BrainStuff Classics: What Determines Your Hair Color?

There's a lot of natural variation in the color of human hair. Learn the physical explanation for the difference in this classic episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff production of iHeart Radio. Hey brain Stuff,
Lauren bog Obam here with a classic episode from our
archives featuring former host Christian Sager. Today's topic is an
excellent bit of everyday science. What determines your hair color?
And why do we go gray? A brain Stuff, it's

(00:22):
Christian Sager. Sometimes you're right in the middle of cleaning
up the drain in the shower and you start pondering
questions like why is my hair color different color from
my mom's hair, or my neighbor's hair or my roommates
disgusting soggy three ft long wolf tail drain wad? What's
the real difference between blonde hair, black hair, red hair,

(00:45):
and everything in between? Well, the main structural ingredient in
human hair is a protein called keratin. It's what your
hair and fingernails are made of. But also what's behind
the silky sheen of wool bear claws and horse hooves. Mmmm,
don't you just want to run your fingers through those hoofs?

(01:07):
But keratin on its own is not very colorful, And
if all humans had in our hair was keratin, we'd
look like eighteenth century French aristocrats in powdered wigs because
we'd all have the same sort of white, colorless hair.
But keratin is not the only ingredient in human hair.

(01:27):
To create natural color, you need to add pigment. This
is done by cells in the skin called melana sites.
These melano sites create the natural pigment known as melanin
and deliver it to the cells that create the keratin
for your hair, and this melanin comes into varieties you
melanin and THEO melanin. You melanin is a dark pigment

(01:49):
that gives hair a brown or black color. Pio melanin
is a lighter pigment that gives hair a red, orange,
or yellowish color. Both of these are present in varying degree,
as a person might have had a little of each,
or a lot of one and almost none of the other.
So someone with black or dark brown hair probably has
a lot of you melanin. A redhead has a lot

(02:12):
of THEO melanin, and blonds, well, they don't have very
much of either one. So what happens when we get
older and start to go gray, Well you can probably guess.
Over time, melano sites start to die off, and any
new hair that grows has less pigment, so it looks
gray or white. But you might be asking what determines

(02:33):
the you melanin to feel melanin mixture to begin with?
Who writes that recipe? Well, primarily it's your genes. For example,
the melano corton one receptor or m C one R gene.
When the protein associated with this gene is active in melanocytes,
it stimulates them to make you melanin, the pigment that

(02:53):
colors black or brown hair. When m C one r
is not active in the melanocytes cells, they make mostly
fio melon and instead and Hello Weasley's. But the mc
one r gene is not the only genetic factor that
controls hair color. Like most of your traits, hair color
is actually affected by more than one genetic variable. For example,

(03:16):
in a study in the journal Natural Genetics linked blonde
hair in Northern Europeans to a genetic mutation in one
single nucleotide controlling gene expression in hair follicles. They even
bred mice with the same tiny mutation, and the mice
had lighter colored fur than mice without the mutation. Today's

(03:43):
episode was written by Joe McCormick and produced by Tyler Klang.
The brain Stuff is production of I Heeart Radio's how
Stuff Works. To hear more from Joe, check out his
new podcast Invention or the old standby Stuff to Blow
your Mind, of course. For more on this and lots
of other hairy topics is that our home planet, how
stuff Works dot com. And for more podcasts for my
heart Radio, visit the i Heart Radio app, Apple Podcasts,
or wherever you listen to your favorite shows. H