fingernails, nails, hair, skin, death, flipfact, flipfacts, flipscience

FlipFact of the Day: Watch your favorite post-apocalyptic zombie film or TV show, and chances are you’ll spot some of the shambling monsters sporting lengthy wisps of hair and long, cracked, ready-to-scratch fingernails. The fact that these undead horrors look like they need a haircut and a manicure doesn’t really strike us as odd, does it? Perhaps it’s because we’ve been told that even after humans die, their hair and fingernails continue to grow. Here’s the thing, though: That little “fun fact” is about as real as the zombies themselves.

On average, our fingernails grow at a rate of 0.1 mm (0.004 in). Human hair growth rate, on the other hand, varies based on ethnicity and a number of other factors; based on a 2005 study, Asians grow hair at roughly half an inch per month. Our hair and nails grow because of a protein called keratin, and a complex hormonal regulation process facilitates the production of new hair and nail cells. All of these stop, though, when we die.

But if that’s the case, then why do human nails and hair look a bit longer after a person dies? That’s the result of the skin shrinking as the body dries up after death (postmortem dehydration). As the skin shrivels up, the parts of the hair and nails that used to be covered by it end up getting exposed, creating the illusion of continued growth.

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Author: Mikael Angelo Francisco

Bitten by the science writing bug, Mikael has years of writing and editorial experience under his belt. As the editor-in-chief of FlipScience, Mikael has sworn to help make science more fun and interesting for geeky readers and casual audiences alike.