In this episode, we climb up, down and all around our evolutionary family tree. When did we branch off from our more ape-like ancestors? And will we evolve one day into a different species altogether? We'll meet a bearded scientist from 160 years ago (no, not Charles Darwin) and eat some sundaes (thanks lactase persistence!). Plus a brand new Moment of Um answers the question: Do insects have the same blood as humans?
More on genetic drift:
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MIGUEL: You're listening to Brains On!--
EMMANUEL: --where we're serious about being curious.
SPEAKER 1: Brains On! is supported in part by a grant from the National Science Foundation.
MIGUEL: Hey, Emmanuel.
EMMANUEL: Yes, Miguel?
MIGUEL: I've been thinking, you know how humans evolved over time? Our species is called Homo sapiens. But we evolved from a different species like maybe a Homo erectus. So does that mean we're still evolving?
EMMANUEL: Whoa.
MIGUEL: Yeah.
EMMANUEL: Like maybe one day there will be a new species that evolved from us? Maybe they'll be super tall and super strong?
MIGUEL: Maybe.
EMMANUEL: And be able to sense when something is going to happen?
MIGUEL: Um, sure.
EMMANUEL: And have super speed and agility?
MIGUEL: Um.
EMMANUEL: And be able to climb buildings and shoot webs from their wrists?
MIGUEL: OK. Now you're just describing Spider-Man. Homo Spider-Man, yes! All right. All right. Let's get some answers for you. Brains On! headquarters, here we come.
[THEME MUSIC]
MOLLY BLOOM: This is Brains On! from American Public Media. I'm your host Molly Bloom. And today my curious co-hosts are siblings Miguel and Emmanuel from San Diego. Hello!
MIGUEL: Hi.
EMMANUEL: Hi.
MOLLY BLOOM: Today's episode started with a pair of questions.
JULIAN: Hello. My name is Julian from Sydney, Australia. And my question is, are humans still evolving? And what are they evolving into?
EMMA: Hello. My name is Emma, and I'm from Nevada City, California. My question is, why aren't apes still evolving into humans?
MOLLY BLOOM: Those are fascinating questions. And Miguel and Emmanuel think so too. They also wrote to us about evolution. Do you remember what your question was that you wrote to us?
MIGUEL: How did humans evolve from apes?
MOLLY BLOOM: So when you look at an ape, do you see the similarities between apes and humans?
MIGUEL: Um, yeah. And they have similar facial features, and they use body language as humans do. And they also have opposable thumbs.
MOLLY BLOOM: Is there anything that primates can do that you're jealous of?
EMMANUEL: Yeah.
MIGUEL: Yes, climb, yeah.
EMMANUEL: And swinging from trees.
MIGUEL: Honestly, if we could just be able to live among the trees, it would help our society instead of just being a ground-based animal that really just taking over the planet.
EMMANUEL: We would lose a lot of pollution.
MIGUEL: Yeah.
MOLLY BLOOM: Very interesting. Well, we've had a lot of listeners curious about evolution. And here are just a few more of them.
[MUSIC PLAYING]
DASHIELL: Hello. My name is Dashiell from New York City. And my question is, how do species evolve into new species?
JONATHAN: My name is Jonathan from Leesburg, Virginia. And my question is, how does evolution work?
PARKER: Hi. My name is Parker from Trumbull, Connecticut. Here is my question. How do animals evolve?
[MUSIC PLAYING]
MOLLY BLOOM: Let's start with the basics. Evolution, what is it, and how does it work?
ALFRED RUSSEL WALLACE: Well, if you want the real scoop on evolution, why not ask someone who helped discover it by studying animals in the wild? Like me?
EMMANUEL: Wow, is that--
ALFRED RUSSEL WALLACE: Why, yes, it is me.
MIGUEL: Charles Darwin?
ALFRED RUSSEL WALLACE: Alfred Russel Wallace. What? No. I'm not Charles Darwin.
MIGUEL: I just thought. Dude with gnarly white beard, study animals, discovered evolution, seems like Charles Darwin.
ALFRED RUSSEL WALLACE: I'm Alfred Russel Wallace, the other dude with a gnarly white beard who studied animals and discovered evolution.
MOLLY BLOOM: Oh, right. Alfred Russel Wallace, you came up with the theory of evolution around the same time as Charles Darwin in the mid 1800s.
ALFRED RUSSEL WALLACE: Yes. Thank you.
MOLLY BLOOM: But you both did it on your own in completely different parts of the world. Darwin worked on the Galapagos Islands. And you were in what's now Indonesia.
ALFRED RUSSEL WALLACE: Nah, I remember it like it was 160 years ago.
MOLLY BLOOM: It was 160 years ago.
ALFRED RUSSEL WALLACE: I had studied all the wonderful creatures there-- bizarre birds, brilliant butterflies, so many kinds of beetles. Seriously, why are there so many beetles? Anyway, by studying these animals in old fossils, it was clear to me that over generations and generations, animals and plants changed, they evolved. They'd slowly develop new traits, and those traits would be passed on. And eventually, future generations would be so different that they'd basically be something totally new. But how and why? Then it hit me.
[SUSPENSEFUL MUSIC]
I was stuck in the jungle, and I had a terrible fever. As I lay in bed, tossing and turning, thinking all this over, I had a revelation. The driving force was competition. The animals that had traits to help them outcompete the others would thrive. Those that didn't would perish. I was-- how do you say it-- totally mind blown.
EMMANUEL: That sounds like the survival of the fittest.
MIGUEL: Or natural selection.
ALFRED RUSSEL WALLACE: Exactly! The traits that helped animals survive would be passed on to the next generation because animals with those traits survived to pass them down to their kids. Let me give you an example. Imagine that you have a cow-like critter that lives in the jungle.
EMMANUEL: Does this jungle cow still moo?
ALFRED RUSSEL WALLACE: Sure, sure.
[COW MOOS]
All day, these jungle cows look for food. They either eat the grass on the ground, or they reach up and eat leaves on the trees. Now, imagine every jungle cow is a little different. Some have shorter legs, some have more spots, some have longer necks. These are just natural variations you'd find in any group of animals.
MOLLY BLOOM: Just like with people, some are shorter, some have more freckles, some have longer arms.
ALFRED RUSSEL WALLACE: Very good, Molly. Now, sometimes being different can be an advantage. Can you see how?
EMMANUEL: Well, the jungle cows with longer necks could reach the leaves from tall trees.
MIGUEL: And the shorter ones would have an easy time eating all the grass because they're already closer to the ground.
ALFRED RUSSEL WALLACE: Yes. Yes, that's it precisely. As this generation says, you've nailed it. So both the longer-necked cows and the short-legged cows do really well just eating all the food and being super healthy. They have lots of kids who look like them.
MOLLY BLOOM: So what about jungle cows who don't have long necks or short legs? The ones with medium legs and medium necks.
ALFRED RUSSEL WALLACE: Well, they have more trouble bending down to eat the grass, so the short-legged cows snatch it all up first. They also can't reach as many leaves as the long-necked cows. So they don't eat as much, they don't stay healthy, and they don't have many kids. Over time, they die off.
[COW MOOS WEAKLY]
MIGUEL: Sad jungle cow.
ALFRED RUSSEL WALLACE: But the other two groups, the long-necked cows--
[LONG MOO]
--and the short-legged cows--
[SHORT MOO]
--they keep doing well. The long-necks start to have babies, and some even have longer necks. They do really well and outcompete the long but not quite as long necks. Same with the short-legged cows. They have some kids with even shorter legs, who have an even easier time eating all the grass. They outcompete other short-leggies.
MOLLY BLOOM: These two groups of jungle cows are starting to sound pretty different from each other. Do the long-necked cows even know they're related to the short-legged cows?
ALFRED RUSSEL WALLACE: Well, that's how new variations of animals come about. If this goes on for hundreds and thousands, maybe millions of years, eventually, both types of jungle cow will have evolved into two different creatures.
MOLLY BLOOM: Wow. You came up with all this when you had a fever?
ALFRED RUSSEL WALLACE: Yeah. It was a bad fever, but good for my imagination.
MIGUEL: So how come everyone thinks Charles Darwin discovered evolution?
EMMANUEL: Yeah, not you, Alfred Russel Wallace.
ALFRED RUSSEL WALLACE: Well, Darwin did discover it. We both had similar ideas around the same time. In fact, our work was presented at the same conference in 1858. It's just after that, Darwin wrote a book called On the Origin of Species, while I stayed in the jungle where I was so happy. So he got all the fame and glory, but I'm not salty about it.
MOLLY BLOOM: You are very gracious.
ALFRED RUSSEL WALLACE: Well, I led a good life. And so what? Maybe my name isn't synonymous with the idea of evolution-- yet. Now that I've been on Brains On!, I'm pretty sure my time to shine is about to start. I feel-- what is it again-- #blessed.
MOLLY BLOOM: Well, thanks for dropping by, Alfred.
EMMANUEL: Yeah, thanks.
MIGUEL: Later.
ALFRED RUSSEL WALLACE: Bye.
KIDS: B-B-B-Brains On!
MOLLY BLOOM: So like Alfred Russel Wallace explained, over time, a certain animal may start out as one thing and then evolve into another thing, which brings us to this question.
LANDIS: My name is Landis from Madison, Wisconsin. My question is, how did monkey-like creatures evolve into humans?
MOLLY BLOOM: We didn't evolve from the apes alive today. Instead, both of us evolved from a common ancestor.
MIGUEL: That means a long time ago, there was an ancient relative of both humans and great apes. It probably lived in the trees, and over time, it evolved into different kinds of animals.
MOLLY BLOOM: Some of those animals went extinct, but others lost most of their fur, started walking upright, and eventually became us. Others became chimpanzees, bonobos, gorillas, and orangutans.
EMMANUEL: So the apes alive today won't evolve into humans, but over a long time, they may evolve into something new.
MOLLY BLOOM: When a creature evolves into something new, we say it became a new species.
MIGUEL: To help us understand more about the species and how they change, we're joined by Ellie McNutt.
MOLLY BLOOM: She's studying how humans evolved to walk on two feet at Dartmouth College.
MIGUEL: Hi, Ellie.
ELLIE MCNUTT: Hi.
MOLLY BLOOM: Thanks so much for being here, Ellie. And we're going to start by posing this question to you that was sent to us from Reed in Sydney, Australia.
REED: Did mammoths evolve into elephants? And if so, why did people say mammoths went extinct?
ELLIE MCNUTT: So the first kind of way to make this make a little more sense is to think that evolution is not sort of a linear path. It's not just one thing turning into another over and over and over again, kind of up some ladder or towards some goal. Evolution is a big tree branching out to the side, and there are side branches and dead ends. So what we say sometimes is like, mammoths and elephants share a common ancestor. So there was an organism that then turns into both mammoths and the elephants we know today, eventually.
The side branch that is mammoths dies out completely. So the sort of branch got cut off. It stops, and that's what we mean when we say something has gone extinct, like now that branch is ended. And there may be branches that continue that trace back to a similar route, but they are the ones that we would say are still sort of evolving. Everything alive today is under some evolutionary pressure. Mammoths didn't overnight become elephants. Mammoths and elephants are separate things that share an ancestor. They're like cousins to one another.
MIGUEL: When we think of evolution, many times we think of monkeys evolving into apes and then evolving into hominids and humans. Is that really how we evolved?
ELLIE MCNUTT: The simple answer is no because it's not this linear monkeys into apes into sort of the chimps and us. It's that branching pattern. So we have a common ancestor with monkeys and apes and the other great apes. But all of those things are alive today. As you go back into the past, you see our ancestors who have some of the same characteristics as the primates that are alive today, and they have some different ones. Though nothing is stuck in time, right?
A chimpanzee isn't sort of a fossil of 6 million years ago. They have been changing just as much as we have. So it's sort of a more complicated picture. We have kind of if you trace back these sort of the grandmothers of our species in common, but we as cousins have sort of diverged further and further away from each other. So it's not quite so simple or so kind of direct path. There's no goal, like becoming human isn't the pinnacle of things. That's not how evolution works. It's just you want to be the best animal you can be in the place where you are such that you stay alive long enough to pass your genes on to your offspring.
[MUSIC PLAYING]
MOLLY BLOOM: We're going to hear more from Ellie a little later. But first, it's time for another mystery. It's time for the mystery sound.
SPEAKER 2: (WHISPERS) Mystery sound.
MOLLY BLOOM: Here it is.
[MYSTERY SOUND]
Any guesses?
MIGUEL: Um, maracas or beans in a jar, I guess.
EMMANUEL: Yeah, like rice in a jar.
MOLLY BLOOM: Ooh, rice or beans. I think we're hungry. Well, we're going to be back with the answer a little later in the show. Do you guys know what a wormhole is?
MIGUEL: Um, yeah. A wormhole is like a portal, I guess, between one place in space to another theoretically.
MOLLY BLOOM: Yes, very good. Yeah, it's a place in the universe that connects two different spots. It may be billions of light years away or maybe just a few feet. And like you said, they're just theoretical, which means they haven't been proven to exist yet, but that will not stop our imaginations. So we want to hear from our listeners, what do you think it's like to travel through a wormhole? Emmanuel, why don't you go first?
EMMANUEL: I feel like you'd have nausea.
MOLLY BLOOM: [LAUGHS] Probably, yes.
MIGUEL: I think, I mean if they do exist, you might not get through alive because I mean it could do something to your body. And when you come out the other side-- if you do at all-- you might not be the same person. You might be someone completely different, maybe with the same personality but with different physical features.
MOLLY BLOOM: Whoa. Well, we are doing an episode soon about wormholes, and we want to hear what you think it's like to go through one. So you can record your answer and send it to us at brainson.org/contact.
MIGUEL: While you're there, you can also send us your ideas, mystery sounds, drawings, and questions.
EMMANUEL: That's what Elena did.
ELENA: What type of blood does insects have? Do they have the same as me?
MOLLY BLOOM: We'll have an answer to that question during our Moment of Um the end of the show. And we'll also read the latest group of listeners to be added to the Brains Honor Roll.
MIGUEL: Keep listening.
You're listening to Brains On! from American Public Media. I'm Miguel.
EMMANUEL: I'm Emmanuel.
MOLLY BLOOM: And I'm Molly. Today we're talking evolution. The first big idea about evolution came from Darwin and Wallace-- natural selection.
EMMANUEL: They realized that over time, animals changed, but they didn't know what caused those changes.
MIGUEL: Today, we know that these small changes happened because of something called DNA.
MOLLY BLOOM: Or deoxyribonucleic acid, if you're fancy. It's something hidden deep in every cell of every living thing. It's sort of like the blueprint or recipe for how to build a life form.
MAN 1: All right. Let's build some cells here.
EMMANUEL: For humans, our DNA is a combination of instructions we get from our parents.
MAN 1: Always check the DNA before we start construction.
MIGUEL: Some DNA is inherited from the mother and some from the father to make a new combination for the kid.
MAN 1: Hmm, looks like we're building a baby human here. All right, let's get to it.
MOLLY BLOOM: That's why we say, you've got your father's nose or your mother's eyes. It was their DNA that helped your cells grow into those features.
EMMANUEL: And combining our parents' DNA can lead to new traits. But sometimes DNA randomly mutates.
[TAPPING]
MIGUEL: That creates changes too. These changes called mutations don't come from any parent. They just happen. And once they happen, they might get passed down to future generations.
MOLLY BLOOM: So those are two ways that DNA can change and over time lead to new traits. When those traits are useful, they spread in a population thanks to natural selection.
MIGUEL: Like we saw with the jungle cows. Moo.
MOLLY BLOOM: [LAUGHS] Exactly. Other times, a trait spreads just by random chance, like how you can't always tell why a YouTube video goes viral, but suddenly, everyone is watching it.
EMMANUEL: Right. Sometimes two versions of a trait are good enough, and one just happens to get more common.
MOLLY BLOOM: Or maybe a natural disaster changes the population, like a hurricane comes through, and it wipes out a bunch of butterflies in a specific region. And just by chance, most of the dead butterflies all had spotted wings. Then spotted wings won't get passed on, not because of natural selection but because of just random Earth weirdness.
MIGUEL: When that happens, we call it genetic drift.
MOLLY BLOOM: That's an important part of evolution too. Traits don't have to be ideal or perfect to get shared. They just have to be good enough.
ROBOTIC VOICE: Brains, Brains, Brains On!
MOLLY BLOOM: All right. Let's go back to that mystery sound. You guys ready to hear it again?
[MYSTERY SOUND]
OK. So last time you were thinking beans, rice, maracas. Any new thoughts?
MIGUEL: It sort of sounded like there was a bit of, like, paper ruffling like that, like pulling paper because I've done this origami where it, like, it pops, like you make paper pop.
MOLLY BLOOM: Interesting.
MIGUEL: And it sort of sounds like that.
MOLLY BLOOM: Emmanuel, any guesses that you have?
EMMANUEL: Maybe sandpaper?
MOLLY BLOOM: Ooh. Good guesses. All right, well, here with the answer is producer Menaka Wilhelm.
MENAKA WILHELM: Hi, Miguel. Hi, Emmanuel. You guys were really close. What you just heard were sprinkles.
MIGUEL: Oh. That actually makes a lot of sense.
MOLLY BLOOM: [CHUCKLES]
EMMANUEL: Yeah.
MOLLY BLOOM: Are you guys sprinkle fans?
MIGUEL: My brother is. I'm not really much--
EMMANUEL: Yes, I am.
MOLLY BLOOM: Sprinkles on everything. Well, I also love sprinkles, rainbow in particular. But Menaka, does this have anything to do with evolution, or are we just going to make some sundaes?
MENAKA WILHELM: I mean, yeah, I love sprinkles, but I personally prefer the portability of a waffle cone. But today sundaes seem more appropriate, less risk of drippage. Oh, right. But yeah, anyway, I'm really here to talk about some of the traces of evolution that we can see in us today. I have this checklist of evolutionary adaptations for us to go through, and that's why there's about to be an ice cream party. The first trait on my list is the ability to eat or drink dairy. So can you guys eat ice cream?
MIGUEL: I can eat ice cream, and I would like rocky road.
EMMANUEL: I can eat ice cream, and I would like cookies and cream.
MOLLY BLOOM: So you both can? Did you say can?
MIGUEL: Yeah.
EMMANUEL: Yeah.
MOLLY BLOOM: OK. I also am able to eat ice cream, and I would love chocolate, please, Menaka.
MENAKA WILHELM: Perfect. So three sundaes coming up-- cookies and cream, rocky road, chocolate. Mint chocolate chip for me, so that makes four. And check, check, check, check, four lactose digesters.
MIGUEL: So what made humans able to digest dairy?
MENAKA WILHELM: Good question. I asked an expert to weigh in on that.
DORSA AMIR: My name is Dorsa Amir.
MENAKA WILHELM: Dorsa is an evolutionary anthropologist. She studies how we evolved and how our minds developed.
DORSA AMIR: All mammals have the ability to break down the sugar in milk, which is called lactose.
MENAKA WILHELM: But only baby mammals can do this. They use an enzyme called lactase. Their DNA has instructions that say, make lactase. And lactase karate chops lactose.
DORSA AMIR: So a baby drinks breast milk, and they can break that down, and that becomes a really important energy source for them. But after a few years-- so usually, up until two or three years-- after that, we lose the ability to do so. We can't produce that enzyme anymore.
MENAKA WILHELM: And without lactase, lactose causes digestive distress.
[STOMACH GRUMBLING]
Ugh, not fun.
DORSA AMIR: But in some populations, what you actually get is something called lactase persistence. So this is the case where those enzymes continue to be produced into adulthood. It's a really weird thing that no other mammal experiences. And it was largely because we started being able to use the milk from other animals into adulthood.
MENAKA WILHELM: And that lactase persistence is a trait that developed in some people thanks to--
[DRUM ROLL]
--a genetic mutation!
[GRAND MUSIC]
Once some people had that trait, it spread because being able to drink milk is useful, especially if you're hungry and there are cows around.
MOLLY BLOOM: Interesting.
MENAKA WILHELM: And in evolutionary terms, this trait is basically brand new. It's only like 10,000 years old or maybe less in some areas. OK. Let's move on to an older trait. Does anyone have a tail?
MIGUEL: Nope.
EMMANUEL: Nope.
MOLLY BLOOM: Uh, me neither.
MENAKA WILHELM: That's good, since my checklist says humans stopped having tails somewhere around 20 million years ago. But what about tailbones?
MIGUEL: We all have tailbones at the end of our spines.
MENAKA WILHELM: You're totally right, Miguel. A really, really long time ago, our ancestors use tails to balance in the trees. And eventually, tails became less important, but we've still got a tailbone left over. We call these leftover hints of past traits vestigial. So our tailbones are vestigial. Here's Dorsa again.
DORSA AMIR: As babies are developing in the first few weeks, as an embryo is developing, we actually still develop a tail. But then as time goes on in the following weeks, we actually get rid of it. So it's not the most efficient system, but that's the way that evolution has kind of figured out how to get rid of the tail.
MENAKA WILHELM: So three vestigial tailbones plus mine. Check, check, check, check. OK, how about chocolate sauce? Should I heat some up for those sundaes?
MOLLY BLOOM: Yes.
[MICROWAVE HUMMING]
What's our next adaptation on the checklist?
MENAKA WILHELM: Oh, good. There's the chocolate sauce. Oh, right. And next on the list, the palmaris longus muscle. If you take your hand and bend your palm towards you and push your pinky and your thumb together, do you see anything happening like right where your hand meets your arm at your wrist?
MOLLY BLOOM: Hmm, yeah. It looks like-- I do have a thin kind of like muscle, rope thing kind of sticking out.
MENAKA WILHELM: Do you guys have it, Miguel, Emmanuel?
MIGUEL: Uh, not really, since I have a jacket on, but I'm trying to do it.
MOLLY BLOOM: Can you roll up your sleeve?
MIGUEL: Yeah, it's what I'm doing right now.
MOLLY BLOOM: Emmanuel, do you see it?
EMMANUEL: Yeah, I see it. Yeah.
MENAKA WILHELM: So when I push my thumb really hard against my pinky, as hard as I can push with my fingers, and then I move my hand like it's pointing at my shoulder, this little skinny band, like Molly said, is starting to stick out of my wrist. And that's the tendon that connects to the palmaris longus muscle. But not everyone has it. Do you guys see it now?
MIGUEL: Uh.
MOLLY BLOOM: Not everyone has it, so it's possible it's not there.
MIGUEL: I think I have a bit of it. I don't-- at this point, I'm just like--
[LAUGHS]
MOLLY BLOOM: So three and a half checks, maybe.
MIGUEL: Yeah. OK, so three and a half. So check, check, check, and ch. Scientists think that this muscle used to help our ancestors around 15 million years ago. They might have used it to grab things or to stabilize their wrists when they were mostly hanging out in trees. But it doesn't do much for us anymore.
MOLLY BLOOM: OK. So it's a vestigial trait just like our tailbone.
MIGUEL: Hey, is there whipped cream for my sundae?
MENAKA WILHELM: Yes and yes. Our tailbones and palmaris longus were once useful, but now we don't need them. OK. Our last one, lest these sundaes get warm. Goosebumps-- do you get them? Can you make yourself get them?
EMMANUEL: Check on both.
MIGUEL: Check them both.
MENAKA WILHELM: What about you, Molly?
MOLLY BLOOM: I also get goosebumps. I don't know if I can make myself get them.
MENAKA WILHELM: Yeah, I definitely can't make myself get them, but I do get them if I'm cold, which is a lot. OK, so check, check, check, check. Four goosebumpers, but only Miguel and Emmanuel can do goosebumps on command.
[GOOSE HONKS]
Goosebumps are left over from when our ancestors had more fur. With a shaggier coat, goosebumps could puff up your fur to make you look bigger to scare off threats. Or they could also trap more heat to warm you up.
EMMANUEL: So it makes sense that we get them when we're scared or cold?
MENAKA WILHELM: Right!
MIGUEL: So if these traits don't totally help us anymore, will humans ever get rid of them?
MENAKA WILHELM: I'll let Dorsa answer that. I've got to find the cherries to complete these masterpieces.
DORSA AMIR: For something to really disappear entirely, it should be something that prevents you from surviving and reproducing in the best way possible. So there has to be active selection against it. It must be actively doing something harmful. And if it's not doing that, it's really easy for it to just kind of carry on through the generations untouched.
So for these things to really fully go away, someone who does have that versus someone who doesn't have that should be much worse at surviving. And it doesn't seem like these really get in the way of our survival in any important way. And so that's probably why they're going to be around for a long time.
MIGUEL: So the human species is probably sticking with tailbones and goosebumps at least for now, huh?
MENAKA WILHELM: Yeah, but it's kind of cool that all these leftovers tell us where we've been in an evolutionary sense.
EMMANUEL: Yeah, it is. Thanks for joining us, Menaka.
MENAKA WILHELM: Any time. Here are the cherries and--
[SPRINKLES SHAKING]
--the sprinkles from the beginning. Shall we begin on the sundae-eating portion of this segment?
MIGUEL: Yes.
EMMANUEL: Yes.
MOLLY BLOOM: Thank you for the sundaes, Menaka.
MENAKA WILHELM: Absolutely. See you guys later!
SINGERS: Ba, ba, ba, ba, ba, ba, ba, ba, ba. Brains On.
MOLLY BLOOM: Now we know where to look for some hints of our evolutionary past. But what might the future bring?
MIGUEL: Once again, we asked our pal Ellie McNutt, the evolutionary anthropologist.
ELLIE MCNUTT: So humans are still evolving. It's sometimes kind of tempting to think that evolution doesn't apply to us because we just don't have this idea that it's something that happened in the past or because of all the technology and things we surround ourselves with, it's not still occurring. In the last 10,000 years, if you look around, people with blue eyes wouldn't have existed. Blue eyes are a relatively recent evolution. You can watch changes happen to bacteria, right? Because their generation time is incredibly slow.
But humans, you know, I don't know whether it's 70, 80 years for your average lifespan. So that's an incredibly long time. And even though sometimes little changes can have great big effects, it still takes a long time for those things to spread throughout a population.
MIGUEL: Could humans ever evolve so much that a new species would branch off?
ELLIE MCNUTT: Absolutely. It's funny, it's happened a lot throughout our lineage, but because we're the only hominin species still alive today, it kind of seems like a crazy idea that we could ever split into another species. But it would require some pretty special circumstances. So we'd have to have a population of humans that were separated from our kind of major population for a long time. Speciation doesn't happen quickly.
A group of humans moved to Mars and lived there, and we never went back and forth. Maybe that might be enough to cause species to diverge, depending. So it's possible. The circumstances would have to be kind of pretty special. But it's certainly something that can happen to us.
[THEME MUSIC]
MOLLY BLOOM: Over time, the traits that species have change.
MIGUEL: Sometimes they change so much that they become an entirely new species.
EMMANUEL: Natural selection and genetic drift are both responsible for these changes.
MOLLY BLOOM: And you can see clues about how humans have evolved left over in our bodies today.
EMMANUEL: That's it for this episode of Brains On!
MIGUEL: Brains On! is produced by Marc Sanchez, Sanden Totten, and Molly Bloom.
MOLLY BLOOM: Menaka Wilhelm is our rock star fellow. Our engineers this week were Veronica Rodriguez, Johnny Vince Evans, Kurt [? Conan, ?] and Heath [? Cole. ?] Many thanks to Gabriel Nunez-Soria, Stuart Bloom, Jeremy [? Berg, ?] Kelly Harris, and Chris Walker.
EMMANUEL: You can send your ideas, questions, drawings, and mystery sounds to us any time.
MIGUEL: Just head the brainson.org/contact.
MOLLY BLOOM: And you can send us your wormhole travel ideas there too.
EMMANUEL: Now before we go--
MIGUEL: --it's time for a Moment of Um.
[CHORUS OF UMS]
ELENA: Hi. My name's Elena, and I'm from Portland, Oregon. My question is, what type of blood does insects have? Do they have the same as me?
CLAIRE RUSCH: I'm Claire Rusch, and I study insect brains. I'm a biologist. I would say that the biggest, very obvious difference between human blood, vertebrate blood, and insect blood is the color.
Our blood is red because of the molecule that is going to carry oxygen around. So we have a molecule that is called hemoglobin. It's inside the red blood cell, which are named red blood cell because of that. This molecule, that contain iron. And when it's in contact, the iron, when it's in contact of oxygen, it turn red.
In insect, they don't have this molecule, the hemoglobin. They have another kind of molecule that is composed of copper and not iron. And when copper and oxygen are linked together, are in contact of one over another, it turn blue. But I work a lot with bees, and their blood tend to be mostly transparent.
Small insect like bees or flies, what they do is they have kind of a system of pipe or tube inside them that are directly in contact with the outside, with the air, so they don't need to have this internal system to carry oxygen around because they are so small that it's not required. So when you smash an insect, and it turn red, usually it's because it was an insect that was biting you or another animal that has red blood.
[CHORUS OF UMS]
MOLLY BLOOM: My blood is racing through my veins, and these names are going to race from my lips. It's time for the Brains Honor Roll. These are the dedicated and creative listeners who keep us going by sending us their ideas, questions, mystery sounds, and drawings.
[LISTING HONOR ROLL]
[MUSIC PLAYING]
MIGUEL AND EMMANUEL: Thanks for listening.
EMMANUEL: --where we're serious about being curious.
SPEAKER 1: Brains On! is supported in part by a grant from the National Science Foundation.
MIGUEL: Hey, Emmanuel.
EMMANUEL: Yes, Miguel?
MIGUEL: I've been thinking, you know how humans evolved over time? Our species is called Homo sapiens. But we evolved from a different species like maybe a Homo erectus. So does that mean we're still evolving?
EMMANUEL: Whoa.
MIGUEL: Yeah.
EMMANUEL: Like maybe one day there will be a new species that evolved from us? Maybe they'll be super tall and super strong?
MIGUEL: Maybe.
EMMANUEL: And be able to sense when something is going to happen?
MIGUEL: Um, sure.
EMMANUEL: And have super speed and agility?
MIGUEL: Um.
EMMANUEL: And be able to climb buildings and shoot webs from their wrists?
MIGUEL: OK. Now you're just describing Spider-Man. Homo Spider-Man, yes! All right. All right. Let's get some answers for you. Brains On! headquarters, here we come.
[THEME MUSIC]
MOLLY BLOOM: This is Brains On! from American Public Media. I'm your host Molly Bloom. And today my curious co-hosts are siblings Miguel and Emmanuel from San Diego. Hello!
MIGUEL: Hi.
EMMANUEL: Hi.
MOLLY BLOOM: Today's episode started with a pair of questions.
JULIAN: Hello. My name is Julian from Sydney, Australia. And my question is, are humans still evolving? And what are they evolving into?
EMMA: Hello. My name is Emma, and I'm from Nevada City, California. My question is, why aren't apes still evolving into humans?
MOLLY BLOOM: Those are fascinating questions. And Miguel and Emmanuel think so too. They also wrote to us about evolution. Do you remember what your question was that you wrote to us?
MIGUEL: How did humans evolve from apes?
MOLLY BLOOM: So when you look at an ape, do you see the similarities between apes and humans?
MIGUEL: Um, yeah. And they have similar facial features, and they use body language as humans do. And they also have opposable thumbs.
MOLLY BLOOM: Is there anything that primates can do that you're jealous of?
EMMANUEL: Yeah.
MIGUEL: Yes, climb, yeah.
EMMANUEL: And swinging from trees.
MIGUEL: Honestly, if we could just be able to live among the trees, it would help our society instead of just being a ground-based animal that really just taking over the planet.
EMMANUEL: We would lose a lot of pollution.
MIGUEL: Yeah.
MOLLY BLOOM: Very interesting. Well, we've had a lot of listeners curious about evolution. And here are just a few more of them.
[MUSIC PLAYING]
DASHIELL: Hello. My name is Dashiell from New York City. And my question is, how do species evolve into new species?
JONATHAN: My name is Jonathan from Leesburg, Virginia. And my question is, how does evolution work?
PARKER: Hi. My name is Parker from Trumbull, Connecticut. Here is my question. How do animals evolve?
[MUSIC PLAYING]
MOLLY BLOOM: Let's start with the basics. Evolution, what is it, and how does it work?
ALFRED RUSSEL WALLACE: Well, if you want the real scoop on evolution, why not ask someone who helped discover it by studying animals in the wild? Like me?
EMMANUEL: Wow, is that--
ALFRED RUSSEL WALLACE: Why, yes, it is me.
MIGUEL: Charles Darwin?
ALFRED RUSSEL WALLACE: Alfred Russel Wallace. What? No. I'm not Charles Darwin.
MIGUEL: I just thought. Dude with gnarly white beard, study animals, discovered evolution, seems like Charles Darwin.
ALFRED RUSSEL WALLACE: I'm Alfred Russel Wallace, the other dude with a gnarly white beard who studied animals and discovered evolution.
MOLLY BLOOM: Oh, right. Alfred Russel Wallace, you came up with the theory of evolution around the same time as Charles Darwin in the mid 1800s.
ALFRED RUSSEL WALLACE: Yes. Thank you.
MOLLY BLOOM: But you both did it on your own in completely different parts of the world. Darwin worked on the Galapagos Islands. And you were in what's now Indonesia.
ALFRED RUSSEL WALLACE: Nah, I remember it like it was 160 years ago.
MOLLY BLOOM: It was 160 years ago.
ALFRED RUSSEL WALLACE: I had studied all the wonderful creatures there-- bizarre birds, brilliant butterflies, so many kinds of beetles. Seriously, why are there so many beetles? Anyway, by studying these animals in old fossils, it was clear to me that over generations and generations, animals and plants changed, they evolved. They'd slowly develop new traits, and those traits would be passed on. And eventually, future generations would be so different that they'd basically be something totally new. But how and why? Then it hit me.
[SUSPENSEFUL MUSIC]
I was stuck in the jungle, and I had a terrible fever. As I lay in bed, tossing and turning, thinking all this over, I had a revelation. The driving force was competition. The animals that had traits to help them outcompete the others would thrive. Those that didn't would perish. I was-- how do you say it-- totally mind blown.
EMMANUEL: That sounds like the survival of the fittest.
MIGUEL: Or natural selection.
ALFRED RUSSEL WALLACE: Exactly! The traits that helped animals survive would be passed on to the next generation because animals with those traits survived to pass them down to their kids. Let me give you an example. Imagine that you have a cow-like critter that lives in the jungle.
EMMANUEL: Does this jungle cow still moo?
ALFRED RUSSEL WALLACE: Sure, sure.
[COW MOOS]
All day, these jungle cows look for food. They either eat the grass on the ground, or they reach up and eat leaves on the trees. Now, imagine every jungle cow is a little different. Some have shorter legs, some have more spots, some have longer necks. These are just natural variations you'd find in any group of animals.
MOLLY BLOOM: Just like with people, some are shorter, some have more freckles, some have longer arms.
ALFRED RUSSEL WALLACE: Very good, Molly. Now, sometimes being different can be an advantage. Can you see how?
EMMANUEL: Well, the jungle cows with longer necks could reach the leaves from tall trees.
MIGUEL: And the shorter ones would have an easy time eating all the grass because they're already closer to the ground.
ALFRED RUSSEL WALLACE: Yes. Yes, that's it precisely. As this generation says, you've nailed it. So both the longer-necked cows and the short-legged cows do really well just eating all the food and being super healthy. They have lots of kids who look like them.
MOLLY BLOOM: So what about jungle cows who don't have long necks or short legs? The ones with medium legs and medium necks.
ALFRED RUSSEL WALLACE: Well, they have more trouble bending down to eat the grass, so the short-legged cows snatch it all up first. They also can't reach as many leaves as the long-necked cows. So they don't eat as much, they don't stay healthy, and they don't have many kids. Over time, they die off.
[COW MOOS WEAKLY]
MIGUEL: Sad jungle cow.
ALFRED RUSSEL WALLACE: But the other two groups, the long-necked cows--
[LONG MOO]
--and the short-legged cows--
[SHORT MOO]
--they keep doing well. The long-necks start to have babies, and some even have longer necks. They do really well and outcompete the long but not quite as long necks. Same with the short-legged cows. They have some kids with even shorter legs, who have an even easier time eating all the grass. They outcompete other short-leggies.
MOLLY BLOOM: These two groups of jungle cows are starting to sound pretty different from each other. Do the long-necked cows even know they're related to the short-legged cows?
ALFRED RUSSEL WALLACE: Well, that's how new variations of animals come about. If this goes on for hundreds and thousands, maybe millions of years, eventually, both types of jungle cow will have evolved into two different creatures.
MOLLY BLOOM: Wow. You came up with all this when you had a fever?
ALFRED RUSSEL WALLACE: Yeah. It was a bad fever, but good for my imagination.
MIGUEL: So how come everyone thinks Charles Darwin discovered evolution?
EMMANUEL: Yeah, not you, Alfred Russel Wallace.
ALFRED RUSSEL WALLACE: Well, Darwin did discover it. We both had similar ideas around the same time. In fact, our work was presented at the same conference in 1858. It's just after that, Darwin wrote a book called On the Origin of Species, while I stayed in the jungle where I was so happy. So he got all the fame and glory, but I'm not salty about it.
MOLLY BLOOM: You are very gracious.
ALFRED RUSSEL WALLACE: Well, I led a good life. And so what? Maybe my name isn't synonymous with the idea of evolution-- yet. Now that I've been on Brains On!, I'm pretty sure my time to shine is about to start. I feel-- what is it again-- #blessed.
MOLLY BLOOM: Well, thanks for dropping by, Alfred.
EMMANUEL: Yeah, thanks.
MIGUEL: Later.
ALFRED RUSSEL WALLACE: Bye.
KIDS: B-B-B-Brains On!
MOLLY BLOOM: So like Alfred Russel Wallace explained, over time, a certain animal may start out as one thing and then evolve into another thing, which brings us to this question.
LANDIS: My name is Landis from Madison, Wisconsin. My question is, how did monkey-like creatures evolve into humans?
MOLLY BLOOM: We didn't evolve from the apes alive today. Instead, both of us evolved from a common ancestor.
MIGUEL: That means a long time ago, there was an ancient relative of both humans and great apes. It probably lived in the trees, and over time, it evolved into different kinds of animals.
MOLLY BLOOM: Some of those animals went extinct, but others lost most of their fur, started walking upright, and eventually became us. Others became chimpanzees, bonobos, gorillas, and orangutans.
EMMANUEL: So the apes alive today won't evolve into humans, but over a long time, they may evolve into something new.
MOLLY BLOOM: When a creature evolves into something new, we say it became a new species.
MIGUEL: To help us understand more about the species and how they change, we're joined by Ellie McNutt.
MOLLY BLOOM: She's studying how humans evolved to walk on two feet at Dartmouth College.
MIGUEL: Hi, Ellie.
ELLIE MCNUTT: Hi.
MOLLY BLOOM: Thanks so much for being here, Ellie. And we're going to start by posing this question to you that was sent to us from Reed in Sydney, Australia.
REED: Did mammoths evolve into elephants? And if so, why did people say mammoths went extinct?
ELLIE MCNUTT: So the first kind of way to make this make a little more sense is to think that evolution is not sort of a linear path. It's not just one thing turning into another over and over and over again, kind of up some ladder or towards some goal. Evolution is a big tree branching out to the side, and there are side branches and dead ends. So what we say sometimes is like, mammoths and elephants share a common ancestor. So there was an organism that then turns into both mammoths and the elephants we know today, eventually.
The side branch that is mammoths dies out completely. So the sort of branch got cut off. It stops, and that's what we mean when we say something has gone extinct, like now that branch is ended. And there may be branches that continue that trace back to a similar route, but they are the ones that we would say are still sort of evolving. Everything alive today is under some evolutionary pressure. Mammoths didn't overnight become elephants. Mammoths and elephants are separate things that share an ancestor. They're like cousins to one another.
MIGUEL: When we think of evolution, many times we think of monkeys evolving into apes and then evolving into hominids and humans. Is that really how we evolved?
ELLIE MCNUTT: The simple answer is no because it's not this linear monkeys into apes into sort of the chimps and us. It's that branching pattern. So we have a common ancestor with monkeys and apes and the other great apes. But all of those things are alive today. As you go back into the past, you see our ancestors who have some of the same characteristics as the primates that are alive today, and they have some different ones. Though nothing is stuck in time, right?
A chimpanzee isn't sort of a fossil of 6 million years ago. They have been changing just as much as we have. So it's sort of a more complicated picture. We have kind of if you trace back these sort of the grandmothers of our species in common, but we as cousins have sort of diverged further and further away from each other. So it's not quite so simple or so kind of direct path. There's no goal, like becoming human isn't the pinnacle of things. That's not how evolution works. It's just you want to be the best animal you can be in the place where you are such that you stay alive long enough to pass your genes on to your offspring.
[MUSIC PLAYING]
MOLLY BLOOM: We're going to hear more from Ellie a little later. But first, it's time for another mystery. It's time for the mystery sound.
SPEAKER 2: (WHISPERS) Mystery sound.
MOLLY BLOOM: Here it is.
[MYSTERY SOUND]
Any guesses?
MIGUEL: Um, maracas or beans in a jar, I guess.
EMMANUEL: Yeah, like rice in a jar.
MOLLY BLOOM: Ooh, rice or beans. I think we're hungry. Well, we're going to be back with the answer a little later in the show. Do you guys know what a wormhole is?
MIGUEL: Um, yeah. A wormhole is like a portal, I guess, between one place in space to another theoretically.
MOLLY BLOOM: Yes, very good. Yeah, it's a place in the universe that connects two different spots. It may be billions of light years away or maybe just a few feet. And like you said, they're just theoretical, which means they haven't been proven to exist yet, but that will not stop our imaginations. So we want to hear from our listeners, what do you think it's like to travel through a wormhole? Emmanuel, why don't you go first?
EMMANUEL: I feel like you'd have nausea.
MOLLY BLOOM: [LAUGHS] Probably, yes.
MIGUEL: I think, I mean if they do exist, you might not get through alive because I mean it could do something to your body. And when you come out the other side-- if you do at all-- you might not be the same person. You might be someone completely different, maybe with the same personality but with different physical features.
MOLLY BLOOM: Whoa. Well, we are doing an episode soon about wormholes, and we want to hear what you think it's like to go through one. So you can record your answer and send it to us at brainson.org/contact.
MIGUEL: While you're there, you can also send us your ideas, mystery sounds, drawings, and questions.
EMMANUEL: That's what Elena did.
ELENA: What type of blood does insects have? Do they have the same as me?
MOLLY BLOOM: We'll have an answer to that question during our Moment of Um the end of the show. And we'll also read the latest group of listeners to be added to the Brains Honor Roll.
MIGUEL: Keep listening.
You're listening to Brains On! from American Public Media. I'm Miguel.
EMMANUEL: I'm Emmanuel.
MOLLY BLOOM: And I'm Molly. Today we're talking evolution. The first big idea about evolution came from Darwin and Wallace-- natural selection.
EMMANUEL: They realized that over time, animals changed, but they didn't know what caused those changes.
MIGUEL: Today, we know that these small changes happened because of something called DNA.
MOLLY BLOOM: Or deoxyribonucleic acid, if you're fancy. It's something hidden deep in every cell of every living thing. It's sort of like the blueprint or recipe for how to build a life form.
MAN 1: All right. Let's build some cells here.
EMMANUEL: For humans, our DNA is a combination of instructions we get from our parents.
MAN 1: Always check the DNA before we start construction.
MIGUEL: Some DNA is inherited from the mother and some from the father to make a new combination for the kid.
MAN 1: Hmm, looks like we're building a baby human here. All right, let's get to it.
MOLLY BLOOM: That's why we say, you've got your father's nose or your mother's eyes. It was their DNA that helped your cells grow into those features.
EMMANUEL: And combining our parents' DNA can lead to new traits. But sometimes DNA randomly mutates.
[TAPPING]
MIGUEL: That creates changes too. These changes called mutations don't come from any parent. They just happen. And once they happen, they might get passed down to future generations.
MOLLY BLOOM: So those are two ways that DNA can change and over time lead to new traits. When those traits are useful, they spread in a population thanks to natural selection.
MIGUEL: Like we saw with the jungle cows. Moo.
MOLLY BLOOM: [LAUGHS] Exactly. Other times, a trait spreads just by random chance, like how you can't always tell why a YouTube video goes viral, but suddenly, everyone is watching it.
EMMANUEL: Right. Sometimes two versions of a trait are good enough, and one just happens to get more common.
MOLLY BLOOM: Or maybe a natural disaster changes the population, like a hurricane comes through, and it wipes out a bunch of butterflies in a specific region. And just by chance, most of the dead butterflies all had spotted wings. Then spotted wings won't get passed on, not because of natural selection but because of just random Earth weirdness.
MIGUEL: When that happens, we call it genetic drift.
MOLLY BLOOM: That's an important part of evolution too. Traits don't have to be ideal or perfect to get shared. They just have to be good enough.
ROBOTIC VOICE: Brains, Brains, Brains On!
MOLLY BLOOM: All right. Let's go back to that mystery sound. You guys ready to hear it again?
[MYSTERY SOUND]
OK. So last time you were thinking beans, rice, maracas. Any new thoughts?
MIGUEL: It sort of sounded like there was a bit of, like, paper ruffling like that, like pulling paper because I've done this origami where it, like, it pops, like you make paper pop.
MOLLY BLOOM: Interesting.
MIGUEL: And it sort of sounds like that.
MOLLY BLOOM: Emmanuel, any guesses that you have?
EMMANUEL: Maybe sandpaper?
MOLLY BLOOM: Ooh. Good guesses. All right, well, here with the answer is producer Menaka Wilhelm.
MENAKA WILHELM: Hi, Miguel. Hi, Emmanuel. You guys were really close. What you just heard were sprinkles.
MIGUEL: Oh. That actually makes a lot of sense.
MOLLY BLOOM: [CHUCKLES]
EMMANUEL: Yeah.
MOLLY BLOOM: Are you guys sprinkle fans?
MIGUEL: My brother is. I'm not really much--
EMMANUEL: Yes, I am.
MOLLY BLOOM: Sprinkles on everything. Well, I also love sprinkles, rainbow in particular. But Menaka, does this have anything to do with evolution, or are we just going to make some sundaes?
MENAKA WILHELM: I mean, yeah, I love sprinkles, but I personally prefer the portability of a waffle cone. But today sundaes seem more appropriate, less risk of drippage. Oh, right. But yeah, anyway, I'm really here to talk about some of the traces of evolution that we can see in us today. I have this checklist of evolutionary adaptations for us to go through, and that's why there's about to be an ice cream party. The first trait on my list is the ability to eat or drink dairy. So can you guys eat ice cream?
MIGUEL: I can eat ice cream, and I would like rocky road.
EMMANUEL: I can eat ice cream, and I would like cookies and cream.
MOLLY BLOOM: So you both can? Did you say can?
MIGUEL: Yeah.
EMMANUEL: Yeah.
MOLLY BLOOM: OK. I also am able to eat ice cream, and I would love chocolate, please, Menaka.
MENAKA WILHELM: Perfect. So three sundaes coming up-- cookies and cream, rocky road, chocolate. Mint chocolate chip for me, so that makes four. And check, check, check, check, four lactose digesters.
MIGUEL: So what made humans able to digest dairy?
MENAKA WILHELM: Good question. I asked an expert to weigh in on that.
DORSA AMIR: My name is Dorsa Amir.
MENAKA WILHELM: Dorsa is an evolutionary anthropologist. She studies how we evolved and how our minds developed.
DORSA AMIR: All mammals have the ability to break down the sugar in milk, which is called lactose.
MENAKA WILHELM: But only baby mammals can do this. They use an enzyme called lactase. Their DNA has instructions that say, make lactase. And lactase karate chops lactose.
DORSA AMIR: So a baby drinks breast milk, and they can break that down, and that becomes a really important energy source for them. But after a few years-- so usually, up until two or three years-- after that, we lose the ability to do so. We can't produce that enzyme anymore.
MENAKA WILHELM: And without lactase, lactose causes digestive distress.
[STOMACH GRUMBLING]
Ugh, not fun.
DORSA AMIR: But in some populations, what you actually get is something called lactase persistence. So this is the case where those enzymes continue to be produced into adulthood. It's a really weird thing that no other mammal experiences. And it was largely because we started being able to use the milk from other animals into adulthood.
MENAKA WILHELM: And that lactase persistence is a trait that developed in some people thanks to--
[DRUM ROLL]
--a genetic mutation!
[GRAND MUSIC]
Once some people had that trait, it spread because being able to drink milk is useful, especially if you're hungry and there are cows around.
MOLLY BLOOM: Interesting.
MENAKA WILHELM: And in evolutionary terms, this trait is basically brand new. It's only like 10,000 years old or maybe less in some areas. OK. Let's move on to an older trait. Does anyone have a tail?
MIGUEL: Nope.
EMMANUEL: Nope.
MOLLY BLOOM: Uh, me neither.
MENAKA WILHELM: That's good, since my checklist says humans stopped having tails somewhere around 20 million years ago. But what about tailbones?
MIGUEL: We all have tailbones at the end of our spines.
MENAKA WILHELM: You're totally right, Miguel. A really, really long time ago, our ancestors use tails to balance in the trees. And eventually, tails became less important, but we've still got a tailbone left over. We call these leftover hints of past traits vestigial. So our tailbones are vestigial. Here's Dorsa again.
DORSA AMIR: As babies are developing in the first few weeks, as an embryo is developing, we actually still develop a tail. But then as time goes on in the following weeks, we actually get rid of it. So it's not the most efficient system, but that's the way that evolution has kind of figured out how to get rid of the tail.
MENAKA WILHELM: So three vestigial tailbones plus mine. Check, check, check, check. OK, how about chocolate sauce? Should I heat some up for those sundaes?
MOLLY BLOOM: Yes.
[MICROWAVE HUMMING]
What's our next adaptation on the checklist?
MENAKA WILHELM: Oh, good. There's the chocolate sauce. Oh, right. And next on the list, the palmaris longus muscle. If you take your hand and bend your palm towards you and push your pinky and your thumb together, do you see anything happening like right where your hand meets your arm at your wrist?
MOLLY BLOOM: Hmm, yeah. It looks like-- I do have a thin kind of like muscle, rope thing kind of sticking out.
MENAKA WILHELM: Do you guys have it, Miguel, Emmanuel?
MIGUEL: Uh, not really, since I have a jacket on, but I'm trying to do it.
MOLLY BLOOM: Can you roll up your sleeve?
MIGUEL: Yeah, it's what I'm doing right now.
MOLLY BLOOM: Emmanuel, do you see it?
EMMANUEL: Yeah, I see it. Yeah.
MENAKA WILHELM: So when I push my thumb really hard against my pinky, as hard as I can push with my fingers, and then I move my hand like it's pointing at my shoulder, this little skinny band, like Molly said, is starting to stick out of my wrist. And that's the tendon that connects to the palmaris longus muscle. But not everyone has it. Do you guys see it now?
MIGUEL: Uh.
MOLLY BLOOM: Not everyone has it, so it's possible it's not there.
MIGUEL: I think I have a bit of it. I don't-- at this point, I'm just like--
[LAUGHS]
MOLLY BLOOM: So three and a half checks, maybe.
MIGUEL: Yeah. OK, so three and a half. So check, check, check, and ch. Scientists think that this muscle used to help our ancestors around 15 million years ago. They might have used it to grab things or to stabilize their wrists when they were mostly hanging out in trees. But it doesn't do much for us anymore.
MOLLY BLOOM: OK. So it's a vestigial trait just like our tailbone.
MIGUEL: Hey, is there whipped cream for my sundae?
MENAKA WILHELM: Yes and yes. Our tailbones and palmaris longus were once useful, but now we don't need them. OK. Our last one, lest these sundaes get warm. Goosebumps-- do you get them? Can you make yourself get them?
EMMANUEL: Check on both.
MIGUEL: Check them both.
MENAKA WILHELM: What about you, Molly?
MOLLY BLOOM: I also get goosebumps. I don't know if I can make myself get them.
MENAKA WILHELM: Yeah, I definitely can't make myself get them, but I do get them if I'm cold, which is a lot. OK, so check, check, check, check. Four goosebumpers, but only Miguel and Emmanuel can do goosebumps on command.
[GOOSE HONKS]
Goosebumps are left over from when our ancestors had more fur. With a shaggier coat, goosebumps could puff up your fur to make you look bigger to scare off threats. Or they could also trap more heat to warm you up.
EMMANUEL: So it makes sense that we get them when we're scared or cold?
MENAKA WILHELM: Right!
MIGUEL: So if these traits don't totally help us anymore, will humans ever get rid of them?
MENAKA WILHELM: I'll let Dorsa answer that. I've got to find the cherries to complete these masterpieces.
DORSA AMIR: For something to really disappear entirely, it should be something that prevents you from surviving and reproducing in the best way possible. So there has to be active selection against it. It must be actively doing something harmful. And if it's not doing that, it's really easy for it to just kind of carry on through the generations untouched.
So for these things to really fully go away, someone who does have that versus someone who doesn't have that should be much worse at surviving. And it doesn't seem like these really get in the way of our survival in any important way. And so that's probably why they're going to be around for a long time.
MIGUEL: So the human species is probably sticking with tailbones and goosebumps at least for now, huh?
MENAKA WILHELM: Yeah, but it's kind of cool that all these leftovers tell us where we've been in an evolutionary sense.
EMMANUEL: Yeah, it is. Thanks for joining us, Menaka.
MENAKA WILHELM: Any time. Here are the cherries and--
[SPRINKLES SHAKING]
--the sprinkles from the beginning. Shall we begin on the sundae-eating portion of this segment?
MIGUEL: Yes.
EMMANUEL: Yes.
MOLLY BLOOM: Thank you for the sundaes, Menaka.
MENAKA WILHELM: Absolutely. See you guys later!
SINGERS: Ba, ba, ba, ba, ba, ba, ba, ba, ba. Brains On.
MOLLY BLOOM: Now we know where to look for some hints of our evolutionary past. But what might the future bring?
MIGUEL: Once again, we asked our pal Ellie McNutt, the evolutionary anthropologist.
ELLIE MCNUTT: So humans are still evolving. It's sometimes kind of tempting to think that evolution doesn't apply to us because we just don't have this idea that it's something that happened in the past or because of all the technology and things we surround ourselves with, it's not still occurring. In the last 10,000 years, if you look around, people with blue eyes wouldn't have existed. Blue eyes are a relatively recent evolution. You can watch changes happen to bacteria, right? Because their generation time is incredibly slow.
But humans, you know, I don't know whether it's 70, 80 years for your average lifespan. So that's an incredibly long time. And even though sometimes little changes can have great big effects, it still takes a long time for those things to spread throughout a population.
MIGUEL: Could humans ever evolve so much that a new species would branch off?
ELLIE MCNUTT: Absolutely. It's funny, it's happened a lot throughout our lineage, but because we're the only hominin species still alive today, it kind of seems like a crazy idea that we could ever split into another species. But it would require some pretty special circumstances. So we'd have to have a population of humans that were separated from our kind of major population for a long time. Speciation doesn't happen quickly.
A group of humans moved to Mars and lived there, and we never went back and forth. Maybe that might be enough to cause species to diverge, depending. So it's possible. The circumstances would have to be kind of pretty special. But it's certainly something that can happen to us.
[THEME MUSIC]
MOLLY BLOOM: Over time, the traits that species have change.
MIGUEL: Sometimes they change so much that they become an entirely new species.
EMMANUEL: Natural selection and genetic drift are both responsible for these changes.
MOLLY BLOOM: And you can see clues about how humans have evolved left over in our bodies today.
EMMANUEL: That's it for this episode of Brains On!
MIGUEL: Brains On! is produced by Marc Sanchez, Sanden Totten, and Molly Bloom.
MOLLY BLOOM: Menaka Wilhelm is our rock star fellow. Our engineers this week were Veronica Rodriguez, Johnny Vince Evans, Kurt [? Conan, ?] and Heath [? Cole. ?] Many thanks to Gabriel Nunez-Soria, Stuart Bloom, Jeremy [? Berg, ?] Kelly Harris, and Chris Walker.
EMMANUEL: You can send your ideas, questions, drawings, and mystery sounds to us any time.
MIGUEL: Just head the brainson.org/contact.
MOLLY BLOOM: And you can send us your wormhole travel ideas there too.
EMMANUEL: Now before we go--
MIGUEL: --it's time for a Moment of Um.
[CHORUS OF UMS]
ELENA: Hi. My name's Elena, and I'm from Portland, Oregon. My question is, what type of blood does insects have? Do they have the same as me?
CLAIRE RUSCH: I'm Claire Rusch, and I study insect brains. I'm a biologist. I would say that the biggest, very obvious difference between human blood, vertebrate blood, and insect blood is the color.
Our blood is red because of the molecule that is going to carry oxygen around. So we have a molecule that is called hemoglobin. It's inside the red blood cell, which are named red blood cell because of that. This molecule, that contain iron. And when it's in contact, the iron, when it's in contact of oxygen, it turn red.
In insect, they don't have this molecule, the hemoglobin. They have another kind of molecule that is composed of copper and not iron. And when copper and oxygen are linked together, are in contact of one over another, it turn blue. But I work a lot with bees, and their blood tend to be mostly transparent.
Small insect like bees or flies, what they do is they have kind of a system of pipe or tube inside them that are directly in contact with the outside, with the air, so they don't need to have this internal system to carry oxygen around because they are so small that it's not required. So when you smash an insect, and it turn red, usually it's because it was an insect that was biting you or another animal that has red blood.
[CHORUS OF UMS]
MOLLY BLOOM: My blood is racing through my veins, and these names are going to race from my lips. It's time for the Brains Honor Roll. These are the dedicated and creative listeners who keep us going by sending us their ideas, questions, mystery sounds, and drawings.
[LISTING HONOR ROLL]
[MUSIC PLAYING]
MIGUEL AND EMMANUEL: Thanks for listening.
Transcription services provided by 3Play Media.
