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I'm Sick Because of the Social Structures of Early Hominins

2026-03-20 · explainer · Hank · 7:09 · watch on YouTube

Topic: Science & nature (also: Health, Personal life) · mode: Explainer

Sick with shingles, Hank tells John how the varicella zoster virus causes chickenpox, hides dormant in nerve ganglia and re-emerges as shingles, and argues that this two-phase cycle evolved because small, isolated early hominin groups would otherwise have let the virus burn out. That old trait now makes the virus hard to eradicate.

What is said

The parts of the video and what is said in each (★ — how much it matters to the video).

00:00:00 — Hank has shingles and researches it; shingles turns out to say something about early hominins

  • ★★★ Hank has shingles; when sick he researches his disease until he finds it bizarre and fascinating and lets that distract him, which he has done with shingles before. — 00:00:00
  • ★★ Hank says shingles is even weirder than he thought and, unexpectedly, tells us something about the evolution of early hominins. — 00:00:00

00:00:29 — The varicella zoster virus life cycle: chickenpox, dormancy in the ganglia, reactivation as shingles

  • ★★★ Hank says chickenpox and shingles are both caused by the same virus, the varicella zoster virus (VZV). — 00:00:29
  • ★ Hank notes diseases are not always named for their virus: SARS-CoV-2 is the virus, COVID the disease it causes. — 00:00:29 · COVID-19 pandemic
  • ★★ Hank says VZV infection starts when an inhaled particle infects lung cells, then moves into the immune system, which carries it through the body, including to the skin. — 00:00:29
  • ★★ Hank says the virus leaps from white blood cells into skin cells and, unlike most viruses, fuses many skin cells into big multinucleated virus-making machines. — 00:00:58
  • ★★ Hank says the fused cells pop to form the blisters, and chickenpox spreads through the air mostly as breathed-in pus, not droplets of spit. — 00:01:24
  • ★★ Hank says the virus then quietly infects nearby nerves and migrates along them without alerting the immune system until it reaches the ganglia and goes dormant. — 00:01:53
  • ★★ Hank says about two to five percent of ganglia cells hold single-digit numbers of dormant viral particles. — 00:01:53
  • ★★ Hank says later in life the virus can reactivate, especially when the immune system struggles, travelling painfully along the nerves back to the skin to form shedding blisters. — 00:01:53
  • ★★★ Hank says someone without chickenpox immunity infected from shingles blisters gets chickenpox, not shingles. — 00:02:22

00:02:51 — Why the virus evolved dormancy: measles needs large populations, while small hominin groups forced VZV's ancestor to wait for new unexposed cohorts

  • ★★★ Hank calls this weird: life rarely evolves such a complex dormancy-and-return trick when a disease already survives by being very infectious, and today the shingles step does nothing for the virus. — 00:02:51
  • ★★ Hank says measles needs no such trick: it infects and moves on, since new unexposed children are always being born, who get measles unless vaccinated. — 00:02:51 · vaccine

  • ★★★ Hank explains the difference by age: measles is younger than the technology of writing, while shingles is older than humans. — 00:03:21

    “measles is younger than writing”

  • ★★ Hank says people infected once with measles or VZV never get it again; nobody gets chickenpox twice. — 00:03:21

  • ★★ Hank says both diseases are very contagious, which is no problem for them now because many humans live close together, so uninfected children are always available. — 00:03:21
  • ★★ Hank says measles cannot survive in a group of fewer than about 400,000 people, except that is mostly not how humans live now. — 00:04:01
  • ★★★ Hank says VZV-like viruses are very old: a simian version also has chickenpox-like and shingles-like phases, so their common ancestor had the trait. — 00:04:01
  • ★★★ Hank says the virus's ancestors used this strategy long before humans existed, and had to evolve it or go extinct. — 00:04:30
  • ★★★ Hank says that in small hominin groups with little contact, a measles-like infection would burn through and leave the whole group immune, and so die out. — 00:04:30
  • ★★★ Hank says a measles-like infection could not exist until after agriculture, which is why measles appeared only after agriculture. — 00:04:30
  • ★★★ Hank says VZV's ancestor evolved to lie dormant for decades and re-emerge once a new unexposed cohort was born, its shingles blisters then starting chickenpox through the young. — 00:05:00
  • ★★ Hank says chickenpox would sweep the young community, and later their shingles would reinfect the next cohort: a two-phase life cycle for millions of years. — 00:05:29
  • ★★ Hank says VZV no longer needs the trait, spreading like measles between populations as chickenpox, but a million years ago it needed to hide for decades. — 00:05:29

00:06:16 — VZV is technically eradicable but its ancient dormancy trait makes eradication hard; sign-off

  • ★★★ Hank says the trait had to fit not just its hosts' biology but their social structures, which he finds cool even though it sucks. — 00:06:16
  • ★★★ Hank says VZV is technically eradicable: like measles and smallpox, it infects only humans, no other animals. — 00:06:16
  • ★ Hank says nobody is sure why chickenpox is called that; it has nothing to do with chickens. (playful) — 00:06:16
  • ★★★ Hank says eradicating VZV would be very hard: it lies dormant for decades, so unless everyone stays vaccinated for its whole life cycle, it will break back out through shingles. — 00:06:16 · vaccine
  • ★★★ Hank concludes that by luck the virus evolved a complex trait for a world before people were people, and that trait now helps it evade modern technology. — 00:06:50

In the description and comments

  • ★★ The description thanks everyone who helped develop, distribute and support the chickenpox and shingles vaccines. — video description
  • ★★ The description says Hank is happy to be in the last generation for whom chickenpox and shingles will be normal. — video description

Threads in this video

Where the stories that moved here went next

Mentioned

Central: Chickenpox · evolution · Hominini · measles · Shingles · Varicella zoster virus · Virus latency

Also: Concepts: agriculture · Eradication of infectious diseases · herd immunity · immune system · SARS-CoV-2 · Simian varicella virus · smallpox · vaccine

Events: COVID-19 pandemic

Only in the description or credits: Varicella vaccine · Zoster vaccine

Also centred on Chickenpox: Here's Why Younger People are Getting Shingles

Also centred on measles: We Will Eradicate Measles · Why the Deadliest Virus Was the Easiest to Kill

Also centred on Shingles: Here's Why Younger People are Getting Shingles · Tuberculosis and Hank's Shingles

Also centred on Varicella zoster virus: Here's Why Younger People are Getting Shingles

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