KATHY: Tobin.

TOBIN: Yes Kathy.

KATHY: You know what’s something we have in common?

TOBIN: That when we have insomnia, we buy things online.

KATHY: Oh my god, that’s so true. I just bought something. Ok but what I’m talking about is we both at some point in our lives worked at Radiolab here at WNYC.

TOBIN: Yes we did. You did a summer at Radiolab, I worked on the first season of Radiolab presents More Perfect.

KATHY: And suffice it to say, we are both huge fans of everyone there.

TOBIN: Yes We are! And that is why this week, while we’re taking a much needed Thanksgiving break, we are playing an episode of a Radiolab series called Gonads.

KATHY: Gonads is a 6-episode series about reproduction, hosted by Molly Webster. Amazing reporter. And we chose this episode specifically because it goes into the super fascinating nature of chromosomes, which sounds complicated, but trust me, it’s super interesting.

TOBIN: And If you like this episode, you’ll probably want to listen to the rest of the series, which you can find at radiolab.org/gonads.

KATHY: We’ll be back next week. Enjoy the episode.

TOBIN: Kathy, Tobin, out.

RADIOLAB INTRO: You’re listening to Radiolab, from WNYC.

MOLLY: Gonads. Episode three. I’m Molly Webster.

MARY: Hello?

MOLLY: Hello, are you still there?

MARY: I’m still here

MOLLY: And this is my mother, Mary Webster.

MARY: Yeah

MOLLY: But, yeah no. the bed bugs are such a freaking pain

MARY: Oh it sounds awful

MOLLY: You have to vacuum all of the baseboards, you have to vacuum the floors, you have to vacuum the door jambs because they crawl up the walls when they’re trying to get away

MARY: Oh Molly that sounds awful

MOLLY: And it just--

MOLLY: So, recently I called my mom for...I guest to catch up, but also

[MUSIC] “I’m calling from the other side”

MOLLY: I had a work question

[MUSIC] “have you ever stopped and wonder why”

MOLLY: That’s been bugging me...

[MUSIC] “a part of you was left behind”

MOLLY: ...Was on my mind.

MARY: Yeah.

MOLLY: So I asked her, mom.

MOLLY: I’ve been working on this story and it made me wonder what you would have named me if I was a boy.

MARY: You would have been named Daniel

MOLLY: Huh

MARY: Dad always like the name, and if we ever had a boy, Dad said he was gonna name him Daniel and I said, sure. If that’s what you want, go for it. You know, because he didn’t want a junior, he wanted a Daniel. He wanted a little Danny, hee hee

MOLLY: Instead, he got a Judy, Chrissy, Peggy, and Molly

JAD: Your poor father

MOLLY: My lucky father!

MARY: If you had come out boys, you would’ve been Daniel, yes

MOLLY: Wait, all of us?

MARY: No, we wanted Daniel for a boy, not for everybody.

MOLLY: You were just ready

MARY: Well we didn’t know when a boy came out if it was gonna be a Daniel, you know what I mean. That was it.

MUSIC - Daniel, Daniel, Daniel...

MOLLY: So this is just going to sound ridiculous, but I called my mom because all these stories that we’ve doing in this series, they do make you think about fate. Like even if you think about the first one where there are the primordial germ cells and they’re holding on to all sorts of possibilities and futures...and then

MUSIC - Chromosomes

MOLLY: Chromosomes step in. And peeuugh no more infinity. You’re just like shunted onto a path. I guess I--I guess asking my mom about Daniel was just like a clumsy way of getting back to what feels like a really pristine moment, like a moment where no decision had been made, where you exist totally unblemished by life and choice and fate. Unless--

[MUSIC OUT]

MOLLY: Maybe life isn’t so fateful

DAVID Z: [COUGHS]

MOLLY: Case in point - David Zarkower.

DAVID Z: Hello.

MOLLY: Hi.

DAVID Z: I'm just going to say I don't like correcting people but I'll just correct you my name is pronounced Zar-Cove-Er.

MOLLY:  Zar-Cover-Er?

DAVID Z:  Zar-Cover-Er.

MOLLY: Because it is a W right? I'm not misspelling in my head?

DAVID Z: Is it a W, just for the sake of my parents, I pronounce it with like a V. It's essentially Polish.

MOLLY: That's good. And you work at the University of Minnesota?

DAVID Z: Yup that's right.

MOLLY: What do you do there.

DAVID Z: Genetics, cell biology and development.

MOLLY: That's that seems scary.

DAVID Z: It's broad

MOLLY: Anyways, the reason I called Zarkower was because I came across this series of experiments that he did that just like straight up… kicked me in the gonads.

DAVID Z: Okay so

MOLLY: To begin

DAVID Z: This was back in the early 1990s.

MOLLY: Zarkower was working in a lab, doing genetics stuff

DAVID Z: In worms and flies and mice and things. And

MOLLY: One day

DAVID Z: Presto, we got lucky

MOLLY: Bum bah dah dah -  he and his team discovered a brand new gene

DAVID Z: Yep, that’s right

MOLLY: They saw it in mice and gave it a name

DAVID Z: I am unfortunately responsible for this. It’s DMRT1

MOLLY: D-M-R-T-1?

DAVID Z: DMRT 1 - yep.

JAD: DMRT 1.

MOLLY: I keep trying to say D-R-M-T-blah blah blah

DAVID Z: Yeah. It's a nightmare. I'm very sorry for that.

MOLLY: And what was interesting, was that this gene was in mice.

DAVID Z: But also in humans.

[MUSIC IN]

MOLLY: And, in the male mouse, it was expressing itself in the, um, testis? I never know how to say it. Testis?

JAD: Testes. Testes

MOLLY: Testes. Testicles?

DAVID Z: Testis.

MOLLY: Is that a single?

DAVID Z: Yeah.

JAD: Hm

MOLLY: OK.

DAVID Z: So yeah we found this gene and humans had it in the testis. And the question we had was whether it was doing something or not

MOLLY: Like you’ve got genes in your eyes that’re making chemicals, that are making your eyes the color they are

DAVID Z: This gene, DMRT1.

MOLLY: What is it doing?

DAVID Z: We wanted to know if it's involved in maybe making sperm.

MOLLY: Or

DAVID Z: Maybe it just hangs around, it doesn’t matter

MOLLY: Doesn’t do anything

DAVID Z: You know we don't know.

MOLLY: And so they’re like let’s mess around with it and see what happens. But you can’t do that experiment in humans

DAVID Z: No

MOLLY: So instead, they get some adult male mice

DAVID Z: Perfectly normal fertile males

MOLLY: That are making sperm

DAVID Z: And we use some fancy molecular genetic tricks.

MOLLY: And so basically

DAVID Z: It's kind of a mean trick but it's genetics.

MOLLY: They cut the gene out

DAVID Z: We did that, and then--

MOLLY: And then they take a slice of the testis, and they look at it under the microscope

DAVID Z: And it didn’t look like what we would have expected

[MUSIC]

MOLLY: And what they expect to see is that these are the cells that help make sperm in the testis. And normally they’re kind of tall and lean

DAVID Z:  long and skinny.

MOLLY: But suddenly

DAVID Z: They were different

MOLLY: With DMRT1 gone they had gotten smaller and rounder. And Zarkower was like

DAVID Z: This was not something that was supposed to happen.

MOLLY: What is going on here?

DAVID Z: What are these things?

MOLLY: Then he realized that the cells are making estrogen. And he was like--

[MUSIC OUT]

DAVID Z: Oh. I think what is happening is that the cells in the testis

MOLLY: Turned into ovary cells

JAD: Wait, what

MOLLY: And--

JAD: Wait this is a male mouse.

MOLLY: Yes

JAD: So you’re saying this male mouse now has ovary cells in its testicles?

DAVID Z: Yes, these are cells that are changing their sex

MOLLY: That’s insane. Can we just have like a, exclamatory moment. Like, were you like, whoa is that--that’s possible, that happened. What is--You know?

DAVID Z: What do you say? For us anyway, the greatest of all scientific exclamations is that's weird. So we had a that's weird moment.

MOLLY: And just to take this weirdness like one step further a group of scientists did a similar experiment in adult female mice, where they did like the same

DAVID Z: Fancy molecular genetic tricks

MOLLY: Only this time they knocked out a female gene in the ovary. And when they went to look at it

DAVID Z: The ovary is trying to kind of reorganize itself into a testis.

[MUSIC IN]

JAD: Wait.

MOLLY: Mhm

JAD: You’re saying in both cases there’s one gene that’s flipping the sex from male to female or back

MOLLY: Yes

JAD: One gene?

MOLLY: One gene.

JAD: How many genes do we have in our body?

MOLLY: I don’t know… like tens of thousands?

JAD: Whoa, and just one is doing this!

MOLLY: Which is …

JAD: Weird

MOLLY: A weird concept to think of because we typically connect like sex or gonads to chromosomes--at least I do like an X and a Y--

JAD: Right

MOLLY: Is a girl and a boy so how could a gene step in and reverse that

JAD: Yeah because I thought chromosomes were lots of genes. They were these massive things. One gene is so tiny.

MOLLY: Genes are tiny, chromosomes are much bigger. And I think the answer to that is that when you get down to sex like what makes us one sex or the other, it’s not--it doesn’t work exactly like we thought. Like take for example the X and Y idea. This like chromosomal narrative we have of biological sex, it’s a specific way of thinking about things from a certain moment in history that we are potentially starting to rethink?

JAD: Huh

MOLLY: I think it’s helpful to see sort of like the history of how we understand sex in a slightly longer timeframe. So… let me bring in this guy

DAVID P: I’m David Page, biology professor at MIT

MOLLY: OK, where do we start?

DAVID P: Oh my gosh. Well we’re gonna go--let’s see. We could go off the rails in any number of directions here, all of which would be quite productive, but let’s see. So, um. Let’s go back to the 1890s

[MUSIC IN]

MOLLY: Yeah. That definitely is 1890s

DAVID P: So

MOLLY: So, genetics was in its infancy. Mendel, peas, all that was happening

DAVID P: And people had been pondering for millenia, where do boys and girls come from?

MOLLY: Now, when it came to how you looked, people thought, mom and dad clearly involved.

DAVID P: Because people had realized, you know, that children ended up growing up looking something like their mother and their father.

MOLLY: Like maybe you have a chin like your dad, a nose like your mom, and hair that’s a little bit of both

DAVID P: There was a kind of blending

MOLLY: Of mom and dad to make you, you

DAVID P: Right. But

[MUSIC SHIFT]

MOLLY: When it came to why you were the sex you were

DAVID P: Mmmm

MOLLY: That was a mystery

DAVID P: Because

MOLLY: There was no blending

DAVID P: You ended up being like either your mother or your father

MOLLY: One or the other

DAVID P: Therefore, it must not have anything to do with heredity. It had to be imposed from the outside in some way.

MOLLY: So people came up with all kinds of ideas for what made you a boy or a girl

DAVID P: The phase of the moon at the moment of conception

MOLLY: Cold dark moon, definitely a girl

DAVID P: The state of the economy

MOLLY: Wouldn’t be surprised, down economy, girl

DAVID P: Yep

MOLLY: Everything that was bad was given to women. [laughs]

DAVID P: There was what the mother ate

MOLLY: Mom’s body heat, stress

DAVID P: All sorts of crazy things. And then

[MUSIC OUT]

DAVID P: in 1923

MOLLY: We started looking elsewhere

[MUSIC IN]

CLIP: But how do we inherit our characteristics?

MOLLY: For an answer

CLIP: Chromosomes

DAVID P: Chromosomes

MOLLY: Chromosomes

CLIP: Determine our physical appearance and our sex

MOLLY: In 1923 a  scientist looking down the barrel of a microscope discovers two new chromosomes.

DAVID P: An X and a Y

CLIP: Called the sex chromosomes

MOLLY: But I just want to hit pause here

[MUSIC SLOW EFFECT]

JAD: OK

MOLLY: I came to find out actually from David Page that X and Y chromosomes do not look like an X and Y

JAD: Wait, they don’t look like the letters?

DAVID P: Oh, no, no, no

MOLLY: No when they first discovered them

DAVID P: They were blobs

MOLLY: Under the microscope they just looked like these misshapen clumps

DAVID P: I’d say kidney bean-like

MOLLY: The X looked bigger, the Y looked smaller. But that’s it.

JAD: That’s so interesting. Like, I--because there’s something about the shape of the X and the shape of the Y which read as gendered letters.

MOLLY: That feels so--yeah

JAD: Because like the Y has a little stem on it which is sort of--

MOLLY: Penis-like. There’s like a duality of something in like the X which feels like, you know, ovaries and breasts or something. Like there is like--there is something about those letters, so I was

MOLLY: Totally shocked. When he was like,

DAVID P: There’s no real reason people gave them those letters, it was totally arbitrary.

[MUSIC IN]

MOLLY: Anyways. When they found these chromosomes

DAVID P: It was clear that if you had

CLIP: XX

DAVID P: Two X chromosomes, you would develop as a female

CLIP: A girl

DAVID P: Anatomic female. And if you had a Y chromosome

MOLLY: So you’re XY

DAVID P: You would develop as an anatomic male

CLIP: That’s right. A boy

DAVID P: That was the thinking

CLIP: So you see, Roger and Susan are boys--

MOLLY: But then that idea, it got more complicated

DAVID P: Yeah

MOLLY: Yeah, when did you intersect with this story?

DAVID P: Um, the summer of 1979

MOLLY: Page was at MIT

DAVID P: First year of medical school. And the DNA revolution

CLIP: So far tonight, we’ve been bringing you news of the world around us

DAVID P: Was just beginning

CLIP: Now we have news of the incredible world inside us

MOLLY: He was involved in what he describes as like the precursor

DAVID P: To

CLIP: The Human Genome Project

DAVID P: What would become the Human Genome Project. Working with a group of senior scientists who were envisioning maps of the Human Genome

CLIP: An encyclopedia of man. We’ll know the complete set of instructions, which make people

DAVID P: And we began to look back at some exceptional human individuals, who had not been understood previously

CLIP: That saliva test

DAVID P: Women

CLIP: Revealed that Maria had a set of X and Y chromosomes

DAVID P: Who had an X and a Y chromosome

CLIP: Like most men, women usually have a pair of X’s

MOLLY: And they’re also looking at men

DAVID P: Who had an altogether male anatomy

MOLLY: Penis, testes

DAVID P: But whose chromosomes appeared to be those typical of a female XX

MOLLY: And for Page and other scientists they were like, oh there must be something more happening here than just like the chromosome. There must be something deeper going on here

DAVID P: So we might actually be on the trail now of the secret

MOLLY: So scientists across the world started looking at these people’s chromosomes

DAVID P: And what we found was that a few XY females were actually missing a little bit of the Y chromosome.

MOLLY: With these XY women, a little bit of the Y wasn’t there

DAVID P: And the bit of the Y that the XY females were missing, was the same bit that was present in the XX males.

MOLLY: Meaning somehow a little bit of the Y chromosome had gotten onto one of the X’s of these XX males

DAVID P: And so it was becoming very clear that this must be the bit that matters

MOLLY: And around 1990

CLIP: Other news this day, scientists say they’ve made a major discovery

MOLLY: Scientists in Britain announced they’d found this one gene on the Y chromosome

CLIP: The genetic trigger on the Y chromosome that determines whether a baby will be a boy or a girl

MOLLY: What they found is that of the 200 some odd genes on the Y chromosome, there was this one single gene that acted as the switch.

CLIP: The master switch

DAVID P: The grand master switch

CLIP: Which determines the child’s sex

MOLLY: So it’s not X and Y as a whole, it’s one tiny piece.

[MUSIC IN]

MOLLY: So back in the first episode, there were those primordial germ cells and they had to go on this super long journey to get to the gonad cathedral, and on the journey, when they got to the cathedral, they were full of potential, right. They could be anything. They could be male, they could be female, they could be whatever your version of anything is. And then when they get there, there’s a moment where like we said fate stepped in and whoooosh swept all their possibility away and said you are one thing. And this is the thing you will be. This gene is fate. This gene these scientists discovered, if it shows up, Then you shoot off down the path that is sperm, testis, male. And if it doesn’t show up, you shoot down the path of egg, ovary, female. And the scientists gave this gene a name SRY.

JAD: Uh-huh

MOLLY: Which is like sorry

JAD: [laughs]

MOLLY: You’re a man, sorry

JAD: [laughs] JAD: So it sounds like we’ve gone from crazy ideas about what makes a boy or a girl to chromosomes to now like this little gene

MOLLY: Yeah   

JAD: But the SRY gene that you just mentioned is different than the gene that I just heard about from--I’m forgetting his name

DAVID Z: Zarkower

MOLLY: Zarkower

DAVID Z: Zarkower, yeah

MOLLY: Zarkower

JAD: Zarkower, yes

MOLLY: It is I think--

JAD: Is that the same gene, or is it--

MOLLY: DMRT-1 is a different gene than SRY. But this, this is what’s so crazy about DMRT-1. Okay. Primordial germ cells, they’re in the embryo, they’re waiting to become something and then sorry shows up

DAVID Z: But it just comes on for about a day, and then it goes away

MOLLY: But once it turns on it then starts this like cascade of Gene after gene after gene. That all sort of say, you’re male, you’re male, you’re male. And what all of  these genes do is they create chemicals that send out signals that start forming and shaping the testis.

DAVID Z: And, as soon as the testis begins to develop

MOLLY: On turns the fourth gene

DAVID Z: DMRT-1

MOLLY: Zarkower’s gene

DAVID Z: And it clearly is important for finishing the job of making a testis

MOLLY: But the thing is, most of these other genes that make the testis turn off. But DMRT-1

DAVID Z: It doesn’t go away at that point. It stays active

MOLLY: Forever. In the womb when the testis is just growing, and then when you’re born, and through you know childhood, your teenage years, adulthood like until you die, DMRT-1 is on. And if you take it away, like Zarkower did, the cell will actually change sex, which leads you to believe that DMRT-1 is actually preventing a cell from switching sexes.

BLANCHE: That’s right, so--

MOLLY: I called Blanche Capel, who is the geneticist from our first episode. And she explained that what all this means is that that other path, that path that you did not take in the gonad cathedral, it never went away. It’s actually still there. You carry it with you always. It’s just that that gene has been shushing it.

BLANCHE: Yeah

MOLLY: Wait, I’m repressing the other pathway my whole life, like--

BLANCHE: I think--we think so, yeah

MOLLY: Really

BLANCHE: Yeah

MOLLY: There’s like a parallel universe male Molly?

BLANCHE: [laughs] Yes, I think there is. There’s a parallel universe male Molly.

MOLLY: Wow. That’s just cool [laughs]

JAD: Wait, when you say this gene has been shushing the other Molly, what does that even mean?

MOLLY: Huh. OK so you can think of it like this. The code for that other Molly, who I’ll call Daniel. That code is still in my cells. And Zarkower says that what this gene does is it sort of--one of the things this gene does is it sort of patrols and it makes sure that Daniel genes don’t turn on.

DAVID Z: Basically what this gene’s been doing, it turns out, is playing whack-a-mole. Basically just going around and being like, Daniel no, off. Daniel, no. Off. [pooh pooh pooh] And it does this, maybe, every day. It’s like an election that’s always being kind of challenged. SRY cast the deciding vote and male happened, but there’s recount every now and then. And, uh, if DMRT-1’s not there to say nope, still male, then you can go the other way.

JAD: So now I understand why you’re so obsessed with Daniel. Because it’s not just an idea, he’s like trying to get out!

MOLLY:  And it does go both ways. Like, you know, there’s SRY and there’s DMRT-1 but they have found these key genes in ovaries that you can turn on and off and have similar results.

JAD: Why would our--why would our bodies be set up this way? Like you think once the decision gets made, that you just make that decision and be done with it. Why would there always be the possibility of un-making the decision?

MOLLY: That is a good question. And I will answer that question after the break.  But first, I’m gonna call my sisters. Ha!

[MUSIC] - You Daniel, you complete me, you Daniel...

[MIDROLL]

TOBIN: And We’re back.

Kathy: Back to an episode of the Radiolab special series Gonads with reporter Molly Webster.

MOLLY: Everyone say say their name or hello

CHRISSY: Ok it’s Chrissy

JUDY: It’s Judy

MOLLY: Peggy?

PEGGY: Yeah

MOLLY: Hi, how are you

PEGGY: I’m great

MOLLY: And these are my sisters, Judy, Chrissy and Peggy.

MOLLY: Ok so i’m going to tell you guys the thing. It’s not even that big a deal but it’s sort of just funny.

SISTERS: Oh my god, Oh no, Ok, What the fuck? You’re pregnant

MOLLY: I’m not pregnant. I’m not-- No no.  I just want to tell you about some reporting that i’ve been doing. And then a funny thing that mom and dad told me. That’s all it is

SISTER: ok. Mom had an affair?

MOLLY: Oh god. That would be--

SISTER: One of us doesn’t belong… It’s Chrissy….Yeah

MOLLY: This is ridiculous. Um the third episode is basically about how we all carry in us like the opposite self that we never became. So um So I called mom because I was like so what would male Molly have been like? Did you guys have like a name for male Molly? And they were like oh um we would have called you Daniel.

SISTER: No that was what they were supposed to call me! They were so desperate to use Daniel

MOLLY: And it turns out we were all supposed to be called Daniel

SISTER: That is the big reveal? There is an inner Daniel Webster?

MOLLY: Yes!

SISTER: Jesus, Molly!

MOLLY: Oh man… are you surprised that your name would have been Daniel Webster? That you would have been a Daniel?

SISTERS: No….No...I think we all knew that right?

MOLLY: Peggy did you know that?

PEGGY: No I didn’t know that!

SISTER: I don’t feel like my inner Daniel Webster would have that much of a different life than I have so--

SISTER: But I think you guys honestly--not to railroad this conversation, but I think you guys lucked out because I was the one that was raised with the hopes that there was some Daniel lingering in me

SISTER: Isn’t Daniel Webster like a famous dude in history?

MOLLY: Yes

SISTER: Oh...I took a picture of a statue of him once and sent it to dad, because I was supposed to be Daniel.

SISTER: Who is Daniel Webster

SISTER: He’s a boring white dude

Molly: Well of course he is. We knew that part.

SISTER: He served as senator for Massachusetts and was the under-secretary of state under three presidents

SISTER: Well someone googled fast

SISTER: I think he was just like a regular old white lawyer dude

SISTER: yeah they were all racist or sexist or ageist or just a douchebag [LAUGHTER]

SISTER: Alright, well

MOLLY: Great.

SISTER: That was funny

MOLLY: Peggy got her giggles in, it’s all been worth it. Alright, that’s all I got.

SISTERS: Bye..We love you Molly

MOLLY: I love you guys, goodbye

SISTERS: Love you...Bye...Bye Molly you’re amazing.

MOLLY: OK bye

SISTER: I’m sorry about your bedbugs. Bye [LAUGHTER]

MOLLY: OK. So you catch everybody up, we have learned that we are all carrying around with us another path. We all have our own inner Daniel Websters, and we’re constantly shushing it--or them whatever. So my question for Zarkower was like why would I carry this path with me if I’m always turning, like if I’m just turning it off

DAVID Z: Ummmm

MOLLY: Do you have any answer to that?

DAVID Z: [LAUGHS] I wish I had the answer. So we don't really have an answer. It could be as boring as well it doesn't really matter because normally no molecular geneticist comes in and hacks out DMRT-1 or turns on FOX-L2 or whatever. So why solve a problem that you haven't created? That's quite possible but boring. The more interesting answer is that this is an evolutionary holdover from from a common ancestor with fish.

[BUBBLE MUSIC IN]

MOLLY: OK so this ancestor would be our great grandparent, 16 million times removed which means 400 million years ago. A fish swam out of the depths of the ocean, crawled onto land and took like squelching steps forward and forward and forward through millions of years of luck and chance and fate until finally getting to

[SPLASH SOUND IN]

MOLLY: You. And me. And

[MUSIC OUT]

BOB: Hello

MOLLY: Hello

BOB: Can you hear me?

MOLLY: Yes. Can you hear me?

BOB: Yes I sure can.

MOLLY: Bob

BOB: My name is Bob Warner. I'm a research professor

MOLLY: Studies evolution and marine biology

BOB: At UC Santa Barbara.

MOLLY: What's your attraction to the ocean?

BOB: Uh well the whole idea that there is a different world under there

[SPLASH SOUND IN]

[MUSIC IN]

MOLLY: Well, I'm just going to Attenborough the [BLEEP] out of this.

JAD: [LAUGHS]

MOLLY: So down in the waters around the Florida Keys there swims a remarkable fish

BOB: A bluehead wrasse.

[MUSIC SHIFTS]

MARSHALL: It is a very common coral reef fish

MOLLY: This is Marshall Phillips

MARSHALL: Graduate student at North Carolina State University.

MOLLY: She, like Bob, studies blueheads.

MARSHALL: Yes.

MOLLY: Anyways down in the Keys are some

MARSHALL: Primo spots.

MOLLY: Nice patches of reef

BOB: That might have a group of say a dozen -

MARSHALL: Blue heads

[MUSIC SHIFTS]

BOB: And in that group there will be a single large brightly colored male

MOLLY: Just one of them.

MARSHALL: Yeah

MOLLY: About the size of your hand

MARSHALL: With a blue head

MOLLY: And a shiny blue-green body

MARSHALL: And it has white and black stripes right behind its head.

MOLLY: That go black white black

MARSHALL: That we very technically call the Oreo.

MOLLY: And if he's got a big Oreo

MARSHALL: Well, that's a sexy male. [laughs]

MOLLY: And then the rest of the group is essentially a harem of lady fish

[MUSIC SHIFT]

BOB: And the ladies in the group

MARSHALL: Are little and yellow

BOB: Very pretty.

MOLLY: They kind of swim a little bit slower, watching out for things

BOB: Where the male is

MARSHALL: Flashy, darting all around

BOB: Much more aggressive.

MOLLY: And so this one male and this harem of females will basically spend their entire lives on this one patch of reef

BOB: Where they mate every day.

MOLLY: Each female with that one male

MARSHALL: All it entails is the male and the female will dart up in the water column together

MOLLY: And then at the same time he’ll release his sperm, and she’ll release her eggs

MARSHALL: And then they dart right back down.

MOLLY: And then a different female, same male go up, eggs, sperm

MARSHALL: And dart back down

MOLLY: And then again, different female same male, they go up

MARSHALL: Down.

MOLLY: And this is what they do every day.

MARSHALL: Over and over

MOLLY: Kind of sounds like a cult of the 1960s

JAD: [LAUGHS]

MOLLY: But say something happens to this male

MARSHALL: Say a predator comes along. And he chomps that male.

MOLLY: So the alpha male

BOB: Is eaten up

MOLLY: Dead

BOB: Yep

MOLLY: Gone. Now the question is what happens to the ladies. You would think it would be chaos because their whole systems been thrown out of whack

[SOUND EFFECT]

MARSHALL: But

[SOUND EFFECT]

MARSHALL: Within minutes to hours

MOLLY: Life finds a way

[MUSIC IN]

MOLLY: Somehow, the ladies pick who will be the next male

BOB: The ladies have it pretty well worked out who's the largest

MOLLY: Do they all start like eyeballing each other, like--

MARSHALL: They don’t line up or anything, like, am I bigger than you, no I-- But somehow they figure it out

MOLLY: And so once they establish who the largest female is she starts to change her behavior. She gets a little more friendly

[MUSIC SHIFTS]

BOB: Towards the other females

MOLLY: She’ll like swim up to them

MARSHALL: do this little wiggly dance.

MOLLY: Sort of waving her pectoral fin at the ladies

[MUSIC SHIFTS]

MARSHALL: Which isn’t really something they do as a female. Ever.

MOLLY: And then

MARSHALL: As time goes on

MOLLY: Her body starts to change

MARSHALL: She will get a little bit bigger

MOLLY: How do you just suddenly get bigger?

MARSHALL: Testosterone

MOLLY: Her brain starts sending signals to produce tons of testosterone

MARSHALL: Testosterone is taking over.

MOLLY: And as she starts to grow

MARSHALL: A little bit of blue starts to appear right at her nose.

MOLLY: Her scales start to change color.

MARSHALL: Then sort of spread backwards right at her chin and spread outwards

MOLLY: Until her head is entirely blue, and then these dark stripes start to form

MARSHALL: Those will eventually become that black white black Oreo

MOLLY: And the other thing that starts to happen is her ovaries start to disintegrate.

BOB: These are the most valuable cells in the body and now suddenly they're being destroyed.

MOLLY: And then they start to rebuild themselves into testes that start producing

BOB: Sperm really rapidly.

JAD: Wow

MARSHALL: It’s nuts. It’s absolutely incredible.

MOLLY: And then

[MUSIC CHANGE]

MOLLY: Sex cult is back.

BOB: There’s a new dominant male at the top of the heap

MARSHALL: But at first he’s not very good at being a male.

MOLLY: Like he doesn’t quite know when to dart up and when to spawn.

MARSHALL: It's just like a teenager who doesn't know how to talk to girls

MOLLY: But eventually, he gets the hang of it

MARSHALL: And can produce baby blueheads

[MUSIC SHIFTS]

MOLLY: [IN DAVID ATTENBOROUGH VOICE] And the cycle of life continues.

JAD: [laughs] That’s a good Attenborough

MOLLY: Thank you.

JAD: That is crazy that they just disintegrate their insides and then rebuild

MOLLY: But this is--the funny thing is if you ask Bob about this stuff

BOB: No, in fact--

MOLLY: About how these little lady fish completely transform he’s like, meh

BOB: Yeah I hate to admit that but, yeah.

MOLLY: It’s not that shocking

BOB: The shocking thing is how many

[MUSIC IN]

BOB: --fishes change sex.

MOLLY: it turns out it's a lot of fishes.

BOB: Nearly all the wrasses

MOLLY: Your blueheads, your ferries, your flashers

BOB: Uh, parrot fishes.

MOLLY: They actually look like parrots.

BOB: They change sex. Most of the big groupers

MOLLY: The tiny gobies

BOB: Damsel fishes. Everyone asks about clownfish

MOLLY: Finding Nemo.

BOB: Yes they change sex

MOLLY: But they do it a little differently.

BOB: They go from male to female

MOLLY: Up with the clownfish matriarchy.

JAD: [LAUGHTER]

MOLLY: Bob says we're dealing with like

BOB: Hundreds.

MOLLY: A whole lot of sex changing fish

BOB: Easily.

PAT WALTERS: Wow. Hundreds.

BOB: Yeah.

MOLLY: But here's the really crazy thing.

[MUSIC CHANGE]

MOLLY: It’s not just fishes

BOB: Some shrimps. Worms

BLANCHE: Alligators

MOLLY: If you include all the animals in which their sex goes a different way than you would thinK

BLANCHE: Flies. Lobsters

MOLLY: It’s [BLEEP] bananas

BLANCHE: Lizards. Birds

MOLLY: Mussels snails slugs

BLANCHE: Chickens

JAD: Chickens?

MOLLY: Oh, eels

BLANCHE: Frogs. It's just amazing. And wait til we get to turtles.

[MUSIC OUT]

MOLLY: It's a whole zoo in this conversation.

BLANCHE: [LAUGHS] I know.

MOLLY: So why would fish--why would why would any animal change sex?

DAVID P: Well I think sex change increases your fitness. You have more young, either eggs that you produce or eggs that your fertilized than you would as a--as a single sex

MOLLY: Hm.

MOLLY: In other words, it just ensures that you can pass on your genetic material. Like if you’re the fishes on the reef, and the male disappears, you’re stuck and there’s no-- your DNA goes nowhere. But if you become a male, you can make sure that your DNA goes somewhere and then like all the other fishes in your little kingdom go somewhere.

JAD: OK so now let me ask you the next obvious question. You’ve told me that we come from the fish, that they’ve got this flexi-sexy thing. And that we have it to some degree. Daniel lurks within you and is being actively suppressed, every single day. So can we be like the fish?

MOLLY: Yeah it does make you think of that. Zarkower says that ever since he did those mouse experiments, he gets this question a lot.

DAVID Z: Yeah, you know, there’s some interest from the transgender community in whether this could be something that could be helpful. But, we can’t do it--we technically can’t alter--

MOLLY: Zarkower says it’s unethical and at this point probably even technically impossible to take that gene away. And even if we could, removing a gene just won’t physically reorganize us in the way the fish do. He says at most

DAVID Z: You might be able to produce your own natural sex hormones of the type that’s more aligned with your gender identity

MOLLY: Oh

MOLLY: Pretty crazy you could even get the body to do that. But the reason we can’t actually do the full on switch is because humans male and female humans have developed internal reproductive plumbing that is so different from each other, it would be impossible at the drop of a hat to switch

JAD: Well so then then this makes me confused, is this--to use Blanche’s word from a few episodes ago--is this bi-potentiality that still is there

MOLLY: Yeah

JAD: latent, being supressed--is that a legacy thing, that’s just fading away or is it there for a reason? It’s there for a reason in the fish. Is it there for a reason in us?

MOLLY: Does it serve a purpose

JAD: and therefore will be with us --always

MOLLY: Always. Or maybe even get stronger. No I asked Blanche that.

BLANCHE: I don’t know, I don’t know. I don’t have a good answer for that. But it--

MOLLY: Do you think anyone does? Or is this like--

BLANCHE: No.

MOLLY: Hm

BLANCHE: No, I don’t think anyone does. I think we’re all trying to figure out why it would be the
case. And most people ask the same question you ask, why would this be true? And I don’t know why it would be true

MOLLY: Even if we don’t know why, just knowing that that other path is there, just below the surface, you know almost like wanting to express itself, does make you think a different way about how rigidly we define ourselves

BLANCHE: I think we like to bin people as male or female and we’ve always put people in two piles. But I think there’s a tremendous amount of middle ground. Even when you’re just talking about things like the level of testosterone you’re making or the level of estrogen you’re making or, um, the shape of your genitalia or, uh--many other features we bin as male or female. I think there is a lot of variation between the two piles. And maybe we just haven’t appreciated the variation that exists naturally in our population

[MUSIC IN]

MOLLY: This episode was reported by me, Molly Webster, and produced by Matt Kielty. With additional production help by Rachael Cusick. Pat Walters was our editor. Scoring, mixing and original music by Alex Overington and Matt Kielty. The Gonads theme and the Ballad of Daniel Webster were written, performed and produced by Majel Connery and Alex Overington. Special thanks for this episode go to Erica Todd, Andrew St Clair, Robin Lovell-Badge, and Sarah Richardson. Thank you to composer Erik Friedlander, for allowing us to use his work Frail As A Breeze Pt. 2, and musician Sam Prekop, whose work, A Geometric, from his album The Republic is out on Thrill Jockey. I think you should sign up for the Radiolab newsletter. You might think, eh, newsletter, what’s the big deal? Everyone’s got one. But in our newsletter you are going to get a bunch of staff picks telling you about super cool things we discovered while recording this series. Sign up at radiolab.org/newsletter or text “gonads” to 701-01. Radiolab Presents: Gonads is Rachel Cusick, Pat Walters, Jad Abumrad and me, Molly Webster. See you next time.

VOICEMAIL: Hi, it’s Annette Udal calling from Newcastle, California. Radiolab was created by Jad Abumrad and is produced by Soren Wheeler. Dylan Keefe is our Director of Sound Design. Maria Matasar-Padilla is our managing director. Our staff includes: Simon Adler, Maggie Bartolomeo, Becca Bressler, Rachael Cusick, David Gebel, Bethel Habte, Tracie Hunte, Matt Kielty, Robert Krulwich, Annie McEwen, Latif Nasser, Malissa O’Donnell, Arianne Wack, Pat Walters, and Molly Webster. With help from Shima Oliaee, Carter Hodge, and Liza Yeager. Our fact-checker is Michelle Harris. How’d I do guys?

 

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