The real reason why all Irish men's beards are red

There's nothing that gives away a person's Irish heritage like a head of flaming red hair. For Irish guys, even if they're dark-haired or blond, they always have beards that are at least a little bit red. If you've ever wondered why, you're in luck. We can explain, but it's more complicated than you're probably expecting. We'll answer a few questions here, but let's start with a big one: how is it possible that Irish guys who don't have red hair still have reddish beards?

Vice's Motherboard had the exact same burning desire for knowledge, so they got in touch with Erfocentrum, the Dutch national information center for genetics and all things hereditary. The center's Petra Haak-Bloem told it straight: everything your science teacher taught you about genetics was so simplified it was largely wrong, particularly when it comes to hair.

Hair color isn't determined by a simple equation of dominant vs. recessive genes. It's what Haak-Bloem calls an "incomplete dominant hereditary trait." You don't just inherit one hair color gene each from mom and dad. You actually inherit all the possibilities that any of your ancestors ever had and then all those genes hash it out. While that might make some dads feel better about their mystery babies, it doesn't explain why red is so prevalent.

Your hair coloring is all about your body's ability to produce different types of melanine. People with blonde, brunette, or black hair are producing different levels of eumelanine, while redheads produce something else entirely, called pheomelanine. Anyone who inherits two certain mutated genes ends up being a carrot top, but you can see the effects of your pheomelanine production even if you only get one mutated gene. Since that mutation isn't completely overridden by dominant traits, it shows up in red beards. (It can also give you reddish highlights in other places, but we're not here to get personal.)

So it doesn't take much to end up with a bit of ginger in your beard, just a distant (or not-so-distant) ancestor who carried this pretty common gene mutation. Which brings us to another question: Ireland, what's up with all the redheads?

Eupedia has spent years collecting information on European genetics, even going as far back as prehistory and Neanderthals. They confirm that Ireland is, indeed, leading the way in the redhead population, and it isn't an unwarranted stereotype. (That whole "alcoholism" thing is unwarranted, though. According to the World Health Organization, Ireland doesn't even break the top 20.) According to Eupedia, up to 30 percent of the Irish population is redheaded, numbers followed by Scotland, Wales, and Cornwall. And there aren't just extra redheads in northern Europe — there are almost no redheads in southern Europe or the Mediterranean. It's such a drastic contrast that the 45th parallel can be thought of as a sort of redhead boundary, complete with "No redheads allowed" and "Gingers keep out" signs. Why? The Sun.

Mediterranean peoples still carry the genes for red hair, but over the years those genes have been weeded out. Ask any Irish redhead if they tan or burn in the sun, and they'll probably say they burn just looking out the window on a sunny day. That's not an ideal skin tone for someone living in the Mediterranean, and over generations, fatal, sun-related skin cancers have greatly reduced the number of redheads south of the sunny 45th parallel to the point where they're pretty much extinct.

On the other hand, that same skin tone is a benefit in northern countries where nights are long, weather is bad, and we're not even exaggerating about how dark and dismal it gets. Entire ancient cultures formed belief systems and festivals to remind the Sun it was going to have to come back. It was a very real fear: families even extinguished all their hearthfires and relit them from Samhain bonfires in hopes of sending the Sun a message: please come back. In the meantime, pale skin and red hair increased the amount of vitamin D early Celts could absorb during the long winters, in turn increasing the survival rate among redheads and multiplying their numbers.

So, there you have it. Irish men have red beards because of complicated hair color genetics and because they live in an undeniably beautiful country that doesn't get much sun. Having pale skin and red hair is perhaps the strangest survival trait anyone has ever evolved in the history of forever.