Fetal Consequences

Summary

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Radiolab – "Fetal Consequences"

Date: May 1, 2012
Hosts: Jad Abumrad & Robert Krulwich
Main Guest: Dr. Kirby Johnson (Tufts University)
Theme:
Exploring the mysterious phenomenon of fetal cells lingering in mothers' bodies for decades, and the mixed—sometimes poetic, sometimes unsettling—consequences this may have for their health.

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Overview

This episode of Radiolab delves into the science and emotional resonance of “fetal microchimerism”—the surprising fact that cells from a fetus cross into the mother’s body during pregnancy and can remain there for decades, possibly even a lifetime. Hosts Jad Abumrad and Robert Krulwich revisit an early story reported by Krulwich and get an update from research scientist Dr. Kirby Johnson about what we now know, what remains uncertain, and what it all means for both science and relationships.

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Key Topics and Insights

1. The Initial Science: Fetal Cells Remain for Decades

[02:58 – 04:30]

• Kirby Johnson explains that for much of medical history, it was believed the placenta formed a near-impenetrable wall between fetus and mother.
• New findings show that dozens or even hundreds of fetal cells cross into the mother’s bloodstream and tissues, persisting for decades—"40 years after conception...fetal cells are still floating around inside the mother" (Kirby Johnson, [04:08]).
• This is true even in cases of miscarriage or abortion; cells from all pregnancies linger.

2. Two Competing Hypotheses: Harmful vs. Helpful

[04:49 – 06:14]

• Hypothesis 1 (The "Bad Hypothesis"): Fetal cells contribute to autoimmune diseases (e.g., lupus, rheumatoid arthritis) that are more common in women.
  • "Maybe it’s her fetal cells, her own babies taking a poke at her." (Narrator, [05:13])
• Hypothesis 2 (The "Good Hypothesis"): Fetal cells help heal and repair their mother’s tissues after injury or illness.
  • "The son or daughter cells stay in mom...to protect, defend and repair her for the rest of her life..." (Narrator, [05:52])

3. Striking Case Study: Healing the Liver

[06:25 – 07:30]

• Story of a woman with hepatitis and a history of five pregnancies:
  • Her liver biopsy revealed "sheets of fetal cells" at the site of liver damage, far beyond what’s typical ([07:07]).
  • She recovered without intervention—prompting speculation: "Could that lead us to think...she was saved by her kids?" (Robert Krulwich, [07:41])
  • Johnson responds poetically yet cautiously: "It's the most likely explanation...But it has to be right, and we can't be led astray by our own desire for it to be true." ([07:53 – 08:15])

4. Current Animal Studies and Evidence

[08:15 – 08:58]

• Animal studies show fetal cells rush to sites of disease or damage (e.g., cancer, infection).
• "There’s a lot of evidence now...that these cells may actually be repairing tissue that is protecting the mom." (Carol Artlett, [08:42])
• The "bad hypothesis" is losing traction: "I can't recall a single study that's been truly reproduced to verify the bad fetal cell hypothesis." (Kirby Johnson, [08:58])

5. A Personal and Poetic Scientific Quest

[09:34 – 10:00]

• Johnson reflects on his own mother’s illness: "If there's some way where I...contributed to the extension of my mother's life, even if it was a few days, that would make all of the years that I spent doing this research worthwhile." ([09:34])

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Update: Six Years Later—Complexity Deepens

6. Progress and New Tools

[10:06 – 11:41]

• Johnson now tracks fetal cells in mice using green fluorescent protein, making them glow visibly. "It is like the movies...it is shiny, glowing green." (Kirby Johnson, [11:25])
• Fetal cells show up in many organs—even in the brain.

7. Mixed Roles: Helpers and Harmers

[11:56 – 14:07]

• Evidence shows fetal cells can help repair tissues (e.g., after liver damage), but in autoimmune cases, "their behavior seems to suggest that they are attacking the mom, actually attacking maternal tissue." (Kirby Johnson, [12:40])
• The outcome depends on numerous variables: the type of disease, location in body, the father's genetics, number of pregnancies, pregnancy losses, and maternal age.
  • "It gets longer... The number of pregnancies, also pregnancy loss... maternal age, that's another very important variable." (Kirby Johnson, [14:10])
• "Good kids and bad kids. You have good days and bad days, good cells and bad cells." (Kirby Johnson, [13:58])

8. The Limits of Knowledge and the Drive for Truth

[14:32 – 18:56]

• Krulwich asks if the ambiguous, messy reality diminishes Johnson's enthusiasm.
  • "Whether or not the truth is wonderful or the truth is horrible, that's what I want to find out, regardless of what the end personal outcome is." (Kirby Johnson, [17:07])
  • On the value for him and his late mother: "...At least I know what the truth is. And both as a son and as a scientist, that would be of value to me." (Kirby Johnson, [17:58])

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Notable Quotes & Moments

• On the poetic wish for fetal cells to be protectors:
  "[It] does touch the heartstrings of even the most hard-nosed research scientist. But it has to be right, and we can't be led astray by our own desire for it to be true."
  — Kirky Johnson ([06:07], [08:15])

• On the ambiguity of science and personal connection:
  "You might even come out the villain. Doesn't that sap your enthusiasm?"
  — Robert Krulwich ([16:50])

  "As a scientist, I want to find the truth. Whether or not the truth is wonderful or the truth is horrible, that's what I want to find out."
  — Kirby Johnson ([17:07])

• On the messiness of the findings:
  "The cells can be good or bad. Depends on the disease, the location, and the dad. But we're not really sure why."
  — Jad Abumrad ([14:01])

• A Mother's Day reflection:
  "I don't know that mothers really need a day. They should basically own the calendar. But since here we are chronologically near Mother's Day. Happy Mother's Day."
  — Jad Abumrad ([19:03])

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Timeline of Key Segments

• [02:58 – 04:30] – Discovery of fetal cells remaining in mothers for decades
• [04:49 – 06:14] – Competing hypotheses: harm vs. healing
• [06:25 – 07:30] – Case study: fetal cells in liver disease
• [08:15 – 08:58] – Animal studies and mounting evidence
• [10:06 – 11:41] – Technical update: tracking fetal cells in glowing mice
• [11:56 – 14:07] – Mixed effects: when fetal cells help or harm
• [14:32 – 18:56] – Reflections on uncertainty, science, and motive

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Tone and Style

The episode mixes playful banter, earnest science, and poignant reflection. Krulwich’s probing is both charming and direct; Johnson emerges as a thoroughly human scientist, candid about both his hopes and disappointments. There is a searching tone throughout—a willingness to embrace both poetry and uncertainty in pursuit of answers.

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Conclusion

"Fetal Consequences" beautifully illustrates the complexities at the intersection of biology, personal history, and scientific rigor. The story resists easy answers but offers instead a glimpse into how science advances—not toward tidy truths, but through messiness, questions, and deep personal investment.

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Transcript

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[Jad Abumrad]

Wait, you're listening. Okay.

[Robert Krulwich]

All right.

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Okay.

[Jad Abumrad]

All right. You're listening to Radio Lab, Radio Lab.

[Narrator/Reporter]

Shorts from WNY.

[Best Buy/Lowe's Announcer]

And npr.

[Jad Abumrad]

Hey, I'm Jan Abumra.

[Robert Krulwich]

I'm Robert Krolwich.

[Jad Abumrad]

This is Radiolab, the podcast. And before we really get rolling, I just want to say one thing. We're gonna be in LA next week, May 8th, 9th and 10th, we're gonna be at the Royce Theater for three nights with our live show in the Dark, which includes palabolist and dance troupe, the singer songwriter Tao Nguyen and the comedian Demetri Martin. Awesome lineup. You can still get [e-mail] inthedark folks who've seen this show, tell your LA peeps to come check it out. Yeah, I don't know what we're doing today, so you, you go, well.

[Robert Krulwich]

Cause here's what we're doing. Maybe six years ago I just returned to National Public Radio and for the first story I did.

[Jad Abumrad]

Can we just put that in context? I mean, you started National Public Radio. You did kind of start.

[Robert Krulwich]

I was at it near the beginning.

[Jad Abumrad]

And then you went away to do great things on TV for 23 years.

[Robert Krulwich]

I was missing. And then I just popped back again.

[Jad Abumrad]

Yeah. Okay.

[Robert Krulwich]

So when I popped back, I brought this puzzle back with me. It was about motherhood, actually. And it's. Well, you'll hear.

[Narrator/Reporter]

Why don't I just play you the.

[Robert Krulwich]

Piece that I aired back in.

[Jad Abumrad]

Gosh, 2006.

[Robert Krulwich]

2006, 2006.

[Jad Abumrad]

It's another time.

[Kirby Johnson]

NPR's Robert Krulwich has the story.

[Narrator/Reporter]

For years it was thought as soon as a baby is conceived, once it starts to grow inside a mom, it gets its own very private space.

[Kirby Johnson]

There is, there's a placenta. Placenta was thought to be a fairly impenetrable barrier.

[Narrator/Reporter]

So says Dr. Kirby Johnson of Tufts University, the baby and its cells stay on the baby side, the mommy cells stay on the mom, and nature keeps them separate until it's time to go. But here's the surprise. When scientists at Tufts took blood from ordinary pregnant moms, we would find, for.

[Kirby Johnson]

Example, in a teaspoon of blood, dozens, perhaps even hundreds of cells from the baby. From the baby.

[Narrator/Reporter]

So baby cells were slipping out of the placenta into the moms. But because babies do have different genes.

[Kirby Johnson]

One would expect them to be attacked fairly rapidly. You would expect them to be cleared within hours, if not days. What we've found is that that is not the case, not anywhere near the case.

[Narrator/Reporter]

It turns out that baby cells stay in their moms not for days or weeks, but for decades, four to five.

[Kirby Johnson]

Decades following the last pregnancy.

[Narrator/Reporter]

So 40 years after conception, that son or daughter who could now be a middle aged pharmacist or something, yet their fetal cells, their baby cells, are still floating around inside the mother. Yes, even his 60 year old mother.

[Kirby Johnson]

70, 80, perhaps 90 year old women.

[Narrator/Reporter]

You sure of this?

[Kirby Johnson]

Absolutely.

[Narrator/Reporter]

Yeah.

[Best Buy/Lowe's Announcer]

These cells last essentially forever in the mom. In the mom.

[Narrator/Reporter]

And says Carol Artlet, who studies fetal cells at Thomas Jefferson University in Philadelphia, even if a woman has a miscarriage or an abortion, even if there is no baby, the cells of an unborn child will stay in the mother for decades. But why? What exactly are they doing in there for years and years and years?

[Best Buy/Lowe's Announcer]

That's a good question.

[Narrator/Reporter]

Well, one early hypothesis, and it's not the nicest idea, says Kirby Johnson, is that certain autoimmune diseases such as lupus.

[Kirby Johnson]

Rheumatoid arthritis, scleroderma, are much more common in women than men. And that's one component of the hypothesis, is that this prevalence in women is due to fetal cells.

[Narrator/Reporter]

So later in life, when the mother's joints inflame, maybe it's her fetal cells, her own Babies taking a poke at her. In fact, Kirby's mom did have an autoimmune disease. It was a bad one. And for a while Kirby thought, well, his cells were responsible.

[Kirby Johnson]

So I apologized immediately and said, well, there's nothing much I can do about it.

[Narrator/Reporter]

Yeah, yeah, but it's like, stop it, Kirby.

[Kirby Johnson]

But you know what? I was always doing that to my mother, always causing problems. And it was just another on the long line of those kinds of things.

[Narrator/Reporter]

But happily, the folks at Tufts proposed an alternative, a second theory to explain what fetal cells are doing in the moms.

[Kirby Johnson]

Well, theory number two is the polar opposite of theory number one.

[Narrator/Reporter]

The good fetal cell hypothesis proposes that the son or daughter cells stay in mom not to hurt her, but to protect, defend and repair her for the rest of her life whenever she gets seriously ill. And that's a more attractive idea.

[Kirby Johnson]

It's such a personal thing, and it does touch the heartstrings of even the most hard nosed research scientist.

[Narrator/Reporter]

But they all have mothers.

[Kirby Johnson]

But they all have mothers.

[Narrator/Reporter]

And happily, they now have evidence, more and more evidence, says Kirby Johnson. That looks like the good hypothesis may be correct. For example, here's a case.

[Kirby Johnson]

Well, this was a woman who came into a neighboring hospital in Boston with symptoms of hepatitis. She was an intravenous drug user and.

[Narrator/Reporter]

She had had five conceptions. She'd had one child, two miscarriages, two abortions. That's five in all. She could be carrying, therefore, a lot of fetal cells.

[Kirby Johnson]

And they examined her, and in she had a liver biopsy.

[Narrator/Reporter]

And the doc said, well, why don't we send her liver to the lab to see if there are any fetal cells gathering where she's got trouble.

[Kirby Johnson]

And when they looked, we found hundreds and hundreds of fetal cells.

[Narrator/Reporter]

Normally they'd expect five or ten cells.

[Kirby Johnson]

But this was very large. We saw literally sheets of cells, whole.

[Kirby Johnson (continued interview)]

Areas that seemed to be normal, meaning.

[Narrator/Reporter]

That those fetal cells had gathered at the liver and like stem cells, they just turned themselves, in this case, into healthy liver cel.

[Kirby Johnson]

This woman did not desire to have any further treatment done. In fact, she wanted to get back to her normal life and be left alone.

[Narrator/Reporter]

And so she left the hospital with hepatitis. But when they checked months later, they.

[Kirby Johnson]

Learned that she is completely healthy. No signs of further liver damage, so.

[Robert Krulwich]

No medical intervention, but just a huge number of her baby's fetal cells.

[Narrator/Reporter]

Could that lead you to think the poetic thought that she was saved by her kids?

[Kirby Johnson]

We want to think that.

[Robert Krulwich]

I know you do.

[Kirby Johnson]

It's the most likely explanation.

[Narrator/Reporter]

But in science, there is Such a thing as a too dangerously beautiful idea.

[Kirby Johnson]

That's right. Right. And we say the same thing to ourselves because it shows such a basic, wonderful thing. But it has to be right, and we can't be led astray by our own desire for it to be true.

[Narrator/Reporter]

So they are systematically testing the good hypothesis and the bad hypothesis, all these ideas on laboratory mice. And when they see mother mice with all kinds of diseases, infectious disease, cancer.

[Kirby Johnson]

Ovarian cancer, endometrial cancer, cervical cancers, we find fetal cells there. We know that fetal cells over and over and over and over and over.

[Narrator/Reporter]

And over and over, suggesting that fetal cells regularly rush to the places where they're needed in the mom. And, says Carol Artlet, there's a lot.

[Best Buy/Lowe's Announcer]

Of evidence now starting to come out that these cells may actually be repairing.

[Narrator/Reporter]

Tissue that is protecting the mom. While the other hypothesis, that fetal cells hurt the moms there, the more they look, the less they find.

[Kirby Johnson]

I can't recall a single study that's been truly reproduced to verify the bad fetal cell hypothesis.

[Narrator/Reporter]

So while no one knows in the end which way it'll go, I think.

[Kirby Johnson]

That that's something that we're going to see within the next five years or less.

[Narrator/Reporter]

So far, a sense is building that fetal cells probably stay in mothers for decades to defend and to protect them, which increasingly is a quiet consolation to Kirby Johnson, because it's now more likely that his cells and his brother's cells were helping their mom, not hurting. And even though his mother did die, Kirby's beginning to feel differently.

[Kirby Johnson]

Maybe if it wasn't for my brother and I, she may have passed a few years earlier. Maybe we bought her a couple of extra years of time so she could have a few more birthdays and a few more mother's days. And that if I can just say that, that there's some way where I can even have the remotest thought that I contributed to the extension of my mother's life, even if it was a few days, that would make all of the years that I spend doing this research worthwhile.

[Narrator/Reporter]

Robert Grillwich, NPR News, New York.

[Jad Abumrad]

Hmm.

[Robert Krulwich]

So it's been more than five years, as I said, since I talked to Kirby Johnson. Six years, really. So I figured he might have an answer by now.

[Kirby Johnson (continued interview)]

Hello.

[Robert Krulwich]

Hi, Kirby.

[Radiolab Promo Announcer]

Hi, Robert.

[Kirby Johnson (continued interview)]

How are you?

[Narrator/Reporter]

I wanted to know, what do you.

[Robert Krulwich]

Now know about what those fetal cells are really doing?

[Kirby Johnson (continued interview)]

Right.

[Robert Krulwich]

So when we last left it, you were tipping between two possibilities. One is that they do some harm. They aggravate conditions later in the mother's life or or the opposite, that they help in the mother's life.

[Kirby Johnson]

Right.

[Robert Krulwich]

And do you now have a sense of which was Right?

[Kirby Johnson (continued interview)]

Well, I think it's more complicated than we originally thought, like you would expect.

[Robert Krulwich]

Isn't that always the case?

[Kirby Johnson (continued interview)]

Yeah, but what we're able to do, though, now is more specifically argue for or argue against one of those different hypotheses.

[Robert Krulwich]

So here's how he's addressed the question, because this is a completely new development. He's working with mice, and he's taken the glow from another animal.

[Kirby Johnson (continued interview)]

It comes from some sort of fish, a greenish glow, the green fluorescent protein.

[Robert Krulwich]

That exists in nature. He's plopped it onto the fetal cells of a pregnant mouse.

[Kirby Johnson (continued interview)]

Right, exactly.

[Robert Krulwich]

So what is that like? Is that if you do a tummy scan on a pregnant lady mouse, can you look inside? Is that going to the movies and see?

[Kirby Johnson (continued interview)]

Absolutely. It is like the movies. It is shiny, glowing green, and it's extreme, extremely easy to see. I mean, a child could. Could say that, oh, that's green.

[Robert Krulwich]

So he can look at the mouse, and he can see from the little.

[Narrator/Reporter]

Bits of green glow where the fetal cells are.

[Kirby Johnson (continued interview)]

And we find these cells virtually anywhere we look like the lung, spleen, liver, bone marrow, the heart. We even find them in brain tissue.

[Robert Krulwich]

Which will help figure out what they're doing.

[Jad Abumrad]

So he can track them.

[Robert Krulwich]

Yeah. Yes, here I am.

[Kirby Johnson (continued interview)]

And we've removed.

[Robert Krulwich]

And now that he has tracked them, he says, all right, what I said before about fetal cells probably helping moms, I think that in many cases is still true. If you've got a mom who's suffering, say, from some liver disease or something, you can see fetal cells doing something there.

[Kirby Johnson (continued interview)]

And these cells may be able to contribute to tissue repair after an injury or chemical or environmental assault. So these are helpers. Helpers, definitely. Yeah.

[Narrator/Reporter]

But. But unlike six years ago, now he.

[Robert Krulwich]

Suspects that if a mother has, say, rheumatoid arthritis or some kind of autoimmune.

[Kirby Johnson (continued interview)]

Disease where the maternal immune system seemingly attacks itself in this autoimmune fashion.

[Narrator/Reporter]

Now he sees other kinds of fetal.

[Kirby Johnson (continued interview)]

Cells that seem to be causing a problem.

[Robert Krulwich]

Their behavior seems to suggest that they.

[Kirby Johnson (continued interview)]

Are attacking the mom, actually attacking maternal tissue.

[Robert Krulwich]

So that's the go get mommy group.

[Kirby Johnson (continued interview)]

Right. And the unfortunate go get mommy group.

[Jad Abumrad]

Wait, so there are some kinds of fetal cells that are good, some that are bad, and it's seems to depend on what, again, on, like, where it is in the body or what disease?

[Robert Krulwich]

Well, it seems to depend on a longer and longer list of variables, so including, for Example, who the father was that turns out to be.

[Jad Abumrad]

How does that matter?

[Robert Krulwich]

Well, remember, every fetal cell is half mom and half dad.

[Kirby Johnson (continued interview)]

We actually do see differences in the cells that are present in the mother depending upon the genetic background of the father.

[Robert Krulwich]

And you can have bad daddies and good daddies, you.

[Kirby Johnson (continued interview)]

That is entirely possible. I think we would say good daddies and less good daddies. But what we're.

[Robert Krulwich]

Is that because you're at a university and you never like to call daddies bad.

[Kirby Johnson (continued interview)]

No one's a bad daddy.

[Jad Abumrad]

But wait a second. Does he know how to explain the difference? Like why one dad would be good and one wouldn't be bad?

[Robert Krulwich]

I don't think he knows yet. No.

[Kirby Johnson (continued interview)]

We haven't been able to quite delineate why one cell may be doing something good or maybe be doing something bad. It may be the very same cell type.

[Robert Krulwich]

Ooh. So it might even switch sides during the course of life.

[Kirby Johnson (continued interview)]

It possibly could. I mean, it's sort of like behavior. You get good kids and you got bad kids.

[Robert Krulwich]

You have good days, and you got.

[Kirby Johnson (continued interview)]

Bad days, bad days. You got good cells and you got bad cells.

[Jad Abumrad]

This is getting complicated. So the cells can be good or bad. Depends on the disease, the location, and the dad. But we're not really sure why.

[Robert Krulwich]

That's not the end of the list. We actually. It gets longer.

[Kirby Johnson (continued interview)]

There's a number of other variables. The number of pregnancies, also pregnancy loss, whether it's through miscarriage or through termination. Maternal age, that's another very important variable.

[Robert Krulwich]

So who's your daddy? How old are you when you're pregnant? How many times have you been pregnant before?

[Kirby Johnson (continued interview)]

Yes. And many other influences. It's impossible to quote.

[Robert Krulwich]

Wait a second. So this is. So when we got to the poetry part of our interview back then, you said to yourself, my brother and I either roughed up our mother or gave her a few more, you know, birthdays.

[Kirby Johnson (continued interview)]

Right. It's possible that one of us had a more positive impact than the other. I mean, there's obviously no way of knowing that. But any normally inquisitive mind would start to wander, to say, well, what if this. Or under what circumstances?

[Robert Krulwich]

See, my mind is wandering wildly now because when we last did this story.

[Kirby Johnson (continued interview)]

And that's what we want you to do, we want people.

[Robert Krulwich]

No, I don't want to. It'd be a much better story if it had been decided for me, if it had gone clearly one way or the other. But the story you're now telling me is that you and your brother can now Meet for coffee and you can look into each other's eyes and you will not know between the two of you whether you helped your mom, whether you hurt your mom, whether you did both, whether your contribution was bigger or less than the hap stance of your dad's genetic makeup. And, and, and, and, and, and this is getting a much harder to be a much harder story to tell it.

[Kirby Johnson (continued interview)]

It is much harder to tell.

[Robert Krulwich]

So what are you, as the story gets blurrier and blurrier, why are you still in the game?

[Kirby Johnson (continued interview)]

A lot of this is driven, as you know, by the issues that my mother has or had. And I still have that in the back of my mind, and I can't get that out of my mind that a lot of the issues that my mother had recur in the literature.

[Robert Krulwich]

What that means is that the diseases that killed his mom are the very kinds of diseases that show up in his, in his research.

[Kirby Johnson (continued interview)]

And we, towards the end, we had conversations about fetal cells, and it made us closer. And I could share my scientific background and the work that I was doing in a way that comforted her, I think, to a certain degree, to know that I was investigating something that was directly related to her health issues. And towards the end, we had a lot of real nice conversations about the work that I was doing and the, the latest discoveries. And she would always ask one of the, after she would ask how I was, she would say, how was the work?

[Robert Krulwich]

But here's what, what. But I think there's a chance that your fetal cells in your mom sometimes helped and sometimes hurt. So you're not going to come out the hero. You might even come out the villain. Doesn't that SAP your enthusiasm for this a little bit?

[Kirby Johnson (continued interview)]

At some level, of course, I would want to think that my cells contributed in some small way to some improvement to my mother's health. If I find out that it wasn't the case, well, that's the truth. And as a scientist, I want to find the truth. Whether or not the truth is wonderful or the truth is horrible, that's what I want to find out, regardless of what the end personal outcome is.

[Robert Krulwich]

And what if the truth is? Well, some of the time you helped, some of the time you hurt, much of the time it didn't matter. Doesn't that hurt you a little bit? Can you get up the next morning and say, let's find out how unimportant I am?

[Narrator/Reporter]

Well.

[Kirby Johnson (continued interview)]

That is a very difficult question. I know if I were to be able to go to my mother, if I put my best effort forward to finding the truth. And even if it was a negative or was a mixed bag or perhaps was even not really much of anything, at least I know what the truth is. And both as a son and as a scientist, that would be of value to me. I may feel unfortunate that I, that I wasn't able to do something more than the, you know, the, the emotional support that I could provide my mother. But I have to look at it as finding the truth.

[Jad Abumrad]

That's nice.

[Robert Krulwich]

So that's where we at land. Yeah.

[Narrator/Reporter]

Happy Mother's Day.

[Robert Krulwich]

Oh, Mother's Day.

[Jad Abumrad]

Oh, yeah, this is Mother's Day. I mean, kind of. That's two weeks before. I don't know that mothers really need a day. They should basically own the calendar. But since here we are chronologically near Mother's Day. Happy Mother's Day.

[Robert Krulwich]

You're welcome.

[Jad Abumrad]

You've written about this on your blog, right?

[Robert Krulwich]

I have, yeah. Yeah.

[Jad Abumrad]

I should say, we should say where that is.

[Robert Krulwich]

It's called Krulwich Wonders. So you just write K R U L W I C H Wonders into any search engine and there it is. And this, this, this issue and other things many times a week. So, yeah, check it out.

[Jad Abumrad]

It's pretty good.

[Tom Giffen Jones (Listener Message)]

Start of MESSAGE hi, my name's Tom Giffen Jones from Denver, Colorado. I am a Radiolab listener. Radiolab is supported in part by the National Science foundation and by the Alfred P. Sloan foundation, enhancing public understanding of science and technology in the modern world. For more information about [e-mail]. thanks.

[Kirby Johnson (continued interview)]

End of message.

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