What Determines Your Hair Color?

There's a lot of natural variation in the color of human hair. What's the physical explanation for the difference?

Learn more about your ad-choices at https://www.iheartpodcastnetwork.com

See omnystudio.com/listener for privacy information.

Episode Transcript

Speaker 1 (00:02):
Welcome to brain stuff from how stuff works a brain
stuff it's Christian saga. 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 foot long wolf tail drain wad?

(00:27):
What's the real difference between blonde hair, black hair, red hair,
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.

(00:49):
Don't you just want to run your fingers through those hooves?
But keratin on its own is not very colorful, and
if all humans having 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. To

(01:12):
create natural color, you need to add pigment. This is
done by cells in the skin called melano 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 that

(01:34):
gives hair a brown or black color. THEO melanin is
a lighter pigment that gives hair a red, orange, or
yellowish color. Both of these are present in varying degrees.
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 red head has a

(01:57):
lot 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, melanocytes 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

(02:18):
determines 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 ur gene.
When the protein associated with this gene is active in melanocytes,
it stimulates them to make you melanin, the pigment that

(02:39):
colors black or brown hair. When m c one r
is not active in the melano syites cells, they make
mostly feel melanin instead and hello Weasley's. But the mc
one our 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 gene attic variable.

(03:01):
For example, 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.

(03:30):
Check out the brain stuff channel on YouTube, and for
more on this and thousands of other topics, visit how
stuff works dot com.