Why are there lefties and righties?
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No matter what kind of traveler you are, you can find inspiration with Unpack 25. Explore more travel trends and find yours somewhere to look forward to at Expedia.com slash Unpack 25. This is Unexplainable or Not, the game show where we finally get some answers. This week, our guest is Jonquan Hill. She's the host of Explain It to Me, Vox's new podcast all about answering listener questions. Welcome, JQ. Thank you.

Hello. I'm so excited to try to answer whatever y'all give me. Yeah, you ready to explain science to us? Um, no, but I will try my best. Okay, so Unexplainable or Not is a game show where you have to guess what we know and what we don't. You're going to hear three scientific mysteries, and you're going to hear them from me, from our supervising producer, Meredith Hodnot. Hey there. And from our senior reporter producer, Bird Pinkerton.

It's me. I'm the best one. No contest. So two of these mysteries are still unexplainable, but one of them has recently been solved. After you hear all the mysteries, you're going to get a chance to guess which one you think scientists have actually explained.

And this week, in honor of your show, Explain It To Me, we're going to be telling you mysteries inspired by a listener question. Ooh, I love this. Actually, one of your listeners. Yay! Your producer, Sophie, sent us this question. So here it is.

Hi, my name is Piper. I consider myself to be a relatively intelligent person, at least of average intelligence, but I'm 24 and still get my left and right confused. I've met a couple people like that in my life, and I'm wondering what's wrong with us, for lack of a better word. Why do some people have a harder time than others distinguishing their left and right?

So we love this question so much that we wanted to spin up a whole game show around it. Three mysteries all about left and right.

I love this. What's your relationship to your left and your right? Okay. So now I'm a gym girly. Like in a perfect world, I get up early and I go to the gym before work. The world is often not perfect. But I sometimes work with a personal trainer and he'll tell me like, okay, your left hand. And I'll raise my right. Oh, man.

I consider myself a very smart person, but when it comes to physical activity, I'm a clumsy little potato. I don't know why. So I understand where Piper is coming from on this. Very relatable. Okay, so this is a perfect question for you. Yeah. And actually, Bird is going to start with Piper's question.

Yeah, so, Jonklin, like you, I also cannot tell my left from my right, which was great, because when we were first introducing these questions, Noam was like, I just don't know about this, because, like, I feel like everyone can tell their left from their right. And I was like, hmm, interesting, Noam. Drag me! What a fun assumption to make. Um...

So to research this, I called up Ineke van der Ham. She's a professor at Leiden University who studies spatial functioning. So that's everything from like how we remember where our car keys are to like how do we try and get from point A to point B. I feel like this woman could save my life in multiple ways. Yeah.

And so I read her this question, basically. I, like, read her Piper's thing in full. And the very first thing she said is that, quote, there is nothing wrong with this person. This is a natural phenomenon. You're really dragging me. This is terrible.

Noam's the weirdo. Shocking. So she said essentially like our front is not the same as our back. Our top, like our head is not the same as our bottom, our feet. So it's not hard to sort of tell those apart. But left, right, like we're kind of symmetrical, right? So it's understandable that it's harder.

But it is super weird here, right? Because there are some people, noam, who just can do this automatically. Like, they just know, I'm never going to stop. And then there are some people like me, like JQ, the normies of the world, who, you know, they have to, like, make a little L with their fingers and be like, okay.

Is this L normal or is it backwards? Like, oh, the normal L is left side. For me, as like a little dyslexic child, I was like, but they're both Ls. I don't understand. Okay. And then there's a third gory, which is Meredith, who's just lost.

But UNICA wound up doing a large study where they basically showed people like a stick figure with little ball hands. So one hand was white and one hand is red. And the figure could be like facing you or facing away. And they would basically ask people to say like, is the red hand on this stick figure on the left side or the right side, for example? Yeah.

And it turns out that, like, when the stick figure was turned away from people, so the stick figure's right was their right and left was their left, it was way easier for them to tell left and right apart, which suggests, potentially, that we're all kind of consulting our own bodies in some way to figure out left and right in the world. Like, whether or not we can do that more automatically, we're referring to ourselves in doing this. But...

That still doesn't really answer the question of like, why do some people do this automatically and others like myself, like you, why do we have a harder time? That is still something that she needs to figure out. Or is it? And did she already solve it? Oh, my gosh. So what's your initial reaction? What do you think? You think we know the answer to left right confusion? Oh, man.

This could be me being delusional because, again, I think this woman could fix me. But maybe we found it out. I think maybe. Maybe. Maybe. Okay. So next up, I've got a mystery for you, which is why are there lefties in the first place?

Ooh, I was almost left-handed, but I switched at the end. What do you mean you were almost left-handed? The end of what? That's a direct quote from my mom. Like, okay, so apparently when I was a little kid, I would do everything with my left hand, like everything. And then all of a sudden it was like, okay, write your name. And once that started, I was just like, all right, right hand. I was almost left-handed, but didn't quite make it. Okay, so that feels like some kind of social influence.

And when I started thinking about this question, I kind of thought that was what was behind lefties and righties. Like, you'll often hear that the reason there are so few lefties is because all these countries and cultures have been really anti-lefty. You know, sinister. The word sinister is from Latin for left. Oh, I didn't realize that. Gauche is French for left. Bird told me that. Blame the French. Yeah.

But it's not just a social thing. You can see this actually really early on. So when you take an ultrasound by the 15th week in the womb, a fetus will already show a hand preference. Oh, wow. So 85% of fetuses are just moving their right hand a lot more than their left. I was going to say, what are they doing with their right hand? They're just kind of moving it around. Okay. Got things to do. And it's not just humans. Like chimps are mostly righties. Gorillas are mostly righties. Dogs, cats, whatever.

even crabs have handedness or some kind of like clawedness where they have one preferred claw. So it's definitely not just a social thing. But

then what is it? Like, where do lefties come from? So I talked to Veronica Odinsova, who's a researcher at Fry University in Amsterdam. And she said there are a couple basic ideas of what might make someone a lefty. So the first one is genetics, right? Like, maybe there's a gene somewhere that makes you a lefty. So...

Some studies have kind of compared identical twins with fraternal twins, and they basically come to the point where scientists say it's about 25 percent genetics. It plays a role, but it's not the main thing that makes someone a lefty. And when I asked Veronica what the main cause is, she basically said scientists just think it's random. So here's what that means.

There's lots of just stuff happening in our bodies all the time. Like, genes set out rules for stuff to happen. But then all the cells and everything inside the cells, they're all just bouncing around. So random. Yeah. This one scientist I read called it a jitter in the system. Oh, my gosh. Which is just kind of this crazy way to think about what's going on in our bodies. Like, we think there's this order, and it just seems like we're walking agents of chaos all the time. Mm.

That actually. Yeah. Yeah. And there are apparently like 41 gene locations that influence left handedness. What? Yeah. And then we're trying to imagine how these 41 genes are coding for all these things that are bouncing around all the time. Like we haven't figured out the math that could predict this. And we still can't explain what's going on other than just saying it's random. Yeah.

Do you ever stop and think, wow, being a person is so wild. Like our hearts are beating and we're breathing and we're not even thinking about it. And we've been doing it this whole time. But maybe we have figured this out and we have gotten the math right. And we do know why lefties and righties are the way they are. Ooh.

It's also possible. I don't know. I just feel like if you're... I will be honest. I was not the best in math. Me neither. Like, when my friends were, you know, in AP calculus, I was like, I will put all my brain power towards those English AP classes. Like, that was my vibe. So I am convinced that people who are good at math can, again...

Fix me. I'm convinced. Okay. So our third and final mystery comes from our supervising producer, Meredith Hodnot. All right. So we've been talking a lot about handedness this whole time. So let's take a look at them. You got fingers, you got thumbs, you got palms, you know, hopefully all in the right number and in the right order. And they're mirror images of each other.

You see this when you, like, put on a left glove on your right hand, the thumb's on the wrong side, it's all backwards. Well, this handedness shows up all the time in chemistry. Oh. It's called chirality from the Greek word for hand. And I talked to researcher Furkan Ozturk about this.

He said that two molecules can have all the same parts and be connected in all the same ways and yet be mirror images of each other. Basically a left and right-handed version of the exact same molecule. So in a lot of chemical reactions, like man-made chemical reactions in the lab, the left and right-handed versions are all mixed up together in like a 50-50 ratio. But sometimes...

A molecule's chirality matters a lot. Like, I was an organic chemist before I got into audio. Oh my gosh! Why? But were you good at math, Mara? I honestly wasn't that great at chemistry. I treated it a lot like cooking. I was just like, oh,

bit of this, a little bit of that. And unfortunately, that doesn't work out the best for yields. And then you were like, I know what to do, podcasting. That's the way to go. So sometimes when I was at the bench and like working on a reaction, it'd be like off by half. And I just like couldn't figure out why. And it'd be like making a cake and like only having half of the flour mix in and just the other half just like refusing to participate. Yeah.

And it'd be because I was using a mixture of both the left and right-handed molecules and only one was working. Oh, my gosh. I mean, there's like a pretty classic tragic example of

The medicine thalidomide was prescribed to pregnant people in the 1950s as a mixture of both the left and right-handed versions. And one version of the molecule was like a really effective treatment for morning sickness. And the other one caused severe birth defects. Oh, my gosh. Even though they were the exact same molecule, just different mirror images of each other. Right.

So this is something that, you know, scientists have known about for a while. But the crazy thing is that there's one place where we don't see a mixture of left and right-handed molecules together.

And this is in all the molecules that have to do with life. Again, people. Wow. So this is like DNA, RNA, proteins, sugars, like throughout the natural world. So like not man-made chemicals in a lab. Right.

These life molecules only exist in one mirror form or the other. It's never a mixture. DNA is always right-handed and proteins are always left-handed. And this is a mystery that has stumped biologists and chemists for over 150 years because this homochirality or same-handedness is

is basically a signature of life as we know it. And not just humans, right? Like plants, everything? From like the tiniest microbe to the most complex organism. Like life is this big, weird bucket. It's really hard to define. There aren't a lot of things that are connecting all living things on Earth.

But on a molecular level, whatever life uses a chiral molecule, it only uses one handedness. So to have something like this be such like a bedrock fundamental truth of life, the reason why must go all the way back to like the very origins of life itself. Yeah.

Okay, so, JQ, what do you think? Do you think we've figured out why life only has one kind of molecule, either left or right, but not both? I don't know. That's a huge-ass mystery, y'all. That's a big ol' mystery. Yeah, it's true. All right, so we got three mysteries. There's the mystery of left-right confusion. There's the mystery of why are there lefties in the first place?

And then we've got this mystery of why molecules of life are either lefty or righty, but never both. They're all unexplainable, or at least they all were unexplainable at one point. One of these mysteries has recently been figured out. And you'll have a chance to guess after the break. Support for Unexplainable comes from Bombas. As the weather gets colder...

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It's unexplainable or not, JQ, welcome back. Hey. So we got three mysteries, but one of them has had a recent breakthrough. Mystery one, why do some people struggle to tell their left from their right? Mystery two, what makes someone a lefty? And mystery three, why does life have this weird rule about only having either left or right-handed molecules? So without making your final guess,

Tell me what you're thinking after you've heard all three mysteries.

Okay. First of all, I want to know the answer to all of these. And the fact that there is no answer to two of them has me shaking my fist at the sky. I'm leaning towards left-right blindness just because I feel like knowing why we're right and left-handed and knowing why molecules are also right and left-handed, I realize it's not the same problem, but it feels like the same problem to me.

Okay. So you think left-right confusion is the thing? Yes. But that could also be because I want to get an answer for Piper and for me also. That makes sense. So is that your final answer, left-right confusion? Yes. All right. Left-right confusion. Locking it in. Boop, boop. Meredith, sound effects? Do-do-do-do-do. So, JQ, here's your answer. Turns out that a lot of molecules exist as symmetrical pairs.

Oh! Turns out we've had a breakthrough on why molecules of life only exist as either left or right-handed. Wait, explain! Meredith, care to explain? Yeah, so we just heard from Furkan Ozturk, and he's a postdoc at Harvard and Cambridge University. I'm a physicist by training, and I'm working on origins of life. And

And Furkan and his collaborators might have found a clue to why the chemistry of life never uses a mixture of right and left molecules. So because this is such a fundamental thing across all of life on Earth, he started thinking about the origins of life. Without figuring out why homochiral reality happened, we cannot really understand how life emerged on Earth.

To be clear, we have not solved the origins of life. I was about to say, girl, you about to bring some news to me? I was locked in. That would be a much bigger deal, and you would not be hearing about it on a game show.

Scientists do have a whole bunch of different theories of how life could have started. And one of those theories is that life could have started with a molecule involved with the genetic blueprints for life, a building block for a molecule called RNA.

So not something from life itself, but a potential, you know, precursor. And this building block molecule just happens to be chiral. So it's one of those kinds of molecules that have mirror images. So both a left and a right-handed version. And with all this in mind, Furkan focused on magnets. Most magnetic minerals...

And electrons, through their spin, can strongly couple to molecules' chiral structure. It turns out that chiral molecules, they can either be attracted to or repelled by a magnetic field, depending on whether they're left or right-handed. And minerals, rocks with lots of iron in them, can be magnetized by the Earth's magnetic field. They're very abundant on early Earth.

They have been detected in minerals that date back to like 4 billion years old. And it was everywhere. So Furkan thought that these magnets might have been like a physical way of organizing like a primordial soup of left and right-handed molecules. And it could have had like a knock-on effect.

and ended up making a bunch of other life molecules single-handed as well. So Furkan decided to put this to the test.

What we did is in the lab, we made these magnetic minerals. We magnetized them with magnetic fields. And he put a 50-50 mixture of left and right-handed molecules, this RNA building block, on top of a magnet. Just a regular magnet? I imagine it's very strong. Yeah, just a regular magnet. Like in a way, like recreating that primordial soup on top of a magnetized lake bed in early Earth.

And then that's where the magic happens. The soup began to form crystals. And the crystals that formed on the magnetic mineral was only one-handed. The magnet was separating these left- and right-handed molecules from each other, locking all the right-handed ones into a solid crystal and leaving all the left-handed ones just solid.

floating around in the soup. So while we still don't know the origins of life, this might be a clue to some pretty fundamental early earth chemistry that made life possible. I was like very, very excited and right away emailed like our collaborators and he got back to us like immediately and he said like, you bloody well done cracked it.

Furcon still has a lot of questions. Like he used a really strong magnet in his experiments. So he wants to try it again on like naturally formed magnetized rocks from across the world to see if it could happen under even more naturalistic conditions.

Other sorting forces might have played a role like polarized light or radiation from cosmic rays. But solving this mystery won't just give us insight on our own history. You know, it'll help us look out into the universe and decide, you know, where life could have developed.

somewhere else in this big old universe of ours. Wow. I feel like I'm going to be thinking of it a lot more. And the next time I work with my personal trainer and he's like, you don't know your right from your left. I'll be like, no. And no. So one last thing before you go, even though you didn't win, we do have a consolation prize for you. Is it your friendship? I think we have two consolation prizes for you.

We've got a tradition on our show where at the end of the game show, I write a song about the revealed mystery. Ah, I love music. So I sampled one of my favorite left-right songs and I wrote something for you. Yay!

We're gonna get funky. Spin to the left. Spin to the right. Any way you're looking, it's symmetrical. Let's go to work. Some molecules might have a left and a right. But life just isn't that flexible. Everybody clap your hands. Proteins slide to the left. DNA slide to the right. If you don't have anything to do with life.

Wow. I don't know. You tell me. The key just might be if they're only left or right.

Take them to the bridge. Wow.

I love my job. Me too. We need to create a line dance for this song specifically. We need like slide to the left and then everyone's like, which left? Yeah, and then you actually slide to the right. That's amazing. Wow.

That's it for Unexplainable or Not. Thank you to JQ for coming on the show. Thank you to our presenters, Bird Pinkerton. You're welcome. And Meredith Hodnot. Anytime. And thanks to our audience for joining us. If you have a mystery or a solved mystery you want us to tell on an upcoming game show, let us know. You can write us at unexplainable at vox.com. We read all the emails. And that's it for Unexplainable or Not. We're gonna get funky, funky, funky.

This episode was reported by Bird Pinkerton, Meredith Hodnot, and me, Noam Hassenfeld. Production and music from me, editing from Meredith, who also runs our team, mixing and sound design from Christian Ayala, fact-checking from Anouk Douceau, and tons of great vibes from Mandy Nguyen.

Thanks so much to Jonklin Hill for playing our game this week. You can find her show Explain It to Me wherever you listen. They cover questions like, is my dentist scamming me? Or why do people say like so much? It's a great listen. Don't miss it. Special thanks this week to Noemi Globus. And thanks as always to Brian Resnick for co-creating our show. If you have thoughts about the show, send us an email. We're at unexplainable at Vox.com. And you can also leave us a review or a rating wherever you listen. It

It really helps us find new listeners. You can also support this show and all of Vox's journalism by joining our membership program today. You can go to vox.com slash members to sign up. And if you signed up because of us, send us a note. We'd love to hear from you. Unexplainable is part of the Vox Media Podcast Network, and we'll be back next week. ♪ Everybody clap your hands ♪ ♪ Proteins slide to the left ♪ ♪ DNA slide to the right ♪ ♪ And if you don't have anything to do with life ♪

Criss-crossed magnets in the ancient earth. Made stars in the ancient world. Molecules of life picked a side and they didn't. Criss-crossed.

Thank you.

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