Learn about why we now know what a dinosaur's cloaca looks like. You’ll also learn why smells change with context from food science expert Harold McGee.
Learn about why we now know what a dinosaur's cloaca looks like. You’ll also learn why smells change with context from food science expert Harold McGee.
We now know what a dinosaur's cloaca looks like by Grant Currin
Additional resources from food science expert and author Harold McGee:
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Find episode transcript here: https://curiosity-daily-4e53644e.simplecast.com/episodes/scientists-finally-found-a-dinosaur-cloaca
[THEME MUSIC] ASHLEY HAMER: Hi. You're about to get smarter in just a few minutes with Curiosity Daily from curiosity.com. I'm Ashley Hamer.
NATALIA REAGAN: And I'm Natalia Reagan. Today you'll learn about why we now know what a dinosaur's cloaca looks like. You'll also learn why smells change with context from food science expert Harold McGee.
ASHLEY HAMER: Let's satisfy some curiosity.
NATALIA REAGAN: For the first time ever, researchers have discovered the fossilized rear end of a dinosaur that leaves nothing to the imagination. And I mean nothing. We're not talking bones. They found the fossilized remains of the soft tissues, and it turns out that this dinosaur sported a pretty efficient backside. The species in question is called Psittacosaurus. More like "psittoc-ass-aurus," if you know what I mean. It was related to triceratops, but it had a look all of its own.
These beauties were the size of a yellow lab. They walked on two legs, and they had a face like a turtle, with a horn on each cheek. Their tails were adorned with a tuft of long feather-like bristles, and now we know way too much about what was going on under that tail. Specifically, these researchers found the fossilized remains of the dino's cloaca. That's an all-purpose opening used for both waste and reproduction.
A lot of paleontologists already suspected that dinosaurs had a cloaca. That's because birds, dinosaurs, and alligators, dinosaurs' closest living relatives, have them, too. The big news is that we have hard evidence for this soft orifice. See, nearly all bodies are completely lost to time shortly after death. They get eaten or they decay. But sometimes, when everything happens just right, a bone is preserved. Even less often? A whole skeleton will survive. That's why pretty much everything we know about dinosaurs is based on a surprisingly small number of fossilized individuals.
There's nothing in the laws of physics that says any part of the body has to be preserved. It's more of a right place, right time kind of thing. Animals are dying constantly, so it makes sense that some fraction of those corpses would end up somewhere safe from decay and scavenging, like a tar pit or under a heap of volcanic ash. The 100-million-year-old cloaca is such a choice find because fossilized soft tissues are way less common than fossilized bone. There are a lot of reasons for that.
One big one is that flesh offers a lot of easily available energy to all kinds of organisms, from vultures to microbes. That's why soft tissue only ends up being preserved under precise circumstances. A corpse has a better-than-average chance of preservation if an animal dies in a volcanic explosion or in a desert, where the sun can dry it out before other organisms can start to chow down. So this cloaca was definitely a serendipitous discovery. More like "seren-dupe-itous"
So if you're so inclined, check out the picture of the fossil. We've linked it in the show notes. So while you're there, take some time to appreciate just how lucky we are to have inherited that fossilized rear end.
ASHLEY HAMER: Have you ever noticed how something can smell terrible in one context but wonderful in another? I'd never drink something that smelled like crayons or band-aids, but if those smells waft from a glass of scotch, suddenly it smells delicious to me. Or how about when two completely unrelated things smell similar? Like the way old books have a hint of vanilla. If you've ever wondered why that happens, well, today's guest is just the expert to tell you.
Harold McGee is a leading expert on the science of food and cooking, who recently turned his sights on smells with a new book Nose Dive-- A Field Guide to the World's Smells. In our conversation, I asked him, how can two totally different things smell the same?
HAROLD MCGEE: Well, that's where chemistry is a wonderful guide, because it turns out that these different things that you wouldn't think would smell like each other smell like each other because they share molecules. So smells are triggered by volatile molecules, that is to say little bits of the world around us that are small enough that they can fly out of whatever it is that they're in and into the air. And once they get into the air, then we can draw them into our noses and detect them.
And so those odd combinations, things that smell like each other, that you wouldn't expect smell like each other because they do share molecules. They share individual molecules that are in those materials and often for different reasons, but give them that common characteristic.
ASHLEY HAMER: Wow. So what happens when those volatile molecules go into our noses?
HAROLD MCGEE: Well, we have a set of about 400 different olfactory receptors in our nose, and they're there specifically for the purpose of detecting volatile molecules and reporting on those molecules to our brain. And they act in a combinatorial way, so it's not that for every smell, there's a receptor. It's that the pattern of receptor activation that comes from a particular smell registers in the brain as that particular smell.
And what happens is that the receptors report their activity to the brain, and then the brain makes sense of that and integrates that with our database of past experiences. It integrates it with the other inputs from senses, from taste, from vision, from hearing, and puts all those things together into a coherent composite perception, which is the perception of smell.
ASHLEY HAMER: So we're not just chemical sensors. We're actually interpreting those inputs. And that suggests that, maybe in a different context, something could smell completely different. Is that right?
HAROLD MCGEE: That's right. In fact, the very same molecule in two different things can give us two very different impressions. There's a wonderful experiment that was done by Rachel Herz at Brown University a decade or so ago. She took one single molecule, butyric acid, and presented it to people, subjects, in the experiment and asked them what the molecule reminded them of. And depending on how she described the scene, that molecule could be either disgusting or wonderful, because butyric acid is a molecule that's found in aged cheeses, like Parmesan, but it's also found in vomit.
And so if you're thinking about cheese, it's nice. If you're thinking about being sick, then it's disgusting. And so the context has a very strong influence on how it is that our brain interprets exactly the same molecule. One of the most important for me for just continuing to enjoy and to increase my enjoyment of the physical world was the discovery that even though something can initially be off-putting-- a smell can be off putting, disgusting, something you would maybe not want to encounter again-- but if you're writing a book about it and you're trying to describe it, then you do sniff it over and over again. And it can come to be interesting in its own right.
So I went to Singapore, and I experienced durian fruit, which are this very strange combination of oniony and garlicky and skunky and fruity, like strawberry, all at the same time, all wrapped up in one, which at first, while reading about it, I thought that sounds terrible, and my first smell and taste were not very pleasing. But because I kept tasting in order to be able to describe it better and to just register the experience, I really got to enjoy it, if nothing else than for that strange combination, which is so unusual and so unique.
So that was a discovery for me, that even things that are not necessarily, at first sniff, pleasant can end up being a source of fascination and interest.
ASHLEY HAMER: Again, that was food science expert and author Harold McGee. His new book is called Nose Dive A Field Guide to The World's Smells, and you can find a link to pick it up in today's show notes. Harold McGee will be back tomorrow to talk about the smells that existed before Earth was born.
NATALIA REAGAN: Let's recap today's takeaways.
ASHLEY HAMER: Well, we learned that scientists made an astounding find of a dinosaur's cloaca, the hole that they used to expel wastes and to reproduce. This is a super-rare discovery since soft tissue really doesn't preserve very much.
NATALIA REAGAN: We're so lucky. But we are. So I have two chickens, Jeanette and Carol, and I actually call the cloaca "the hat trick of holes," if you're familiar with hockey. Hat trick in hockey is essentially getting three goals in a row. And so the cloaca is responsible for expelling feces and urine, usually at the same time, and then, of course, the sex. So I call it "the hat trick of holes." That's where they do all the things. And it's very efficient.
ASHLEY HAMER: Right.
NATALIA REAGAN: Right? One to rule them all. I like that this gives us a chance to talk about how hard it is to create a fossil, because fossils, you have to have a perfect environment to create an actual fossil. If you think about it, so many things have died. And one thing to note is that when animals die, and they're going to be scavenged, generally they'll go for the softest parts of the body, which include the eyeballs and the rear end.
So that's another reason why this is an extraordinary find, because you would think that, yeah, this poor little Psittacosaurus died. I don't know what exactly would have come along scavenging its poor little lifeless body. But it would have probably gone for its eyes and its cloaca, and it did not.
ASHLEY HAMER: So it's like finding fossilized Halloween candy where all the Snickers are left.
NATALIA REAGAN: Yeah, like that. So this is really rare. This is such a lucky find.
ASHLEY HAMER: Yeah.
NATALIA REAGAN: We also learned that molecules that make up smell can somehow seem almost altered because of the context. So when you're sniffing them in one context, they might smell good, but in a different context, ooh, not so great. So I think that really, I don't know, changes the way I smell the world around me, honestly, like what smells good and why.
ASHLEY HAMER: Yeah. Do you want to know an embarrassing smell that I think smells good?
NATALIA REAGAN: Yeah.
ASHLEY HAMER: Is a women's locker room. And the reason is because the smell of women's sweat reminds me of ballet class when I was little. I'm thinking when I was seven or eight. And there were all the older girls who I looked up to and who are doing serious workouts in there. Their rehearsals were very intense, and so they would sweat a little bit. And I remember that was a very specific smell, and that will always remind me of being a little kid who was looking up to these idols of mine.
NATALIA REAGAN: Oh, that's really sweet. I love that. So olfactory senses, it's one of those things where I think that as humans, we don't rely on it, obviously, as much as, say, a dog or a cat. We don't use it quite like that, but it really does imprint memory on us, you know what I mean? Like the smell of my granny's house. My granny was from Kentucky, and it was very humid and musty in there.
And it's like I'll walk into a place, and I'll smell it for whatever reason. And it's probably a mixture of mustyness. She at one point had a wood-burning stove. So it brings back, like you said, a flood of memories, and there's something really lovely about that. Perfume, your grandma's perfume, and you're just like, wait a minute. Grandma? Where are you?
ASHLEY HAMER: Yeah, absolutely.
NATALIA REAGAN: Today's first story was written by Grant Currin and edited by Ashley Hamer, who's the managing editor for Curiosity Daily.
ASHLEY HAMER: Scriptwriting by Natalia Reagan. Today's episode was edited by Jonathan McMichael, and our producer is Cody Gough.
NATALIA REAGAN: Remember, the nose knows. And join us again tomorrow to learn something new in just a few minutes.
ASHLEY HAMER: And until then, stay curious.