Radiolab – "Cellmates" (April 6, 2016)

Episode Overview

This Radiolab episode, hosted by Robert Krulwich and Jad Abumrad, dives into one of the most profound mysteries in biology: how simple, single-celled life on Earth suddenly leaped in complexity, leading to the enormous diversity of large, complex organisms – everything from jellyfish to trees to humans. Drawing on the research and theories of evolutionary biochemist Nick Lane and science writer Ed Yong, the episode unpacks the remarkable and improbably singular event that made complex life possible: the union of two different types of simple cells, an event that gave rise to mitochondria, the "cellmates" inside every complex cell.

The episode also features an introduction to the new WNYC Studios comedy podcast "2 Dope Queens," with guests Phoebe Robinson and Jessica Williams.

Key Discussion Points and Insights

1. The Three Great Mysteries of Biology

• Mystery #1: Where did life come from?
  Robert Krulwich introduces this as the mysterious spark that created life from lifeless chemicals about 4 billion years ago.
  "All of a sudden, for some reason which we have never really been able to understand, lifeless chemicals suddenly produce a pulse and you get life." (02:46, Robert Krulwich)

• Mystery #3: The appearance of consciousness
  Only one known species evolved self-awareness—another deep unsolved question.

• Mystery #2: The great leap in complexity — the episode's focus
  For about two billion years, life remained simple and microscopic, little more than "bags of chemicals." Then, in a seeming instant, much larger and more complex cells appeared, eventually leading to multicellular life.

2. The Energetic Barrier to Complexity

• Energetic canyon:
  Ed Yong explains why simple life remained simple for so long:
  "There is a barrier. There is an energetic canyon that simple cells find themselves trapped in." (08:01, Ed Yong)

• Getting bigger and more complex isn't just a matter of accumulating more resources; it also requires much more energy to power bigger structures and more DNA.
  "You don't get bigger for free. Every new step takes extra energy." (08:44, Robert Krulwich)
  "If you're going to increase the size of your company by a thousand times, you're going to need to pay them all." (08:48, Ed Yong)

3. The Merger: How Complex Life Began

• The accident of cell fusion:
  The core hypothesis is that about 2 billion years ago, in one single, extremely improbable event, two simple cells from different domains of life—an archaean and a bacterium—merged.
  "One of them is an archaean little blob and one of them is a bacterium. ... They merge." (10:21, Ed Yong; 11:23, Nick Lane)

• Rarity:
  Such mergers are vanishingly rare and usually disastrous for the engulfed cell—but not this time. Instead, the "guest" bacterium survived, thrived, and even divided inside its host.
  "For the most part, cells don't get inside other cells. And when they do ... for the most part it doesn't work out. ... But not this time." (11:50, Nick Lane & Robert Krulwich)

• The birth of mitochondria:
  The engulfed bacterium evolved into mitochondria, organelles crucial for providing the massive increase in energy needed for complexity.
  "They are a very specific kind of bacteria that we now call mitochondria." (14:14, Robert Krulwich)

• Lightning in the cell:
  Mitochondria produce energy at an intensely concentrated scale—
  "If you shrink yourself down to the size of a molecule and feel the strength of the electric field ... it's actually 30 million volts per meter, which is equivalent to a bolt of lightning." (14:36, Nick Lane)

4. Why Mitochondria Made Complexity Possible

• Having internal powerhouses (mitochondria) allowed cells to massively increase their DNA, experiment with different gene functions, and ultimately become the ancestors of all animals, plants, and fungi.
  "Now, they can support enormously larger genomes. ... The descendants did so well. They've taken over the world." (15:28, Nick Lane)

• Single Origin of Complexity:
  All complex multicellular life today descends from this single event.
  "It comes down to one merger between two cells that made one cell. And then everything comes from that. You, me, the redwood tree, or the hummingbird, a fungus ... Every type of life that we can see with our naked eyes ... come from that single cell." (16:08, Ed Yong)

5. Evidence for the Theory

• Genetic fingerprints:
  All complex organisms have DNA and cell structures clearly traceable to both archaea and bacteria—evidence of the original merger.
  "You can see very clearly that the original DNA of those two cells, those two cells that merged into one, they're inside us." (17:21, Robert Krulwich)

• Structural similarity:
  Across all plants, animals, and fungi, internal structures (including mitochondria) are near-identical, pointing to a single ancestor.
  "They all have that nucleus, that's internal skeleton. They would have mitochondria, those are the lightning bolts, the descendants of that first little guy that got swallowed." (18:02, Ed Yong & Robert Krulwich)

6. Implications for Life Elsewhere in the Universe

• The fusion event was so improbably rare that it likely never happened twice.
  "So there is no trajectory towards necessary complex life. The universe is not pregnant with the idea of us. ... complex life is [not] an inevitable outcome." (21:11, Nick Lane)

• Microbial life might be common, but complex, conscious alien life may be extremely rare.
  "The odds of finding your Star Wars cantina are significantly reduced. The odds of finding, like, a bacterium somewhere, probably reasonable." (22:17, Ed Yong)

7. Related Ideas: Cooking and Human Consciousness

• The "energy canyon" concept may also explain jumps in human evolution, such as the leap enabled by cooking, which allowed us to get more energy out of our food and possibly develop higher intelligence.
  "Maybe it increases the amount of energy that you can get from your food by 25, 30, 40, 50%, maybe more." (19:29, Nick Lane)
  "That is when the genus Homo humans, in the first full flowering of the sense of that word, emerged." (20:05, Nick Lane)

Notable Quotes & Memorable Moments

• On the great merge:
  "All of our cells ... they all look something like those original cells, very, very similar. They all have that nucleus, that's internal skeleton. They would have mitochondria, those are the lightning bolts, the descendants of that first little guy that got swallowed." – Ed Yong (17:56)

• On cosmic improbability:
  "That merger and the harmonious continuance of that merger was so breathtakingly improbable that only once did it take." – Ed Yong (20:53)

• On implications for extraterrestrial life:
  "We think the universe is so vast ... there must be life on other worlds. But I think what this tells us is that we will probably find life elsewhere, but it will probably be microbial." – Ed Yong (21:48)

Timestamps for Important Segments

• 02:31 — Introduction of the episode’s three mysteries (Robert Krulwich)
• 04:47–07:21 — The long era of simple cells and the glass ceiling for complexity (Nick Lane)
• 07:42–09:41 — The "energetic canyon" that simple cells couldn't cross (Ed Yong)
• 10:03–13:56 — The endosymbiotic event: one cell engulfs another and creates something new (Nick Lane, Ed Yong)
• 14:25–15:39 — Mitochondria as cellular powerhouses and their impact on genome size (Nick Lane)
• 16:08–17:56 — All complex life descends from one merger; evidence in our DNA and cell structures (Ed Yong)
• 18:12–18:42 — Mitochondria’s overwhelming presence in our bodies (Nick Lane)
• 19:00–20:05 — The cooking hypothesis and energy surpluses linked to human brain development (Soren Wheeler, Nick Lane)
• 21:11–22:17 — The rarity of complex life and its implications for the universe (Nick Lane, Ed Yong)

2 Dope Queens Introduction (Comedy Segment)

Introduction & Chemistry (27:57–30:08)

• Jad introduces Phoebe Robinson and Jessica Williams, who joke about their friendship and imaginary relationship with actor Michael Fassbender.
• "All it takes is, like, two black people to make something cool. That's the rule. If we ... had our shoes on the wrong foot ... as long as it's two black people doing it." – Jessica Williams (29:00)
• The two recount how they met and instantly hit it off on stage:
  "We murdered this stage. Homicide, first degree murder. Law and order, baby." – Phoebe Robinson and Jessica Williams (29:42)

About the Podcast (30:16–34:00)

• "2 Dope Queens" is a live comedy show podcast, with sets from their favorite comedians, focusing on diversity and inclusivity, especially for women and people of color.
• Sample comedic bits from Michelle Buteau and Naomi Ekperri highlight the show's humor and representation.
• "If you're jogging at those hours, you got two options, okay? You're either gonna find a dead body or become a dead body. Stop it with the jogging." – Jessica Williams (32:45)
• Phoebe and Jessica express pride in what they're creating:
  "We really love doing it ... we really do deliver on that." – Jessica Williams (34:02)

Conclusion

"Cellmates" blends investigative science with accessible analogies and fun, leveraging the energetic, inquisitive style that Radiolab is known for. The episode reveals how every complex living thing shares a single, wildly improbable origin—a tangling together of two primitive cells, the ultimate "cellmates." The ramifications are humbling and cosmic, suggesting the rarity of complex life not just on Earth, but across the universe.

The bonus introduction to "2 Dope Queens" brings warmth and humor, highlighting Radiolab’s commitment to showcasing diverse, creative voices.

For references, books mentioned include:

• Nick Lane: "The Vital Question"
• Richard Wrangham: "Catching Fire"
• Ed Yong: "I Contain Multitudes"

More at radiolab.org