StarTalk Radio – “Replaceable You” with Mary Roach

Host: Neil deGrasse Tyson
Guests: Mary Roach (science writer), Chuck Nice (comedian), Gary O'Reilly (sportscaster), Bill Nye (science advocate)
Aired: December 12, 2025

Overview:

In this lively episode of StarTalk, Neil deGrasse Tyson and panel dive into Mary Roach’s new book, "Replaceable You: Adventures in Human Anatomy." The conversation explores the wild past, quirky present, and tantalizing future of medical advances in replacing, repairing, and augmenting the human body. With humor and insight, the group discusses regenerative medicine, prosthetics, organ transplants, and the evolving boundaries between biology and technology.

Key Discussion Points & Insights

1. Introduction & Mary Roach’s Unique Angle

• Mary Roach’s writing focuses on underexplored corners of science, blending humor, deep research, and compelling storytelling.
• She takes inspiration from real people and unusual stories, not just sci-fi or pop culture, to approach topics from unexpected directions.
• Quote:
  • “I go and I target some unsuspecting expert researcher, scientist, and I use them as an unpaid tutor, basically.” — Mary Roach (06:00)
  • “It’s a unique niche in the nonfiction-verse.” — Chuck Nice (05:48)

2. Historical Background: Replacement Parts for Humans

• Origins: Replacement parts for humans have been pursued since at least 1500 BC.
• First Chapter - The Nose:
  • Nasal mutilation was common as punishment for crimes in ancient cultures.
  • Famous astronomer Tycho Brahe had a fake nose, and intricate nose repair “industry” emerged as a result.
  • Innovations: Early surgeons like Frank Tettemore (1894) devised prosthetic noses using glasses and celluloid, while Gaspari Tagliacozzi (1500s) pioneered surgical reconstruction with skin flaps.
• Quote:
  • “It was a pair of glasses…and you would hang a celluloid plastic nose off the glasses. At the bottom, to hide the line, there was a mustache. So it’s basically Marx glasses—a medical version.” — Mary Roach (19:11)
  • “So the literal meaning of the word ‘deface’ would be to just slash, lop off your nose?” — Chuck Nice (18:20)

3. The Struggle for 'Wholeness' and Amputation Choices

• Stories include patients seeking elective amputations for nonfunctional limbs and the difficulty of finding surgeons willing to perform these procedures.
• The discussion pivots to how technology does not always solve for individuality or the bias toward “fixing” rather than adapting differently abled bodies.
• Quote:
  • “It’s specifically about how hard it is if you want to get something off…and that bias for wholeness.” — Mary Roach (10:07)

4. Bionics and Pop Culture vs. Medical Reality

• Six Million Dollar Man & Star Wars inspired public imagination but are far from today’s real-world technology.
• Real prosthetics are heavy, expensive, and require constant charging—not seamless or perfect.
• Prosthetic hands are a technical feat, especially the challenge of replicating complex, independent finger movement; arms are less commonly replaced than legs due to practical and technical obstacles.
• Quote:
  • “Everybody thinks that’s easy, but it’s not easy. Those arms, they’re heavy…they’re like $15,000, insurance doesn’t pay, so it’s just not there yet.” — Mary Roach (12:53)

5. Prosthetics: Tech Advances and Limitations

• State-of-the-art legs: Prosthetics with AI and microprocessors can adjust gait and help prevent falls, but are costly and not waterproof.
• Osseointegration: Attaching prosthetics directly to the bone allows for better sensation and movement, but carries infection risk.
• Antiperspirants for residual limbs illustrate the pragmatic side of living with prosthetics.
• Quote:
  • “If you could do that—setting aside the infection issue—it’s great, 'cause now you have sensation through the bone. You can tell what surface you’re walking on.” — Mary Roach (27:12)

• Humor break:
  • “Residual limb antiperspirant. Did you know that was a thing?” — Chuck Nice (27:37)

6. Organ Transplants: New Hurdles and Innovations

• Heart transplants: Limited by how long organs remain viable after extraction—new machines can extend shelf life by simulating heart/lung function (extracorporeal membrane oxygenation, or ECMO).
• Rejection: Major obstacle for complex organ (and face/hand) transplants—body tends to attack foreign tissue.
• Xenotransplantation: Recent attempts to use genetically modified pig organs (e.g., kidneys) in humans; limited success so far, requiring genetic editing for compatibility.
• Quote:
  • “Some of the face transplant people need like a second face because they’re having rejection issues…People are asking to have hands taken off.” — Mary Roach (32:07)
  • “You gotta genetically edit those suckers, those pigs…knock out [the alpha gal] protein, now the body's a little more accepting.” — Mary Roach (32:41)

7. The Bioengineering Frontier: Chimerism, 3D Printing & Scaffolds

• Chimerism: Future potential where pigs could gestate human-compatible organs via stem cell edits and gene editing.
  • The vision: people have their “own personal pig for spare parts.” (34:13)
• 3D bioprinting: Current state is at “Wright Brothers stage”—labs can print simple structures (mouse ventricles, heart valves) but fully functional, implantable human organs remain decades away. AI and improved cell scaffolding might accelerate progress.
• Quote:
  • “How long before we’re printing an organ you could install in a body? He said, ‘We are kind of in the Wright Brothers stage.’” — Mary Roach (46:18)

8. Extreme Body Replacements and the Ethics Thereof

• Unusual examples:
  • The “finger penis” in Georgia, where a man’s finger was used to reconstruct his penis after cancer.
  • “You could crook it up like a finger…and in order to show how strong it was, they hung a ceramic water pitcher on it.” — Mary Roach (44:47)
• Whole body transplants: Theoretical (à la “head transplants”), but not currently possible—main challenge is reconnecting nerves, especially the spinal cord.
• Ethical questions loom around creating humans from one’s own pluripotent stem cells and gene editing for “designer” organs or immortality.
• Quote:
  • “If you take someone’s blood cells…regress them to pluripotency, direct them to become an egg or sperm...in theory you could create another human being with only your own genetic material.” — Mary Roach (50:51)
  • “Are there ethicists working in tandem with these efforts, or are they brought on only when it’s too late?” — Chuck Nice (51:33)

9. Cosmic Perspective: What if Nature Has the Answer?

• Tyson proposes that rather than inventing mechanical replacements, perhaps the more profound solution is unlocking regeneration—as seen in newts, lobsters, and worms—at the genetic level for humans.
• Quote:
  • “Maybe the solution…is not inventing a kidney or heart or limb…Maybe it’s going into our DNA, splicing in that which regenerates organs in other animals…the future of this is you just go in and…another organ grows.” — Neil deGrasse Tyson (52:29)

Notable Quotes & Moments

• Mary Roach: “Journalist, science communicator, and writer…nonfiction author. Funny. Sometimes.” (06:43)
• On rejection: “Some of the face transplant people need a second face…People are asking to have hands taken off.” (32:07)
• On pig organ farms: “I went to China. They call 'em piggeries. Facial recognition for pigs!” (35:12)
• 3D printing organs: “We are kind of in the Wright Brothers stage.” (46:18)
• On ethics: “There are ethicists who are publishing papers about this with warnings and everything. But I don’t know if…I hope so.” (51:41)
• Cosmic Perspective: “We see a problem, a challenge, and then we try to address that problem…maybe the future of this is you just go in and they twiddle with your DNA and another organ grows.” — Neil deGrasse Tyson (52:29)

Timestamps for Key Segments

• Mary Roach’s Introduction & Philosophy: 05:54 – 07:20
• Origins of Nose Replacement: 16:03 – 20:45
• Techniques in Historic and Modern Reconstructive Surgery: 19:11 – 20:45
• Prosthetic Limbs and Bionics—Current State: 23:28 – 26:00
• Osseointegration & Prosthetic Advances: 26:13 – 28:06
• Organ Transplantation Innovations: 29:29 – 31:07
• Xenotransplantation & Genetically Modified Animal Organs: 32:28 – 34:13
• 3D Printing of Organs/Scaffolds: 37:03 – 39:29; 45:51 – 47:50
• The "Finger Penis" & Extreme Replacements: 41:19 – 45:35
• Ethical Considerations & Reproductive Technology: 50:32 – 51:54
• Cosmic Perspective – Regeneration in Nature & The Future: 52:24 – 56:43

Tone and Style

• The panel maintains StarTalk’s signature blend of humor and scientific rigor, with several moments of raucous laughter and playful banter, particularly around bizarre or eyebrow-raising anecdotes. Tyson grounds the discussion with cosmic reflections, and Roach offers unique, first-person accounts of being “on the ground” among scientists and in surgical suites worldwide.

Summary

"Replaceable You" explores the limits of medical technology and bioengineering, from prosthetic noses of the 1500s to visions of printed organs and chimeric spare-part pigs. While we’re far from the sci-fi fantasies of instant replacement, rapid progress is being made—albeit often in unexpected ways and always accompanied by philosophical and ethical dilemmas. Mary Roach’s journalism illuminates both the technical marvels and curious humanity at the heart of these advances.

Listen if you want:

• To laugh while learning about the wildest corners of medical science
• Real stories behind headlines about biotech, prosthetics, and transplants
• To ponder the ethical and cosmic implications of becoming our own repairmen—or our own “newts”

Final thought from Tyson:
"Perhaps that's in our future. A future not yet visible to us, but maybe nature has that in store." (52:29–56:43)