Short Wave — "Parasites Have Haunted Us For Millions Of Years"

NPR | Hosts: Regina Barber, Emily Kwong
Aired: October 24, 2025
Guests:

• Dr. Karma Nanglu, Paleontologist, University of California, Riverside
• Dr. Danielle DeCarle, Paleontologist, University of Toronto

Episode Overview

This spooky-season episode delves into the ancient world of parasites — those notorious organisms that live in or on other creatures, often causing harm. Hosts Regina Barber and experts Karma Nanglu and Danielle DeCarle unravel the deep history of parasitism, from its fossil record stretching over half a billion years to recent fossil discoveries that challenge our understanding of these creepy hitchhikers. With humor and a touch of nerdiness, the conversation covers unforgettable fossil detective stories and explains why the true diversity and behavior of ancient parasites might still be hiding in museum basements.

Key Discussion Points

1. Parasites: A Haunting Legacy

• Parasites as Childhood Fears:
  • Regina shares her phobia of parasites, referencing horrifying examples like tapeworms and cordyceps fungi that inspired "The Last of Us."
    • "Parasites scare me... I think of cordyceps... or I think of people finding a tapeworm in their bodies after eating raw meat." – Regina Barber (01:08)
• How Old Are Parasites?
  • Ancient fossils show evidence of parasitism dating as far back as 515-516 million years ago, notably small worm-like animals attaching to shelled creatures called brachiopods.
    • "We have fossils as old as about five hundred fifteen, five hundred sixteen million years old that have evidence of parasites on them." – Karma Nanglu (01:36)

2. The “Riddler” Mystery Fossil

• Detective Work in Paleontology:
  • Karma describes grappling with a fossil marked by a question-mark-shaped trace, nicknamed “The Riddler,” which puzzled scientists for years.
    • "We had no explanation at the time for what this thing could possibly be. They did have a name for it though, The Riddler, like the Batman villain." – Karma Nanglu (02:25 / 02:33)
  • After comparing modern parasitic worms, they identified the trace as the work of ancient spionid worms, showing behavioral evidence millions of years old.
    • "It’s a kind of aquatic worm... to actually show behavior in fossils is really really rare." – Regina Barber (06:51)

3. What Makes an Organism a Parasite?

• Parasitism Defined:
  • Danielle provides a scientific overview, describing parasitism as a form of symbiosis in which one organism (the parasite) benefits at the expense of the other (the host).
    • "Parasitism is a specific form of symbiosis where you have one organism... that gains nutrients at the expense of the host." – Danielle DeCarle (04:54)

4. Fossil Evidence of Ancient Parasites

• Fossil Finds and Amber Inclusions:
  • Examples include parasitic worms found in fossil amber, where nematodes are seen emerging from insect hosts, essentially capturing a "photo" of parasitism in ancient times.
    • "There are actually fossils of insects in amber... we can actually see nematodes emerging from them." – Danielle DeCarle (05:44)

5. The Origin of Leeches: Surprising Discoveries

• The “First” Leech Fossil:
  • Karma and Danielle recount finding the earliest leech fossil – a major breakthrough. Contrary to assumptions, this leech did not likely feed on vertebrates’ blood, but possibly preyed on invertebrates like trilobites instead.
    • "We found the first leech fossil that has ever been recorded." – Danielle DeCarle (03:07)
    • "Instead of parasitizing vertebrates... we think our fossil might have been a parasite of invertebrates, or even a predator." – Danielle DeCarle (09:02)
• Scientific Rejection and Collaboration:
  • Karma initially thought a fossil was a leech, but colleagues rejected the idea before eventually discovering the true leech fossil.
    • "I felt crushed. Absolutely crushed... but no, they were pretty upfront, which is what you want in a scientific colleague." – Karma Nanglu (10:49 / 10:52)
• Implications:
  • This find pushes the origin of leeches back by 200 million years and alters the understanding of their lifestyle and habitat evolution.
    • "It tells us that this group of animals... are like two hundred million years older than we thought." – Danielle DeCarle (12:47)

6. The Hidden Potential of Museum Collections

• Basement Fossil Treasures:
  • Both guests emphasize that museum basements and collections hold many undescribed and misunderstood fossils — possibly including groundbreaking specimens like the Riddler and the first leech.
    • "There’s huge potential for discovering new fossils in collections that already exist." – Danielle DeCarle (14:05)
  • Modern technology, such as CT scanning, is opening up new possibilities for reevaluating older fossils and finding hidden traces of organisms or their behavior.
• Exceptional Fossil Sites:
  • Sites like Waukesha (Wisconsin) are compared to “opening your eyes" during a movie, offering rare glimpses into the complete ecosystem, including soft-bodied creatures.
    • "This site in Wisconsin called Waukesha is one of these sites of exceptional preservation... you get to open your eyes for a very brief moment." – Karma Nanglu (14:58)

Notable Quotes & Memorable Moments

• Regina’s Submission to Spooky Science:
  • "Parasites scare me... the ones that in real life burst out of the head of ants and control them when they're dead." (01:08)
• On Scientific Discovery:
  • "It's courage, right? Like you had the courage to be wrong and because of that... we stumbled upon this amazing discovery. If you hadn't had the courage to be wrong, we'd all still be leechless." – Danielle DeCarle (12:25)
• The Essence of Paleontology:
  • "If you think about the history of life... imagine watching that movie but you’re squinting the entire time, but once in a while you get to open your eyes and see the whole picture." – Karma Nanglu (14:58)

Timestamps for Key Segments

• Parasites in Pop Culture & History: 01:08 – 01:36
• Earliest Evidence of Fossil Parasites: 01:36 – 02:25
• Cracking the “Riddler” Fossil Mystery: 02:25 – 03:07, 06:08 – 08:02
• What Is Parasitism? 04:54 – 05:34
• Various Fossil Parasites Described: 05:44 – 06:08
• Discovery of the First Leech Fossil: 09:02 – 10:11, 12:04 – 13:44
• Role of Museum Collections & Technology: 14:05 – 15:31

Tone & Takeaways

The episode’s conversational, humorous, and spooky vibe makes complex science accessible and enjoyable. The hosts and guests use detective analogies, pop culture references, and mutual ribbing to keep things light while delivering surprising scientific insights about the persistence and evolution of parasites — and the untapped potential lurking in museum drawers.

For more bite-sized science intrigue, subscribe to Short Wave and check out the show’s back catalog.