years ago, But that's not a fossil. We'll not still bone. A fossil is a bone or a piece of um once living organic material that's undergone a transition from uh, an organic state to an inorganic state. That's what a fossil is. It's gone through the process of fossilization. And most of these fossils, the vast majority of fossils, are found in sedimentary rock. Before we're go any further, we should probably do a little brief primerun sedimentary rock, right, which is awesome. Yeah, it's pretty easy to Uh. We've talked about the Earth's core um and layers. When I think we talked about earthquakes and maybe some other stuff. We all know that there's the intercore, outer core. We got the crust. Crust is the thinnest layer, and that's where the fossils are. That's where the goods are. And uh, most of the rocks in the crust are sedimentary rocks that you've been talking about off and on for the past eight minutes, right, and that's like silty sandy stuff that hardened over the years, right, I mean, but the the Earth. Remember we talked about, oh, what was it, clouds. I can't remember what podcast it was, but we talked about how much sand is transferred from Africa to South America annually. Yeah, it wouldn't clouds, but yeah, if you you remember the one I'm talking about. Okay, So, the Earth's geo biogeochemical processes equal a lot of movement of particulate matter. Right. The Earth is dynamic, baby, it is. It's also very fluid. To write, a lot of that matter is at at one point as suspended particles in water that's moving around, right. Yeah. So um, as this as the water leaves and the sediment is deposited, it builds up and up and up. Over time, it hardens into rock and eventually we have sedimentary rock, yeah, which is below our feet. We don't normally see it unless say, the Colorado River um winds over it for you know, millions and millions and millions of years, revealing the sedimentary rock that's in the Earth's crust. Grand Canyon exactly. So you're talking about, Yeah, I forgot the Grand Canyon Park So you know how I said the Earth was dynamic, baby, Yeah, Uh, that's important. I didn't just throw that in there as a factoid. It's important because when these plates shift around, that's how fossils are. On Earth. Things can be moved great distances and pushed to the surface eventually or close enough to where a dig can unearth it. And it's like, just because it's fossilized doesn't mean it's stuck in that one spot forever, because Earth is always moving. So the point of all this is is sedimentary rock um is, like you said, dynamic. It moves around. Sometimes fossils pop up or it becomes exposed all of the Colorado River um, and that is where fossils are, right Chuck. Yes, So let's say that at some point in time there was a dinosaur or a sabertooth tiger or a cyanobacteria woly mammoth wooly mammoth, sure um, and it's um hanging out around a riverbed and it has a massive heart attack and falls over in the river bed and very quickly it becomes covered with sediment and silt, right Yeah, And that's important because once it starts getting covered up with stuff, it's sort of being protected from like all of fossil. Let's just break the news. All of fossil means is that something has been protected from the natural decomposition process. Otherwise we just decompose like everything else, and you wouldn't see it anymore. You've just totally betrayed Tracy in the tone she lent to this, that the whole drama drawing out suspense. But that's true. So what you said was right. So you'd fall over in a riverbed, you start getting covered up with the sediment and silt, and it's it's immediately starting to protect you in a way. Um, not you, but whatever, the wooly mammoth, the wooly mammoth. Um. The thing is the in this sediment, in this silt, you can't really hide from macrobacteria, uh and other forms of life that are basically dedicated to breaking down organic matter, soft tissue, hair, eyeballs, um, genitalia, all that kind of stuff. It eventually becomes broken down and what's left is the hard stuff the bone, right, But the bone also has organic material within it as well. Yeah, and that'll break down. We're talking blood cells, collagen, fat, that's going to break down to the key here is the inorganic parts of the bone remain intact. And it's the other keyword here's porous. Yeah. You take calcium, I imagine for your hips. Yeah, sure, glucosamine, calcium. Sure. So what you're doing is, um, you're fortifying the calcium that's already in your hips, supposedly, um, because the bone is made in large part of calcium, which is a mineral, which is inorganic. So it's all the organic stuff dies out. What's left is, like you said, the inorganic like calcium, whatever, minerals, and that holds the shape, right, Yeah, the initial structure is kept intact. Right, But like you said, this bone is also porous. That's the key. And over time, um, other mineral sediment kind of um, it enters into these these microscopic pores iron right, carbonate yea and fortifies this, ultimately turning this but what was once an organic bone into an inorganic rock in the shape of the bone. But for all intensive purposes, it's still the bone. It still has that original calcium. It's still the same thing. It's not like a replica of it. It's just become fossilized. Yeah, and Tracy in the article uses a pretty good example. I thought, it's like filling a sponge with glue. The sponge is gonna keep the shape, but the glue is gonna ooze through all the spots that it can ouze harden, and there you go. You've got a hard sponge, hard sponge, which is basically what a fossil is. And this takes place Josh over the course of millions of years, the sediment reinforcing the bones eventually becoming rock. It's not the kind of thing that happens willy nilly over thousands of years. It's a long time, and it's just this isn't just um happening by itself. All of the surrounding area UM is being deposited with sediment as well. It's also turning into rock um. And then the ultimate test of time for a fossil is that it can withstand the pressure of the that's mounted by the hardening rock sedimentary rock that's growing around it, so it can be crushed. Is that how A lot of fossils are definitely crushed, crushed the death poor guys um. But if it survives and you can find this, you will eventually be able to get to it. And then you remove the rock from around the fossil, and there's your bone that you can take to the Natural History Museum and get at least five dollars for when you were a kid, Josh, let me ask you this. Did you ever go into the woods on a little nature course from like a science center, let's say, and do a cast plaster cast of a animal footprint? Did you ever do that? No? Really, really, I did that. We went and found like deer hoof prints, you fill it with plaster, and there was some way of doing it where you an inverse plaster cast of a deer hoof print. That can happen actually in a way that with trace fossils, so you can you know, sediment can act the same way. And one of these, let's say, uh, the wooly mammoth makes a footprint in some loose but sturdy soil that fills up with sediment and creates basically a mold, just like I did as a kid with the plaster cast. Yeah, as long as the sediment that fills it in is lighter or thinner, yeah, than the soil that the impression is made in, then yeah, it would it would, it would preserve that track. Yeah, and plants can do the same thing. It's not just bones we're talking about. Um. It can also fill in in a different way, I guess the opposite way to where it makes a basically a cast of the foot that made the track. Oh yeah. And then so it's like a kind of like a fossil of a ghost foot that's not really there, but it makes the foot. It's like an inverse cast. Okay, yeah, of not the track, but the foot that made the track. Yeah. Yeah, got cool. You know what other another my favorite trace fossil is it's not a track way, it's copper light. I changed my mind. That is a good one. That's dunge. It's poop, fossilized poop. That's right. I can tell you a lot about an animal. It can tell you about its fiber intake. It can tell you about what size it's poop was, um, chuck. You know. In the eighties, the CIA found out much about Gorbachof and his health. They found out he had like cancer or some sort of chronic illness um by stealing his poop when he was when he came on a state visit to the US. They took his poop and analyzed it, and when they he was in the US, they des grabbed it from the toilet. Did he not flush? I just want more specifics. You probably don't have. As far as I understand, they probably it's hotel room or wherever he was staying. They were prepared to do this. This was like toilet rigged. Probably, yes, But wherever Reagan went, they had a portable toilet that he used. It was the only one he was allowed to use. I'm not kidding, so no one could steal his poop. Talk about paranoid. Yeah, seriously, when you point one finger, there's three pointing back at you. You know what I mean? Yeah? Yeah? Uh so, Josh, that is sedimentary rock and that's to me one of the cooler ways you can get a fossil. Uh petrified would too? Don't leave that one out. Oh yes, it's basically the same thing that we just described for bone, but for wood. Yeah, hard as a rock because it is a rock. Here you go, alright, So, like I just said, um, that was sedimentary rock and that's kind of fun. But you can also uh get a fossil. Has that funny because one dies in a cave that's really dry. Yeah, desiccation. Yeah, desiccation is basically, uh, sort of a mummification, but it's not like we think of with mummification with the Egyptian tombs or anything like that. Well, that's because there's no reservation techniques that have been undertaken. It's natural. Basically, it dries out. It's like throwing an orange in a dehydrator. So when it's really dry, there's not gonna be any place for bacteria to thrive. That's the reason beef jerky is not um refrigerated. If you refrigerate your beef jerky, you're you're doing something wrong. Yeah, that's true. Well, if you have beef jerky long enough to need refrigeration, then you're doing something wrong or something really really right. Uh. So desiccation actually works so well sometimes that it can preserve the skin and soft tissues as well, which is something that sedimentary rock cannot do. Have you been to the Smithsonian I have they have um a very cool I guess a prehistoric cow or a musk ox I can't remember, but it's the thing's head, um, much of its back, I guess, the cape, two of its legs, and the skin is still there. It's just right there. Probably it's tens of thousands of years old and it's just sitting right there. Did they could they read build it or just put the parts up? It's just the parts, but it's laid out so that like it gives you the impression of what you're looking at, but its face is still there. It's very cool. Uh. My favorite kind of fossil, though, Josh, is I'm gonna say that, like every five minutes is a frozen fossil, because if you get trapped, let's say your wooly mammoth trapped in ice, not only is that going to keep other like vultures and things from picking up your bones and skin, but it's also going to keep it from breaking down and you can get hair fully preserved sometimes if you're in skin and like a big mammoth. Have you seen pictures of Liuba? Now? Liuba is a baby wooly mammoth that was found um by a reindeer herder in Siberia and um it was pounds or something like that, but it would have gotten up to several tons. It is adorable because it is a fully preserved wooly mammoth baby with the wrinkles in the skin and everything. Yet it spent forty five years in the permafros, but it's like completely intact. It's very cute. That's why it's my favorite. It's one of the cutest dead things you'll ever see. Another couple of ways you can get a fossil josh, which are not my favorite aur tar librea tar pits, although that is one of my favorites, which librea tar pit is actually redundant because Librea means the tar, so it's calling it the tar tar pit and not the tartar. Did I ever tell you about when I shot a commercial there? Have you? Did you go by there in l A? No? I want to. I forgot about it when we're there last Well, for those of you haven't been, it's right in the middle of Los Angeles, like south of Hollywood on Wilson Boulevard, and it's um. The main tar pit is uh. Tar pits are fenced off, obviously, and they have little recreations. It's it's actually the saddest thing you'll ever see. The recreation they have in there is of a like I guess it's a mother wooly mammoth trapped in the tar trying to get out and the father and the baby on shore like howling at her. It's awful, but it's still active, like all the tars bubbling up and everything. And shot a commercial there once and I was on the other side of the property, far away from the main pit, and I looked down and there was a little mini tar pit, a little tar puddle about a foot wide, bubbling right beneath my feet. I could have scooped it up with my finger if I had been so inclined. Yeah, instead, you're like, that stinks. Well, it's just crazy to think that that's still like it's happening. Apparently, Um I looked it up. There's um there's like you said, main pits that are chained off and that are still being excavated. But they have them like in neighborhoods all around the area and parks. They're just kind of all over the place around there. That's like parts of stone Mountain popping up all over the place. We used to have We had a big chunk of stone mountain in our backyard growing up, all right. For those of you don't know, Stone Mountain is the world's largest exposed piece of granite, and it is right here in our home state, and it takes like thirty minutes to hike, but you still get to get to the top and be like I just hiked a mountain, which I have, Josh. You can also get a pete mossy pete can preserve life forms, including human beings like Tolin Man was. It was that Toland Man. I don't know about him. How do you know all these people people? The first the first um multi syllable word I could spell was archaeology. Really, I've always been interested in that. I could see that, Yeah, Tolin Man. Also, it doesn't you can hate archaeology like some people hate art, and you'll still be interested in Totland man Um he was. He's found in Denmark. He lived years ago and he was murdered, uh sacrificially, they think, and cast into the peat bog, which pete is just decomposing moss and lots of it, but it has a tendency. I think it's anaerobic, so um tissue is preserved really well. But it's this guy that they dug up, and he's so well preserved that when they found him in the nineteen fifties, they called the cops because they thought they'd found a murder victim really like a recent one. He looks kind of funny, but he's got his whiskers are preserved. He's wearing a cap. He still has this the garrett around his neck. Um, it's really awesome. So what is he dated at? Like three four hundred BC? Is the one who was killed and he's wearing a hat yeah, sheepskin, leather cap. Yeah, no last chance garage for him? No? Well uh? And then my favorite way, Josh, that you can get a fossil is uh, you're joking? Did you say it again? I did? Is amber? They just keep getting better and better, like the movie Jurassic Park. Yeah, that's how we get dinosaurs again. Yeah, dino d n A. So you found something on on whether or not that's feasible, right, yeah, because I always wondered. You know, when you see Jurassic Park, you see the little video they made it clearly to explain to the movie going audience how this is done. It's better than Ellen Page running around. What was that movie inception? Um, so the mosquito flies in tree residentry resident eventually becomes hard as copal, than it eventually becomes inert as amber. You get the little mosquito in there. They extracted the dino DNA from the blood of the mosquito, filled in the gaps with I think frog DNA, and that was all there was to it. And at the time I thought boom. But being bon Jovi, yeah, at the time, I thought that seems plausible, and it sort of is. But I did look up today and there was a researcher that was interviewed at the or closer to that time. I think that basically debunked it and said, we could potentially maybe get some DNA, even though it's really fragile and loses his signature really quickly. Even if you could get the DNA, he said that you couldn't construct a dinosaurs just you can't fill in the blanks like that. There's way too many blanks. You have a giant frog, yeah, with little tiny arms forearms that Steven Spielberg made us belief when you saw those dinosaurs walk across that field. That guy can make me believe in anything. That aliens came to the American Southwest, that there was a World War two, that um each phone home. Yeah, good stuff. Though, where are we here, chuck it. We're kind of painting this picture where if like you just stick a shovel anywhere on the Earth, you're gonna yield like all sorts of bones and fossils. Note no, it's not um First of all, a mere fraction that I don't think could possibly be calculated, because we rely on the fossil record to show us what existed back when, and it's incomplete. Therefore we've entered to catch twenty two. But there's just a mere fraction of all of the species and organisms that's ever lived that become fossilized um Like. Basically, a perfect storm of chance has to occur for a fossil to be created. As we've seen, even when it is created, it can still be crushed into oblivion. Um. And so there are few and far between. To begin with, what we have to figure out where to find them. While then you got to find it. That's the other problem. And the way we find it is by identifying rock that will likely have the type of fossil that we're looking for. Yeah, so you want something that from that year. So if you know that this animal from yeah, if you if you know this this animal lived, you know, thirty million years ago, you're gonna go find rock that you know is thirty million years old and start poking around and you know, looking this sort of a very chance thing, and we know that, um, we know, like say a layer of rock or strata of rock is thirty million years old because of a technique we have called radiocarbon dating. Right, yeah, you want to do this one? Well? Sure, Carbon fourteen dating is what a lot of people toss around because it's probably the most well known, But that can only take you back sixty thousand years. We're talking millions and billions of years. So they need to uh study isotopes like potassium forty and uranian two thirty eight because that goes back millions of years. Evidently. The half life yeah, and the half life is where an atom loses half of its life isotopes to decay. Yeah, okay, and these the this um radioactive decay takes place at a predictable rate depending on the atom, the type of atom. Right, Yeah, that's how I understand it. So if we find a type of atom missing x number of isotopes, we can say, well, this is roughly thirty million to thirty one million years old, or thirty million to thirty million and three hundred years old. I'm not sure what window we can date it to, right, but I think it's enough so that you know, we have a rough estimate of of you know, when this fossil lived in the sediment was buried around it. So, Josh, let's say that you're lucky enough and skilled enough as an intrepid paleontologist to come across your fossil. What do you do? Well, as I said, you dig it up and take it to the museum and sell it for five Smolan Well, I don't know about that, but you should call a museum. Even if you think you know what you're doing, Uh, you're probably gonna need some help if it's something major. I think you should probably go on the assumption that you don't know what you're doing unless you're a trained paleontologist. Um. Part of the problem is is we assume that these fossils, being rocks, are sturdy. That's not always the case. So there's a lot of danger of damage um in a just an average joe trying to excavate him. Also, if you just pull a bone up and walk away with it, Uh, it immediately loses context. Yeah, it's like removing a piece of evidence from a crime scene almost exactly. I can't do that. Well, you're not supposed to. Uh. So you know, they have these huge cranes and uh digging tools where they can remove huge slabs of earth, which is a really good way to do it. And sometimes if they're you know, if it's something that could be fragile, they will remove the entire slab, cast it in plaster and just go ahead and ship that thing off to a facility to handle it from there. And the cool thing is is, even though rock has formed around this bone, yeah, that's key right up right, all up on it, all up in it. If you um flake it away properly, if you flake the surrounding sedimentary rock away, um, you're going to find that there's what's called the plane of weakness, which is where the bone and the rock are still on this very microscopic level. They're not fused together. You're gonna hit that and the rock should chip right away, right and and leave the bone. Yeah, And I think sometimes they missed it with water too, to soften it up and help the whole process. Another thing too, if they find that is really brittle, they can actually reinforce the bone with resin and thin glue. But you need to be careful there too, which is pretty much helping along the fossilization process. Yeah, I would think so. I mean it's the same thing. It's like artificial forcing it with something sturdy. Well, and then you can date it using your little mass spectrometer that's in your pocket, and or a cat scan sometimes they use cat scans computer imaging stuff like that. Yeah, I didn't I didn't get how they were dating it from cat scan. I don't know if they're dating it with a cat scan or just sussen the whole thing out. Gotcha. I don't think it's a dating situation. Tracy was just throwing out some extra tools of the trade. Huh Yeah, exactly, gotcha. So, um, chuck, what is all this worth? I mean, we we have a thirst for knowledge. Obviously people think bones are very cool, But ultimately, what's the pursuit of paleontology to to put together the piece of the puzzle of how we got here? Right? I mean that's what I think. Yeah, that's my understanding as well. Yeah, you can learn a lot by not only finding the fossil, but finding what was with the fossil in that same strata. Ah, I can tell you, like, hey, this is a t rex bone and there's also a bit of pine tree, so we know pine trees were around, and they may have eaten pine trees while not the t rex because they were carnivores, right, Um, yeah, they were herbivore. Let's say, you know what I mean, Abronosaurus. Sure. Um. And ultimately all of these fossils come together, plant and well, everything that we can get our hands on to form what is called the fossil record, right, and this is basically the record of life on Earth. Uh. It's also used to support evolution big time. And uh it's here that paleontology gets most contentious, right yeah, sure, because there's, um, the the idea that beings evolved if you go far enough back from a single common ancestor, right. And so if we can put together a complete fossil record, we would be able to see how everything alive today evolve from this common ancestor or common ancestors. Right. Yeah. The problem is fossil records incomplete, and one of the really key parts that it's often missing are called transitional fossils. Right. My favorite kind of fossil, Josh is a transitional fossil. And one example Tracy used was the baleen whale. Uh. There there's a picture of one actually in the article twenty five million year old fossil of of the baleen whale with sharp teeth. Um. Today's bailing whales don't have sharp teeth, but we know that once before this had sharp teeth and legs. So this is a transitional fossil that shows, well, they used to have legs and sharp teeth, then they just had sharp teeth, and now they don't have legs or sharp teeth. They're defenseless, which is why they're baling whales, right and not sharks or megalodon's right. Um. And so a transitional fossil is one that that pops up between old and new, and it makes sense. Our understanding of evolution is that it takes a little while, and um, something like teeth aren't just gonna go away in one generation. It's gonna take more and more and more, and then um, we should be able to find them along the way where maybe the teeth gets smaller. There's fewer and fewer um baling whale teeth in the average baling whale mouth, and you're putting together the puzzle exactly. UM. Again, the fossil records a little incomplete, and there aren't as many transitional fossils as I think people would like to. UM have tied all together, right, UM, and then some of the UH. Some of the explanations are Probably the most famous explanation for this is that UM evolution isn't gradual. I think it's Stephen J. Gould came up with the idea of punctuated equilibrium, and that is basically that UM evolution takes place suddenly in these huge quick fits and starts, which would explain why there's not like teeth don't go away in a generation, but they go away a lot faster than we used to suspect. And that's why these UM fossils UM, accompanied with the idea that not every animal that's ever died has become fossilized, explained why there's huge gaps in the fossil record, which will inevitably always be incomplete. Is that a hypothesis at this point? I guess it is not a theory yet I don't. I don't think so. I think it is a hypothesis. I got one more thing, Okay, I'd like to finish with my favorite kind of fossil, and that is a living fossil. And that, Josh, is when you've got a plant or animal that looks so much like ancient fossils that they consider a living fossil. Allah, the horseshoe crab. Right, apparently the horseshoe crab has not changed. Didn't need too. It's perfect. I look at it, it's gorgeous. What else, oh, Genko baloba plants. And then a word that I don't know, the Cela cant. What is that? Uh, it's this horrid looking fish that they remember that VW commercial where he's like it's like the Ceila camp and the guys like what they're looking in the trunk and he's like a full size spare tire. He's like, it's like a Ceila cant. They used to think it was extinct. There was a fish, and then they found it like in the nineteen thirties again. But it's this dinosaur looking fish. Oh, I think I've seen him that they thought was extinct for millions of years and they called him and I think in South America, off the coast of South America, and they're still around. And the horseshoe Crab and Stephen J. Gould in the Genko Baloba. Well, it's it for fossils, right, that's all I have. I think we've got the point across. It's an overview. A fossil is a rock. Just remember that, Okay if you want to learn more about fossils. Um Seriously, this is one of the better articles on the site. Tracy did a great job with it. Type fossils into the search bar, the handy search bar, and how stuff works dot com, which means it's time for listener mail. Josh, we made a young girl cry. That's what I'm gonna call this one. Okay, It's probably happened more than once. Uh I, guys and Jerry. My name is Ali. I'm from Indiana. I was in the I S s M, a band contest, playing a difficult marimba solo today. I was pretty nervous, but being first chair and the only female percussionist in my school really brought up my confidence. I went in, I choked, and I stumbled through my piece. You could get a gold, silver bronze, or a participation metal. Got the bronze, which is equivalent to a score of an F. I was really upset. Wait, what is participating? That's sub f I didn't even know they made medals. I thought it was just a ribbon. It's probably a ribbon. I was really upset. I got home. I was trying to cheer myself up by listening to your podcast on What's the Deal with Stinkholes. I really love the show, and I've listened almost everyone, But in the beginning, you guys talked about how much the Bronze medals suck. Remember that. Oh yeah, so we didn't lift spirits very much, Josh and Chuck. I just want to let you know that the two of you made me cry then from Ali and I have since written Alie back and apologized, and she said that she's feeling much better now and uh, it wasn't our fault. And I told her that I've choked under pressure many times in my life and it happens, and it will happen again, and it doesn't mean you don't have the goods with your solo every single time. Yeah, but you know you pick yourself up. It sounds like you gave her some good advice to choke. I think so she's getting receptive to it. It's like a sweet girl. I think that's an excellent lead in. If you have a story about choking, not physically choking, but you there's something you're good at and you didn't do it. Well, say you're a television reporter in Los Angeles and you're supposed to report on the Grammys like that. So you're a podcaster and you have to do a show about the sun to give one too, but we want to hear about it. You can send it to us via email. Just type in where it says to stuff podcast at how stuff works dot com. For more on this and thousands of other topics, does it how stuff works dot com. Want more how stuff works, check out our blogs on the house stuff works dot com home page

Hey, ever you wanted, it's me Josh, And for this week's s Y s K Selecta, I've chosen How Fossils Work, which actually is one of the most scientifically interesting, amazing, mind bending episodes that we've ever done. And I just listened to it and it still holds up. So I hope that you enjoy it. And as they say on with the show, welcome to Stuff you should Know from house Stuff Works dot com. Hey, and welcome to the podcast. I'm Josh Clark with me as always as the intrepid paleontologist Charles W. Chuck Bryant. It's terrible' no I like it. Okay, I wish I was a paleontologist. Let your new nickname or intrepid at least, let's just go with paleontologists. That'd be great. Okay, we're talking fossils today, Dude, this isn't really interesting stuff. It really is. And um, you can tell that Tracy Wilson are esteemed head of the writing editor. I think she's site director director, right. Um you can tell that she was very, very excited. She took her time and really doled this one out. I think um savor is the right word. You can feel it her smiling through the keyboard. Yeah, she's very happy to write how fossils work. And um, we're happy to do it because it's one of those very comprehensive articles on the site that you just has everything you need. Sedimentary rock, flat bones versus round bones, leaf impressions, has it all. Unless you're an intrepid paleontologist. Then we'll get an email saying it actually wasn't very comprehensive. You guys royally screwed this up. We just wait until we get into punctuated versus gradual evolution. Chuck. Um, you've heard of Lucy right, the Australia Kiss. Yeah, okay, Well, um, she was I think three point two million years old. That's one old lady. It really is the earliest hominid we've found as far as I know. Um. But there is a part of her foot missing. It's always been missing that we've never found before. So this thing, this bone, was so essential and we couldn't tell how she walked until recently. Why because the missing bone, we couldn't tell how she walked exactly. We we we can tell so much from bones that when we don't have the right bones we can't tell anything. So she may have been in a knuckle dragger, she may have hopped. We didn't know. Well. Recently, UM, some people from the University of Missouri or Missouri, depending on whether or not you live in the state. UM found the Uh, the group of foot bones needed to show what kind of walker Lucy was. And she walked up right? How was her gate? Upright? Upright? Just like a human. She had a hitch and her get along, she had a pepper and her step. Possibly she knew she'd be famous one day. She was loved with duc But but consider this, right, Okay, three point two million year old footbones were found, and we could tell from them how she walked. This is the state of the field that you remember paleontology. Pretty cool. This is how advanced it is. And yet it's really just kind of using common sense to figure out what old bones mean. Common sense and science. Fossils go, let's talk about it, Chuck, what are some of the different kinds of fossils. Uh, well, one of my favorite kinds of trace fossil. Yeah, that's actually one of my favorites too. It's like, um, that Jesus footprint thing. Footprints in the sand. Yeah, sort of is josh um. That is when it's actually not part of the organism at all, but it's um like tooth marks in a chunk of wood from a saber tooth tiger. Or footprints or footprints or track ways as Tracy calls them. Yes, footprints tracks. It's just unnecessary, but it has a pleasant tone, you know science. Yeah, like they're not footprints, they're track ways. I'm bored in Ethiopia, let's call him track ways. So trace fossils is one. Of course, there's bone fossils, right, the most famous fossils. Yeah, those are great too. They got nothing on trace fossils. So actually, bone fossils, that's that's what you really want. If you're going to reconstruct the dinosaur for your museum. You can't deal it with footprints, No, you can't. You need the bones, you do. And the bones are of course the most famous ones in the dinosaur. Bones are the most famous of all the bone types. Right. So there's something that I think um is often missed by lay people such as myself, um and in that when you find a bone, right, so you find like a big old dinosaur bone, it's really geologically speaking, it's not a bone any longer. It's not like you find a bone buried in your yard that was an animal from like, you know, thirty five years ago, But that's not a fossil. We'll not still bone. A fossil is a bone or a piece of um once living organic material that's undergone a transition from uh, an organic state to an inorganic state. That's what a fossil is. It's gone through the process of fossilization. And most of these fossils, the vast majority of fossils, are found in sedimentary rock. Before we're go any further, we should probably do a little brief primerun sedimentary rock, right, which is awesome. Yeah, it's pretty easy to Uh. We've talked about the Earth's core um and layers. When I think we talked about earthquakes and maybe some other stuff. We all know that there's the intercore, outer core. We got the crust. Crust is the thinnest layer, and that's where the fossils are. That's where the goods are. And uh, most of the rocks in the crust are sedimentary rocks that you've been talking about off and on for the past eight minutes, right, and that's like silty sandy stuff that hardened over the years, right, I mean, but the the Earth. Remember we talked about, oh, what was it, clouds. I can't remember what podcast it was, but we talked about how much sand is transferred from Africa to South America annually. Yeah, it wouldn't clouds, but yeah, if you you remember the one I'm talking about. Okay, So, the Earth's geo biogeochemical processes equal a lot of movement of particulate matter. Right. The Earth is dynamic, baby, it is. It's also very fluid. To write, a lot of that matter is at at one point as suspended particles in water that's moving around, right. Yeah. So um, as this as the water leaves and the sediment is deposited, it builds up and up and up. Over time, it hardens into rock and eventually we have sedimentary rock, yeah, which is below our feet. We don't normally see it unless say, the Colorado River um winds over it for you know, millions and millions and millions of years, revealing the sedimentary rock that's in the Earth's crust. Grand Canyon exactly. So you're talking about, Yeah, I forgot the Grand Canyon Park So you know how I said the Earth was dynamic, baby, Yeah, Uh, that's important. I didn't just throw that in there as a factoid. It's important because when these plates shift around, that's how fossils are. On Earth. Things can be moved great distances and pushed to the surface eventually or close enough to where a dig can unearth it. And it's like, just because it's fossilized doesn't mean it's stuck in that one spot forever, because Earth is always moving. So the point of all this is is sedimentary rock um is, like you said, dynamic. It moves around. Sometimes fossils pop up or it becomes exposed all of the Colorado River um, and that is where fossils are, right Chuck. Yes, So let's say that at some point in time there was a dinosaur or a sabertooth tiger or a cyanobacteria woly mammoth wooly mammoth, sure um, and it's um hanging out around a riverbed and it has a massive heart attack and falls over in the river bed and very quickly it becomes covered with sediment and silt, right Yeah, And that's important because once it starts getting covered up with stuff, it's sort of being protected from like all of fossil. Let's just break the news. All of fossil means is that something has been protected from the natural decomposition process. Otherwise we just decompose like everything else, and you wouldn't see it anymore. You've just totally betrayed Tracy in the tone she lent to this, that the whole drama drawing out suspense. But that's true. So what you said was right. So you'd fall over in a riverbed, you start getting covered up with the sediment and silt, and it's it's immediately starting to protect you in a way. Um, not you, but whatever, the wooly mammoth, the wooly mammoth. Um. The thing is the in this sediment, in this silt, you can't really hide from macrobacteria, uh and other forms of life that are basically dedicated to breaking down organic matter, soft tissue, hair, eyeballs, um, genitalia, all that kind of stuff. It eventually becomes broken down and what's left is the hard stuff the bone, right, But the bone also has organic material within it as well. Yeah, and that'll break down. We're talking blood cells, collagen, fat, that's going to break down to the key here is the inorganic parts of the bone remain intact. And it's the other keyword here's porous. Yeah. You take calcium, I imagine for your hips. Yeah, sure, glucosamine, calcium. Sure. So what you're doing is, um, you're fortifying the calcium that's already in your hips, supposedly, um, because the bone is made in large part of calcium, which is a mineral, which is inorganic. So it's all the organic stuff dies out. What's left is, like you said, the inorganic like calcium, whatever, minerals, and that holds the shape, right, Yeah, the initial structure is kept intact. Right, But like you said, this bone is also porous. That's the key. And over time, um, other mineral sediment kind of um, it enters into these these microscopic pores iron right, carbonate yea and fortifies this, ultimately turning this but what was once an organic bone into an inorganic rock in the shape of the bone. But for all intensive purposes, it's still the bone. It still has that original calcium. It's still the same thing. It's not like a replica of it. It's just become fossilized. Yeah, and Tracy in the article uses a pretty good example. I thought, it's like filling a sponge with glue. The sponge is gonna keep the shape, but the glue is gonna ooze through all the spots that it can ouze harden, and there you go. You've got a hard sponge, hard sponge, which is basically what a fossil is. And this takes place Josh over the course of millions of years, the sediment reinforcing the bones eventually becoming rock. It's not the kind of thing that happens willy nilly over thousands of years. It's a long time, and it's just this isn't just um happening by itself. All of the surrounding area UM is being deposited with sediment as well. It's also turning into rock um. And then the ultimate test of time for a fossil is that it can withstand the pressure of the that's mounted by the hardening rock sedimentary rock that's growing around it, so it can be crushed. Is that how A lot of fossils are definitely crushed, crushed the death poor guys um. But if it survives and you can find this, you will eventually be able to get to it. And then you remove the rock from around the fossil, and there's your bone that you can take to the Natural History Museum and get at least five dollars for when you were a kid, Josh, let me ask you this. Did you ever go into the woods on a little nature course from like a science center, let's say, and do a cast plaster cast of a animal footprint? Did you ever do that? No? Really, really, I did that. We went and found like deer hoof prints, you fill it with plaster, and there was some way of doing it where you an inverse plaster cast of a deer hoof print. That can happen actually in a way that with trace fossils, so you can you know, sediment can act the same way. And one of these, let's say, uh, the wooly mammoth makes a footprint in some loose but sturdy soil that fills up with sediment and creates basically a mold, just like I did as a kid with the plaster cast. Yeah, as long as the sediment that fills it in is lighter or thinner, yeah, than the soil that the impression is made in, then yeah, it would it would, it would preserve that track. Yeah, and plants can do the same thing. It's not just bones we're talking about. Um. It can also fill in in a different way, I guess the opposite way to where it makes a basically a cast of the foot that made the track. Oh yeah. And then so it's like a kind of like a fossil of a ghost foot that's not really there, but it makes the foot. It's like an inverse cast. Okay, yeah, of not the track, but the foot that made the track. Yeah. Yeah, got cool. You know what other another my favorite trace fossil is it's not a track way, it's copper light. I changed my mind. That is a good one. That's dunge. It's poop, fossilized poop. That's right. I can tell you a lot about an animal. It can tell you about its fiber intake. It can tell you about what size it's poop was, um, chuck. You know. In the eighties, the CIA found out much about Gorbachof and his health. They found out he had like cancer or some sort of chronic illness um by stealing his poop when he was when he came on a state visit to the US. They took his poop and analyzed it, and when they he was in the US, they des grabbed it from the toilet. Did he not flush? I just want more specifics. You probably don't have. As far as I understand, they probably it's hotel room or wherever he was staying. They were prepared to do this. This was like toilet rigged. Probably, yes, But wherever Reagan went, they had a portable toilet that he used. It was the only one he was allowed to use. I'm not kidding, so no one could steal his poop. Talk about paranoid. Yeah, seriously, when you point one finger, there's three pointing back at you. You know what I mean? Yeah? Yeah? Uh so, Josh, that is sedimentary rock and that's to me one of the cooler ways you can get a fossil. Uh petrified would too? Don't leave that one out. Oh yes, it's basically the same thing that we just described for bone, but for wood. Yeah, hard as a rock because it is a rock. Here you go, alright, So, like I just said, um, that was sedimentary rock and that's kind of fun. But you can also uh get a fossil. Has that funny because one dies in a cave that's really dry. Yeah, desiccation. Yeah, desiccation is basically, uh, sort of a mummification, but it's not like we think of with mummification with the Egyptian tombs or anything like that. Well, that's because there's no reservation techniques that have been undertaken. It's natural. Basically, it dries out. It's like throwing an orange in a dehydrator. So when it's really dry, there's not gonna be any place for bacteria to thrive. That's the reason beef jerky is not um refrigerated. If you refrigerate your beef jerky, you're you're doing something wrong. Yeah, that's true. Well, if you have beef jerky long enough to need refrigeration, then you're doing something wrong or something really really right. Uh. So desiccation actually works so well sometimes that it can preserve the skin and soft tissues as well, which is something that sedimentary rock cannot do. Have you been to the Smithsonian I have they have um a very cool I guess a prehistoric cow or a musk ox I can't remember, but it's the thing's head, um, much of its back, I guess, the cape, two of its legs, and the skin is still there. It's just right there. Probably it's tens of thousands of years old and it's just sitting right there. Did they could they read build it or just put the parts up? It's just the parts, but it's laid out so that like it gives you the impression of what you're looking at, but its face is still there. It's very cool. Uh. My favorite kind of fossil, though, Josh, is I'm gonna say that, like every five minutes is a frozen fossil, because if you get trapped, let's say your wooly mammoth trapped in ice, not only is that going to keep other like vultures and things from picking up your bones and skin, but it's also going to keep it from breaking down and you can get hair fully preserved sometimes if you're in skin and like a big mammoth. Have you seen pictures of Liuba? Now? Liuba is a baby wooly mammoth that was found um by a reindeer herder in Siberia and um it was pounds or something like that, but it would have gotten up to several tons. It is adorable because it is a fully preserved wooly mammoth baby with the wrinkles in the skin and everything. Yet it spent forty five years in the permafros, but it's like completely intact. It's very cute. That's why it's my favorite. It's one of the cutest dead things you'll ever see. Another couple of ways you can get a fossil josh, which are not my favorite aur tar librea tar pits, although that is one of my favorites, which librea tar pit is actually redundant because Librea means the tar, so it's calling it the tar tar pit and not the tartar. Did I ever tell you about when I shot a commercial there? Have you? Did you go by there in l A? No? I want to. I forgot about it when we're there last Well, for those of you haven't been, it's right in the middle of Los Angeles, like south of Hollywood on Wilson Boulevard, and it's um. The main tar pit is uh. Tar pits are fenced off, obviously, and they have little recreations. It's it's actually the saddest thing you'll ever see. The recreation they have in there is of a like I guess it's a mother wooly mammoth trapped in the tar trying to get out and the father and the baby on shore like howling at her. It's awful, but it's still active, like all the tars bubbling up and everything. And shot a commercial there once and I was on the other side of the property, far away from the main pit, and I looked down and there was a little mini tar pit, a little tar puddle about a foot wide, bubbling right beneath my feet. I could have scooped it up with my finger if I had been so inclined. Yeah, instead, you're like, that stinks. Well, it's just crazy to think that that's still like it's happening. Apparently, Um I looked it up. There's um there's like you said, main pits that are chained off and that are still being excavated. But they have them like in neighborhoods all around the area and parks. They're just kind of all over the place around there. That's like parts of stone Mountain popping up all over the place. We used to have We had a big chunk of stone mountain in our backyard growing up, all right. For those of you don't know, Stone Mountain is the world's largest exposed piece of granite, and it is right here in our home state, and it takes like thirty minutes to hike, but you still get to get to the top and be like I just hiked a mountain, which I have, Josh. You can also get a pete mossy pete can preserve life forms, including human beings like Tolin Man was. It was that Toland Man. I don't know about him. How do you know all these people people? The first the first um multi syllable word I could spell was archaeology. Really, I've always been interested in that. I could see that, Yeah, Tolin Man. Also, it doesn't you can hate archaeology like some people hate art, and you'll still be interested in Totland man Um he was. He's found in Denmark. He lived years ago and he was murdered, uh sacrificially, they think, and cast into the peat bog, which pete is just decomposing moss and lots of it, but it has a tendency. I think it's anaerobic, so um tissue is preserved really well. But it's this guy that they dug up, and he's so well preserved that when they found him in the nineteen fifties, they called the cops because they thought they'd found a murder victim really like a recent one. He looks kind of funny, but he's got his whiskers are preserved. He's wearing a cap. He still has this the garrett around his neck. Um, it's really awesome. So what is he dated at? Like three four hundred BC? Is the one who was killed and he's wearing a hat yeah, sheepskin, leather cap. Yeah, no last chance garage for him? No? Well uh? And then my favorite way, Josh, that you can get a fossil is uh, you're joking? Did you say it again? I did? Is amber? They just keep getting better and better, like the movie Jurassic Park. Yeah, that's how we get dinosaurs again. Yeah, dino d n A. So you found something on on whether or not that's feasible, right, yeah, because I always wondered. You know, when you see Jurassic Park, you see the little video they made it clearly to explain to the movie going audience how this is done. It's better than Ellen Page running around. What was that movie inception? Um, so the mosquito flies in tree residentry resident eventually becomes hard as copal, than it eventually becomes inert as amber. You get the little mosquito in there. They extracted the dino DNA from the blood of the mosquito, filled in the gaps with I think frog DNA, and that was all there was to it. And at the time I thought boom. But being bon Jovi, yeah, at the time, I thought that seems plausible, and it sort of is. But I did look up today and there was a researcher that was interviewed at the or closer to that time. I think that basically debunked it and said, we could potentially maybe get some DNA, even though it's really fragile and loses his signature really quickly. Even if you could get the DNA, he said that you couldn't construct a dinosaurs just you can't fill in the blanks like that. There's way too many blanks. You have a giant frog, yeah, with little tiny arms forearms that Steven Spielberg made us belief when you saw those dinosaurs walk across that field. That guy can make me believe in anything. That aliens came to the American Southwest, that there was a World War two, that um each phone home. Yeah, good stuff. Though, where are we here, chuck it. We're kind of painting this picture where if like you just stick a shovel anywhere on the Earth, you're gonna yield like all sorts of bones and fossils. Note no, it's not um First of all, a mere fraction that I don't think could possibly be calculated, because we rely on the fossil record to show us what existed back when, and it's incomplete. Therefore we've entered to catch twenty two. But there's just a mere fraction of all of the species and organisms that's ever lived that become fossilized um Like. Basically, a perfect storm of chance has to occur for a fossil to be created. As we've seen, even when it is created, it can still be crushed into oblivion. Um. And so there are few and far between. To begin with, what we have to figure out where to find them. While then you got to find it. That's the other problem. And the way we find it is by identifying rock that will likely have the type of fossil that we're looking for. Yeah, so you want something that from that year. So if you know that this animal from yeah, if you if you know this this animal lived, you know, thirty million years ago, you're gonna go find rock that you know is thirty million years old and start poking around and you know, looking this sort of a very chance thing, and we know that, um, we know, like say a layer of rock or strata of rock is thirty million years old because of a technique we have called radiocarbon dating. Right, yeah, you want to do this one? Well? Sure, Carbon fourteen dating is what a lot of people toss around because it's probably the most well known, But that can only take you back sixty thousand years. We're talking millions and billions of years. So they need to uh study isotopes like potassium forty and uranian two thirty eight because that goes back millions of years. Evidently. The half life yeah, and the half life is where an atom loses half of its life isotopes to decay. Yeah, okay, and these the this um radioactive decay takes place at a predictable rate depending on the atom, the type of atom. Right, Yeah, that's how I understand it. So if we find a type of atom missing x number of isotopes, we can say, well, this is roughly thirty million to thirty one million years old, or thirty million to thirty million and three hundred years old. I'm not sure what window we can date it to, right, but I think it's enough so that you know, we have a rough estimate of of you know, when this fossil lived in the sediment was buried around it. So, Josh, let's say that you're lucky enough and skilled enough as an intrepid paleontologist to come across your fossil. What do you do? Well, as I said, you dig it up and take it to the museum and sell it for five Smolan Well, I don't know about that, but you should call a museum. Even if you think you know what you're doing, Uh, you're probably gonna need some help if it's something major. I think you should probably go on the assumption that you don't know what you're doing unless you're a trained paleontologist. Um. Part of the problem is is we assume that these fossils, being rocks, are sturdy. That's not always the case. So there's a lot of danger of damage um in a just an average joe trying to excavate him. Also, if you just pull a bone up and walk away with it, Uh, it immediately loses context. Yeah, it's like removing a piece of evidence from a crime scene almost exactly. I can't do that. Well, you're not supposed to. Uh. So you know, they have these huge cranes and uh digging tools where they can remove huge slabs of earth, which is a really good way to do it. And sometimes if they're you know, if it's something that could be fragile, they will remove the entire slab, cast it in plaster and just go ahead and ship that thing off to a facility to handle it from there. And the cool thing is is, even though rock has formed around this bone, yeah, that's key right up right, all up on it, all up in it. If you um flake it away properly, if you flake the surrounding sedimentary rock away, um, you're going to find that there's what's called the plane of weakness, which is where the bone and the rock are still on this very microscopic level. They're not fused together. You're gonna hit that and the rock should chip right away, right and and leave the bone. Yeah, And I think sometimes they missed it with water too, to soften it up and help the whole process. Another thing too, if they find that is really brittle, they can actually reinforce the bone with resin and thin glue. But you need to be careful there too, which is pretty much helping along the fossilization process. Yeah, I would think so. I mean it's the same thing. It's like artificial forcing it with something sturdy. Well, and then you can date it using your little mass spectrometer that's in your pocket, and or a cat scan sometimes they use cat scans computer imaging stuff like that. Yeah, I didn't I didn't get how they were dating it from cat scan. I don't know if they're dating it with a cat scan or just sussen the whole thing out. Gotcha. I don't think it's a dating situation. Tracy was just throwing out some extra tools of the trade. Huh Yeah, exactly, gotcha. So, um, chuck, what is all this worth? I mean, we we have a thirst for knowledge. Obviously people think bones are very cool, But ultimately, what's the pursuit of paleontology to to put together the piece of the puzzle of how we got here? Right? I mean that's what I think. Yeah, that's my understanding as well. Yeah, you can learn a lot by not only finding the fossil, but finding what was with the fossil in that same strata. Ah, I can tell you, like, hey, this is a t rex bone and there's also a bit of pine tree, so we know pine trees were around, and they may have eaten pine trees while not the t rex because they were carnivores, right, Um, yeah, they were herbivore. Let's say, you know what I mean, Abronosaurus. Sure. Um. And ultimately all of these fossils come together, plant and well, everything that we can get our hands on to form what is called the fossil record, right, and this is basically the record of life on Earth. Uh. It's also used to support evolution big time. And uh it's here that paleontology gets most contentious, right yeah, sure, because there's, um, the the idea that beings evolved if you go far enough back from a single common ancestor, right. And so if we can put together a complete fossil record, we would be able to see how everything alive today evolve from this common ancestor or common ancestors. Right. Yeah. The problem is fossil records incomplete, and one of the really key parts that it's often missing are called transitional fossils. Right. My favorite kind of fossil, Josh is a transitional fossil. And one example Tracy used was the baleen whale. Uh. There there's a picture of one actually in the article twenty five million year old fossil of of the baleen whale with sharp teeth. Um. Today's bailing whales don't have sharp teeth, but we know that once before this had sharp teeth and legs. So this is a transitional fossil that shows, well, they used to have legs and sharp teeth, then they just had sharp teeth, and now they don't have legs or sharp teeth. They're defenseless, which is why they're baling whales, right and not sharks or megalodon's right. Um. And so a transitional fossil is one that that pops up between old and new, and it makes sense. Our understanding of evolution is that it takes a little while, and um, something like teeth aren't just gonna go away in one generation. It's gonna take more and more and more, and then um, we should be able to find them along the way where maybe the teeth gets smaller. There's fewer and fewer um baling whale teeth in the average baling whale mouth, and you're putting together the puzzle exactly. UM. Again, the fossil records a little incomplete, and there aren't as many transitional fossils as I think people would like to. UM have tied all together, right, UM, and then some of the UH. Some of the explanations are Probably the most famous explanation for this is that UM evolution isn't gradual. I think it's Stephen J. Gould came up with the idea of punctuated equilibrium, and that is basically that UM evolution takes place suddenly in these huge quick fits and starts, which would explain why there's not like teeth don't go away in a generation, but they go away a lot faster than we used to suspect. And that's why these UM fossils UM, accompanied with the idea that not every animal that's ever died has become fossilized, explained why there's huge gaps in the fossil record, which will inevitably always be incomplete. Is that a hypothesis at this point? I guess it is not a theory yet I don't. I don't think so. I think it is a hypothesis. I got one more thing, Okay, I'd like to finish with my favorite kind of fossil, and that is a living fossil. And that, Josh, is when you've got a plant or animal that looks so much like ancient fossils that they consider a living fossil. Allah, the horseshoe crab. Right, apparently the horseshoe crab has not changed. Didn't need too. It's perfect. I look at it, it's gorgeous. What else, oh, Genko baloba plants. And then a word that I don't know, the Cela cant. What is that? Uh, it's this horrid looking fish that they remember that VW commercial where he's like it's like the Ceila camp and the guys like what they're looking in the trunk and he's like a full size spare tire. He's like, it's like a Ceila cant. They used to think it was extinct. There was a fish, and then they found it like in the nineteen thirties again. But it's this dinosaur looking fish. Oh, I think I've seen him that they thought was extinct for millions of years and they called him and I think in South America, off the coast of South America, and they're still around. And the horseshoe Crab and Stephen J. Gould in the Genko Baloba. Well, it's it for fossils, right, that's all I have. I think we've got the point across. It's an overview. A fossil is a rock. Just remember that, Okay if you want to learn more about fossils. Um Seriously, this is one of the better articles on the site. Tracy did a great job with it. Type fossils into the search bar, the handy search bar, and how stuff works dot com, which means it's time for listener mail. Josh, we made a young girl cry. That's what I'm gonna call this one. Okay, It's probably happened more than once. Uh I, guys and Jerry. My name is Ali. I'm from Indiana. I was in the I S s M, a band contest, playing a difficult marimba solo today. I was pretty nervous, but being first chair and the only female percussionist in my school really brought up my confidence. I went in, I choked, and I stumbled through my piece. You could get a gold, silver bronze, or a participation metal. Got the bronze, which is equivalent to a score of an F. I was really upset. Wait, what is participating? That's sub f I didn't even know they made medals. I thought it was just a ribbon. It's probably a ribbon. I was really upset. I got home. I was trying to cheer myself up by listening to your podcast on What's the Deal with Stinkholes. I really love the show, and I've listened almost everyone, But in the beginning, you guys talked about how much the Bronze medals suck. Remember that. Oh yeah, so we didn't lift spirits very much, Josh and Chuck. I just want to let you know that the two of you made me cry then from Ali and I have since written Alie back and apologized, and she said that she's feeling much better now and uh, it wasn't our fault. And I told her that I've choked under pressure many times in my life and it happens, and it will happen again, and it doesn't mean you don't have the goods with your solo every single time. Yeah, but you know you pick yourself up. It sounds like you gave her some good advice to choke. I think so she's getting receptive to it. It's like a sweet girl. I think that's an excellent lead in. If you have a story about choking, not physically choking, but you there's something you're good at and you didn't do it. Well, say you're a television reporter in Los Angeles and you're supposed to report on the Grammys like that. So you're a podcaster and you have to do a show about the sun to give one too, but we want to hear about it. You can send it to us via email. Just type in where it says to stuff podcast at how stuff works dot com. For more on this and thousands of other topics, does it how stuff works dot com. Want more how stuff works, check out our blogs on the house stuff works dot com home page