How Replaceable Are You?

Summary

Podcast Summary: Short Wave – How Replaceable Are You?

Host: Regina Barber (NPR)
Guest: Mary Roach, nonfiction author (book: Replaceable You)
Date: December 10, 2025
Duration: ~15 minutes

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Episode Overview

In this lively and science-filled episode of Short Wave, host Regina Barber talks with Mary Roach about the remarkable, bizarre, and sometimes funny science behind replacing human body parts. Drawing from Roach’s book, Replaceable You, the episode delves into medical advances—from artificial tears and burn treatments to full organ “remakes” using unlikely body parts. The conversation explores the limitations of current technology, the creativity of surgeons, and how close (or far) we are from becoming real-life cyborgs.

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Key Discussion Points & Insights

The Challenge of Replacement: Are We Truly Replaceable?

• Imperfection in Artificial Replacements
  • Mary Roach shares a surprising insight about our inability to perfectly replicate even something as “simple” as tears.
    • “So artificial tears, he’s like, yeah, they'll help for an hour or two, but they kind of wash away the good stuff. So we don’t even have, we can’t really even replace tears.” (Mary Roach, 00:53)
• Regina’s Cyborg Dreams Dashed... for Now:
  • Jokingly laments the limitations: “So my cyborg dreams may not become a reality just yet, but science has still made huge progress when it comes to fixing the human body when it fails.” (Regina Barber, 01:39)

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Advances in Burn Treatments

• Traditional vs. Modern Skin Grafting
  • Third-degree burns devastate the body's own ability to heal.
    • “Third degree burns are really tough because the cells that would regenerate from below… those are destroyed. So the body tries to heal by contracting, kind of pulling like a drawstring.” (Mary Roach, 01:56)
  • Modern techniques can culture a patient’s skin off-site or use “spray-on” skin, enabling faster and less painful recovery.
    • “There are ways now to culture the person’s skin off site… you can take a biopsy, and they can grow out these very thin layers of the person’s own skin. There’s spray on skin.” (Mary Roach, 01:56)

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Can We Replace the Lungs? The Story of the Iron Lung

[Segment starts at 04:07]

• Mary Roach details the history of the iron lung, which served as a life-saving device during the polio epidemics.

• Comparison: Iron Lung vs. Modern Ventilators

  • Iron lungs use negative pressure (imitating natural breathing), while mechanical ventilators force air into lungs (positive pressure).
    • “The iron lung works the same way [as natural breathing]. It’s called negative pressure ventilation.” (Mary Roach, 04:40)
  • Iron lungs allow for more “natural” breathing, but with limitations—no control over inhale/exhale, and a physically uncomfortable tight seal around the neck.
    • “Your breathing feels the way your breathing does when you're not in an iron lung, except that you have absolutely no control over when you're going to inhale and when you're going to exhale… you have this thing around it... like somebody is choking you.” (Mary Roach, 05:28, 06:20)

• Personal Anecdote:

  • Roach attempted to sleep overnight in an iron lung.
    • “I lasted about seven minutes.” (Mary Roach, 06:51)

• Pros and Cons of Modern Mechanized Breathing

  • Ventilators require intubation (can’t speak or swallow), have risks like lower-lung issues, cognitive decline, and muscle atrophy if used long-term.
    • “If you’re sedated on positive pressure for days and weeks, then you start to get sometimes cognitive issues. Muscle deterioration… you don’t want to be on a positive pressure ventilator for extended period of time.” (Mary Roach, 07:11, 07:59)

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Remaking Organs: The Vagina Dialogue

[Segment starts at 08:35]

• Surgeons sometimes use sections of the colon to construct vaginas when the “usual” methods aren’t possible.
  • “The colon… it makes a lot of sense. You know, it’s tubular, it’s moist, it’s pink, it’s stretchy.” (Mary Roach, 09:05)
  • This process is mostly used in gender-affirming surgery or in complex reconstructive cases.

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The Penis Rebuild: Middle Finger Transplants

[Segment starts at 10:10]

• Roach tracks down an eyebrow-raising surgery, first heard about via a stem cell researcher: rebuilding a penis using a patient’s middle finger (with modifications).
  • “I… imagined the finger removed and installed pretty much as is, you know, with the nail.” (Mary Roach, 10:45)
  • Travels to Tbilisi, Georgia (the country!) to investigate.
  • Reality: The finger is wrapped in skin, not just transplanted as a finger.
  • Memorable Moment: Amusingly, the reconstructed organ could even support a ceramic water pitcher, as shown in an after-surgery photo.
    • “It looked quite normal, except that it does actually bend at the knuckle… There’s an image of the penis kind of bent upward partway along, and there’s a ceramic water pitcher being held by the penis.” (Mary Roach, 12:02)

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The Future: Toward Cyborgs and Bioprinting

[Segment starts at 12:31]

• Roach tempers the excitement for immediate cyborg upgrades:
  • “Not yet, Gina, but it’ll happen. I mean, it’ll happen. All these things are on the way. Same with bioprinting.” (Mary Roach, 12:50)
• Bioprinting is still in its infancy.
  • “We’re kind of at the Wright brothers stage, if you want to compare it to aviation.” (Mary Roach, 13:20)
  • Emphasizes excitement—early-stage scientists achieved flight, but “a long way off from thousands of flights going back and forth every day.”

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Notable Quotes & Memorable Moments

• On Artificial Body Parts:
  “Is there anything that we humans have built or designed or cooked up that is 100% perfect or pretty much just does what the original part does?... we can’t really even replace tears.” (Mary Roach, 00:53)

• On Being in an Iron Lung:
  “I will say your breathing feels the way your breathing does when you’re not in an iron lung, except that you have absolutely no control over when you’re going to inhale and when you’re going to exhale. The machine has taken over.” (Mary Roach, 05:28)

• On Human Ingenuity:
  “I can’t think of any other body part that would do double duty as a vagina… it’s tubular, it’s moist, it’s pink, it’s stretchy.” (Mary Roach, 09:05)

• On the Middle-Finger Penis Rebuild:
  “It looked quite normal, except that it does actually bend at the knuckle… there’s a ceramic water pitcher being held by the penis.” (Mary Roach, 12:02)

• On the State of Bioprinting Organs:
  “We’re kind of at the Wright brothers stage, if you want to compare it to aviation.” (Mary Roach, 13:20)

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Segment Timestamps

• 00:24 — Regina’s childhood fantasies and the premise of Replaceable You
• 00:53 — Mary Roach on the limits of artificial body parts (tears)
• 01:56 — Burn treatments and skin culture advances
• 04:07 — The history and mechanics of the iron lung
• 05:28 — Personal experience: Trying the iron lung
• 07:11 — Iron lung vs. modern ventilators, pros and cons
• 08:35 — Surgical creation of vaginas using the colon
• 10:10 — Penis reconstruction using middle fingers and a funny aftermath
• 12:31 — The future: Cyborgs and organ bioprinting

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Conclusion

This episode serves up a fast-paced, entertaining, and thought-provoking look at just how “replaceable” the human body is—with plenty of surprising historical context and eyebrow-raising medical facts. Roach’s humor and curiosity, paired with Barber’s insightful hosting, make for a compelling listen, whether you hope to be a future cyborg or just marvel at the creativity of medical science.

“Not yet, Gina, but it'll happen.” (Mary Roach, 12:50)

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Transcript

[NPR Announcer]

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[Regina Barber]

When I was younger, I was excited to get older. And not just my 20s and 30s, but maybe even my 60s and 70s. At the time, the Golden Girls were cool. I loved science, and I thought if any part of my body didn't work anymore, it could probably be replaced. My heart, my lungs, my legs. But I recently read a book that made me think again. It's called Replaceable youe by nonfiction author Mary Roach.

[Mary Roach]

First, fairly far along in the process of writing this book, I was like, is there anything that we humans have built or designed or cooked up that is 100% perfect or pretty much just does what the original part does? And I thought, okay, the tears. How about tears? Have we got a perfect artificial tear? You know, And I found this guy who works for Tear lab and he spent decades working on tears. And we got onto a zoom call and I said, okay, so artificial tears, he's like, yeah, they'll help for an hour or two, but they kind of wash away the good stuff. So we don't even have, we can't really even replace tears.

[Regina Barber]

So my cyborg dreams may not become a reality just yet, but science has still made huge progress when it comes to fixing the human body when it fails. And Mary covers a lot of that progress in her book, from hair to pig organs to her experience visiting a burn unit at a hospital in Boston.

[Mary Roach]

Third degree burns are really tough because the cells that would regenerate from below, like on a second degree burn, those are destroyed. So the body tries to heal by contracting, by kind of pulling like a drawstring. But there are ways now to culture the person's skin off site. So rather than waiting for, for the place that you took the skin to heal so you can take more skin, you can take a biopsy, and they can grow out these very thin layers of the person's own skin. There's spray on skin, which you're spraying cells over the wound area.

[Regina Barber]

Today on the show How Replaceable Are you? We join Mary Roach on her adventure through the human body and learn how far we are from going. Full Cyborg Network. I'm Regina Barber, and you're listening to Shortwave, the science podcast from npr.

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[Regina Barber]

So Mary Roach, we're going to focus the rest of this episode on three chapters from your book. We're going to start with the lungs. You write about the history of the human lung and the invention of something called the iron lung, which was particularly important, like during the polio epidemics in the 1940s and the 1950s. And for someone who doesn't know, polio is a disease caused by a virus that can lead to paralysis, including chest paralysis, so patients can no longer breathe on their own. And the iron lung helps with breathing. How does the iron lung work?

[Mary Roach]

People think about ventilators, and they think about when somebody is intubated and put on a ventilator. That's a system where you're kind of just blowing up. You're forcing air under pressure. You're forcing air like a balloon, like you're blowing up a party balloon. So you're forcing air into the lungs, but we don't breathe that way. Breathing is a very, it's a very natural state of affairs where your muscles are expanding. The muscles of your diaphragm and your rib cage, they open out the area, so they're lowering the pressure so the air rushes in. And the iron lung works the same way. It's called negative pressure ventilation.

[Regina Barber]

But you actually went in an iron lung. What was that like?

[Mary Roach]

I did. I did. I was in an iron lung. And it is, I mean, I haven't been on a positive Pressure ventilator, which is a whole. I mean, most people are sedated when they're on them, so I can't compare it. But I will say your breathing feels the way your breathing does when you're not in an iron lung, except that you have absolutely no control over when you're going to inhale and when you're going to exhale. The machine has taken over. So if you're trying to talk with somebody, and this is something. I mean, I know that when you speak, you're speaking on the exhale. You can't speak and inhale.

I just tried to do it. So that's what happens. Wow. So I would be talking to this guy whose iron lung I was in, and I would try to just talk normally, and it just cuts you off.

[Regina Barber]

That's cool.

[Mary Roach]

Which is a weird. Yeah, it's kind of a weird thing. So it's this very relaxed, kind of luxuriant breathing. But the other thing about the iron lung, your head is outside, and it has to be a tight seal, so you have this thing around it kind of like. So you're simultaneously breathing in this very luxuriant way and feeling like somebody is choking you. Because it has to be a tight fit.

[Sponsor Voice]

Right.

[Mary Roach]

It's not choking you literally, but it is a tight.

It's not a comfortable way to spend the night. And I thought, I'm gonna sleep in the iron lung.

[Regina Barber]

Did you last the whole night?

[Mary Roach]

I lasted about seven minutes.

[Regina Barber]

We started talking about this with. Now we have this kind of, like, ventilator, as you said, like blowing up, like a party balloon. How does that compare to the iron lung? Is it much, much better? Are there pros and cons? What is the difference?

[Mary Roach]

Yeah, for sure. Well, a positive, you know, positive pressure ventilator, you've got to intubate the person. So, you know, you've got to thread this tube down, and it's going through the voice box, and it's. So you can't talk, you can't swallow. But what can happen with a positive pressure ventilator is you just, like with a party balloon, you know how the top part inflates easily and the bottom part doesn't, so you can end up with the lower part of the lungs not taking in the air. And people tend to be sedated. And when you're sedated for a period, I mean, it's fine for a short period of time. But if you're sedated on positive pressure for days and weeks, then you start to get sometimes cognitive issues.

Muscle deterioration. And it takes a certain amount of rehab to get you back to a place where you can breathe on your own and move around well on your own. So you don't want to be on a positive pressure ventilator for extended period of time. But people who were in iron lungs, they were in there for weeks, months.

People in them would often regain some muscle control, so they'd be able to get by during the day outside, but then they'd sleep in the iron lungs. So they weren't always 24, 7.

[Regina Barber]

Yeah. So we're going to talk about the next chapter, the vagina dialogue. This is the chapter that focuses on vaginas made from parts of the intestine. Like, and I hadn't heard of the surgery before, and I was, like, fascinated that using the colon could create this, like, new organization. What is the process like, and why the colon?

[Mary Roach]

Yeah, this was a chapter where I was just fascinated by the body's kind of adaptability. So what you can do is.

The colon. Well, when you think about it, it makes a lot of sense. You know, it's tubular, it's moist, it's pink, it's stretchy. Right.

[Regina Barber]

That's what you said in your book, that a doctor was like, yeah, okay, makes sense.

[Mary Roach]

I can't think of any other body part that would do double duty as a vagina. I was talking to. He's the doctor Garcia. He's the head of the Cedars Sinai transgender surgery and health center. And this is a technique that is sometimes used if the more common way of building a vagina doesn't work out. It's an option. It's not used all that often. You can take an 8 inch. 6 or 8 inch section of the ascending colon, make a cut, and you're going to stitch back the pieces of the colon. Right. So that it's still a working tube, but you can keep. But you can swing down this section that you've liberated, and you keep it attached to the blood supply. Right. It's got a long enough connection to the blood supply. You can swing it down and stitch it in place, and there you have a vagina.

[Regina Barber]

Yeah. So this chapter, it kind of led you to this other realm of, like, replaceable, I'm just gonna say it, penises. And you traveled to Georgia to pursue this, like, story you had heard about, of, like, middle fingers being used to rebuild penises. What kind of research is happening in Georgia? What happened?

[Mary Roach]

Well, let me tell you. Okay, fascinating. This came up. I was having a conversation with a. She actually. Does she's a stem cell researcher. But somehow, in the course of the conversation, she mentioned she saw a paper.

About a technique whereby a man's. The man had had cancer and his penis was rebuilt using his middle finger. I, of course, imagined the finger removed and installed pretty much as is, you know, with the nail. So I was determined to talk to this surgeon who is. I found out in Tbilisi, in Georgia.

[Regina Barber]

The country. The country.

[Mary Roach]

Georgia.

[Sponsor Voice]

The country.

[Mary Roach]

Yes, the country. And I wrote to him in English, in Georgian, using Google Translate. God knows what that note said in Russian.

[Regina Barber]

So here talking about replacement penises.

[Mary Roach]

I would love to see actually.

[NPR Announcer]

How.

[Mary Roach]

That actually read to somebody who speaks Georgian. So I went there and I showed up, the surgeon wasn't there, apparently on vacation. And I'm like, but we've come all the way from America. To which the logical response would be, well, you're a couple of idiots. But I was able to talk to another surgeon there who kind of showed me the images of the procedure. It's not as is. It's wrapped in skin.

[Regina Barber]

It's not just a finger on a body.

[Mary Roach]

I don't know why he chose to use the finger. But I will say the penis at the after photo, it looked quite normal, except that it does actually bend at the knuckle in order to show how strong it was. I get.

There's an image of the penis kind of bent upward partway along, and there's a ceramic water pitcher being held by the penis.

[Regina Barber]

That was the funniest part, I think, of that chapter for me.

[Mary Roach]

The ceramic water pitcher.

[Regina Barber]

This is so great. So after working on this book, in your opinion, what does the future look like for transforming the human body? Am I going to be a cyborg? Because I would really like that.

[Mary Roach]

Not yet, Gina, but it'll happen. I mean, it'll happen. All these things are on the way. Same with bioprinting. I spent time at a lab, a bioprinting lab, the Feinberg Lab at Carnegie Mellon, which is doing really cool stuff. But I said, so how far are we from printing an organ that can be implanted and ready to go in a human being? And he said, we're kind of at the Wright brothers stage, if you want to compare it to aviation.

[Regina Barber]

I see.

[Mary Roach]

Which is both really exciting. I mean, the Wright brothers, my God, they got the thing off the ground and down to the end of the pasture. Pretty cool. But a long way off from, you know, thousands of flights going back and forth every day.

[Regina Barber]

Thank you so much for talking to us today and sharing this book with the world.

[Mary Roach]

Oh, thank you, Gina. It was so fun to talk to you.

[Regina Barber]

If you liked this episode, give us a follow on the platform you're listening to us from. You can also check out our episodes on synthetic cells and the first pig kidney transplant. We'll link to those episodes in our show. Notes this episode was produced by Rachel Carlson and edited by our showrunner, Rebecca Ramirez. Tyler Jones checked the facts. Kwesi Lee was the audio engineer. Beth Donovan is our vice president for podcasting, and I'm Regina Barber. Thank you so much for listening to Shorewave from N.

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