Perplexed by the question, Adriaan Schiphorst from Motherboard called up Petra Haak-Bloem from Erfocentrum, a Dutch organisation that promotes genetics and awareness of genetic disorders, to get the answers.
She told him it’s all down to the MC1R-gene. The gene coding for hair colour is called "incomplete dominant hereditary traits," meaning hair color isn’t as simple as one gene coding for one color of hair. The genes can be expressed differently in different areas of your body, like your head, beard, eyebrows or pubes.
Haak-Bloem explained that it’s all to do with the genes that code for the amount of different pigments, called melanin, in your hair. She explained that hair color is dependent on two of these pigments: eumelanin, the black pigment, and pheomelanin, a red pigment.
She added: “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 protein plays an important part in converting pheolmelanine into eumelanine.
“When someone inherits two mutated versions of the MC1R-gene (one from each parent), less pheomelanine is converted into eumelanine. The [pheomelanine] accumulates in the pigment cells and the person ends up with red hair and fair skin.”
Haak-Bloem also said that if you only inherited one of these mutated genes, red hair can appear in sporadic places because of the variety of ways the gene can be expressed.
So, there you have it. That odd ginger beard in your family isn’t just the product of extramarital activity with a crimson-locked lothario.