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Why are there so many blonde and brunette men who have red beards? Surely if they have a ginger beard their head hair should be red too, right? Wrong.

Hair pigmentation is the result of genes that have ‘incomplete dominance’. What does this mean? Let’s take a trip back to high school science. Do you remember learning about dominant genetic traits? One example is being able to roll your tongue. You only need to get the tongue rolling version of that gene from one parent in order to be able to do it yourself, because the tongue rolling version is dominant over the non-tongue rolling version. On the other hand, incomplete dominance is a different story. There isn’t one gene for hair color that is dominant over another, it’s a kind of genetic free for all, which helps explain the wide variety of natural hair colors that exist.

The simplified version goes like this: there are two pigments that control the color of our hair and skin, and they are controlled by our genes. These two pigments are different forms of melanin, a natural pigment produced by specialized cells called melanocytes. There is a red pigment (pheomelanin) and a black pigment (eumelanin). The combination of these two pigments is responsible for the color of our skin and hair, similar to how an artist can mix many different colors from only primary colors. Black hair has lots of black pigment, blonde hair has very little black pigment, and red hair has lots of red pigment.

One of the genes that controls the amount of these two pigments is called MC1R. This gene encodes a protein called ‘melanocortin 1’ which acts like a switch. If the gene is normal the special melanocyte cells make the black pigment. If there is a mutation in this gene, the cells make red pigment. The simplified version is that if someone has two copies of the mutated MC1R gene (one from mom, one from dad) they will be a redhead. This doesn’t happen often, as shown by the fact that only around 2% of the population has red hair.

The same doesn’t apply to beard hair though. The cells in a person’s body don’t all operate in the same way, the hair follicles that produce beard hair and head hair don’t abide by the same genetic rules. For beard hair, a man only needs to have one copy of the mutated MC1R gene in order to have a red beard. A study in the UK showed that 40% of people in their study have one copy of the mutated gene. This helps explain why ginger beards are much more common than red hair!

Unfortunately, as is often the case, the whole story is more complicated than this. The MC1R gene only accounts for around 80% of redheads. There are at least eight other genes that have recently been linked with red hair, and there are thought to be 20 or more genes that play a role in hair color.

For even more detail about MC1R you can may like to read this article.