Jun 15, 2018

Gonads: The Primordial Journey

At two weeks old, the human embryo has only just begun its months-long journey to become a baby. The embryo is tiny, still invisible to the naked eye. But inside it, an epic struggle plays out, as a nomadic band of cells marches toward a mysterious destiny, with the future of humanity resting on their microscopic shoulders.

If you happened to have caught this show on air, you can find the second half of our broadcast version here. 

This episode was reported by Molly Webster, and produced by Jad Abumrad. With scoring and original composition by Alex Overington and Dylan Keefe. Additional production by Rachael Cusick, and editing by Pat Walters. The “Ballad of the Fish” and “Gonads” was composed and sung by Majel Connery, and produced by Alex Overington.

Special thanks to Ruth Lehmann and Dagmar Wilhelm.

Radiolab is supported in part by Science Sandbox, a Simons Foundation initiative dedicated to engaging everyone with the process of science. And the Alfred P. Sloan Foundation, enhancing public understanding of science and technology in the modern world. More information about Sloan at www.sloan.org.

Support Radiolab today at Radiolab.org/donate.

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JAD ABUMRAD: Hey, this is Jad. Very proud to present to you guys starting today here on Radiolab, a miniseries from producer Molly Webster.


[CHOIR: "It's been a my goal as a fish. It's been my goal. For so long I've waited to be full. I've waited to carry you. All of you. All of you."]


MOLLY WEBSTER: Hi, I'm Molly Webster.


[CHOIR: “I'm so full of eggs.”]


MOLLY: For the last ...


[CHOIR: “I have so many eggs.”]


MOLLY: ... I don't know, I'd say three years ...


[CHOIR: “It's too much for me.”]


MOLLY: I've been ...


[CHOIR: “It's too much for me.”]


MOLLY: ... doing a lot of reporting about how humans make more of themselves, right? Like, science stories, ethical stories. And we came up with this idea that, you know, rather than me reporting only on reproduction for the next 10 years at Radiolab, that what if we just put them all together in a series? And so we're about to do that. For the next month, we're gonna do the series, and the name of the series is Gonads.


[DISCO MUSIC: “Gonads!”]


MOLLY: Gonads. I know what you're thinking: why?


MOLLY: I'm gonna ask you a question. You can say no. What do you think about the word "gonads?"


WOMAN: Gonads? That's crazy question.


WOMAN: It's almost like that word "moist," where it gives you, like, a little uhh!


MOLLY: Yes, that word does have certain connotations.


MOLLY: What do you think of?


WOMAN: Gonads? Isn't that nuts?


MAN: It's a slang term for balls.


MAN: Balls.


MAN: Testicles.


WOMAN: Testicles.


WOMAN: Balls.


WOMAN: Definitely balls.


MAN: Definitely balls.


MAN: You got cojones, like ...


WOMAN: It's just used in, like ...


MAN: Stupid boy humor.


WOMAN: So almost, like, toxic masculinity situation.


WOMAN: You just think, like, sweaty balls and male jokes, pretty much.


WOMAN: Like, kick you in the 'nads?


MOLLY: Great. Would you think it has anything to do with ladies?


MAN: No.




MAN: No.


WOMAN: Oh, no.


MOLLY: Did you know that ladies actually have gonads also? That gonads are both testes and ovaries?


WOMAN: Oh, really?


MOLLY: That it's actually for men and women.


MAN: Really?


WOMAN: I did not know that.


WOMAN: I did not know that.


WOMAN: Did not know that.


MOLLY: 90% of the people I talked to ...


WOMAN: Didn't know that.


MOLLY: They didn't know it.


WOMAN: Who would have thought women and men both have gonads?


WOMAN: Culture. They've stolen the word and made it male.


MOLLY: And I think it's time we reclaim this word. Like, as a citizen, as a human, as a lady, as a science lover, I'm taking the word back.


[DANCE MUSIC: “It's gonad time!”]


MOLLY: Okay. So this is episode one, and this whole series, like, kind of came into being with a single phrase.


KUTLUK OKTAY: Oh right, the duck is in the house.


MOLLY: From this guy.


MOLLY: Can you say for me your name and how you identify yourself?


KUTLUK OKTAY: I'm Kutluk Oktay. I am an ovarian biologist. So I have a research laboratory at Yale University School of Medicine.


MOLLY: So Oktay, he is the one who said that ...


KUTLUK OKTAY: Gonads are magical organs. [laughs] They are! That's our magical organ.


[CHOIR: “Gonads are magic! Magic!”]


MOLLY: So Oktay is Turkish.


KUTLUK OKTAY: You know, I was a curious kid.


MOLLY: He grew up in Istanbul.


KUTLUK OKTAY: I was a Trekkie as a child. And as -- and when I was 10 years old, I would, you know, look into universe and the skies and -- and trying to understand, you know? Make sense of this whole thing.


MOLLY: What was it about the sky that attracted you?


KUTLUK OKTAY: It was the concept of infinity. You know, we're just living a mundane life on this planet without thinking of anything but our routine concerns. But at the same time, we've got this vast space around us and mostly we have no clue.


MOLLY: Mm-hmm.


KUTLUK OKTAY: We live oblivious to that fact. And I would lose sleep over that when I was a kid.


MOLLY: Really?




MOLLY: Fast-forward. Oktay goes to medical school in Turkey. He becomes a doctor, specifically an OB-GYN.


KUTLUK OKTAY: So I had to deliver a lot of babies, probably 20,000 or so.




MOLLY: That's like birthing a small town.


KUTLUK OKTAY: And then, you know, having -- after having made 20,000 delivery I said, you know, perhaps this is not my calling. I wanted to be a little bit more -- more towards the beginning of the process. You know, when you're an obstetrician you're dealing with the finished product, right?


MOLLY: Well, I just think that's a crazy statement, because most people think babies are the very beginning of the process. I'm not sure what gets more beginning than like a small baby.


JAD: Popping out of a lady.


MOLLY: That feels ...


JAD: That feels like the starting line.


MOLLY: We've started something!


JAD: Yeah.


MOLLY: But in Oktay's case, there was, like, some sense that most of the decisions, most of something had already been decided by the time the baby gets out.


KUTLUK OKTAY: And that whole process is fascinating.


MOLLY: So we dragged him into the studio to talk about magical gonads. Basically, just to figure out why are they magical?


MOLLY: I'm interested how you settled on that word.


KUTLUK OKTAY: Yeah. What did I say? You know, I think magical for many reasons. One is their origin, you know? They ...


MOLLY: And he told me what he learned when he started studying this stuff was that the origin of the gonad, like, its creation, is sort of the beginning, because it starts with this whole saga that is so involved and so extreme, that the baby itself does kind of feel like an afterthought. He calls it ...


KUTLUK OKTAY: The Great Migration.


MOLLY: The Great Migration.




MOLLY: Oktay got me into this story, and so I ended up calling a bunch of people about it.


BLANCHE CAPEL: In my lab, we have a slogan that says "Gonads or Go Home." We have t-shirts.


MOLLY: You don't! You do?


BLANCHE CAPEL: We do. We have a t-shirt.


MOLLY: That is Blanche Capel.


BLANCHE CAPEL: Professor in cell biology at Duke University Medical Center.


MOLLY: She essentially studies all the parts of the story we're about to tell you. Okay, so to place this story in time ...


BLANCHE CAPEL: It begins at about, oh, two or three weeks in humans, I bet.


MOLLY: Let's say day 24, just to be safe. Which basically means a sperm fertilized an egg 23 days ago. It could be petri dish, it could be sex, who knows? But inside this woman's uterus, there's a little organism that has been growing for 24 days.


PAT: What does the embryo look like at that point?


MOLLY: That's my comrade-in-arms, Pat Walters, who's the editor of the series.


BLANCHE CAPEL: Actually, I don't know how to describe this very well to you. I could send you a picture.


MOLLY: Does it kind of look like a tadpole?




BLANCHE CAPEL: That's not so wrong.


KUTLUK OKTAY: It looks like a tadpole. And if you look at very early embryos, it's like curled up.


BLANCHE CAPEL: There's a tail.


KUTLUK OKTAY: Got a little tail.


MOLLY: There's, like, the sort of ball of the embryo that's, like, forming the developing body, and then it has this, like, sweep of a tail that's coming off. And if you zoom into the tail, you'll see a little region.


BLANCHE CAPEL: It's called the allantois.


MOLLY: Called the allantois.


BLANCHE CAPEL: Which is the trash bag of the embryo. Before the embryo has an excretory system, it dumps things that it doesn't want in the allantois.


MOLLY: Urine flows in and out there. It's where gas exchange with the mother happens.


PAT: So ...


MOLLY: It's kind of a terrible place.


PAT: It's like a foreign planet.


JAD: This isn't actually part of the embryo itself?


MOLLY: No, it's sort of in the hinterlands. The allantois I always imagined was -- is the -- where Harrison Ford was camped out in Blade Runner 2049, which is like that vast dust desert.


JAD: Super orange dust, yeah.


MOLLY: And there's, like, windstorms, and -- and, like, wind blowing over the desert. I imagine it like that. And it's here where you find some cells ...


KUTLUK OKTAY: These very specialized cells, germ cells.


BLANCHE CAPEL: The germ cells.


KUTLUK OKTAY: Primordial germ cells.


MOLLY: These are the cells that are gonna go on that Great Migration, and put the magic in the gonad.


BLANCHE CAPEL: They -- they're a very interesting cell type. They're -- they're set aside very early in embryogenesis.


MOLLY: And how many are there? Are there, like, a thousand? Two thousand?


BLANCHE CAPEL: I think they're something like 40.


MOLLY: Wait, that's it?




JAD: 40. Biblical number.


MOLLY: And the irony here is -- is these cells sort of like huddled at the edges of this wasteland, might actually be the most important cells in the body. Because after the embryo grows, after the baby gets born, after that baby goes through puberty and one day maybe decides to have a kid, these cells which are present at the very beginning, these cells are in charge of making a next generation of you.


KUTLUK OKTAY: I mean, that's the meaning of life, right? That's the origin of life, these cells. Everything else, I mean we think it's brain, heart et cetera, but I think everything else is there to support the survival of the germ cell.


BLANCHE CAPEL: They're the stem cell of the species, right?


MOLLY: So stem cell means a cell that can create other cells. An originator cell.


BLANCHE CAPEL: We have stem cells for lungs, stem cells for heart, stem cells for neurons.


MOLLY: These cells are the only cells that can make, on their own, all the other kind of cells. They can make a whole person.


BLANCHE CAPEL: So it's a -- they have a remarkable underlying pluripotency.




MOLLY: Do you think they know that?


KUTLUK OKTAY: Well, that's -- I mean those are very difficult questions to answer.


BLANCHE CAPEL: I don't know. I think germ cells know they're really special cells, but I don't think they know what they're gonna become.


JAD: Wait, can I ask you a question? If they're so special, why do they start out in the trash?


PAT: Yeah, that seems like a bad place.


BLANCHE CAPEL: You would think. It's very curious that the germ cells arise near that position, and it's unclear why.


MOLLY: Or you hide your most precious object in the trash dump! [laughs] This has, like, got the best Mission Impossible, like Murder On the Orient Express.


BLANCHE CAPEL: Yup. Maybe that's the plan, I don't know.


MOLLY: In all seriousness, for some reason -- and scientists don't know exactly why -- it seems like evolution has decided to set these cells aside at the beginning of development, which means they have to make a journey back to the middle of the embryo where their destinies will be revealed.


KUTLUK OKTAY: And if they make it there, we make it there.


MOLLY: If they don't ...




MOLLY: Okay. Okay. So -- so they hang around this dusty wasteland for a few days huddled against the elements.


JAD: I wonder what that's like for them to be stuck there.


MOLLY: I imagine if I was in that situation, I would just, like, be, like, wondering how this was my lot in life. This is some sort of cosmic joke? Like, I have a sense -- I have a sense I may be important, but I'm just here.


JAD: Don't know why.


MOLLY: In the wasteland. So they hang out like that for a couple of days, and then, "Doo doo!" There's a call. They hear a call. They maybe smell a call.


JAD: Let's say "hear."


BLANCHE CAPEL: There's a signal ...


MOLLY: They're called into action.




KUTLUK OKTAY: The cells start migrating.


BLANCHE CAPEL: They literally move.


MOLLY: Wow! What -- wait. So how does a cell march?


BLANCHE CAPEL: They actually extend filopodia, which are little cell-like feet.


MOLLY: Okay. Is it, like, it pops out two feet and then it goes walking?


BLANCHE CAPEL: Cells send out extensions, and that extension has a little adhesion molecule on it, like a little sticky spot. So when it puts its foot out it can pull the rest of the cell up to it.


MOLLY: Whoa!


KUTLUK OKTAY: So they take a hike. Hike, hike, hike ...


BLANCHE CAPEL: And interestingly, the germ cells seem to be holding hands, like a long string of paper dolls.


MOLLY: Okay.


BLANCHE CAPEL: And they touch each other. It's as though they are -- the whole crowd is, like, going together.


MOLLY: And after a bit of a hike, they get to the wall of the embryo, which is like, I don't know, a pulsating mass. And somehow ...


BLANCHE CAPEL: This is a very blurry period, I have to say.


MOLLY: They push their way through the wall.


KUTLUK OKTAY: And on the other side, it's just chaos there. It's like a foreign planet.


MOLLY: Because what's happening is -- I mean, the embryo is just, like, dividing, dividing, dividing, dividing, dividing.


BLANCHE CAPEL: You know, the whole embryo is developing very fast at this stage.


MOLLY: Trying to start forming parts. Like, it wants to form organs, it wants to form a nervous system.


BLANCHE CAPEL: There are all kinds of signals flying around to tell the gut to form and to tell the liver to form.


MOLLY: Blood cells are popping up. Neurons.


BLANCHE CAPEL: You know, all these signals are flashing all around, and yet the germ cells ...


MOLLY: Their job is to block it all out.


BLANCHE CAPEL: They migrate right down the middle of the embryo at the mid-line.


MOLLY: Almost like where you could think, like, a spine would be.


BLANCHE CAPEL: Through a forest of signals going around in the embryo.


MOLLY: And these signals are bombarding. Trying to tempt them. Like, "Hey, be a liver cell! Be a liver cell! Come be a liver! Be a liver!" And sometimes these cells are like, "Hmm, wait. Do I want to be a liver? Am I a liver? No, wait. Something tells me I should keep marching."


BLANCHE CAPEL: It seems scary, doesn't it?


MOLLY: Yeah.


KUTLUK OKTAY: Yeah, they go through a battle.


PAT: Hey, do you know if they ever lose one along the way? Like, the chain is going and they're trying to, like, "Don't differentiate! Don't differentiate!" Does, like, the fourth one from the end ever go like, pew! And just become a stomach? And then like, oh crap!


MOLLY: We lost Stan! Keep going!


BLANCHE CAPEL: Hurry! Hurry! It probably happens.


MOLLY: But they try to stay focused together, and they try to resist all of those signals that could divert them from their destiny. They want to stay uncommitted.


DAVID PAGE: These might be the last cells in the developing mammalian embryo to give up their world of possibilities.


MOLLY: This is David Page. He is the director of the Whitehead Institute. Biologist at MIT.


DAVID PAGE: If you see what I'm saying. So basically, when a -- when an egg is fertilized by a sperm, to go back to the -- that beginning, the resulting cell called a zygote, the fertilized egg, has the possibility, has the potential to become every type of cell in the body. And as one cell becomes two and two become four and so on and so on, eventually some cells give up that broad range of possibilities and become committed to narrower occupations and specializations. You know, we have at least 200 or 300 specialized cell types that make up our body. All the other cells make the transition from possibility to reality, and those migrating primordial germ cells are the last cells to give up a wide range of possibilities.


MOLLY: Oh, I like them for their, like, pugnaciousness.


DAVID PAGE: Yes, yes.


MOLLY: Okay, so getting back to the band of 40. We're back in the thick of things. They're marching through the middle of the embryo being, like, pelted and torn at, fighting off all these other signals. And they do this for one day, two days, three days, four, five ...


MOLLY: I imagine the get tired as they go.


MOLLY: Six, seven, eight, nine ...


MOLLY: But the signal that they're following is getting stronger. And then pretty soon, over the horizon on kind of either side of the path, they start to see these mountains.


BLANCHE CAPEL: The urogenital ridge is going to emerge as sort of a mountain off the back wall of the body cavity.


[CHOIR: "You are entering the gonadic region."]


MOLLY: So they're still marching down this path. They're following the signal. The mountains are getting closer and closer. And then at some point, the path in front of them splits. It goes to the left and it goes to the right, and half the cells will go to the left and half the cells will go to the right. Regardless of what direction they go in, they end up at the base of a mountain. And the mountain is a mass of, like, a dense mass of cells, and they come right up to the edge of the mountain wall, and they're able to just, like, push those cells aside and, like, squeeze into the interior of the mountain. Which is an entirely new space.


BLANCHE CAPEL: So the germ cells enter. Enter the gonad.


JAD: Oh, this is the gonad.


MOLLY: Yeah, this is the place that will either be an ovary or a testes.


JAD: And which -- I mean, has it been figured out which it is?


MOLLY: No. At this point, it could go either way.


JAD: Huh.


MOLLY: I think about this place as a cathedral. And the cathedral, it's sort of under construction. And as they walk in, they -- they probably know immediately that this is the place that's been calling them, because that signal they've been following, it's everywhere.


BLANCHE CAPEL: Maybe when they get to the gonad, the whole cell is surrounded by the signal, and that tells the cell to stop. But this is just a guess.


MOLLY: What do you think it's like for the -- for the germ cells? Like, sort of they've been going on this walk, and then they get to a place that says, "Stay here." So I wonder what the "Stay here" like, I don't know, feels like.


BLANCHE CAPEL: Oh, I think it feels like home.


MOLLY: After marching for almost two solid weeks, they finally arrived.


BLANCHE CAPEL: They recognize this is where they belong.


MOLLY: But everyone I talked to said probably still at this point ...


DAVID PAGE: They don't even know what lies ahead for them.


MOLLY: Or even why they're there.


DAVID PAGE: We're anthropomorphizing, but why not?


MOLLY: David Page again.


DAVID PAGE: I would suggest that the primordial germ cells, they have been instructed to migrate to the genital ridge. But they don't know why, and they don't know what they're gonna do when they get there. They have not a clue.


MOLLY: But the clue is coming!


[DISCO: “Gonads! It's gonad time! It's he. It's she. Gonads! It's she. It's he. It's she. Gonad! It's she. It's gonad time!”]


[JEFF PEARSON: This is Jeff Pearson calling from Grand Island. Nebraska. Radiolab Presents: Gonads, is supported in part by Science Sandbox, a Simons Foundation initiative dedicated to engaging everyone with a process of science. Additional support for Radiolab is provided by the Alfred P. Sloan Foundation.]




MOLLY: Okay, so to pick up on the action, the tribe of 40, they find themselves in this cathedral-like space. Technical name?


BLANCHE CAPEL: The mesonephric gonadal region.


MOLLY: I'll call it the House of Gonad.




MOLLY: They're in this beautiful space.


DAVID PAGE: But they don't know why.


MOLLY: But what happens is, immediately when they enter ...


BLANCHE CAPEL: They are surrounded by somatic cells.


MOLLY: I imagine these cells as, like, friendly monks, just gliding around in red robes.


BLANCHE CAPEL: Their job is to just protect you and make sure that nothing bad happens to you.


JAD: So these are the cells that have been calling them?


BLANCHE CAPEL: I don't know.


MOLLY: It's kind of a hard question to answer because the genital ridge had just started forming when the germ cells began their migration. So no one really knows, like, what was sending the signal. But after a few days, some people say a few weeks, these somatic cells that are gathered around the germ cells will lean in real close, and they reveal the destiny. They tell them either one of two things. You will become a sperm. Or you will become an egg.


JAD: What exactly are these monk cells doing, though? I mean, to make them change are they, like, bumping them in some special way? Or ...


MOLLY: No, no, no. They're releasing proteins.


BLANCHE CAPEL: Well, there are molecular signaling cascades that are controlling the male or female fate of the -- of the germ cells.


JAD: And what makes them go one way or the other?


MOLLY: Ugh, that is super complicated, and we're gonna get into it later in the series. So for now, I'll just say ...


BLANCHE CAPEL: In mammals, sex is genetically controlled by whether or not you have two X chromosomes or an X and a Y chromosome.


MOLLY: So it's just basically like your fourth grade biology. If the cells in the cathedral have a y-chromosome, they'll -- they'll say sperm, and if the cells in the cathedral have an XX chromosome, they'll say egg.


JAD: So it's still basically just fate and luck as to what -- which way they go.


MOLLY: Yes, but here's the cool part. If the monks tell the germ cells that they're gonna be sperm, they basically divide a little bit and then the monks, like, take the germ cells and they put them to sleep. They sort of -- I don't know -- entomb them in these, like, catacombs until after birth and puberty. But if the germ cells get told that they're gonna be eggs, something different happens inside of them and they just go nuts.


BLANCHE CAPEL: They divide. They divide quite a lot. Rapidly for a while.


MOLLY: Suddenly, the band of 40 becomes a thousand and two thousand and ten thousand. The monks then take each of these new eggs and embed them in the wall of the cathedral.




MOLLY: Boom!




MOLLY: Boom!




MOLLY: Boom!




MOLLY: Boom!


JAD: They literally shove the eggs into the wall of the House of Gonad?


MOLLY: Yes. And this goes on for months.


KUTLUK OKTAY: As a matter of fact, their numbers probably reach around 6 to 10 million during the fifth month of pregnancy, about 20 weeks of gestation.


MOLLY: That embryonic ovary is gonna have all the eggs it will ever have when it's only five months along.


JAD: Wait, this is all still in utero?


MOLLY: This is all in utero it's happening.


JAD: It has 10 million eggs, and it is still itself months away from being born?


MOLLY: Yes. Theoretically at that point, that is 500 times more babies than Oktay ever delivered in his career in this one developing embryo.


JAD: Fuck!


MOLLY: Yeah, I know.


JAD: God, you know what just occurred to me? Like, if you go all the way back to the beginning of this story you told, Day 24 or whatever it was. You've got this little organism forming, probably the mother doesn't even know it's there yet. But already there are these cells in existence that will be the kid of the kid she doesn't even know she has yet. So her grandkids are in there already. Is that right?


MOLLY: So when you're pregnant with a person, you carry inside of you the cells that will make the next -- oh, you're right, it is granddaughter.


JAD: It's like -- it's like your grandkids are already ...


MOLLY: Inside of you.


JAD: Inside of your unborn child.




JAD: That's bananas!




JAD: Do you think the great grandkids are in there, too?


MOLLY: Well, it's like all this -- that's what she means by stem cell of the species, because it's the same material that makes -- they then -- they not only make the body, they make more eggs and sperm. They make the next generation of egg and sperm. So they're -- so they're both making a generation, but then making the ability for that generation to make another generation.


JAD: Oh, my God! This is like -- this is like humanity.


MOLLY: It's mirrors. You're not only cradling, like, your child, you're cradling, like, infinite future Homo sapiens.


JAD: Wow!


MOLLY: That's the infinity.


JAD: It's crazy that all that is there and you're not even a thing yet. That the first thought -- or thought? I don't know. The first thing that this organism has been programmed to do is not, "Hey, make a -- make a person, make a brain, make a life." No, it's "Make more."


MOLLY: Yeah, it's pretty gnarly.


JAD: Yeah.


BLANCHE CAPEL: You know, many, many people believe that we exist just as a harbor for our germ cells until we can make new people.


MOLLY: Like, we're just their hosts.


DAVID PAGE: In some sense, that's absolutely true. I mean, or as -- as was said a long time ago, a chicken is an egg's way of making another egg.


MOLLY: [laughs] Really? I've never heard that before.


MOLLY: So I was in Michigan a couple of weeks -- months ago. And so I was in Michigan, and I was kayaking on this river that has super sandy bottom and it's pretty shallow. I don't know, it's, like, three or four feet deep. And the cool thing was that the salmon were spawning. Huge fish! They were, like, three to four feet. They were so thick around, and there were so many of them that they would, like, rustle my kayak. And I see something kind of in this one part of the river, like, by itself, and I look and it's a fish. It's a salmon that's lying on the bottom of the river. And I see, like, through the ripply water some, like, pink. So I turn the kayak around to go, like, look at it. And what I realize is the pink is not, like, flesh. The pink is, like, packed eggs. The body was sliced open so you could see into the hollow. And in the hollow were just like -- what felt like millions of these, like, bubblegum pink drops of eggs.


MOLLY: Like, the entire body cavity was packed eggs. And to think that parts of our body, male and female by the way, because the testes do this just little later in life -- to think that parts of our body are like that fish, it felt like just pulling back the curtain and seeing something that I can never unsee.


[DANCE MUSIC: "It's gonad time!"]


MOLLY: This episode was reported by me, Molly Webster, and produced by Jad Abumrad. Original music by Dylan Keefe. Ballad Of The Fish and The Gonads Theme were written, performed and produced by Majel Connery and Alex Overington. Radiolab Presents: Gonads is produced by Rachael Cusick and edited by Pat Walters. One last thing before I go. Later in the series, we're gonna dig into sex-ed, and one of the things that comes up in every conversation you have about sex-ed is a book that somebody read to learn about the birds and the bees. It might have been given to them or they found it, like, in their library book sale. So we want to try and create an online sex-ed library with as many of these books as we can find, for all ages. So go to Radiolab.org/SexEdBooks and tell us about a book you got as a kid and the reason you loved it or didn't. And then we're gonna add it to the shelf. And it's gonna be great. So, that's it. That's our episode, and see you next time. Bye.


[KATRINA: This is Katrina calling from New York City. 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.]