[RADIOLAB INTRO]

JAD ABUMRAD: All right, K.

ROBERT KRULWICH: Yeah.

JAD: I want to start with a parental daydream for a second.

ROBERT: What?

JAD: It's an idea that's been kicking around for me since my kids were born.

ROBERT: Okay.

JAD: Actually, the idea itself is pretty old. It goes back to the 1800s.

SAM KEAN: Right around Napoleon's time.

JAD: To a fellow by the name of Jean-Baptiste Pierre Antoine de Monet, chevalier de Lamarck.

SAM KEAN: Yep.

ROBERT: [laughs]

SAM KEAN: Lamarck, Jean-Baptiste Lamarck.

JAD: Who, according to writer Sam Kean ...

SAM KEAN: He was really one of the first grand theorists in biology. He actually coined the word "biology" too.

ROBERT: Really?

SAM KEAN: Yep.

JAD: His big idea, as you might know, is that what a person does in their lifetime could be directly passed to their kids.

SAM KEAN: Very easily. His famous example was giraffes.

JAD: Lamarck said, "You want to know how a giraffe got its long neck?"

ROBERT: Mm-hmm.

JAD: One day this giraffe, mother giraffe, let's say, was looking up in the tree and saw some fruit, and had to stretch her neck. And stretch again. Whole lifetime of stretching. And then when she had a baby ...

ROBERT: Mm-hmm?

JAD: ... stretching got into the baby. And then that baby would stretch and stretch and stretch, and it would give a little more stretching to its baby. And eventually over the millenia, what you'd get is a creature with a very long neck.

SAM KEAN: Because they're reaching for the tops of trees.

JAD: It makes a kind of common sense, really.

SAM KEAN: It does. It does make kind of a folk sense. He thought it worked with humans, too. His example with humans was a blacksmith. He thought that because they're swinging hammers all day, they got big bulky muscles, and then they would pass the muscles to their children.

JAD: The sneaky idea here is that the blacksmiths, the giraffes, they made it happen. They willed the neck to get longer, the muscles to get bigger.

SAM KEAN: And the key point is that it wasn't something inborn in them. It was something they acquired during their lifetime.

JAD: Which they passed to their kids.

ROBERT: Right.

JAD: And that's wrong. [laughs]

ROBERT: [laughs]

JAD: That's not how it works, we're told.

ROBERT: We now know that that's not the case.

JAD: But wouldn't it be nice if that's how it worked?

[ARCHIVE CLIP, child: Oceans.]

[ARCHIVE CLIP, Jad: Well let's—let's read the book first.]

[ARCHIVE CLIP, child: Read it.]

[ARCHIVE CLIP, Jad: Yeah, let's read.]

JAD: Because, you know, now that I've got these two kids, right?

ROBERT: Yeah.

[ARCHIVE CLIP, Jad: Do you see that owl?]

[ARCHIVE CLIP, child: Yeah! Right there!]

JAD: I find myself thinking, like, okay, I know these kids have their genes—half from me, half from my wife.

ROBERT: Mm-hmm.

JAD: And I know I can't change those genes.

ROBERT: Right.

JAD: And I know fate is gonna give them a couple of random mutations in those genes.

[ARCHIVE CLIP, child: There's the moon.]

JAD: That I have no control over.

ROBERT: Mm-hmm.

JAD: That's just the cold logic of Darwinian evolution.

ROBERT: Yeah.

JAD: Well, it's offensive. I mean, the idea that they could be constrained by their DNA, that maybe one of us gave them a bit of DNA that's gonna hold them back? It's a terrible thought!

[ARCHIVE CLIP, Jad: What's this letter right here?]

[ARCHIVE CLIP, child: A.]

[ARCHIVE CLIP, Jad: How about this one?]

JAD: And so what you do—I think all parents do this, is that you slip into this Lamarckian delusion that what you do with your kids can somehow rewrite all that. That you can somehow by just being nice to them, reading them stories or whatever, that you could somehow break them free of all that.

ROBERT: Rewrite their—their blueprint? Like ...

JAD: I don't know. You don't really say it to yourself that way, but yeah.

ROBERT: You can make a deep difference.

JAD: Yeah, like, you can help them overcome you.

[ARCHIVE CLIP, Jad: What's that called?]

[ARCHIVE CLIP, child: I don't know.]

ROBERT: You can't!

JAD: I know.

ROBERT: That's what Darwin says, you can't.

JAD: I know! I know! Once they're born, their genes are fixed and change does not happen in a generation or two. It happens ...

SAM KEAN: Really ...

JAD: ... really ...

SAM KEAN: Really slowly. Gradually, achingly slowly.

JAD: One parent stretching isn't gonna do anything. See, that's the bummer of Darwinian evolution. As a parent, you are a tiny blip in a very, very, long story.

ROBERT: But this hour, we're gonna fight this sort of sad sack feeling of inevitability and impotence.

JAD: [laughs]

ROBERT: And rewrite the so-called rules of genetics.

JAD: That's right. Today on Radiolab ...

ROBERT: We're gonna lick some rats.

JAD: Starve some Swedes.

ROBERT: Sterilize some women.

JAD: I mean, we're not gonna do that ourselves.

ROBERT: No.

JAD: No, but we're gonna play you stories where ...

ROBERT: These things actually happen.

JAD: Yes. I'm Jad Abumrad.

ROBERT: I'm Robert Krulwich.

JAD: This is Radiolab. Stick around, it's gonna get messy.

ROBERT: Okay, so let's get going and stick with your boy, Lamarck, just for a second.

JAD: Mm-hmm.

ROBERT: Because we were talking to science writer Carl Zimmer, and he told us that back in the early 1900s, this tension between Lamarck and Darwin got extra tense.

CARL ZIMMER: Yeah.

ROBERT: In a sort of fascinating way.

CARL ZIMMER: Right.

JAD: And it all started in Vienna.

CARL ZIMMER: At this really marvelous place called the Vivarium.

ROBERT: The Vivarium.

CARL ZIMMER: Yeah. This was a really radical place at the time, because you have to remember that people studying animals up 'til now, they were basically studying preserved specimens and so on. At the Vivarium, as the name suggests, they had live animals.

[bird calls]

JAD: So it was like a zoo, basically.

CARL ZIMMER: Well, it was a zoo where there was all sorts of experiments going on.

ROBERT: Huh.

CARL ZIMMER: You know, the fact is that taking care of animals, trying to keep them alive in a building is not an easy thing, especially if it's 1903.

ROBERT: But luckily for the Vivarium and for our story, they had a guy.

CARL ZIMMER: Paul Kammerer.

JAD: Who was he?

CARL ZIMMER: So he ...

JAD: And when was he?

CARL ZIMMER: He was born in 1880 in Vienna. Jewish family.

ROBERT: By all accounts a pretty good-looking guy. And in pictures, he has that, you know, that crazy Einstein fuzzy hair thing.

JAD: The genius cut?

ROBERT: Yep.

CARL ZIMMER: He's 22, 23, and he already had this reputation for being amazing at keeping animals alive that otherwise would just die.

JAD: His reputation was that he could get inside the mind of, say, a salamander and know just what it wanted to eat.

ROBERT: Or how much humidity it preferred.

CARL ZIMMER: Right.

ROBERT: He was a born nurturer and he adored animals.

CARL ZIMMER: He actually named his daughter Lacerta, which is a genus of lizard.

ROBERT: [laughs]

JAD: [laughs]

CARL ZIMMER: That's the kind of guy he is.

ROBERT: So of course, the folks at the Vivarium asked him ...

CARL ZIMMER: To build these terrariums and aquariums and stock them with animals.

ROBERT: Including a particular amphibian that plays a very big part in this story.

SAM KEAN: The midwife toad.

JAD: The midwife toad?

SAM KEAN: Right.

JAD: That's writer Sam Kean again, and here's, he says, what you need to know about the midwife toad.

SAM KEAN: Basically, the midwife toad has a strange habit for toads.

JAD: Most toads, he says, love to stay in the water. They like to hang out in the water, and the females like to lay eggs in the water. But with the midwife toad, the female ...

SAM KEAN: Lays her eggs on land, and then the male midwife toad comes along ...

JAD: Grabs the eggs ...

SAM KEAN: And actually kind of sticks them to his back legs like a bunch of whitish grapes, and then hops around with them basically until they hatch.

JAD: So he's gotta live his life as a toad with all this baggage on him?

CARL ZIMMER: Just until they hatch and then until they go off.

JAD: Still, that's a burden. He's carrying a big burden there.

CARL ZIMMER: Is your wife gonna hear this?

JAD: [laughs]

ROBERT: [laughs]

CARL ZIMMER: She carried your kids for nine months and you're like, "That poor male toad!"

JAD: Anyhow, so you got this guy Paul Kammerer who's good with animals. You've got these toads who hate water. And then one day, we can imagine, he gets curious. As he's doing his rounds, he stops by the midwife toad terrarium, and he looks down at that little male toad with grapes stuck to his legs and he wonders how adaptable is that little guy? I mean, he hates water. Females seem to hate laying eggs in the water, but is that the end of the story?

CARL ZIMMER: What would happen ...

JAD: If I made them go ...

CARL ZIMMER: In the water?

JAD: Could they adapt?

CARL ZIMMER: I know what I'll do: I'm gonna set up a terrarium for them, and I'm gonna make it hot, really uncomfortably hot. But I'm gonna give them a basin of water. Nice, cool water.

SAM KEAN: And he would basically turn the heat way, way up in these aquariums until they had to go underwater.

JAD: You can imagine these toads were like, "Dammit! Fine. All right, I'll get in the water." Maybe they'd try and jump back out, but it was still hot so they'd have to jump back in. And since Kammerer kept the heat up, toads basically had to stay there in this watery place that they had not evolved for.

SAM KEAN: Darwin's theory would have said, you know, 90 percent of the toads are gonna die. There's gonna be this massacre of toads, and only a few lucky ones are going to survive.

ROBERT: And those lucky ones, according to Darwin's theory, they would have had to have been born with some random mutation in their genes.

SAM KEAN: That gave them an advantage in this situation.

ROBERT: And that advantage, whatever it was, because it starts with one individual, and then it gets passed onto the kids and then onto their kids, it would take a long, long, long time to spread through the whole population, because generally, that's how evolution works. It takes a while.

JAD: But according to Kammerer, here's what happened when he heated up the toads' little cage.

CARL ZIMMER: They'd spend more time in the water.

JAD: As expected.

CARL ZIMMER: And when it came time to mate, the males and the females, they would mate in the water.

JAD: And at first it didn't go so well because, you know, if you're a land toad and you're trying to have sex in the water, it's kind of hard. You're slippery, partner's slippery. You just haven't evolved for this, and there's no way you can—at least not quickly. But according to Kammerer, shortly after these toads got into the water, they did begin to evolve—fast! They began to grow these little puffy things on their hands.

CARL ZIMMER: These kind of rough, scratchy pads.

SAM KEAN: What's known as a 'nuptial pad.'

ROBERT: Nuptial pad.

SAM KEAN: Right.

JAD: It was just what the males needed.

CARL ZIMMER: So they can grab onto the female and hold tight while they're mating.

ROBERT: And they didn't have these on land?

SAM KEAN: No, they did not have them on land.

JAD: They just appeared in the water?

SAM KEAN: Yep.

JAD: And how long did it take?

CARL ZIMMER: Right away.

ROBERT: Really?

JAD: In just two generations, these toads seemed to have done something that should have taken, I don't know, 50, 100 generations? Maybe more. And Kammerer thought, "Wow!"

SAM KEAN: They can respond to the environment.

CARL ZIMMER: He was revealing it with experiments.

JAD: They're not trapped by their genes.

CARL ZIMMER: Around 1908, he starts publishing all of these results.

ROBERT: And it's big news.

CARL ZIMMER: And ...

JAD: He grabs his toads and he hit the road.

CARL ZIMMER: He hit the lecture circuit and he hit it big.

SAM KEAN: He was known for going around and giving what he called his "big show" lectures, where he would wow whole audiences of people.

CARL ZIMMER: And in 1923, he actually comes to England. There was a newspaper called The Daily Express and they have these headlines that come out. It says, "Race of Supermen." That's the headline for his talk.

JAD: Race of ...?

CARL ZIMMER: And then right below the headline it says, "Scientist's great discovery which may change us all."

JAD: What's he talking about? We're just talking about a toad, I thought.

CARL ZIMMER: He's not just talking about toads anymore, he's gone way beyond toads.

SAM KEAN: He extended this idea to people. He thought that you could kind of engineer societies by changing the environment.

CARL ZIMMER: I just have to read this to you. "The results make it probable that our descendants will learn more quickly what we know well, will execute more easily what we have accomplished with great effort, will be able to withstand what injured us almost to the point of death. Where we sought, they will find. Where we began, they will accomplish."

ROBERT: And this idea won him a lot of fans including, not surprisingly, the Soviets.

SAM KEAN: Yeah, it was a very attractive theory to them in Moscow.

ROBERT: Because the Soviets, they believe in Karl Marx's idea that human beings were an improvable species, that if you can change the conditions around people, you change the people. Here Kammerer was saying, you know, you can do this even on a physical level.

CARL ZIMMER: But, you know, there are a lot of skeptics.

ROBERT: And there were from the beginning. When Kammerer published his results initially, a bunch of scientists immediately began to say ...

CARL ZIMMER: "Wait a minute, hold on here. It would be nice if life was like that but life isn't like that. Life is hard."

JAD: People can't just will themselves into a more perfect form.

ROBERT: According to Darwin, life and changes are ruled by chance.

JAD: And fate.

ROBERT: And to believe anything else, that's naïve. So this whole toad thing? To the Darwinian faction, it didn't scan, really. So some scientists began to ask Kammerer if they could look at his toads, you know, just take a little peek for themselves, and every time ...

SAM KEAN: Kammerer said no, they were his specimens.

JAD: Get your own.

SAM KEAN: It was kind of this struggle for a few years, and then World War I came and that kind of disrupted everything.

ROBERT: Kammerer, for one, was sent off to work as a censor for the Austrian military.

SAM KEAN: And his lab ended up getting destroyed.

ROBERT: Including all his toads.

SAM KEAN: Except he had one. He had one remaining midwife toad.

JAD: So this whole debate, two totally different ways of seeing life ...

CARL ZIMMER: It all came down to this jar with this toad in it. And you have to bear in mind that at this point, it only had one hand left.

ROBERT: [laughs]

CARL ZIMMER: The right hand had been cut off for microscopic slides, and so you could only see one nuptial pad. And it all comes down to this. And all of it was just about to fall apart.

ROBERT: What happened?

CARL ZIMMER: Well, there was an expert on reptiles named G. Kingsley Noble.

SAM KEAN: Gladwyn Kingsley Noble.

ROBERT: What a name! You've gotta like this guy.

SAM KEAN: Yeah, it is.

JAD: Yes, it sounds like trouble.

SAM KEAN: He was for Kammerer.

CARL ZIMMER: He was mighty skeptical. So he actually went to Vienna.

JAD: Visited Kammerer's lab when Kammerer wasn't there.

CARL ZIMMER: And he makes a very careful study of this hand.

SAM KEAN: And when he examined it, he noticed that there was a syringe hole there.

ROBERT: [gasps]

CARL ZIMMER: And he says, "This isn't a nuptial pad. It looks darkened but that's just ink."

JAD: What?

ROBERT: What do you mean ink?

CARL ZIMMER: Ink.

ROBERT: Like the ...

JAD: Ink?

CARL ZIMMER: Ink.

ROBERT: Like squid ink?

CARL ZIMMER: No, like India ink.

JAD: What?

ROBERT: No!

CARL ZIMMER: Yes.

ROBERT: He doctored the toad.

SAM KEAN: That was the implication, except Kammerer tried to defend himself by saying ...

CARL ZIMMER: "Do you think I'm a dummkopf or an idiot? Because that's what I would have to be if I left a forgery with ink standing around openly in the laboratory where so many of my enemies would have entry."

JAD: So how did he explain it?

SAM KEAN: Well, he thought it might have been an assistant trying to frame him because he was Jewish.

JAD: Oh.

SAM KEAN: And, you know, there was kind of antisemitism growing at this time, so he thought that someone had framed him. And six weeks after Noble published his results in Nature, Kammerer sent a letter to Moscow.

JAD: Turning down a job that they'd offered him.

SAM KEAN: Because it would reflect badly on the Soviet state.

CARL ZIMMER: And then ...

JAD: The following day ...

CARL ZIMMER: ... Kammerer puts on a suit, he walks off into the mountains.

SAM KEAN: Outside Vienna on a rocky mountain trail.

CARL ZIMMER: And ...

[gunshot]

CARL ZIMMER: ... he shoots himself.

JAD: Jeez!

CARL ZIMMER: Lamarckism pretty much died there.

JAD: So then over the next 70-some-odd years, Lamarck basically became the poster boy for, like, the big dumb idea, the idea that you want to believe in but that you know isn't true.

CARL ZIMMER: But—but there's, like, some hope here because ...

JAD: Okay. All right, this is interesting. Then Carl told us about this research that showed ...

CARL ZIMMER: That if—if a mother ...

JAD: Well, he couldn't quite remember the details.

CARL ZIMMER: Does what a mother ...

ROBERT: Unusual for Carl.

CARL ZIMMER: ... mouse or rat? I'm trying to remember.

JAD: Was it rats or mice?

MICHAEL MEANEY: No, it was rats.

JAD: Rats.

MICHAEL MEANEY: Yup.

JAD: We ended up talking to the guy who did the work.

CARL ZIMMER: Michael Meaney, I think.

MICHAEL MEANEY: Yep, I'm a professor in the faculty of medicine at McGill University in Montreal.

CARL ZIMMER: I think he's at McGill.

JAD: So here's the backstory: about 30 years ago ...

MICHAEL MEANEY: I was an undergraduate student.

JAD: Michael was in school, and he got interested in a very, very basic question about how things get passed down. Like, have you ever had one of those moments where you suddenly are your dad and it catches you off guard?

ROBERT: Oh, of course!

JAD: I mean, it's pretty common but, like, here's a for instance: my dad for my entire life had this thing where if someone was whistling, he would—like, they could be whistling six tables over in a restaurant and he would turn around and be like, "Stop that!" Like, it was scraping his very nerves. And the other day someone was whistling and I was like, "Stop it!" And it just hit me. I was like, "Oh God, that was him!" It's never appeared until now.

ROBERT: And you wonder, like, where did that come from?

JAD: Is that a genetic hatred of whistling that I just had?

ROBERT: Yeah. [laughs]

JAD: Or did I somehow learn that? That, in a sort of ass backward way, was Michael's question.

MICHAEL MEANEY: How does that happen?

JAD: How do these simple little traits get passed forward? So ...

FRANCES CHAMPAGNE: So we started looking at maternal care.

JAD: Many years later, he and this woman ...

FRANCES CHAMPAGNE: Frances Champagne.

JAD: Who now works at Columbia University, they decided to explore this question ...

FRANCES CHAMPAGNE: Looking at ...

JAD: ... in rats.

FRANCES CHAMPAGNE: So we have our rats in the lab and ...

JAD: They thought, "Let's just see if we can figure out how it is that rat mothers pass down their parenting skills."

FRANCES CHAMPAGNE: That's right.

ROBERT: If you were a great rat mommy, what would you be doing with your rat baby?

FRANCES CHAMPAGNE: You would be licking them quite a lot.

ROBERT: Uh-huh.

JAD: That's what good rat mothers do, they lick their babies a lot. But she says you can tell right away just by looking, that some rat moms don't lick their kids a lot.

FRANCES CHAMPAGNE: There's a normal distribution, right?

JAD: You got your good parents and your bad parents. What they decided to do first was to try to figure out which rat was which, which meant, interestingly, counting all the licks.

FRANCES CHAMPAGNE: Putting this into context. You know, you have a rat mom and they have about 16 to 20 babies.

JAD: All at once?

FRANCES CHAMPAGNE: At once, and we're watching 40 litters at a time.

ROBERT: How do you count the licks? That's—that's too hard!

FRANCES CHAMPAGNE: You have to look at one cage, say, "Are they licking?" Yes? No? Okay, move on to the next cage. Yes? No? Move on to the next cage. Yes? No?

JAD: Wow!

FRANCES CHAMPAGNE: You have to do that for five hours a day for six consecutive days. Move on to the next cage. Yes? No? Move on to the next cage. Yes? No?

JAD: See, this is the story of science that doesn't get told. It's just mind crushing tedium.

FRANCES CHAMPAGNE: Yes, yeah.

MICHAEL MEANEY: Yeah, it drifts into something like a shopping channel.

FRANCES CHAMPAGNE: [laughs]

JAD: In any case, what they saw at the end of all this counting was—well first of all, what they saw was this pattern that rat pups who got licked a lot as babies, when they grew up, they licked their babies a lot, and the rat pups who didn't get licked a lot, when they grew up, they didn't lick their babies a lot.

MICHAEL MEANEY: So the great rat nightmare comes true where the females become their mothers.

JAD: Okay.

ROBERT: I think that makes a lot of sense.

JAD: Actually, it's kind of obvious.

ROBERT: Right.

FRANCES CHAMPAGNE: Right. Yeah.

JAD: I mean, we all know this, that there are cycles of abuse or whatever. You know, like, if you were abused as a kid, you were more likely to abuse your kid, but still, you got to wonder.

FRANCES CHAMPAGNE: Why? Why would that happen?

JAD: How do those cycles perpetuate? I mean, like, with the licking, is it a teaching thing where, you know, the babies become good mothers because ...

FRANCES CHAMPAGNE: They learned it.

JAD: By watching their mothers.

FRANCES CHAMPAGNE: They've seen it and they've repeated the experience.

JAD: Or does it get passed on such a deep level that doesn't even require teaching?

ROBERT: What do you mean?

MICHAEL MEANEY: So that's the reason of course that we work with rats because we can get inside the brain.

JAD: So Michael and Frances looked inside the brains of these rats, and what they saw was that the rats who had been licked a lot as babies, they had more stuff in their head.

ROBERT: What do you mean, more brain cells? More what kind of stuff?

JAD: No, not brain cells. More of this particular kind of protein.

MICHAEL MEANEY: That activates maternal behavior.

JAD: When rats have more of this protein, they will act more motherly. And they had more.

ROBERT: So?

JAD: Well, think about what makes proteins.

ROBERT: Uh ...

JAD: DNA!

ROBERT: Well, yes. Genes and DNA.

JAD: Don't you see? Somehow the mother's tongue is getting all the way down in there and going—boo doo boo—and messing with the baby's DNA.

ROBERT: Is that what you're saying? That the licking is changing the baby's DNA?

JAD: That's what I ...

ROBERT: No!

JAD: ... I'm not quite saying that.

ROBERT: You can't say that. It's against the rules.

JAD: That's against the rules. You can't change your DNA.

MICHAEL MEANEY: Yeah, you can't touch that.

JAD: It's off-limits. But that tongue is doing something to the DNA.

ROBERT: So what is the licking doing then?

MICHAEL MEANEY: That's—that's our challenge.

JAD: Do you have any theories for how this tongue is tickling the DNA, or whatever it's doing?

MICHAEL MEANEY: Um, well so ...

JAD: And then Michael just launched into this thing.

MICHAEL MEANEY: What happens when moms lick their pups is that the pup becomes aroused. The reason they're more aroused is that the mom's licking activates the release of adrenaline and noradrenaline in the pup.

JAD: He says those two chemicals ...

MICHAEL MEANEY: Kick off certain hormonal systems. And one of them is called the thyroid system. Thyroid hormones then get into the brain, and they turn on certain neural chemical signals. And the neural chemical signal that gets activated during licking is serotonin.

JAD: As in the mood chemical?

MICHAEL MEANEY: Yep. So mom's licking activates serotonin, and it's released onto brain cells in the hippocampus.

JAD: You still with me?

ROBERT: I think I'm with you.

JAD: We started with the tongue. Four or five steps later, we are in ...

MICHAEL MEANEY: Brain cells.

JAD: So almost instantaneously, the mother's tongue has reached into the baby's brain cells.

ROBERT: Huh.

JAD: You know, inside these cells, in the center, coiled up in little spools is the DNA. So we're getting close to the moment of truth, because there it is. That's the stuff that makes you you.

ROBERT: Yeah.

JAD: But that you supposedly can't get to. But here's what I did not know about DNA. According to Frances, it's not just sitting off there perfectly preserved, it's in the middle of the cell, it's crowded.

FRANCES CHAMPAGNE: You know, you've got all these chemicals around.

JAD: Racing by.

FRANCES CHAMPAGNE: You know, in the cells.

JAD: And very often, one of them will just go crashing into the DNA, and it'll stick there like a barnacle or a glob of peanut butter.

FRANCES CHAMPAGNE: [laughs] Exactly. Peanut butter. There we go.

JAD: What'll happen is it'll get stuck to one little part of the DNA, and now that little bit of DNA ...

FRANCES CHAMPAGNE: Is very difficult to get at.

JAD: It's basically unusable.

ROBERT: Because it's got the thing stuck to it?

FRANCES CHAMPAGNE: Yeah.

JAD: And these things are called, apparently, methyl groups.

FRANCES CHAMPAGNE: Methyl groups are pretty sticky. They're hard to get off.

JAD: So imagine the DNA in that brain cell. All these chemicals racing by, crashing into it, sticking. And one of the bits that gets covered up is that little bit that makes the proteins that create a maternal instinct. The bit of DNA that will give this baby when it grows up the instincts to be nice to its baby and lick that baby.

ROBERT: And you're saying that part of the DNA is covered up?

JAD: Yes. And when methyl groups stick to that part of the DNA, the maternal instinct is effectively turned off. But if you've got a mom who licks you ...

MICHAEL MEANEY: Mom's licking activates serotonin.

JAD: Serotonin gets into the brain cells, and according to Michael, unleashes ...

MICHAEL MEANEY: A whole series of molecular events inside the cell. The critical part of this ...

JAD: Is that all these changes wake up this little gang of proteins ...

MICHAEL MEANEY: Known as transcription factors.

JAD: And if they see methyl groups sitting on that bit of DNA, they are pissed. And so they bring ...

MICHAEL MEANEY: A lot of friends to the party.

JAD: They all go down to the DNA, surround that methyl and just—pow!—knock it right off the DNA.

MICHAEL MEANEY: That's it. And then they're going to basically revel at that particular spot and turn on that gene.

JAD: So now the genes can make the proteins that make the rats a good mom?

MICHAEL MEANEY: Exactly. Exactly.

JAD: [bleep] That was awesome! [laughs] Wow! That was amazing.

MICHAEL MEANEY: [laughs]

ROBERT: Why are you so thrilled?

JAD: Well think about it, this is nature and nurture slamming into each other. Like, you know when smart people say, "You know, there's no such thing as nature and nurture. It's only interactions of the two," and you're like, "What the hell does that mean?" Well, this is it!

FRANCES CHAMPAGNE: This is real physical, chemical interaction between what's going on in the environment and what's going on with the DNA.

JAD: Because you begin with a mother's lick that ends up with a deep, deep change in the baby—not just the good, warm, fuzzy feeling, but a fundamental shift in who that baby is and who that baby will be.

CARL ZIMMER: You're now hearing Lamarck's name invoked these days because there are things beyond genes that we pass down to our children.

JAD: Now according to Carl, your genes are still fixed.

CARL ZIMMER: We can't rewrite our genes.

JAD: That is impossible so far as we know, but there seems to be this layer on top of the genes.

CARL ZIMMER: This second channel of heredity.

JAD: If the genes are the bottom floor, then this layer on top is sometimes called the epigenome, and that thing can change based on your experiences.

ROBERT: Which, when you think about it, it has a very Lamarckian flavor.

JAD: Yeah.

FRANCES CHAMPAGNE: I think that's where Lamarck's ideas can be woven in and make some sense.

JAD: So do you call yourself a Lamarckian?

FRANCES CHAMPAGNE: Not usually, because it upsets people. And I'm Canadian. I don't like to upset people. [laughs]

ROBERT: [laughs]

JAD: Plus, you know, Lamarck didn't get all the biological details right.

FRANCES CHAMPAGNE: He had no idea about DNA.

JAD: Or very many of them right at all but, you know, his basic idea seems to be true.

FRANCES CHAMPAGNE: I mean, when you think of Kammerer, there was a report in Science outlining a theory about how Kammerer's toads got these characteristics.

JAD: Really?

FRANCES CHAMPAGNE: That invoked these epigenetic inheritance and imprinted genes. And it made it plausible.

JAD: Oh, so redeeming him?

FRANCES CHAMPAGNE: Yeah.

ROBERT: Maybe or maybe not.

JAD: Thanks to Frances Champagne and Michael Meaney and Sam Kean, who writes about Paul Kammerer in his book, The Violinist's Thumb. Also thanks to Carl Zimmer, whose latest is Evolution: Making Sense of Life.

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