[RADIOLAB INTRO]

JAD ABUMRAD: Hello.

ROBERT KRULWICH: Hello.

JAD: Hello.

ROBERT: Hello.

JAD: Today I want to start the show by telling you about a guy—well, a very, very, very important man. Probably one of the most important guys in ...

ROBERT: Guydom.

JAD: Yeah. Okay, tell me the correct pronunciation on, uh, Leokenhoken?

MATTHEW COBB: The way that you should say it is something like leven-herk.

JAD: And here, thankfully, to help with our pronunciation and to fill in the details is professor Matthew Cobb.

MATTHEW COBB: I'm the program director for zoology at the University of Manchester, and I've written a book about this called Generation: The Seventeenth-Century Scientists Who Unraveled the Secrets of Sex, Life, and Growth.

JAD: Okay, so, Leeuwenhoek.

MATTHEW COBB: Yeah, that's fine.

JAD: Okay. So what did he do?

MATTHEW COBB: He was a draper.

JAD: A draper?

MATTHEW COBB: Yeah, so he just sold cloth.

JAD: Oh. Huh.

MATTHEW COBB: He had no scientific training whatsoever. He was interested in microscopes.

JAD: Why would a draper be interested in microscopes?

MATTHEW COBB: It was his hobby. That's what he did. He made these microscopes.

JAD: And he was actually really good.

MATTHEW COBB: That's right.

JAD: Although you have to keep in mind that microscopes at that point in time—we're talking 1670s here—it's not exactly how we think of them now. Back then, they were just ...

MATTHEW COBB: Tiny balls of glass. And that's it.

JAD: And science itself was just a wee little baby.

MATTHEW COBB: You gotta really just put yourself back.

JAD: Okay, there was Leeuwenhoek doing really well with these microscopes, and pretty soon, scientists all over the place were asking him to look at stuff.

MATTHEW COBB: For example, what's in blood? Or what's in sweat? Or what's in semen?

JAD: Dun dun dun.

MATTHEW COBB: This is where it does get rather sordid.

JAD: Okay, so ...

ROBERT: Wait wait, Jad, before you—I would just—this is the point where we should tell our audience that some of the references from here on in will be a bit graphic. If you don't want to hear that kind of stuff ...

JAD: They'll be fine.

ROBERT: No, if you don't want to hear that stuff now, go out to the garden and, you know, check out the rabbits.

JAD: Okay. Now, getting back to the story. It's 1667. Just imagine. And Leeuwenhoek has just received a letter from the Royal Society of London, this big group of scientists, asking him to take a look at a drop of human semen.

MATTHEW COBB: Just to see what's in there.

JAD: And not to be graphic, but one autumn day ...

MATTHEW COBB: Autumn 1677.

JAD: He is in his bedroom.

MATTHEW COBB: Having conjugal relations with his wife, Cornelia.

JAD: He's got his microscope ready, plus a little vial.

MATTHEW COBB: And then, as he put it, within six beats of the pulse after he ejaculated, he got the semen and he put it into this very thin capillary tube, rushed over to the window. His wife's lying there thinking ...

JAD: What the hell are you doing?

MATTHEW COBB: Not again! Come on, will you? Enough with the microscopes already! And then he looks into the semen, and he can clearly see that there's a thing, there's something in there. Some kind of small structure.

JAD: He squints, and he focuses ...

MATTHEW COBB: And he can see all these wriggling things. It is just full, absolutely full, of these tiny eel-like things that he says are a vast number of living animalcules.

JAD: Animalcules?

MATTHEW COBB: Their bodies were rounding and furnished with a long, thin tail. They moved with a snakelike motion of the tail as eels do when swimming in water.

JAD: Wow, so what was he thinking at this point? Do we know?

MATTHEW COBB: I don't know. Putting myself in his place, I'd think, wow!

JAD: Because here's the thing. At this point in time, people didn't really understand where babies came from. They knew it had something to do with sex, but the notion of heredity was still very fuzzy, and how a baby developed was a total mystery.

MATTHEW COBB: What's life? How do you know if something's alive? In those days, one of the main things that they associated with life was movement.

JAD: Movement.

MATTHEW COBB: If stuff moved, it was alive.

JAD: So if movement is the key, you can imagine what Leeuwenhoek must have been thinking staring at these wriggling little beasts in the vial. Because they moved.

MATTHEW COBB: That's right.

JAD: Oh boy, did they move.

MATTHEW COBB: These things are trying to get somewhere. They're thrashing. They're desperate.

JAD: Maybe in this vial is the secret to life. To the soul. This is what people thought. It didn't take long before a pretty fantastic idea began to circulate, which is that not only is the sperm the vehicle of the soul, but if you could somehow zoom all the way down into its little head, you would find, in there, a little man.

ROBERT: Hello.

JAD: Hello.

MATTHEW COBB: This little chap all hunched up.

JAD: A little tiny guy.

MATTHEW COBB: A tiny human.

JAD: The thinking was that one day when the microscopes got better, you'd actually be able to see that tiny little human ...

MATTHEW COBB: With your own eyes.

JAD: Because it had to be there.

MATTHEW COBB: Because if the sperm is the sole source of life, then there must be something in there who'll look pretty much like a human being.

JAD: One problem though.

ROBERT: What?

JAD: If you were one of these folks who believed that the sperm was the soul, well, then you had to ask yourself, what does this say ...

MATTHEW COBB: About God, because it would mean He was creating all these souls, and then he was just wasting them. Leeuwenhoek did a calculation. He worked out that there were more semen, more spermatozoa, in an ejaculate of a cod—he got a cod and he opened it up and saw how many sperm there must be in its ejaculate—and he said there are—he was pretty much right—there are more sperm in this ejaculate than there are human beings alive on the planet, and that's just in one cod.

JAD: What? That's true?

MATTHEW COBB: Yeah.

JAD: Holy moly.

MATTHEW COBB: So you imagine all the men producing all this stuff all the time. That's an awful lot of souls if they're all potential human beings, just ...

JAD: Dying.

MATTHEW COBB: Well, all but one.

ROBERT: How many sperm are in a human ejaculate?

JAD: About 180 million.

ROBERT: Oh, see, that's nothing these days.

JAD: Yeah, it's like Brooklyn.

ROBERT: [laughs] You just live there. All right, this is Radiolab.

JAD: I'm Jad Abumrad.

ROBERT: I'm Robert Krulwich. And our program today is about ...

JAD: By the way, 180 million is still a lot.

ROBERT: It's not a lot. It's not a lot.

JAD: Considering you only have a couple of eggs.

ROBERT: Who has a couple of eggs?

JAD: The lady has a couple of eggs. She has a finite number, whereas the guy is making millions every day.

ROBERT: Mm-hmm. That's right.

JAD: Anyhow, our program today is about sperm.

ROBERT: Yep.

JAD: Stick around. Okay, in all seriousness, before we get started for real, I just want to tell you that this program does actually contain strong sexual material. Nothing too graphic, but this is your warning. Stick around. It'll be great.

ROBERT: Okay, for those of us who remain, let's get back to our basic question.

JAD: The "why so many" question?

ROBERT: Yes. Why is there such a startling asymmetry between the number of sexual cells produced by a male and the very relatively few eggs in a female?

TIM BIRKHEAD: Well, of course, this is the question.

ROBERT: I put the question to ...

TIM BIRKHEAD: One, two, three, four, five, six, seven, eight, nine, ten.

ROBERT: Another—there's a lot of English people on the show today.

TIM BIRKHEAD: I'm Tim Birkhead. I work at the University of Sheffield in the Department of Animal and Plant Sciences.

ROBERT: And he is an expert on sperm.

TIM BIRKHEAD: In birds.

ROBERT: How did you choose this line of work?

TIM BIRKHEAD: Ever since I was a teenager, I was obsessed by birds. I was also obsessed by sex. And I managed to combine the two into an academic career. Isn't that lucky?

ROBERT: And in any case, he says this question of waste ...

TIM BIRKHEAD: Why on earth did God make so many sperm? It just didn't seem very sensible.

ROBERT: Well, this question not only troubled the church, it flummoxed science—flummoxed is I think the right word?

JAD: Flummoxed.

ROBERT: Scientists for a very long time.

TIM BIRKHEAD: It really wasn't until about the 1970s that finally the large numbers of sperm that males transfer to females finally began to make sense.

JAD: What happened in the 1970s?

ROBERT: Well, before the 1970s, bird scientists assumed if a female chose a spouse for the season, she would stick to the spouse for the season. She would be faithful. But in the '70s, when they looked a little more closely, they found there was more to the story.

ROBERT: Springtime in Somerset. The female bushy-tailed whippoorwill is always present in woods like this, always searching for that springtime joy of love. Her love song is very beautiful, as is his. Here he comes. And there is the act of love, consummated rather quickly. Now he's off to get his new sweetheart a juicy worm. She's at home for a time, and she—well, actually, she's hopping off to another bird. Em, it seems to be another male. She of course will remain loyal to this first partner. Oh dear. Cut the tape!

TIM BIRKHEAD: Prior to the 1970s, if people saw females behaving promiscuously, they assumed that there was something wrong with them.

ROBERT: What is wrong with this bird? Do you have another bird? Hey, Lance, have you got another bird?

TIM BIRKHEAD: Hormone imbalances or some kind of misunderstanding.

ROBERT: But then they discovered ...

TIM BIRKHEAD: DNA fingerprinting.

ROBERT: The DNA test.

TIM BIRKHEAD: Which provided a completely unequivocal test of paternity.

ROBERT: They'd go to a nest, say, and look at the five eggs in the nest, test the DNA, and discover that some of those eggs came from different dads.

TIM BIRKHEAD: Indicating that the female had mated with more than one male.

[ARCHIVE CLIP: One of these four men is the father, but she doesn't know which one.]

TIM BIRKHEAD: DNA fingerprinting gave us the evidence that, in fact, the majority of animals, the females are promiscuous.

ROBERT: Really? I mean, this is like, chimp babies? Chickadee babies? Chipmunk babies?

TIM BIRKHEAD: It's almost ubiquitous.

[ARCHIVE CLIP: Let's find out the truth. You are not the father.]

TIM BIRKHEAD: At the moment, I'm only talking about non-humans.

JAD: Right. But what does this ...

ROBERT: Yes.

JAD: ... female promiscuity thing have to do with the why so much sperm question? What's the connection?

ROBERT: Everything. Everything, because once people understood that that was going on, well, then the level of competition between males gets actually much more complicated.

JAD: What do you mean?

ROBERT: Well, if I am chasing a lady, now, not only do I have to worry about a competitor, but I have to worry about all the people I've never met who have been having sex with my girl. There's a whole level of ...

JAD: Oh, you mean like the sperm is competing?

ROBERT: The sperm is competing.

JAD: Not just the makers of the sperm, but the sperm itself.

ROBERT: The sperm itself! So there's outdoor competition, but now there's indoor competition.

TIM BIRKHEAD: Exactly.

ROBERT: If you get my drift.

TIM BIRKHEAD: And one very effective way of competing is simply to produce more sperm than the next guy. Okay, I think we need to step back a little bit. If females are promiscuous, natural selection is gonna favor the male that wins and fertilizes that particular female's eggs. As a consequence of that, males have evolved the most staggering array of adaptations to minimize their own chances of being cuckolded.

JAD: What does cuckolded mean?

ROBERT: Cuckolding means your wife is cheating on you and you don't know it.

JAD: Oh.

ROBERT: So what he's saying is that animals will go to elaborate lengths to be not cheated on. In fact, let me give you three spectacular illustrations, as never before heard on our program. We're going to begin ...

JAD: Which includes most things.

ROBERT: ... with sperm competition as displayed by, first ...

[ARCHIVE CLIP: The rove beetle.]

[ARCHIVE CLIP: Beetle!]

TIM BIRKHEAD: These beetles are amazing.

ROBERT: When the male beetle, the male rove beetle, has sex with a female, says Tim ...

TIM BIRKHEAD: They transfer the sperm in basically a package of sperm called a spermatophore. Once it's inside the female, it starts to swell and expand.

JAD: Like a balloon?

TIM BIRKHEAD: Yeah. In swelling and expanding, it pushes out or away any rival sperm.

JAD: Hey, hey, hey, but the sperm is stuck in a balloon.

ROBERT: Uh-huh.

JAD: It's gotta get out.

ROBERT: Oh, yes, well, but the lady rove beetle has ...

TIM BIRKHEAD: A little structure, a structure like a tube ...

ROBERT: ... that will puncture the spermatophore ...

TIM BIRKHEAD: ... releasing the male's sperm.

JAD: No kidding.

TIM BIRKHEAD: Yeah, it's kind of like science fiction.

JAD: Wow.

ROBERT: But if you think the rove beetle has got something going on, let's meet ...

[ARCHIVE CLIP: The dragonfly.]

[ARCHIVE CLIP: Dragonfly!]

TIM BIRKHEAD: In dragonflies, males have the most elaborate and bizarre penis. It's covered with backward-pointing spines, hundreds of backward-pointing spines.

ROBERT: Kind of like, you know, bristles on a pipe cleaner.

TIM BIRKHEAD: And a very clever guy called Jeff Waage did a very clever experiment. He allowed male dragonflies to mate with females and separated them at different stages during their rather protracted copulation. And what he found was, halfway through the copulation, the male ...

ROBERT: Before he actually does the act.

TIM BIRKHEAD: ... is actually removing his penis from the female, and it's covered with sperm from the previous male and inseminated that female.

JAD: Oh, so he's brushing out the other guys.

TIM BIRKHEAD: Exactly.

JAD: That's rather shocking.

TIM BIRKHEAD: Yep.

ROBERT: But better still—better still is the duck.

JAD: The duck?

ROBERT: The duck.

[ARCHIVE CLIP: Yay, duck!]

TIM BIRKHEAD: Most birds don't have a penis, male birds. Ducks do.

JAD: That's it?

ROBERT: [laughs] No. It goes on.

TIM BIRKHEAD: Across different duck species, the penis size varies from very small to about 14 inches, something absolutely astronomical on a relatively small duck.

ROBERT: And the thing about the duck is—I don't quite know how to put this.

TIM BIRKHEAD: Ducks engage in forced extra-pair copulations.

ROBERT: What he's really saying is that the males are—are—they're raping the females.

JAD: Oof.

ROBERT: But wait. Because the females have a strategy of their own.

TIM BIRKHEAD: A couple of years ago, we were dissecting a female duck, and a postdoc called Patty Brennan called me into the lab. She said, "Look at this. I've just found this funny structure in the female's vagina." And what it was was a side branch.

ROBERT: Meaning instead of one, you know, clear highway right to the egg, this one had a kind of ...

JAD: Off-ramp?

ROBERT: Off-ramp.

TIM BIRKHEAD: I phoned a colleague in France who was a duck expert and he said he'd never seen such a thing, but give him 10 minutes and he'll go and check. So he obviously went off and dissected his own duck, phoned me back, and said, "My God, you're right."

ROBERT: There it was, an off-ramp in the French duck.

TIM BIRKHEAD: By which time we'd finished our dissection, and in fact ...

ROBERT: When the British took a look at their duck ...

TIM BIRKHEAD: In the duck that we looked at, there were two or three separate side branches. Patty then went on to do a comparative study of a lot of different duck species, and what we found was that, in species where the male had an enormous phallus, the female had the most complex vagina we'd ever come across. Some had two or three side branches and a very long spiral like a corkscrew at the end of the vagina. And if you think about it, what seems very likely here is that the female has got these structures to deflect the male. If she's being raped, she might contract part of her reproductive trap to send the male off down a blind alley. If he avoids that, she can just tighten up the spiral so his sperm can't get to the right place.

ROBERT: So what you've got here is a kind of warfare. The male says, "All right, I'm coming in there, like it or not." And the female says, "Well, you're getting nowhere, like it or not."

JAD: Go female ducks.

TIM BIRKHEAD: Remarkable case of females evolving counter-adaptations to keep males at arm's length. Or penis length.

JAD: [laughs]

TIM BIRKHEAD: So to speak.

JOANNA ELLINGTON: So this is Maverick and Buckles. They are African geese.

ROBERT: The British male scientist section of our program is coming briefly to a pause so we can meet an American and a female.

JOANNA ELLINGTON: My name is Joanna Ellington.

ROBERT: Joanna Ellington.

JOANNA ELLINGTON: I am a PhD in reproductive physiology.

ROBERT: We spoke with her at her farm in, yes, Washington state.

JOANNA ELLINGTON: So we have 70 acres here, and I was a veterinarian before I did my PhD.

ROBERT: You are an andrologist?

JOANNA ELLINGTON: Yes. An andrologist, the study of male reproduction.

ROBERT: Andro- for man ...

JOANNA ELLINGTON: ... and -ology is study of. Yes.

ROBERT: Yeah.

WOMAN: Where are the pigs?

JOANNA ELLINGTON: They're right—the pigs are over here, sleeping. They're going to be bred today. We actually have semen flying in from Nebraska. We're gonna go down here to the chicken coop.

ROBERT: And while she's walking to the chicken coop, let me just say, we finally come to a human sperm expert to ask about us.

JAD: Yeah, and? I mean, this competition thing, does it work like that with us?

ROBERT: Well, that's the real surprise to me. We've all seen the sex education films, you know, when you're in fourth or fifth grade.

[ARCHIVE CLIP: The woman's own defense system attacks the sperm. They are unwelcome cells from another organism, and they are potential enemies.]

ROBERT: But when Joanna gave me her version of all this, it was not like that at all. Let me start from the beginning. First ...

JOANNA ELLINGTON: The sperm have to get through the cervix. The woman's cervical mucus has a lot of fibers in it that are criss-crossed.

ROBERT: So you'd think there'd be this big ...

JOANNA ELLINGTON: ... mesh ...

ROBERT: ... barrier that they couldn't get through.

[ARCHIVE CLIP: The barriers are numerous.]

ROBERT: But ...

JOANNA ELLINGTON: When the woman ovulates, the hormones in her body make all those fibers in the cervical mucus line up.

ROBERT: Ooh.

JOANNA ELLINGTON: And they basically make a little highway that the sperm can swim through. Zip, zip, zip.

ROBERT: Not only is she welcoming them in, she's making sure that they don't get lost.

JOANNA ELLINGTON: They are directed to the side that has the egg on it.

ROBERT: Oh, because there are some tubes with eggs and some tubes without?

JOANNA ELLINGTON: Right.

[ARCHIVE CLIP: One fallopian tube leads to the waiting egg, the other to an empty tube.]

JOANNA ELLINGTON: Except for the woman's body says, "Over here guys, this side."

ROBERT: And most surprising of all is that halfway through the journey, there's a rest period in—it's called the fallopian tube.

JOANNA ELLINGTON: The fallopian tube says, "Oh, great. We know that you guys are here. We know that you're pretty fragile guys. So we're gonna change the type of sugar proteins that we make. We're gonna make sugar proteins that you're bathed in and you just hang out here until an egg comes."

ROBERT: Oh, so we're now in the waiting room?

JOANNA ELLINGTON: Yes.

ROBERT: And we're being sugared?

JOANNA ELLINGTON: Yes.

ROBERT: This sounds nice.

JOANNA ELLINGTON: It is nice.

ROBERT: Sounds like a little Roman moment, everybody's lying down and kind of getting a towel wash or something.

JOANNA ELLINGTON: They're very quiet at that point. Metabolically, they're quiet.

ROBERT: The female is essentially telling them, "Shh. Wait. Not yet. Not yet."

JOANNA ELLINGTON: They can live in the fallopian tube for two, three, four days, maybe even a week.

JAD: A week?

ROBERT: Yep. [laughs]

JAD: You're kidding.

ROBERT: Until her egg is ready. That's when she says ...

JOANNA ELLINGTON: "Hey, we just ovulated. You need to let the guys go." And the sperm are released and start swimming up the track.

[ARCHIVE CLIP: They swim in dense bunches ...]

JOANNA ELLINGTON: To meet the egg.

[ARCHIVE CLIP: ... in search of the egg.]

ROBERT: And the rest of it, of course, you know.

JAD: Huh. Never heard about the sugar room before. I mean, that seems like news.

ROBERT: Yeah, in the fallopian tubes? Yeah. Neither had I. This had been discussed by scientists, but there was no evidence to prove that it was so. But Joanna ...

JOANNA ELLINGTON: As a good scientist ...

ROBERT: She was the first to provide the evidence, she says.

JOANNA ELLINGTON: After I had my last son, I told my doctor, I said, "My husband and I are gonna have intercourse. You are going to do my tubal ligation and cut out my tube, and we're going to get pictures of the sperm stored in the human fallopian tube." So we did. [laughs]

ROBERT: [laughs] So you counted your husband's guys.

JOANNA ELLINGTON: Yes, yes.

ROBERT: At the gate.

JOANNA ELLINGTON: Yeah. There weren't very many there. Just a few.

ROBERT: How many were there?

JOANNA ELLINGTON: He had about 20 in the fallopian tube that we looked at.

ROBERT: Oh, man. That seems like a fragilely low number.

JOANNA ELLINGTON: Well, it is, but you have to remember that you only need one.

JAD: Wow, that blows my mind. I mean, that's like 20 little potential souls lost at the gate.

ROBERT: The cool thing is that, yes, there is this level of competition still, but underneath, there is this substrate of male–female cooperation. It's much more an act of teamwork than one would have supposed.

JOANNA ELLINGTON: Hazel's sperm just arrived. Thought I'd let you guys know.

JAD: Oh.

JOANNA ELLINGTON: Come here, girls!

GIRL: ... get pregnant?

JOANNA ELLINGTON: Yeah, they're gonna get pregnant.

JAD: Hazel? Who's Hazel?

ROBERT: That's her pig.

JOANNA ELLINGTON: Hazel!

ROBERT: Is it a big box, or, what is it?

JOANNA ELLINGTON: Uh, it's a white Styrofoam cooler.

JOANNA ELLINGTON: Go ahead and scratch Hazel's back, Sagey.

JOANNA ELLINGTON: We'll end up putting probably about a half a cup into Hazel.

ROBERT: Wow. How long did it take Mr. Pig to make a half a cup?

JOANNA ELLINGTON: [laughs] Pigs make a lot of sperm.

JAD: Robert. We gotta leave the farm.

ROBERT: Not yet. No, come on.

JAD: Come on, we gotta go to break. Sorry.

ROBERT: So you're gonna miss some stuff about the pig.

JAD: Radiolab will continue in a moment.

[ANSWERING MACHINE: Message one ...]

[JOANNA ELLINGTON: Radiolab is funded in part by the Alfred P. Sloan Foundation, the Corporation for Public Broadcasting, and the National Science Foundation. Radiolab is produced by WNYC and distributed by National Public Radio.]

[ANSWERING MACHINE: End of message.]

 

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