How Replaceable Are You? Iron Lungs, Colon-Derived Vaginas, and Finger-Based Penises explored by Mary Roach

Summary

Mary Roach’s Replaceable You examines how far science can push the idea of a body that can be replaced or modified. The episode starts with the iron lung, detailing negative-pressure ventilation, the patient experience, and how it contrasts with modern positive-pressure ventilators. It then moves to the vaginal dialogue, describing vaginal reconstruction from colon tissue and why the colon can be repurposed as a vagina. A striking Georgia story follows, describing penile reconstruction using a finger, wrapped in skin, and what the visual results look like. The discussion concludes with a forward-looking discussion on bioprinting, tissue engineering, and the path toward cyborg-like enhancements, underscoring both the promise and the limits of current technology.

Introduction

In this episode, NPR's Shortwave hosts a discussion with science writer Mary Roach about her book Replaceable You, which surveys the boundaries between biology and technology as people imagine replacing or redesigning body parts. The conversation centers on three major chapters from Roach’s book and uses real-world examples to illustrate how close we are to achieving durable, functional replacements for human tissues and organs.

Iron Lung: History, Mechanics, and Experience

The first major segment examines the iron lung, a device that achieved fame during polio outbreaks by providing negative-pressure ventilation. Roach explains how a ventilator can work in two fundamentally different ways: positive pressure ventilation and negative pressure ventilation. The iron lung creates a seal around the chest, allowing the body’s own muscles to expand and contract while the machine regulates airflow. Roach shares a vivid personal account of spending seven minutes inside an iron lung, noting how breathing becomes a passive process controlled by the machine and how that changes who can speak, swallow, or use their voice. The contrast with modern ventilators—where patients are often sedated, intubated, and connected to a tube—highlights both comfort and cognitive considerations. As Roach points out, long-term reliance on positive-pressure ventilation can lead to cognitive and muscle decline, underscoring why the iron lung, though archaic, offered a different recovery pathway for some patients.

“you can't speak and inhale” — Mary Roach

Colon-Based Vagina: Adaptation and Surgical Innovation

The second section shifts to the vagina dialogue, a surgical technique that repurposes sections of the ascending colon to construct a vagina. Roach conveys the logic behind using colon tissue: it is tubular, moist, pink, and stretchy, making it a reasonable stand-in for a vaginal canal in certain clinical contexts. The discussion includes the surgeon Dr. Garcia from Cedars-Sinai who explains that this option is available when more common vaginoplasty methods are unsuccessful or unsuitable. This segment emphasizes the body’s capacity for adaptation and raises questions about functional outcomes, long-term care, and the ethics of using non-traditional tissues in gender-affirming surgery.

“it's tubular, it's moist, it's pink, it's stretchy” — Mary Roach

Penis Reconstruction in Georgia: Remarkable Cases and Ethics

Roach then recounts a surprising case she learned about in Tbilisi, Georgia, where a penis was rebuilt using a middle finger. The interview describes the research process, the challenges of communicating across languages, and the surprising visual results, including a knuckle bend to demonstrate strength. The narrative underscores how experimental techniques can push boundaries while also raising questions about consent, expectations, and the patient’s quality of life. The Georgia anecdote serves as a provocative example of how far surgical science might go and what that implies for the future of prosthetics and reconstruction.

“it's not just a finger on a body” — Mary Roach

Bioprinting and the Road Ahead

The final portion turns toward bioprinting and organ fabrication, sharing Roach’s experiences in a Carnegie Mellon bioprinting lab and drawing comparisons to the Wright brothers’ early aviation efforts. The discussion emphasizes that while bioprinting and biotechnologies have progressed, the field is still in its infancy relative to real-world, routine organ replacements. Roach frames the future as one of incremental breakthroughs with complex clinical, regulatory, and ethical dimensions, suggesting that true, fully implantable organs may be many years away, but the pace of advancement continues to accelerate.

“we're kind of at the Wright brothers stage if you want to compare it to aviation” — Mary Roach

Conclusion

Throughout the episode, the host and Roach acknowledge both the excitement and the limits of replacing or augmenting parts of the human body. The show closes with a reminder that the future of body modification will likely blend biology with engineering, prompting ongoing conversations about safety, ethics, and accessibility.