Stuff You Should Know - How Natural Selection Works

Episode Date: April 10, 2014

While evolution gets all the spotlight for moving species into better versions of themselves, but really it's natural selection that is the engine driving the process. Learn all about this elegant scientific observation that forms the basis of life. Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privacy information.

I'm Munga Shatikler and it turns out astrology is way more widespread than any of us want to believe. You can find it in Major League Baseball, international banks, K-pop groups, even the White House. But just when I thought I had a handle on this subject, something completely unbelievable happened to me and my whole view on astrology changed. Whether you're a skeptic or a believer, give me a few minutes because I think your ideas are about to change too.

Just a Skyline drive on the iHeartRadio app, Apple Podcast, or wherever you get your podcasts. Attention Bachelor Nation, he's back. The host of some of America's most dramatic TV moments returns with the most dramatic podcast ever with Chris Harrison. During two decades in reality TV, Chris saw it all, and now he's telling all. It's going to be difficult at times, it'll be funny, we'll push the envelope, we have a lot to talk about. Welcome to the Most Dramatic Podcast Ever with Chris Harrison on the iHeartRadio app,

Apple Podcasts, or wherever you get your podcasts. Welcome to Stuff You Should Know from HowStuffWorks.com. Hey, and welcome to the podcast. I'm Josh Clark, and there's Charles W. Chuck Bryant, and there's Noel, which makes us a very special edition of Stuff You Should Know. Harrier than Jerry. Yeah. Edition.

Much Harrier. Noel is weird. Noel, let's see your hair. Man, that has a lot of hair. Hair suit. Yeah. He's like the original King of Leon. He all wrapped up in one.

I used to love those guys back when they were like Tennessee hillbillies. Yeah. Then they got their glam makeover, and I was like, what? It's like Metallica after the black album. Yeah. What happened? What happened Metallica? Lars?

They enjoyed making loads of money, truckloads of money, more than being heavy metal parking lot guys. Yeah, exactly. Hey, Chuck, before we get started, we want to tell everybody. You can follow us on Twitter at SYSK Podcast. You can hang out with us on Facebook.com slash Stuff You Should Know. Our YouTube channel, search Josh and Chuck. It's pretty awesome.

Yeah. And as always, we have a wonderful website, StuffYouShouldKnow.com. That's right. You can hang out with us outside of the podcast if you want. If you want. No pressure. So, how are you doing? I'm great.

I'm super excited about this topic because, A, we're pairing it with our Charles Darwin show. Yeah, which I guess came out last episode, right? Aren't we pairing the two? Like you said? Yeah, I think we're doing Darwin first. Let's do Darwin first. Because I think in the Darwin episode, we say we should do natural selection, so here

we are. But I'm just excited because to me, and I gushed a little at Darwin's feet, this is my own personal statement. I think natural selection is the most exciting and like a beautiful thing that exists. It's just, it really turns my crank. You're like an old-timey car. Yeah. Yeah.

You know, I grew up, this is, again, my personal story. I grew up in churches, most listeners know, which was heavy doses of the creation story. And I remember as a kid even, fully involved in church thinking, like, I just, this doesn't make sense to me. I just, it didn't add up. So natural selection, it just makes sense to you? Yeah, when I finally learned about natural selection, like, really, really understood it and learned it, it just, it made total sense because I can like see it.

It was tangible. I could make sense of it. And again, that's my own story. Right. We don't poo-poo anyone. Oh, no. Or saying anyone should feel anyway. Yeah.

But, yeah. We just explain how things work. Exactly. You know? But I have a personal attachment to this just because I think it's like the grubious thing going. Yeah, no, I know what you mean. Like, it makes uttering complete sense.

It's almost incapable of being appropriated to serve some agenda. It just is what it is. Right. You know? It's just there. It's beautiful. I agree with you entirely. It's an elegant theory.

It's just super neat. Yeah. The wonderful thing is, is like, there's even squabbles in the scientific community over exactly how evolution works and processes and regardless, everyone's still like, yep, natural selection. Yeah. Pretty much perfect. Yeah.

It just makes sense. I'm going to have a t-shirt. Natural selection. It just makes sense. Yeah. I have a feeling we'll be getting an email with something like that eventually. Good. So let's talk about natural selection.

I think a lot of people, including myself, kind of had an idea of what it was. Pretty good idea, but not necessarily understanding the ins and outs of it. And well, that's what we're here for is to explain the ins and outs of natural selection. Yes, sir. So basically, a lot of people interchange evolution and natural selection. Right. That's incorrect. Natural selection is this huge process by which the species adapt and change to survive

in their environments. And the way that that moves along, the mechanism that drives that is natural selection. So they're not one and the same. Natural selection drives evolution. Yeah. And who wrote this one? Was this a? Grabbinowski.

Oh, the Grabster, I should have known. Just very simply puts it very early on the article. Humans best suited to survive in their particular circumstance have a greater chance of passing their traits on to the next generation. That's right. It just makes sense. Exactly. I'm going to try not to say that every 10 minutes, but just know that that's going on

in my head. Yeah. And do you want that on a t-shirt? Sure. And natural selection is like, it's this ongoing, basically never ending process, even when organisms really kind of seemingly stop developing. Yeah. Like they figured it out.

Yeah. But it's, it isn't, it doesn't have its own sentience. It isn't its own thing. Like you can't, you can't attribute it to some sort of creator or creation necessarily, unless you believe that kind of thing. But like if you're, if you, it's very easy to give it a personality, but it's not. Right. It's the byproduct of how organisms exist.

And we exist by our genes and by the fact that those genes change frequently within the lifetime of a person, thanks to what we understand now as epigenetics, but also through reproduction. And from these, these moments, these periods where genes are up for a change, they can completely or even just partially change part of an organism. And that change may or may not help that organism survive in the environment like you just quoted Grabinowski. And if it does, bam, natural selection will root that out and it will propagate that.

Yeah. And Ed also points out Darwin, he did coin the term natural selection and survival of the fittest. And I do think that many people hear survival of the fittest and they think of the lion eating the gazelle, but it's also, like he says, the tree that can disperse its seed where it needs to for those seeds to grow or the bacteria that survives. It's not, you know, animal eating animal, although it can. And so since we're on a Chuck fitness is basically, like you say, a tree's ability to spread

seeds and for those seeds to take root because as Grabster points out, it's not enough for a tree to produce a bunch of seeds, which is its ability to reproduce. Yeah. And its ability to survive long enough to even get to the point to it where it reproduces. Right. That's step one. Yeah. Is to live long enough to be able to reproduce.

Yes. So the second part of it is that that reproduction is as successful as it possibly can be. Yeah. Like it says, not only do you got to do it, you got to do it well. So that tree that spreads tons and tons of seeds, if those seeds happen to catch fire and sunlight, that's not going to be a very good trait. But if they have like a really hard husk that can survive the elements, but then disintegrates when it's digested by a raccoon and then pooped out, then all of a sudden you've got that

step two covered. Yeah. Or if it's just dumb luck, if that tree exists in a place where it's super windy and can disperse the seeds better, then it will propagate. If not, then you may not even know that that tree existed. Exactly. Unless you consult the fossil record. That's right.

Okay, so I guess the whole point to natural selection is that it is an agent of change, but it's also a byproduct of change. And we kind of have to take a step backward to figure out where this change is happening. I already said it a little bit, but it's in our DNA. It's in the DNA of all living things to change. Yeah. Well, traits, we're all born with traits, and we inherit those traits from, you know, who made us, our folks.

But it's not necessarily, that's not necessarily natural selection at work over one generation to the next. Right. There can be differences in traits. Darwin, as we'll see, points that out himself. He's like, let's just get it out of the way. Just because you have brown eyes and somebody else has blue eyes, that's not evolution. No.

I think he uses a good example here of tall versus short folks. Tall people might be basketball players, short people might be jockeys. Right. That's the grabster, not Darwin. Yeah. Yeah. Did they have basketball? When was that invented?

When did Naismith invent basketball? I want to say 1848, but it's probably 1870. No, not too far off. So he makes the point that, you know, if something happened to where like jockeys could reproduce better or basketball players could not reproduce anymore. Yeah. I was trying to imagine what happened. Well, you didn't just make up anything.

I know. I was trying to and like I couldn't come up with it. Well, just make up something like being able to dribble and dunk lowers your sperm count. Oh, that's a good one. See, that's what I'm saying. I think my brain was in understand natural selection mode. So my imagination grew less fertile. Yeah.

So it didn't survive. No, it didn't. And over time, basically, basketball players don't reproduce as much. Jockeys do. And over several generations, people are going to be shorter on average. Right. So it sounds almost dumb. It's so simple, but that's really the basis of it.

It is. And it's one of those things. It's like economics where it's so simple that it's hard to wrap your mind around it because you make it more complex necessarily than it is. Sure. It's very similar for me. And with that basketball example, what just happened was humanity evolved to be shorter. That was the end result.

And that evolution took place because there was a shift in the distribution of traits. So before, lots of basketball players, lots of jockeys, tallness and shortness, which are traits or variations on the trait of height in humans. We have height. We're not two-dimensional. We're inherited by who bore you. Right. Not us, your parents.

We bore you in a different way. So the variations on the trait eventually gave rise to evolution. So within just our generation or even a couple of generations, the differences in eye color, height or something like that doesn't represent evolution. But changes like that can lead to evolution over time. Yeah, if they are changes that either aid or prevent your survival. Right. Like if something happens and all of a sudden human women were all like, we're not going

to mate with anybody but blue eyes, you can bet your Bippy that within two generations there's going to be nothing but blue-eyed kids. Yeah. Or grown adults getting blue contacts. Oh, that's a good idea. Because they're tired of not having sex. Within maybe your eyes would adapt to the context and just absorb them. Something has to happen.

Your imagination is plenty fertile, my friend. And this all goes back if we can go back a little further to something called DNA. That is a chemical structure that is the basis for everything that is. Yes. Is that a good way to say it? It is. And DNA are sequences of traits, sets of traits, and those are the genes. And then there's something called the allel, which is really where it all comes together.

Is it allel or allele? Does it say allel? Uh-huh. Adele? No. Adele disease? Allel. Okay.

Yeah. Yeah, it's allele. So it's like a gene is like a specific sequence of DNA that produces some trait. So height. Like you have a height gene. Yes. Like when that gene is working, like you will grow. Yeah, the expression of the gene is the allele.

Yeah, that's the variation of that trait. So imagine like just a stretch of genes is like a few boxes, say five of them. And three are off. The three that will encode to make brown eyes and two are on. The two that will encode to make blue eyes. So each one's an allele, but the one that's functioning gives you blue eyes. So an allele is just a variation on a trait and a trait is produced by a gene, which is a sequence of DNA.

That variation is produced by an allele, which is a sequence of the gene. Yeah. And how often that allele shows up in a population is the allele frequency. And it's really simple. You hear allele frequency and it sounds like, oh, that's science. But it's really pretty easy. That's what they go to school for us to learn the jargon. Yeah.

So we did a really good episode on population and we're going to be talking about it here again though. So we should just say that a population is a group in one place that have sex with each other. Yeah. So like a zebra in Africa, he makes up all, he should have used real examples because he said, let's say there were zebras in South America, but I see his point. That would be a different population because they can't have sex with the zebras in Africa.

Because zebras can't swim across the ocean. Right. An lion in Africa is in a different population than a zebra in Africa because they don't do it. Right. They can't. It's an abomination. It is.

You come up with a Zion. That'd be kind of cool. I guess. Oh, that'd be sort of like a tiger probably. I don't know. Maybe that's what a tiger is. I think we just figured it out. So you were talking about populations.

Yeah. And alleles. Alleles are a real frequency. So you could conceivably quantify the allele frequency of blue eyes and the human population. Yeah. Because we transcended like the difference between Africa and South America. We have planes now. Sure.

So we all have access to sex with one another as a population. As long as you have a passport. And some money for a plane ticket. So speaking about allele frequency, the point of that whole thing is that with evolution, I guess another way to put it, the way that Gravster puts it is evolution is just a shift or a change in allele frequency. Yeah. And the reason that that change takes place is because those alleles that become more

and more widespread and distributed across the population have made that organism more likely to survive, to reproduce, and more likely to successfully reproduce. Yeah. That's it. That's it. That's evolution driven by natural selection. Do you want to quit? I don't think we could top it at this point.

No, it does get more interesting. Alleles are created in a few different ways. One is called a mutation, which you've probably heard of. These are random changes. Yeah. They are pretty rare. Like the X-Men. Yeah.

Very rare. Very rare mutants are. That's why they got to hang out with the president a lot. Yeah, but the president was also a mutant, wasn't he? Oh yeah, eventually Kelsey Grammer. No, no, no. The president was the guy with the sun with the wings. I thought Kelsey Grammer was the mutant.

No, maybe his son was the mutant and the president. Yeah, the president had a mutant son. But I think Kelsey Grammer eventually was elected president. Blue president. Oh really? Blue Harry president. So to me, the cool thing about mutations is they can be completely new traits that are introduced that are completely different than anything you've ever seen in that species.

It's pretty radical. Another way is just like we've been talking about sex a lot, reproduction just with animals, humans. That's the way that an allele can express itself. Right. It's the mixing together. When your mom and your dad love each other very much and they copulate, their sperm and egg mix together, break down their DNA in this glorious fantastic little mini explosion

inside the womb and then it recombines into a totally new form that shares part of the dad's DNA and part of the mom's DNA to make a new human. Yeah, and you get all the bad traits from each of them. Right. Hopefully you get all the best traits. But that's the point of sexual reproduction, which was itself naturally selected because it increases the potential that you're going to inherit good traits that will let you survive. That's right.

There's just more traits out there. It's like I think it was the sense of smell episode we did where we talked about pheromones, the idea that pheromones among humans, we can still detect them even though we don't know it. Yeah. And the whole reason we can is to smell out other people's immune system and we want somebody with an opposite immune system of ours so when you put the two together, it produces a little mini superhuman who can't be killed.

There was an interesting study, I think, where they just had people smelling things, engaging attraction levels. Right. But it's based on the premise of sexual reproduction, which is combining as many good traits as possible makes somebody with a lot of them, a lot of good traits. And then the final way that alleles are created is genetic recombination. And that would be in the case of like a bacteria who obviously don't go out and have sex with each other, but they do absorb DNA that they get from other bacteria and basically make

it part of them themselves. Yeah. They think that's where the eukaryotes came from. Oh, really? Yeah. The mitochondria was its own thing and it became absorbed by some ancient cell to serve as like the power center of the cell and from that like gave rise to everything with the backbone, everything that's not a bacteria basically.

So fish at first? I guess, yeah. But eventually like it all just came to that and it's still going on today. Wow. There's two organisms in one. Very neat. Yeah. That's super neat.

And then one other thing, like there are three ways that this could happen that new alleles could be introduced, but I wonder if epigenetics will eventually be added to that. You think? Over time? Yeah. Because think about it. I mean, it's a change in gene expression. Yeah.

Right? So yeah, I could see that leading to, I guess, I guess it could be classified as a spontaneous mutation. I guess it would fall under that umbrella. Yeah, but so much leads up to it. I don't know. Yeah. I'm with you.

What's that a fourth? Okay. Epigenetics is officially added as a change to alleles. I'm sure we'll get an email from someone that's super smart that will explain exactly why that won't happen. They're like, first of all, Chuck was right. It's alleles. It's probably.

We're like, hang on. So Chuck, we said that all of this starts at DNA and the fact that it changes. We actually should go back even further than that into the backdrop of nature, the environment. The reason that DNA changes, that traits change over time is because of a little thing called death. We all die. And how to avoid it? Exactly.

It's the combination of those two things. We're all going to die and all organisms appear to be driven by a desire to put off that moment as long as possible. So we have an instinct to survive, right? The problem is, is the processes of nature are trying to put us down all the time. So there is a inherent struggle to survive. So when you combine our desire to live with nature trying to kill us all the time, it forms that struggle.

The struggle to survive gives rise to the changes in genes which eventually are selected and convert to evolution. So it all begins with the struggle to survive and the desire to survive. And this is spelled out by Darwin himself. Yeah. Should we read some of his quotes? Yeah. These are from on the origin of the species, which if you just listened to the Charles

Darwin, you know that was his most famous work that he put out. One of many. But that's his, you know, war and peace. Yeah. His close second was my travels with Timmy about his pet rabbit and he going around the county bothering neighbors. So here are a few of the basic tenets on the origin of the species and with some quotes from Darwin himself.

One is that organisms show variations of variation of traits. Yeah. That's him just getting it out of the way. Like don't be dumb if you think that your dad's blue eyes and your brown eyes are evolution. You're wrong. Okay. I like that better than his quote actually. Let's do that.

Let's do Josh's take on his quote. I'll do it. I can't. All right. Number two is more organisms are born that could ever possibly be supported by the resources here on the planet. That's right. Stop being such an idiot.

There's such a thing as scarcity. Don't you know that? Man, this is great. I feel the birth of a new podcast coming. Oh no. Number three, therefore in conclusion, all organisms must struggle to live. You already kind of covered that. Oh.

Okay. Number four, some traits offer advantages in the struggle. That's right. Those are mutations and as Josh will eventually predict epigenetics. Not always mutations though. Right. Changes to alleles. Sure.

Organisms that have those traits, the ones that will help you survive, are more likely to be successful and reproduce and pass them on. That's fitness. And then finally, successful variations, the ones that we've just talked about that allow you to survive and reproduce more. They accumulate over the years and the generations as they're exposed to something we'll talk about in a minute called population pressure. Right.

And he points out too that this is essentially specific and local. Like if humans had a trait where you cooled extremely easily all the time under all conditions, it wouldn't play very well when you move to the northern latitudes. You die. Yeah. So it would be selected out of populations in the northern latitudes. But if you lived in the tropics, it would probably be selected and propagated over time because you probably have a lot more energy.

You wouldn't just be laying around fanning yourself with palm fronds. Well, you'd do that too. You wouldn't need to though. Yeah, but it's just a nice experience. So I mentioned population pressure and that's a key here to understanding this whole bowl of soup. And we'll talk about that right after this message. I'm Mangesh Atikular and to be honest, I don't believe in astrology, but from the moment

I was born, it's been a part of my life in India. It's like smoking. You might not smoke, but you're going to get secondhand astrology. And lately I've been wondering if the universe has been trying to tell me to stop running and pay attention because maybe there is magic in the stars if you're willing to look for it. So I rounded up some friends and we dove in and let me tell you, it got weird fast. Electric curses, Major League Baseball teams, canceled marriages, K-pop.

But just when I thought I had to handle on this sweet and curious show about astrology, my whole world can crash down. Situation doesn't look good. There is risk to father. And my whole view on astrology, it changed. Whether you're a skeptic or a believer, I think your ideas are going to change too. Like the Skyline Drive and the I Heart Radio app, Apple Podcast, wherever you get your podcasts.

On the podcast, Paydude the 90s called David Lasher and Christine Taylor, stars of the cult classic show, Hey Dude, bring you back to the days of slip dresses and choker necklaces. We're going to use Hey Dude as our jumping off point, but we are going to unpack and dive back into the decade of the 90s. We lived it and now we're calling on all of our friends to come back and relive it. In the podcast packed with interviews, co-stars, friends, and non-stop references to the best decade ever. Do you remember going to Blockbuster?

Do you remember Nintendo 64? Do you remember getting frosted tips? Was that a cereal? No, it was hair. Do you remember AOL Instant Messenger and the dial-up sound like poltergeist? So leave a code on your best friend's beeper, because you'll want to be there when the nostalgia starts flowing. Each episode will rival the feeling of taking out the cartridge from your Game Boy, blowing

on it and popping it back in as we take you back to the 90s. Listen to Hey Dude, the 90s, called on the iHeart Radio app, Apple Podcasts, or wherever you get your podcasts. All right, so here we are in the stew, I called it soup, it's really a stew of evolution and selection. Oh, okay. So we need to talk about population pressure, which is basically anything in a population that makes it tough for your species.

Are you, as an individual, plant or animal to survive it? Yeah, again, because there's such a thing as scarcity that means you compete with people in your species or people outside of your species, right? Like a lion wants to eat you. Yeah, there's always, it's always going on. Yes. And then even if you lived in total harmony with all the plants and animals around you and vice versa, nature's still shooting lightning bolts at you.

Yeah, flying. Yeah, floods, droughts, famine, all that stuff. There is always, as Darwin put it, every organism struggles to survive one way or another. Yeah, and that can really speed things up as far as allele frequency change. If you flooded out an entire country, you're going to see some big changes within a generation or two. It's not necessarily over hundreds of years. That's right.

And that's because when you have something, especially like a flood or a drought or just some severe increase, sudden increase in population pressure, it goes from just background population pressure to something very acute and pronounced. Yeah. A lot of the population dies off. Yeah, like his example is pretty great actually about the fire. Let's say a fire killed all the vegetation under 15 feet and a population of giraffes, anything under 15 feet is going to have a hard time reaching food.

And so they're going to start reproducing and making taller giraffes pretty much as fast as they can. Right. The ones that can't reach food will die off. A lot of them, before they can reproduce, the ones that can reach food will live to reproduce, which will produce those taller giraffes. And what just happened then in that giraffe example is called a population bottleneck. Something happened that took a large population, reduced it down to a smaller amount.

And then usually in that smaller group, there's going to be some traits or whatever that used to be evenly distributed among the population that are now really concentrated and clustered. And like it could be something super rare that is now the trait. Right, exactly. When you have a super rare trait spread out very evenly among a large population, that trait may or may not ever be selected. And if it is selected, it may take a very long time to be selected because there's so many other competing traits.

Yeah. Well, when a lot of those other competing traits are narrow, weeded out, and you have that population bottlenecked, those traits are going to be very pronounced and they're going to be selected very quickly. So you have a very quick change in evolution as a result of sudden acute population bottlenecks. Yeah, it basically becomes the norm. So in that area of where the fire ended up killing shorter giraffes, the norm will now be super tall giraffes.

Exactly. And don't say Chuck, all giraffes are super tall. Super super tall. Super super tall. And this apparently happened to humans. There's a population bottleneck supposedly around 70,000 years ago. There was something called the Toba eruption, a huge super volcano that created like a six to 10 year long winter and dropped the number of humans, homo sapiens down to something

as low as possibly 3,000 people. Wow. Yeah. So they're not on the planet. On the whole planet. Wow. And they're not quite sure like what variations were selected out of that. But you can bet there was an enormous change within 20, 30, 40 years of that event.

Boy, I wonder what it was like before that. Right. It's pretty interesting. So let's say the giraffes, like everything was hunky dory, no fires, no nothing. But just some of them decided that they wanted to see if there really are no such thing as zebras in South America. So they hop on a boat and they sail to South America and they establish a new little giraffe colony there.

Yeah. What will result from that is called the founder effect. And there is a band, by the way, already looked. No. It's got to be one. And it is. Huh. And I listened to their song.

How was it? It was pretty good. What kind of music? You know, sort of. Giraffe. Indie, giraffe-y, shoegaze-y. Oh, okay. Not bad.

Cool. So anyway, yeah, founder effect is when you quite literally when a population founds a new area and don't have sex with that other population anymore. Right. So you can have very different traits from even if it's a giraffe from the ones in Africa because they set up camp in a new place. Right. And it's almost like an unforced bottleneck.

Yeah. You know, like a voluntary bottleneck. Yeah. Nature didn't kill off a bunch of the population. The population just broke off from a larger group to a smaller group and that smaller group's probably going to have some weird trait or two that are going to be selected. Yeah. And then push evolution along faster than usual.

Yeah. All right. Let's talk about this then. Okay. Let me pose a question to you, sir, that I know the answer to. What about things that don't evolve anymore, buddy? What about like the shark that's been about the same for millions of years? Show me your natural selection there.

I got this. Okay. So sharks are a great example because they haven't changed in millions of years. Because they don't need to. Well, because basically they became apex predators a long time ago in their environments and their environments went unchanged enough so that sharks didn't need to change. They are basically as far as natural selection goes. Perfect.

Yeah. They early on figured it out. It was like, all right, I've got my teeth are in our great. My gills are working. I can sense electrical impulses from fish flap. Yeah. I can swim super fast. I can kill everything I see.

As long as something doesn't punch me in the nose, I'm pretty much good. Yeah. Or kill me for my shark fin. Well, that's, yeah, it makes you wonder how sharks are going to evolve now. Yeah. That's a good point. But let's say pre-human fishing. So 200 years ago, up from several million, maybe tens, I don't remember how long sharks

have been around virtually unchanged. The long time. Yeah. So let's say from millions and millions and millions and millions and millions and millions of years ago. Okay. Up to 200 years ago. Uh-huh.

Sharks are virtually unchanged. Yeah. Because they hit their peak and they're fine. But that doesn't mean that they have gone unchanged. Yeah. Or that natural selection hasn't exerted an effect on them. Basically, what happens is they're still undergoing mutations through reproduction. There's new alleles showing up.

But none of them can hold a candle to the perfection that's been achieved by the shark. So they get selected out. They don't get a chance to reproduce in the population or become distributed amongst the population. Yeah. So you still have natural selection weeding out. But rather than changing the shark population or the shark species or family, family, you have natural selection as an agent of stability.

I'm Mangesha Tickler. And to be honest, I don't believe in astrology. But from the moment I was born, it's been a part of my life. In India, it's like smoking. You might not smoke, but you're going to get secondhand astrology. And lately, I've been wondering if the universe has been trying to tell me to stop running and pay attention. Because maybe there is magic in the stars if you're willing to look for it.

So I rounded up some friends and we dove in and let me tell you, it got weird fast. Curses, Major League Baseball teams, canceled marriages, K-pop. But just when I thought I had to handle on this sweet and curious show about astrology, my whole world can crash down. Situation doesn't look good. There is risk to father. And my whole view on astrology, it changed. Whether you're a skeptic or a believer, I think your ideas are going to change too.

On the Skyline Drive and the iHeart Radio app, Apple Podcast, or wherever you get your podcasts. On the podcast, Paydude the 90s called David Lasher and Christine Taylor, stars of the cult classic show, Hey Dude, bring you back to the days of slip dresses and choker necklaces. We're going to use Hey Dude as our jumping off point, but we are going to unpack and dive back into the decade of the 90s. We lived it, and now we're calling on all of our friends to come back and relive it. On the podcast packed with interviews, co-stars, friends, and non-stop references to the best decade ever.

Do you remember going to Blockbuster? Do you remember Nintendo 64? Do you remember getting frosted tips? Was that a cereal? No, it was hair. Do you remember AOL Instant Messenger and the dial-up sound like poltergeist? So leave a code on your best friend's beeper, because you'll want to be there when the nostalgia starts flowing.

Each episode will rival the feeling of taking out the cartridge from your Game Boy, blowing on it and popping it back in as we take you back to the 90s. Listen to Hey Dude, the 90s called on the iHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Yeah, or I guess let's do a hypothetical. If we were going to use shark finning as an example, let's say only sharks with perfectly triangular gray fins were selected out to be finned and cut off for shark fin soup. So that means sharks that have weird spots on their fins would not get killed.

So theoretically, hypothetically, over generations, we might see sharks with only spotted fins. And that probably will happen, because of the sudden and acute population pressure being exerted on sharks by humans. There has to be some sort of forced adaptation that's going to occur. Yeah, I don't know what the criteria for a good fin, though, is, or if they just take them all, like whatever they can catch. Right. But I mean, it could be as simple as something like figuring out that they, like just swimming

deeper and not coming up within the human's grasp. Yeah, it can be a behavior. They'll evolve to, like, just, yeah, to stay, yeah, we should say that's a really good point. A trait isn't necessarily something that is visibly apparent, like at, like, height or something like that. It can be an ability or a proclivity. Like Gravster uses the example of dogs have evolved the trait of hanging out with humans. And Chuck, tell them about the elephants, because that's a pretty good example of what

we're talking about with sharks. Yeah, yeah. Well, elephants, as we know, are killed many times for their ivory tusks. And it's sort of a, well, it's a good news, bad news scenario. You would think, hey, good news, there's some elephants that were being born without tusks at all. Right. So they're not being hunted.

And over the years, now there, it went from, like, two or three percent. One percent. One percent. In 1930. To, like, close to 40 percent now are not born with tusks. Right. So you think that's awesome, because now they're not being hunted, but they need those tusks for digging in defense and things like that.

Right. So they're losing a valuable trait, which is going to put stress on the population as a whole, I would think, over time. But in the near term, it's been selected up because it's keeping the elephants alive, because the ones that were naturally without tusks weren't being killed by poachers, so they were allowed to reproduce more frequently than ones with tusks that were being killed. So yeah, you have a, within a human lifetime, within 70 years or so, the population has evolved.

Yeah. That's what I mean by, like, you can see it happening in front of us. Right. So that's where the debate comes from, where I was saying, like, scientists even debate on how evolution changes or happens. And there's basically the difference between gradualism or punctuated equilibrium. And gradualism is just, over time, very slowly, new alleles appear, and some of them tend to make organisms fitter.

And so they'll eventually, over very long stretches of time, be selected out. And then punctuated equilibrium is, like, we were talking about with the African elephants, where there's a sudden population pressure, and all of a sudden, this organism or species is forced to evolve, and they do, and then after that, everything evens out for a little while and stays the same until the next catastrophic event. Yeah. I don't get it. There are, it says there's an ongoing debate about that, can't they both exist?

I don't understand why they don't both exist. It seems like one is just constant background evolution, and the other one is, like, evolution as a result of, you know, sudden acute crises. Why wouldn't they both exist? I don't know. I don't understand it either. I'll have to look into that. Okay, Chuck.

So let's go a little further and, well, I guess we'll go back to genes, but remember, you know a guy named Richard Dawkins, right? Yeah. He wrote a book in the 70s called The Selfish Gene, and it basically, we were talking about, you know, the debate between gradualism and equilibrium, punctuated equilibrium. Well, Dawkins came along and said, you guys shut up for a little bit. Let's talk about this, the selfish gene, and he just basically reframed the entire way that people look at evolution.

Yeah, I thought, I think it's pretty interesting. The essence of it is that as long as you reproduce, then natural selection doesn't care about you after that. Right. So after you've passed on your genes, that's the important part, and in the case of spiders is one great example. Sometimes the male gets eaten right afterward. Yeah, or like praying mantises, didn't the female eat the male's head?

Do they? Like bite the male's head off? I don't know. And we're talking about praying mantises, so it's okay to say female. In that case though, both those cases, natural selection doesn't care. The male has done his job. He has propagated and passed down the allele, and it doesn't matter if he dies or not right afterward.

It doesn't put any stress on the population. No, and that's like a really, that was a tricky thing before Dawkins came along. It was like, wait a minute, there's a real problem with natural selection. If the whole point is for something to be able to reproduce and reproduce successfully, why would there be adaptations that kills its own? Yeah. Like the organism is killed, like as a result of reproduction, that doesn't make any sense. And Dawkins came along and said, it does make sense if you stop looking at organism and

start looking at the genes. Yeah, basically none of that matters. So he made his point so well that it actually got a little bit out of hand, and it came to be known as, well it was the selfish gene before, but basically it was, he characterized it so well that it became a character. Genes became a character. Just like they had hijacked organisms, and we're using them as husks to pass along themselves, like a virus or something like that.

And Dawkins came out a number of times and is like, no, that's the wrong interpretation. That's not what I mean. But it's still essentially the same thing. It's just... We're just vessels. Yeah. Yeah, we are. We are a means of passing along our genes, and if you look at it through the lens of

natural selection, as long as the genes are able to be passed along, the vessel is no longer necessary. So therefore, the head can be bitten off by the woman. That's right. But like we said, this isn't widespread, but it does help explain things like spiders. Right. You know? But there's a big flaw in this selfish gene theory, right?

Well in Dawkins, theories is a whole. Right. And the flaw is that there's such a thing as altruism. Yeah, and this is, you know, humans and animals that for no reasons based on natural selection desire to help each other. It doesn't benefit you in the least at all. No, as a matter of fact, it can harm you before you're able to reproduce. So even from the genetic level of the selfish gene, it doesn't make any sense because the

genes are allowing the organism to be harmed before it could possibly reproduce. Well, why does someone have an instinct to jump in an icy river to save somebody? Right. And they have found that it is instinctual and that it happens in infants with like zero cultural training. It's like part of us. Yeah, and it's not just humans either. There are plenty of animals that display altruism as well.

Like meerkats are big on altruism. Yeah. And I like the explanation that makes, again, total sense to me, something called kinship. If you've got a couple of different families, Tuk-Tuk's family and Bartok's family, well, Bartok was a composer, but what's another good caveman name? Mongo. Yeah, that's a great one. So Mongo's family is very selfish.

They don't like to share their stuff. They're all competing for the same food. Right. Tuk-Tuk's family is very generous. They like to share things. So over time, they will be a more successful family because they have been altruistic and shown that kinship. And they're improving their chances of success by combining their efforts into a group effort,

right? Yeah. Which is kind of like that Paleolithic warlessness we talked about in the Cave Dwellers episode. Oh, yeah. Where everybody just kind of figured out that they could be more successful if they stopped fighting and started harvesting together. Yeah. And if you kind of look at it like that, like everybody coming together as a group for a

common goal, you're also looking at super organisms. Yeah. Have we done one on ants specifically? No. I think we should. I agree. Because they are about the best example of a super organism. It's basically the little worker ants aren't doing the reproducing.

They can't even reproduce their sterile. That goes to the top dogs. They only get to do that. So all those little worker ants aren't even passing on their genes, but they're still busting their little ant butts for the colony. Yeah. And a super organism basically then is to step back and say, let's not look at ants, but let's look at the ant colony.

As an organism. As one organism. And that explains the altruism in that ant of sacrificing its own ability to pass along its genes in order to serve the colony as a whole. Then it makes sense. Like papa ant is going to pass down the genes. I just need to make sure papa ant has food and water. Right.

And you can also use that same argument to explain why, it would make sense if you jumped in to save your son from a river. That kinship explains that. Sure. But why would you jump in to save someone else's son? Well if you look at it like this kid's part of the same species and shares a lot of the same genes as you, you're ensuring that your species genes are passed along. Yeah, and you get to humble brag on Facebook.

Yeah, I'll bet big time. Oh, pretty boring day. Just saved a kid from the river and the icy river. No biggie. Yeah. Just helped ensure his genes get passed along. I guess a humble brag though would be, well it looks like my shoes are ruined that I just bought jumped into an icy river and saved the kid.

Yeah, that'd be good. We should start just doing fake humble brags on Twitter, Facebook. Oh, this brand new BMW I got has the windshield wipers are busted. Not a day for it. It's raining. That's just being a jerk. Okay. All right, so now we should talk about something that also excites me.

The stigial and atavistic traits. All organisms carry some trait that is really no benefit and really is no longer expressing itself as a means to help you survive. But it's not harming you either, so it hasn't been selected out. So it's just there. And I've got some pretty good examples in the human body. One, some are behavioral, some are actual organs, like the appendix. Many people think the appendix is a vestigial organ.

I heard that it might fight cancer. Well, now scientists are starting to say we think it might fight cancer or it might house bacteria that helps you aid in digestion. So everybody whose appendix we took out, get in line, we're going to put them back in. But for many years, and I think the debate is still out whether or not it is a remnant from primate ancestors when we had to digest like plants like super rich and cellulose or something. Yeah, I got you.

But we don't anymore. So that's why the appendix really does nothing. Back when we were giant termite men. That was a scary time. Sinuses? That was what we were like on the other side of the population bottleneck, giant termite people. Sinuses supposedly may, it's also debated, but they're pockets of air in your face and

no one really knows if they serve any kind of biological function or not. Yeah, and they kind of suck too because they get infected. They can get infected. The coccyx is pretty exciting because it's a tailbone that used to be a tail. And some people are still born with them. Yeah, and the people who are born with tails are adivistic, those are adivisms. It's a vestigial remnant that expresses itself very closely to the way it actually used to be.

It's not just a trace of it any longer. It's like that allele saying, hey, maybe we should go back to tails again. What do you think? Yeah, it's not just so you don't picture a human with a big four foot long monkey tail. It's usually like a bump or something. Didn't George Costanza have a tail and was that one Jack Black, Fairleigh Brothers? Oh, yeah, yeah. Shallow howl.

Yeah, yeah. I think you're right. And he could wag it. I don't remember that. What else? Oh, here's a behavior of vestigial behavior, the palmar grass reflex. Oh, yeah. I thought this was cool.

When you go up to a little stinky dirty human baby and you put your finger in their hand or their foot even, it's going to grab it like super hard and super strong. Yeah, like Popeye basically. Or like a little baby monkey trying to hang on to mama cruising through the jungle. Through the, grabbing onto the coat, their mom's coat. Yeah, so basically that's a behavior they think is like a human baby now doesn't need to grasp hold of something that hard at six weeks old. Yeah.

What's the behavior? Maybe. So we, we played tennis thanks to vestigial behavior and ability. Oh, got it. Being able to grip that racket. Yeah. What's, what article is this from? Is it, um, was it I09 OD?

Yeah, I think so. I09. It was kind of silly, but these are some pretty decent examples. Yeah. We talked about male nipples before. Yeah, we did. We did a whole episode on Goosebumps. The Erector Pilly, I've never heard of this.

Oh, I did a dumpy dump on it. Oh yeah? Yeah. You want to explain what it is real quick? No, you go ahead. Okay. Um, everyone has had Goosebumps. The Erector Pilly are those muscle fibers that give you Goosebumps when you don't even

necessarily want them or need them. Right. There's little muscles that are attached to your hair follicles. Yeah. Whether you have hair there or not any longer. Right. You can dress it up so that your hair stands on and either to make yourself look bigger so you're scary.

Right. Or because you're cold to make your coat fluff out, as in when we used to have coats because we were animals. Another vestigial trait. And my favorite one, aside from tonsils, is the Pleica semilunaris. Did you like how you asked me if I wanted to do it and I was like, no, and then I did it anyway? Yeah, I knew it.

I was going to. Uh, if you look in your mirror and you look at your eyeball and you look in the little inside corner of your eyeball, um, you're going to see a little fold of tissue and it's not the little bump, but it's that little thing in the inside corner of your eye. That is a remnant of a third eyelid. What's it called? What kind of eyelid? It's the PLICA Pleica semilunaris.

And apparently we had third eyelids that were clear so you could like wash your eye and still keep an eye out for predators. Right. And they would come from the sides rather than up and down, they moved horizontally. Exactly. Yeah. Like a snake or a reptile. Yeah, or a bird.

They still have them. We do not, but we still have that in the corner of our eye, even though it does nothing. So here's the thing, we have the genes then to make that. Yeah. If we'd needed it again. So that allele could possibly come back. Like we could have people who were born with that and like if it ended up helping us, um... Like if we could sleep with our eyes open to watch the zombie invasion.

Or to watch TV better, 24 hours a day. Uh, just the fact that we can wiggle our ears. That's a vestigial trait. There's no reason why we should be able to wiggle our ears. Watch this. I can wiggle mine. Can you do them one at a time? You're wiggling your eyebrows.

I'm wiggling my whole face. I know. Can you do them one at a time? That's pretty impressive actually. Yeah. Well that means... It drives, like, you mean going bananas right now, she hates it so much. Uh, that means that maybe Josh's ancestors, uh, were a little closer than mine and as

far as, uh, monkeys directing their ears to listen out for predators. Yeah. No, it means I'm less evolved. Yeah. I have the ability to move ears so I can hear things that I don't need to anymore. Yeah. And I'm fairly hairy. So this has been a depressing episode for me in that respect.

I didn't want to mention any of that stuff. So, uh, Chuck, we talked about, um, African elephants, you want to give a couple more examples of, uh, natural selection and action. The ball worm, sometimes it happens super fast. In the case of the ball worm, it's happening faster than we can create toxins to kill them. Yeah. Like they treat cotton now with, uh... No, they genetically engineered it, so cotton produces it itself.

Yeah. I guess it's not treating. I guess it is in a way. Originally treated cotton, but now cotton is growing with this toxin that is supposed to kill ball worms, but enough ball worms, uh, were immune to that, that they were the ones that went on to do the most reproducing to eat the cotton. Right. So that first generation of ball worms were like, I'm so wasted off this cotton, but I'm

alive. Uh, and then the clovers, some species of clover have a mutation that, uh, made poison cyanide, uh, leak from its cells, causing it to be bitter, therefore it wouldn't be eaten. Isn't that weird? Yeah. Just that the clovers, like, don't eat me. Yeah.

I make cyanide somehow. Yeah. But unfortunately, uh, when the temperature drops below freezing, the cells rupture releases that cyanide into the plant and it kills itself. However, in warm climates, that doesn't happen. So what you end up with is clover in warmer climates that's completely different structurally, cellularly than the one in the colder climate. Yeah.

The warmer ones produce cyanide. The ones in the colder climates don't. Same clover. It's very much like that example of, um, you know, the humans that can cool constantly right playing well in the tropics, but not in North. Pretty cool stuff. Yeah. Man, I love this.

Me too. You got anything else? I got nothing else. Oh, well, let's talk about ourselves a little bit real quick. Really? Yes. What's your sign? I'm a Pisces.

I can't wiggle my ears. Um, no, humans, like we have, like I was saying, we have jets now. So like we're one large population, right? Yeah. Um, that's just one example of how we've essentially taken ourselves out of the evolution game. Yeah. We even more to the point we have such thing as birth control, artificial birth control. Yeah.

Um, we have a lot of different things that we do inadvertently or advertently to, um, to adapt to change ourselves, to change our ability to reproduce whatever. Yeah. So I wonder then, are we, um, out of the evolution game already forever? Will we ever be able to, if we're not, and out of the game? Yeah. Yeah. And I mean, is that the case?

I think transhumanism is to, to say so long suckers the evolution and just be totally in charge. But I also wonder like, um, with birth control, birth control is an artificial, it's, it's unnatural selection. Yeah. It's artificial blockade to reproducing. Right. Which flies in the face of natural selection.

My question is, is natural selection enough of a, um, powerful process that eventually, um, women are going to start evolving in immunity to birth control. Uh, yeah. Or is human ingenuity so strong that it's like we've got natural selection beaten. It's just gone down. It's done for us aside from fires and floods and famines and droughts and all that. But I mean, like on that graduated or gradual background natural selection, right? Or have we taken ourselves out of that?

I wonder. Is it enough of a population pressure to have the effect to begin with? Yeah. Just from the fact that there's so many humans that, that there's scarcity exists. True. So I guess not. I guess we just answered my question, man. I really didn't think it was going to get answered, but it just did.

Wow. We're still under the effects and influence of natural selection. It's a podcast miracle bow before natural selection humans. I want to take a second to say hi to all the sixth through ninth grade science classes who are listening to this right now. I assume there's at least one or two. Hi guys. Hi.

Okay. So natural selection, right? Yes. All right. Uh, if you want to learn more about natural selection, you can type those words into the search bar at housetoforks.com. It will bring up a world class article by the Grabster. Uh, and since I said search bar, it means it's time for listener mail.

Uh, I'm going to call this, uh, we're curing people of disease. Nice. Uh, hi guys. And Jerry, you have a very large, uh, in a very large way, help cure my six year old niece Eva of Lyme disease. For several months, she experienced a series of strange symptoms that didn't seem to relate to one another, including infection, muscle weakness, double vision. After months of testing, her doctors were at a complete loss as to what to do and what

was wrong, uh, because the once cheerful, enthusiastic little girl began to withdraw. She was unable to go to school for periods of time and quit all her beloved after school activities. Oh, um, one day she said to my sister, mommy, uh, there are two of you. One is up here. One is down there. Which one is the real you? Another alarming and creepy, creepy statement was my legs don't work anymore.

Enter uncle Josh and uncle Chuck. After listening to the podcast on how ticks work, I encouraged my sister to have my niece tested for Lyme disease, despite not having any evidence of being bitten or being in a region known for deer ticks. She was tested and indeed did have Lyme disease. That is awesome. Uh, uncle Josh and uncle Chuck really saved the day on this one. Ava was in pain, confused and very afraid because she didn't understand what was happening.

Uh, none of the doctors suspected Lyme disease and I never would have pushed for it without, uh, or even tested for it in the first place. If your podcast hadn't tipped me off to the possibility. That is so cool. This girl owes like her well being to us, uh, and to the doctors that have helped her to a lesser extent. After the treatment, she's back to her old happy studios and energetic self. She's a brilliant young girl and we'll have a bright future.

Thanks to you guys, uh, having her back and making her full recovery possible. Much love Michelle Mariani. That's awesome. Thanks for letting us know that Michelle Ava, right? Yeah, it's really neat. Way to go Ava. Way to, uh, beat that Lyme disease. Stupid ticks.

Hate ticks. I even hate the tick episode. Oh, that was a great one. We need to do a Lyme disease episode when supposedly it's very controversial and I've never really looked into it. Okay. I've heard you could make money selling your blood. I don't know if that's true.

Oh, it is. Oh, okay. Uh, you have to do on the black market though, because they don't pay on the regular market. Gotcha. It's all like, I'm a do-gooder. Right. Um, so, uh, if you want to get in touch with Chuck and I to let us know how we helped you or relative out, we'd love hearing that kind of stuff, or you can just get in touch to

say hi or whatever you want. You can tweet to us at SYSK Podcast, hang out at our Happening Facebook page, facebook.com slash stuff you should know, send us an email to stuffpodcast.discovery.com, check out our YouTube channel, look for Josh and Chuck, and as always, join us at our home on the web, stuffyoushouldknow.com. For more on this and thousands of other topics, visit HowStuffWorks.com. I'm Munga Chauticular, and it turns out astrology is way more widespread than any of us want to believe.

You can find it in Major League Baseball, international banks, K-pop groups, even the White House. But just when I thought I had a handle on this subject, something completely unbelievable happened to me, and my whole view on astrology changed. Whether you're a skeptic or a believer, give me a few minutes, because I think your ideas are about to change too. Listen to Skyline Drive on the iHeart Radio app, Apple Podcast, or wherever you get your podcasts.

Hey guys, it's Cheekies from Cheekies and Chill Podcast, and I want to tell you about a really exciting episode. We're going to be talking to Nancy Rodriguez from Netflix's Love is Blind Season 3. Looking back at your experience, were there any red flags that you think you missed? What I saw as a weakness of his, I wanted to embrace. The way I thought of it was, whatever love I have from you is extra for me. Like I already love myself enough. Do I need you to validate me as a partner?

Yes. Is it required for me to feel good about myself? No. This episode will be on the iHeart Radio app, Apple Podcast, or wherever you get your podcasts.