Science In Action (BBC World Service)

Episode: Researching Pain, Painlessly
Date: April 10, 2025
Host: Roland Pease

Overview

This episode of Science in Action delves into several frontier areas of scientific research. The main theme centers on breakthrough efforts to understand and model human pain circuitry outside of the body, potentially paving the way for new pain treatments beyond addictive opioids. The program also highlights new evolutionary insights into the human pelvis and childbirth, a groundbreaking archaeological discovery about early seafaring hunter-gatherers reaching Malta, and provides an update on the international race to study the near-Earth asteroid Apophis during its close encounter in 2029.

Key Discussion Points and Insights

1. Researching Pain Painlessly: Building the Human Pain Circuit on a Bench

[Starts ~03:00]

Breakthrough in Laboratory Pain Circuits

• Interview with Prof. Sergio Pasca (Stanford University):

  • His team has created an unprecedented four-part neural circuit ("assembloid") from human stem cells, mimicking the pain-sensing pathway that stretches from skin to cortex.
  • The system involves peripheral sensory neurons, spinal cord neurons, thalamic neurons, and cortical neurons.
  • As Prof. Pasca describes:

    "It's the first four-part assembloid, and it tries to mimic this pathway in our bodies that sends sensory information all the way to the cortex." ([03:31])

• Natural Self-Assembly:

  • The neural circuits self-organize when placed in proximity for about 100 days.

    "The human brain, like, builds itself, right, without really a very clear blueprint... there's a fundamental program that seems to be coming with the cells." ([04:24])

• Testing with Pain Stimuli:

  • The circuit responds to capsaicin (the active ingredient in chili peppers), lighting up in ways that reflect pain signaling.
  • This is not full "experience" of pain, as the emotional/aversive component is not modeled.

    "These organoids, they don't cry ouch. But you see, as it were, the equivalent reaction within the brain bit, right?" ([06:57])
    "Our assembly does not contain this secondary pathway of pain... they're able to discriminate, at least to sense...that sensory stimulus." ([07:07])

Implications for Pain Research

• Drug Testing Platform:

  • This system can be used to test painkillers and potential alternatives to opioids at scale, providing a molecular view not possible in patients or animal models.
  • Pasca notes:

    "You can literally make thousands and thousands of this assembloids and start thinking, can we actually find a better drug than an opioid?" ([09:33])

• Applications for Chronic Pain and Hypersensitivity:

  • Could address complex conditions such as chronic pain and sensory hypersensitivity, including in neurodevelopmental disorders like autism.

    "...envision using this system to tackle both issues of hypersensitivity... but also to start thinking, can we actually find better treatments for some of these chronic disorders?" ([08:33])

• Limitations:

  • While promising, the system lacks the emotional pathway of pain and cannot fully replicate all human biological cues.

Memorable Quotes

• "At the end of the day, if you think about the human brain, the human brain builds itself, right, without really a very clear blueprint." – Sergio Pasca ([04:24])
• "It's still surprising that today it's very hard to say that we have a drug that is better than what we derived from poppy seeds thousands of years ago." – Sergio Pasca ([09:33])
• "The advantage of this platform is that it's scalable." – Sergio Pasca ([09:33])

2. The Obstetrical Dilemma: Evolution, Childbirth, and the Human Pelvis

[Starts ~10:37]

New Insights into Pelvic Evolution

• Interview with Dr. Marianne Brazil (Western Washington University):

  • Her research uses genetic and imaging data from 31,000 UK Biobank participants to analyze pelvis variation and its genetic underpinnings.
  • Revisits the "obstetrical dilemma": the evolutionary tension between larger-brained infants (requiring wide birth canals) and bipedal walking (narrower pelvis).
  • The pelvis is also important for supporting internal organs and minimizing pelvic floor disorders.

• Key Findings:

  • There is a trade-off between birth canal size, walking efficiency, and risk of pelvic floor diseases.

    "...we see this kind of compromise that's at play between having a smaller and a larger birth canal." ([14:54])

  • 180 genetic loci in the human genome are now linked to pelvic morphology, opening new research avenues.

    "180 independent positions in our genome that are playing a role in these pelvic measurements..." ([16:39])

• Evolutionary Narrative:

  • Bipedalism's selective pressures shaped the pelvis long before selection for larger brains.
  • Natural selection is limited to existing variation ("just good enough").

Memorable Moments & Quotes

• "Evolution can only act on the variation that exists in a population... it's not a perfect solution. It's just, it's good enough." – Marianne Brazil ([17:45])
• (Joking about possible evolution):

  "Why not just have babies with pointier heads?" – Roland Pease ([20:28])
  "Why don't we have pointy heads?... there would be disadvantages to having pointy heads." – Marianne Brazil ([20:38])

3. Discovery: Hunter-Gatherer Seafaring to Malta

[Starts ~24:01]

New Evidence of Prehistoric Sea Voyages

• Interview with Dr. Eleanor Sherry (Max Planck Institute):

  • Her team's excavation in a collapsed cave (doline) on Malta uncovered stone tools and wild animal bones without pottery, dating to ~8,500 years ago — well before the arrival of farmers.
  • The find shows that Mesolithic hunter-gatherers made intentional open-sea voyages (at least 80 km) to Malta.

• Significance:

  • Challenges the view that such early people "couldn't or didn't want to get to these remote islands" due to lack of technology or the small island's limitations.

    "The dominant model has been that hunter gatherers either couldn't or didn't want to get to these remote islands." – Eleanor Sherry ([26:57])

• Site Details:

  • The cave offered shelter, fresh water, raw materials, and ample hunting.
  • Evidence of hearths and butchering of animals like red deer.

• Implications:

  • Prolonged, intentional occupation (not a one-off or accidental arrival).
  • Raises new questions about seafaring skills and "semi-sedentism" in hunter-gatherers.

Memorable Quotes and Moments

• "Really, when you've been told something for so long that something is not possible, then you struggle to believe it yourself, even when you know it's in front of you." – Eleanor Sherry ([31:38])
• "I think this is one of the best excavated sites in the world at this point." – Eleanor Sherry ([33:32])

4. Asteroid Apophis: International Effort for a Unique Space Encounter in 2029

[Starts ~35:10]

International Collaboration for Asteroid Study

• Interview with Prof. Rick Binzel (MIT):

  • Apophis, a 340-meter asteroid, will pass very close to Earth in April 2029 (within 5.8 Earth radii).
  • This is a "once-in-a-thousand-years" opportunity for science—not a threat (repeatedly: "Apophis will miss the Earth." – [35:34])

• Mission Updates:

  • NASA’s OSIRIS-APEX spacecraft is redirecting to study Apophis after its flyby.
  • ESA is developing "Ramses" (formerly Hera) to rendezvous with the asteroid pre-encounter.
  • JAXA (Japan) is considering instrument contributions and possibly a launch vehicle.
  • Chinese space agency has ambitions, with increasing openness to dialogue; private entities like Blue Origin present services.
  • International collaboration is emphasized as key, recognizing that "asteroid impacts know no borders."

    "This is the way to practice it. This is the way to show the world that...space agencies really do want to work together and we really do care about planet Earth." – Rick Binzel ([38:48])

• Technology and Timing:

  • Time is tight: spacecraft must launch in next few years to catch Apophis.
  • Collaboration challenges include funding, rocket availability, and coordinating many agencies and private entities.
  • Studying Apophis' response to Earth's tidal forces will reveal how such hazardous asteroids are structured—essential knowledge for planetary defense.

Notable Quotes

• "I like to say the dinosaurs who were wiped out by an asteroid impact didn't have a space program. We do, so we don't have an excuse." – Rick Binzel ([41:34])
• "Apophis is coming whether we're ready or not to take advantage of the science opportunity that it's going to present when it safely passes the Earth." – Rick Binzel ([44:44])

Notable Quotes with Timestamps

• Sergio Pasca ([03:31]): "It's the first four-part assembloid, and it tries to mimic this pathway in our bodies that sends sensory information all the way to the cortex."
• Sergio Pasca ([09:33]): "You can literally make thousands and thousands of these assembloids and start thinking, can we actually find a better drug than an opioid?"
• Marianne Brazil ([17:45]): "It's not a perfect solution. Right. It's just, it's good enough. It's whatever is the best available option in a population that allows those individuals to survive and reproduce."
• Eleanor Sherry ([31:38]): "Really, when you've been told something for so long that something is not possible, then you struggle to believe it yourself, even when you know it's in front of you."
• Rick Binzel ([35:34]): "The three most important things are that Apophis will miss the Earth. Apophis will miss the Earth. Apophis will miss the Earth."
• Rick Binzel ([41:34]): "The dinosaurs who were wiped out by an asteroid impact didn't have a space program. We do, so we don't have an excuse."

Timestamps for Key Segments

• Opening and Preview – [01:48]
• Pain Circuitry Breakthrough – [03:00]–[10:37]
• Evolution of the Human Pelvis – [10:37]–[21:03]
• Ancient Seafaring to Malta – [24:01]–[34:48]
• Asteroid Apophis Missions – [35:10]–[45:54]

Conclusion

This episode exemplifies the interconnectedness of today’s science — from cellular neuroscience promising non-addictive pain treatments, to evolutionary compromises in childbearing, to revising our views of ancient human migration, and finally to cooperative planetary defense efforts against asteroid impacts. The episode's guests effectively translated technical detail into accessible, thought-provoking discussion, exemplified by engaging metaphors, personal anecdotes, and apt humor. For listeners who want a deep, varied tour through the latest in scientific discovery, it offers both wonder and practical insight.