Unexplainable

Real-life zombies

October 1, 2025

Key Takeaways Copied to clipboard!

  • A "zombifier" is an organism that manipulates a host's behavior solely for the parasite's benefit, distinguishing it from normal sickness responses. 
  • Zombification mechanisms often involve hijacking the host's existing biochemistry, such as using the spider's molting hormone (ectosteroids) to force web construction for the wasp larva's cocoon. 
  • Pathogens like *Toxoplasma gondii* and rabies are known to manipulate behavior in mammals, suggesting that human behavior can also be shaped by parasitic organisms. 

Segments

Sponsor and Membership Plug
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(00:00:00)
  • Key Takeaway: Vox membership offers ad-free listening and full Vox.com access to support Unexplainable production.
  • Summary: Support for Unexplainable is provided by Anthropic’s Claude AI. Listeners can support the show and receive ad-free episodes by becoming a Vox Member. Membership also grants access to all articles on Vox.com and an exclusive newsletter.
Fungus Zombie Fly Example
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(00:01:28)
  • Key Takeaway: A fungus infects a fly, consumes its fat cells, forces it to climb grass, and then uses the dead fly’s body as a ‘fly fatale’ to attract mates for spore dispersal.
  • Summary: The episode opens by describing a fly infected by a fungus that grows internally, consuming fat reserves. The fungus manipulates the fly to climb high onto grass blades before dying and bursting open to release spores. The dead fly’s swollen abdomen and chemical scent attract live male flies, increasing the chances of new infections.
Defining Zombifier and Zombie
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(00:06:14)
  • Key Takeaway: A zombifier manipulates host behavior only to benefit the parasite, unlike sickness which benefits the host’s recovery.
  • Summary: A zombifier is defined as an organism that manipulates its host’s behavior in a way that only benefits the parasite. A zombie host behaves in ways it normally would not, which is detrimental to its own survival. This manipulation differs from typical illness responses, such as resting when sick, which aids the host.
Hairworm Cricket Zombification
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(00:08:19)
  • Key Takeaway: Hairworms, which reproduce in water, force infected crickets to seek water and jump in so the massive worm can emerge.
  • Summary: Hairworms grow inside terrestrial insects like crickets to many times the host’s length. The worm manipulates the cricket’s behavior to compel it to find water and jump in. Once submerged, the worm slowly spools out of the cricket’s body over several minutes.
Mysteries of Zombification
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(00:10:05)
  • Key Takeaway: Major mysteries include how zombifiers evade the host immune system, what environmental cues trigger manipulation, and the precise biochemical mechanisms of control.
  • Summary: One major mystery is how zombifiers bypass the host’s initial immune response upon infection. Another question concerns the environmental cues that trigger the manipulation phase, such as the fly fungus starting its climb at night. The third key mystery involves the nuts and bolts of how the parasite chemically manipulates complex behaviors like climbing or web-building.
Wasp Manipulating Spider Web
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(00:12:05)
  • Key Takeaway: A wasp larva manipulates an orb-weaving spider into building a reinforced ‘resting web’ before draining the spider dry for its own cocoon.
  • Summary: The wasp larva feeds on the spider until it is ready to pupate. It then manipulates the spider to build a reinforced molting web, which the wasp larva uses as a protective cocoon. Scientists found the larva floods the spider’s brain with ectosteroids, the natural hormone spiders use to initiate molting web construction.
Benefits of Understanding Zombification
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(00:17:46)
  • Key Takeaway: Studying zombification can inform the development of immunosuppressive drugs and provide targeted, environmentally safer pest control methods.
  • Summary: Understanding how zombifiers suppress host immune systems could inform the development of beneficial immunosuppressive drugs for humans. Baculoviruses, which cause caterpillars to dissolve, are already deployed in some regions as targeted, less toxic alternatives to traditional insecticides. Scientists are exploring borrowing these natural mechanisms for agricultural pest control.
Human Susceptibility to Zombification
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(00:21:38)
  • Key Takeaway: Rabies and Toxoplasma gondii are known pathogens that manipulate behavior in mammals, with evidence suggesting T. gondii may shape human risk-taking behavior.
  • Summary: Rabies is a known virus that can heighten aggression in humans. Toxoplasma gondii, whose definitive host is the cat, makes rodents bolder and attracts them to cat urine to complete its life cycle. Studies suggest that humans carrying T. gondii may exhibit increased risk-taking or boldness, mirroring the parasite’s effect on rodents.
Episode Credits and Call to Action
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(00:26:21)
  • Key Takeaway: Mindy Weisberger’s book, Rise of the Zombie Bugs, covers additional zombification stories like those involving cicadas.
  • Summary: The episode concludes by promoting Mindy Weisberger’s book, Rise of the Zombie Bugs, for more horrifying examples. Listeners are encouraged to email feedback to [email protected]. Support for the show is requested via Vox membership at vox.com/members.