Almost 2 out of every 5 men in the world have a red tinge to their beards. Weirdly it’s not just us Irish.

We’ve all pondered it. How come Irish men’s beards, no matter what their hair color is, grow with at least a tint of red in them? It turns out it’s not just our delicious Celtic roots.

Seriously you must have noticed that a lot of Irish men, even those with blonde, brown or black hair, usually have a touch of ginger running through their beards. There’s even a slang term for this. It’s “Gingerbeard,” which according to Urban Dictionary means “A dude with brown, black, or blonde hair, who when he grows a beard, it is entirely red, or red in patches.”

It seems especially dubious if you happen to know the bloke in question’s family and realize there are no redheads in the bunch. Strange indeed but actually pretty common, in fact almost two in five men have reddish beards. So us Irish aren’t that special at all.

Vice magazine spoke to Petra Haak-Bloem, from Erfocentrum, the Dutch national information center about for genetics and hereditary traits.

His explanation got pretty technical. He said “The genes that determine hair color are so-called ‘incomplete dominant hereditary traits.’ This means that there isn’t one single gene that’s dominant over the rest, but all genes influence each other.”

So all the genes that determine hair color are out for themselves so this allows for a lot of possibility and can differ from the top of your head, to your underarms to your pubes and of course your beard.

Haak-Bloem said “Generally speaking, people inherit hair color not only from their parents, but also from their grandparents and earlier ancestors. So it’s entirely possible that one distant ancestor had a hair color that suddenly appears again though a certain combination of genes—and that can be quite unexpected for parents.”

All of this makes sense so far but why exactly do some men have red beards? It turns out the shade of air is determined by the amount of melanin (pigment) in the hair and you DNA encodes this.

Read more: Scientists confirm redhead gene evolved due to lack of sunlight

The expert said “For white people the shades are dependent on two sorts of melanin: eumelanine (black pigment) and pheomelanine (red pigment). Hair cells of dark haired people only contain eumelanine. Blondes have less eumelanine. And redheads’ hair contains mostly pheomelanine.”

“More than a decade ago, researchers discovered that one gene (MC1R) on chromosome 16 plays an important part in giving people red hair. MC1R’s task is making a protein called melanocortin 1. That proteine plays an important part in converting pheolmelanine into eumelanine,” Haak-Bloem tells me. “When someone inherits two mutated versions of the MC1R-gene (one from each parent), less pheomelanine is converted into eumelanine. The feomelanine accumulates in the pigment cells and the person ends up with red hair and fair skin.”

Did you get that?

Basically most men have some red hair sprinkled in to their genetics, even if it wasn’t a trait among their parents or grandparents. If one of the parents hands down the redhead gene and not the other this could be how the "gingerbeard" arises.

What seems apparent is that it’s more common than us Irish think and you boys should wear your ginger beards with pride.

Read more: Top ten reasons to love Irish redheads

* Originally published in 2015.