In the anime Hunter x Hunter (and others, I presume) a character is shown as having super-strong hair, strong enough that a single strand could be tied around a wounded arm to stem the bleeding. I cannot find a clip online, but I believe the scene is from episode 52 (new series) and the character is Silva Zoldyck.

The above example is a world with magic, so, the science of Silva's super-strong hair is not mentioned. The scene goes by quickly, and given what the show has taught the audience about that character already, it's pretty easy to believe he has super-strong hair.

What I want to know is how could such a trait evolve naturally? Which pressures might lead to it, what would it's composition be, and for bonus funsies, what might the applications (or drawbacks) of this wondrous "hair" be?


  • Must be relatively hair-like. It doesn't need to be keratin or a related material, but it must grow continuously in long, loose strands with different potential colorations.
  • Strong enough to function as a tourniquet that could stop a wound exsanguinating intensely enough to be medically concerning. Bonus points if it is strong enough to function as a tourniquet around the flexing bicep of a stereotypically super-buff anime adventurer.
  • Component substances must be plausibly findable in a humanoid anatomy.
  • 6
    $\begingroup$ If you were to wrap an individual hair around a limb, and it was strong enough to act as a tourniquet, it'd cut into the limb like a cheese-wire, and likely cause its own injury. $\endgroup$
    – Monty Wild
    Commented Oct 2, 2023 at 0:54

1 Answer 1


how could such a trait evolve naturally?

It already did, totally by accident.

We evolved hairs as they are for a variety of reasons. Some mammals have it for protection against cold. For some others it is kinda like armor. I don't know exactly why chimps and our commom ancestors have hair for, but we do have it. So there.

Now, our hair has absolutely zero pressure to be usable as a tourniquet. That happened by accident, as is common with so many things. But it did happen. Hair tourniquets are a thing, though usually not a good one:

Hair tourniquet is a condition where hair or thread becomes tightly wrapped around most commonly a toe, and occasionally a finger, genitals, or other body parts. This results in pain and swelling of the affected part. Complications can include tissue death due to lack of blood flow. It occurs most commonly among children around 4 months of age, though cases have been described in older children and adults.

Some people have weak hair. Some people have strong hair. I am a parent now and I see this, almost daily. I find my partner's hair in my baby girl's hands. I once tried to take it out by wrapping a strand around my finger and pulling gently... got the baby to release the hair, but it almost tourniqueted my finger afterwards.

what would it's composition be

Keratin, mostly.

and for bonus funsies, what might the applications (or drawbacks) of this wondrous "hair" be?

Application: you save a lot on certain products targeted at women with low self steem. You don't need Kérastase Paris, Aussie Total Miracle, Nexxus Keraphix, Fekkai Superstrength etc.

Drawback: [redacted]es will envy you. Be prepared for more drama in your life.


While hair isn't as strong as steel, it's just about the strongest material in your body, with a tensile strength rivaling or exceeding that of bone.

  • 2
    $\begingroup$ Chimps etc got hair as inheritance, and likely they form some skin protection allowing to squeeze through the jungle with reduced threat to getting mangled by loose broken branches etc. I wonder why did hair evolve in whatever organism that first managed to grow it, and what were the advantages to keep hairy descendants around, yet it did prove to be great thing to have. Bears say hi. $\endgroup$
    – Vesper
    Commented Oct 2, 2023 at 8:29

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