The Science of Sustainability

Redheads are here to stay

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Red hair genes will be diluted but will not go away.I got a call last week from a reporter in Virginia. Someone had come up to her in a bookstore to offer her condolences about her kind dying out. She is a redhead.

The guy from the bookstore must have read one of the stories about the imminent demise of redheads that flashes across the media landscape every few months. People with red hair have to deal with headlines like:

"Redheads Set for Extinction."
'Will rare redheads be extinct by 2100?'
"Gingers Extinct in 100 Years."

The reporter suspected these stories weren't right and wanted to write a story about it. She called me to get some science to back her up. I was able to reassure her that redheads weren't going the way of the dodo. They'll become much less common, but there will probably always be red haired people around.

To understand why redheads will fade but not disappear, we need to dig a bit deeper into how red hair works. Red hair happens when both copies of the MC1R gene do not work properly. (Remember we have two copies of almost all of our genes–one from mom and one from dad.)

So if you're a redhead, you inherited a nonworking copy of MC1R from both your mom and your dad. If you get a non-working copy from only one of them, then you won't have red hair. You'll be a carrier.

Right now redheads are at an artificially high level in the human population because their recessive red hair genes are concentrated in North America, Europe, and Australia. For example, 10% of Ireland and 2-6% of the U.S. has red hair.

These numbers are maintained because carriers and redheads keep making new redheads with each other. But as barriers go down, their red hair genes will flow out of these populations and into the human gene pool.

Red hair genes will become diluted in this pool but they won't be completely swamped out. Even as redheads decline in numbers, their genes will remain constant. It will just be less likely that two carriers and/or redheads will meet and have babies with red hair.

This is all interesting but it got me to wondering about how many redheads there will be in the distant future when all the mixing is said and done. We can use something called the Hardy Weinberg equation to figure this out.

This equation works great for simple dominant/recessive traits like red hair if we know how many of each gene version there is. To do this, we need to figure out how many redheads and how many carriers there are in the world.

It is easy to figure out how many redheads there are–you can tell who they are just by looking at them. But figuring out carriers is a lot harder. We can make guesses based on the number of redheads (again using Hardy Weinberg) but until we sequence a lot more MC1R genes, they'll only be guesses.

The numbers I have seen floating around are that around 1% of the world's population has red hair and that around 4% carry the red hair version of MC1R. This means that there are around 65 million or so redheads in the world and 260 million carriers. (This sounds high to me but these are the numbers out there.)

When we use these numbers and apply the Hardy Weinberg equation, we end up with a final percentage of redheads of 0.1% or 6.5 million. This is quite a fall from current levels but they are hardly wiped out!

There are lots of assumptions* in these calculations that might cause the number of redheads to actually be more or less than 0.1%. But unless there is some red hair specific catastrophe or people start burning them as witches again, redheads are here to stay.

Dr. Barry Starr is a Geneticist-in-Residence at The Tech Museum of Innovation in San Jose, CA.

*Some assumptions used:

1) There are no barriers to finding partners
2) The 4% carrier number is an accurate one
3) Two non-workingMC1R genes produce red hair in all genetic backgrounds
4) Other assumptions described here

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Dr. Barry Starr

About the Author ()

Dr. Barry Starr is a Geneticist-in-Residence at The Tech Museum of Innovation in San Jose, CA and runs their Stanford at The Tech program. The program is part of an ongoing collaboration between the Stanford Department of Genetics and The Tech Museum of Innovation. Together these two partners created the Genetics: Technology with a Twist exhibition. Read his previous contributions to QUEST, a project dedicated to exploring the Science of Sustainability.
  • Wendy

    What a great read. My husband is not red (though there is a rainbow, including red, in his facial hair)and I am. At this point we have had a 100% rate of redheaded children (2 kids).

    Every time we go to town, I get SO many positive comments on our color. People seem to be fascinated when they see 3 natural reds headed their way.

  • Maureen Fonken

    My husband was platinum blonde as a child. I'm a dark brunette. We have had two children that seem to have some red hair, but one of them got darker at four and would no longer be considered even a strawberry blonde. My 9 year old son, however is only getting redder.

    The other kids? Well, the oldest is like me and the middle two girls both have hair about the color of honey. Most of my kids have hair with some natural wave–except the one girl who used to seem more red haired.

    I am still not convinced about the recessiveness of red hair, though. If it was so recessive, why is it that all the redheads I know have 100% redheaded children?

    I think families like ours ought to be studied more closely to examine the mutation. My son is the only redhead on both sides. Something is going on.

  • http://www.thetech.org/genetics/index.php Barry Starr

    Wendy: In your case the chances of having 2/2 kids with red hair is 1 in 4. That is the same chance as having 2/2 kids be boys so these odds are pretty good.

    Maureen: Hair color other than red is surprisingly confusing and not very well understood (click here for a valiant if too simple attempt to explain it). Red hair, though, is pretty straightforward and it is indeed recessive. As I talk about here, if both parents have red hair then all their kids will have red hair because red hair is recessive (did I say red hair enough in that sentence?). My mother in law has red hair and none of her 9 kids do but her grandson (my son) does. Another classic sign of a recessive gene. Same thing on the other side of my family. My grandpa had red hair and my dad and I don't but my son does.

    I've also looked at my family's MC1R gene and red hair follows a recessive pattern. My wife and I are carriers, my red haired son has two copies, my older son one and my daughter none.

  • http://amyettinger.com Amy

    Dr. Starr,
    Any idea about how rare it is to have red curly hair? Are the red and curly separate recessive genes?

    I really enjoyed your article. Since my redheaded daughter was born 15 months ago, I've heard the story of redhead extinction at least once a month. It puts a certain amount of pressure on the MC1R carriers to keep reproducing!
    Glad that it's finally been debunked.
    Thanks,
    Amy Ettinger

  • http://www.thetech.org/genetics/index.php Barry Starr

    I don't know how common it is (although there was one on Charlie Brown). Curly hair is a little more complicated than red hair…it is something called codominant. Curly+Curly=curly, Straight+Straight=straight and Curly+Straight=wavy (click here and here for more details).

    Isn't the extinction thing weird? Totally not based on real science but it sticks because it sounds so dramatic!

  • Donna

    I find the story of red heads very interesting. Our youngest daughther, daughter is a red head. She has brown and the father is a dark blonde. However my granddaughter is a brilliant red. A color you could not get from a bottle. She is a intellegent 4 year old and she matches her red hair with much brilliant intellengence. I hope to see more red headed people as it is a beautiful natural color.

  • Kaitlyn

    This is a great article, I'm glad i came across it. I am a redhead myself and I'm 15. And all i know is that my older brother has red hair and we got it from my dad who had red hair as well, he's older now so its gone haha. And my aunt is a red head too. So theres a total of 4 of us out of my whole family. There are no redheads on my moms side, and i just think its so interesting to wonder where did my dad and his sister get it from, since i didnt know my grandfather to well and my grandmother doesnt have redhair at all. But i knew for a fact red hair is a recessive gene.

    P.s. i am so excited to see your a Geneticist because that is what i want to go to school for!

  • Susie

    Thanks for the interesting article! I'm redheaded, and my dad had dark brown hair on his head and a red mustache (when he chose to grow it out). Other than that, redheadness skipped 2 generations on my mom's side and 3 on my dad's. Is there research out there about what makes people have different colored hair on different parts of their bodies?

  • Barry Starr

    Most men with red beards and/or mustaches are red hair carriers. Everyone makes lots of red pigment but most people have two working MC1R genes that turn it into a different colored pigment. Most redheads have both of their MC1R genes not hitting on all cylinders and so the red pigment builds up. The end result is red hair. Carriers have one copy that can do its job and one that can't. Most of these people do not have red hair but they can have fair skin, freckles, and a red beard or mustache. What we don't know is why some carriers have these traits and other don't. For some reason, the working MC1R gene can't keep up with all the red pigment getting made when it is located in facial hair.

  • Barry Starr

    You are right that red hair is recessive which means that most likely red hair is on both sides of your family. There are rare exceptions to this (see http://www.thetech.org/genetics/ask.php?id=400) but almost always you have to get red hair from both sides to end up with red hair yourself. Since red hair is recessive, it can hide out in a family tree for hundreds of years before being seen. It can pass silently from generation to generation until it meets up with another red version of the MC1R gene and then BAM, red hair.

  • ginger

    Are there other factors that play into who gets red hair such as gender or which birth order? My great grandma had red hair. 3 of her 3 children had red but none of the following generation (thats 5 people) had any. The 1st born of the generation of 5 gave birth to 2 nonredheads but everyone else had 2 redheads (with exception of 2 boys, belonging to separate parents). I'm thinking the youngest is most likey to carry the recessive trait as well as females. Agree? disagree? I want to know! lol

  • http://www.thetech.org/genetics/index.php Barry

    No, it pretty much is who gets a red gene from both mom and dad. To have a redhead, red hair has to come from both sides of the family. The three redheads married people who weren't carriers. This means that all of their children had one red and one not-red gene…they didn't have red hair but carried the gene. The firstborn either married a noncarrier and so couldn't have red haired kids or married a carrier and it just so happened that they didn't both pass a red hair gene to any of their children. Each child of carrier parents has a 1 in 4 chance for having a redhead. The other kids married carriers or redheads and so had kids. This is how it all usually works although there are exceptions (see http://www.thetech.org/genetics/ask.php?id=400 for example). However, none of these exceptions are gender or birth order based.

  • Sarahkahler

    im a
    red head

  • http://twitter.com/RhesusNegatives Rh Negative Blood

    Red hair has been introduced to Europe through the Celtic tribes known for their M269 R1b marker. The same tribes also have introduced rh negative blood. Not just to Europe, but everywhere there is a high percentage of M269 presence in remote locations such as Nepal. You cannot properly conduct this research without taking into consideration that the majority of rh negative people have red, reddish dish hair or at least a reddish shimmer in their hair. Aside from that, even the medical industry is oblivious to most of those aspects as blood type studies are in their infancy. In addition: Most (if not all) red heads have either rh negative blood or do carry the recessive gene.

    See also: http://www.rhesusnegative.net/work/where-does-red-hair-come-from/

    "Where does red hair come from?"

    http://www.rhesusnegative.net/work/haplogroup-r1b-r-m269-and-the-rhesus-negative-blood-type/

    "Haplogroup R1b (R-M269) and the Rhesus Negative Blood Type"

    ~ Mike Dammann

    http://www.rhesusnegative.net

  • Mia

    That's so interesting. I find it especially interesting because I'm black, but my grandmother (who was also black) had red hair. Probably because we had Scottish blood in us and it was a recessive trait. I however do not have red hair, but the possibility of being a carrier is present… If I interpreted what I read right.

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