Wednesday, January 14, 2015

Red mammals

I am soooo embarrassed. I passed along factoid, and it was untrue.

Here's how it all went down. I made a simple statement in my blog post What color are your blue jeans?  The statement was an inconspicuous factoid, shared with my readers at no extra charge:

"By the way, the pigment responsible for gingers is only found in humans. No kidding. I red that on the internet, so it must be true."

Let me tell you, John the Math Guy fans everywhere. There ain't nothing like an egregious lie to bring down the wrath of ... well, I don't want to play into stereotypes of people based on hair color, but there was a fiery furor, I tell you. 

Redheads react to the error in my blog

The first hint of the upcoming storm came as a post on the blog itself. Janneke Duoma had this to say:

"The red haired cannot be anything else but a Human? Eh...and the fox is.....? Not a human that's for sure but I would swear I saw a red glow on that fur. Tssss... Science prooves me wrong?"

Hmmm... she has a point there. Now, my eyes ain't no speck-trow-foe-tomater, but the red hair of a red fox does kinda look like the red hair of some other "foxes" I know. I had to go back to my source. Where did I learn this dubious factoid?

Actually, I lied about that as well. I said that I "red" it on the internet. Clever misspelling, but a lie. I read it in a book by Hazel Rossotti entitled "Colour: Why the World Isn't Grey". Here is where I got the factoid (on page 93): 

"Red human hair, unlike the red hair of any other mammal, is produced by an unusual pigment which contains iron."

Maybe the world isn't gray, but what about my beard?

(Actually, according to the internet, you can see that I quite enjoyed the book.)

The pigment in red hair

So... I need to play fact checker. Is Rossotti's comment correct?

I start with Wikipedia, to identify the pigment in red hair. The Wikipedia entry on red hair says:

"The pigment pheomelanin gives red hair its distinctive color. Red hair has far more of the pigment pheomelanin than it has of the dark pigment eumelanin."

Wikipedia could be wrong, so let's look a little further. The Causes of Color website agrees with Wikipedia, in that pheomelanin is the pigment that is active in human red hair. 

(BTW: When you are done reading my previous 111 blog posts, have a look at the Causes of Color website. Interesting stuff. But in the mean time, it kinda sounds like pheomelanin is the operative agent.)

The best laid pigments of mice and men

So, we have established that the pigment that Ms. Rossotti is referring to is pheomelanin. But clearly she can't be wrong, since John the Math Guy wrote a glowing review of her book, and I read on the internet that he is a sharp guy. So, obviously, that pigment won't be found in any other mammal.

Well, not quite... 

Pheomelanin can be found in mice and in men, as these two scholarly articles will attest.

"It appears that rodents adaptively modulate eumelanin and pheomelanin contents to achieve cryptic coloration in contrasting habitats even at a microscale."

"The color of hair, skin, and eyes in animals mainly depends on the quantity, quality, and distribution of the pigment melanin, which occurs in two types: black to brown eumelanin and yellow to reddish pheomelanin. ... High levels of pheomelanin are found only in yellow to red hairs of mammals and in red feathers of birds."

How about the red foxes that Janneke mentioned?

"In red foxes, the contribution of pheomelanin to the total hair melanin content was twice as large as in the hybrids."

Red fox in my backyard, in 2009

Red foxes, yup. It seems even dogs make use of pheomelanin.

"Labrador Retrievers are a popular breed of dog in many countries. There are three recognised colours, black, chocolate, and yellow, that result from the interplay among genes that direct production and expression of two pigments, eumelanin and pheomelanin, in the fur and skin of the dog."

These labs are happily oblivious to the interplay among genes
that direct production and expression of eumelanin and pheomelanin

Dare I stop now?  Nay!  Pheomelanin is even found in reptiles!!

"Reptiles, supposedly, do not produce pheomelanin pigments. Because this claim is based on rather weak evidence, we measured the shell pheomelanin content in the Hermann’s Tortoise (Eurotestudo boettgeri). In contrast to expectation, we detected a substantial amount of this pigment. Given the recent interest in the adaptive function of melanin-based color traits, our study opens new avenues of research in reptiles."

I hope that you are also excited about these new avenues of research! In case you were wondering (I'm sure you were) ... "the existence of fungal pheomelanin is still under discussion." Well, I guess that gives organic chemists something to talk about while watching reruns of  Chopped.

One more lie exposed

Guess what?  Remember how Ms Rossotti told me that the pigment in red hair contains iron? I found an article on the chemistry of melanins. Now I don't claim to have much knowledge of organic chemistry - other than the tiny amount that I memorized for an organic chem class in high school and promptly forgot. But, I don't see any big "Fe" symbols in the picture below. I think even that was sadly untrue. 


So, so, so many lies. First, I lied about reading that factoid on the internet. Then the factoid turned out to be another lie, since the same pigment is used for red hair in humans, mice, red foxes, and in Hermann's tortoise. And finally, there is the whole claim that the pigment for red hair contains iron.

The tooth fairy, Mighty Mouse, trickle-down economics, and now the whole "people with red hair have a unique pigment" story... The fox has been caught red-handed in a statement lacking truthiness. So many lies that I have been told. Sigh... I am not going to obsess about it. It would only shake my faith in the whole house of cards that is science.

I want to apologize for my participation in the promulgation of that nasty lie about the pigment in red hair. My only defense is that I was just repeating what someone else told me. This gives me but meager comfort. We should all feel just a tiny bit guilty when we pass along stuff that just ain't true. 


  1. oeps...... Quite an adventure you gave me here! Thanks a lot for all the research, love your way of thinking and writing. Grts Janneke

  2. A very interesting read, as it is always with yo, John. So, many thanks!