The hair color of people with red hair is between orange and reddish. His whitish skin may be full of freckles. Open eyes, usually blue. This is an unbeatable and rare combination that often fascinates everyone. Red-haired people arouse interest and eventually become the center of attention. Have you ever wondered where these people get their distinctive hair color?

The answer, like so many other things in biology, lies in genetics. Specifically, it’s in a group of genes that determine what we look like. Genes that encode proteins whose function determines the color of our skin, eyes, and hair.

They are the “color genes” to which I dedicate my new popular science book on the genetics of pigmentation (NextDoor Publishers, 2022).

We know that out of the 20,000 color genes that all humans have, there are just under 700. Of all, there is one particularly important one (MC1R), which carries the genetic information to produce the type 1 melanocortin receptor. It is a membrane protein of melanocytes, the perfect pigment cells we have at the base of the epidermis. and these are the pigment factories of melanin.

Humans and other mammals can produce two types of melanin: eumelanin, which is dark brown, almost black, and pheomelanin, which is yellowish-red.

The MC1R receptor can receive hormonal stimuli to produce eumelanin, but when inactive or inactive, the melanocyte can only synthesize pheomelanin.

Normally we all make both types of melanin in different proportions depending on the role played by many other color genes, thus contributing to the wide variety of skin and hair color we have. However, there are people who have mutated two copies of the MC1R gene and therefore cannot make eumelanin and only know how to accumulate pheomelanin.

Indeed, these are people with red hair, whose color indicates the type of melanin they accumulate.

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Where does the mutation in the MC1R gene come from?

Our African ancestors accumulated mutations in color genes that made their skin dark. This proved very useful for shielding themselves from the harmful solar radiation occurring between the tropics.

They found a very different environment when they began to migrate to northern Europe to colonize new lands. An environment with very little solar radiation and months of darkness. This lack of sun adversely affected their ability to produce a minimal amount of vitamin D, whose synthesis in the skin is completed thanks to the sun’s ultraviolet radiation.

In these conditions, natural selection was exploited, the appearance of mutations in the MC1R gene, which can take advantage of the weak sunlight reaching northern Europe, turning the skin white.

What evolution couldn’t have predicted was that it would choose white skin to pack red hair and blue eyes in the same package (a non-existent color is an optical effect produced by the limited amount of pigment that redheads have in humans). iris of your eyes).

The red-haired character appeared this way, probably several times during evolution and in different places. Therefore, the northern regions of Europe, mainly Ireland, Scotland, Wales, Iceland, the Netherlands, Norway, as well as the surrounding area of ​​​​the Moscow region have a percentage of red-haired people, which can reach 30% of the population.

Spaniards with English genes

In the rest of the world, as in Spain, they only represent 2 percent. There are special exceptions in our country, where redheads are more common. For example, places of interaction with the British, such as the coasts of Cantabria and Galicia, which were periodically visited by Irish and English sailors. Also in Menorca, which was ruled by the British for most of the 18th century. It was originally founded by the British as well as the different mining districts in Huelva and Murcia.

Being redhead is a result of human evolutionary adaptation to survive the cold, long, dark winters of northern Europe.

In addition, people with red hair have a special sensitivity to temperature and pain. They can detect small changes in both hot and cold temperature earlier than non-redhead people. And they usually require different doses of anesthetics and pain relievers. To operate on a redhead, anesthetists normally need to administer higher doses of anesthetic.

All this is due to the fact that the MC1R receptor belongs to a family of receptors that transmit these sensations, and by mutating it changes the functional balance of all these genes. Finally, it should be noted that people with red hair should especially protect themselves from the sun, with creams and protective clothing, stay in the shade, avoid direct exposure for too long, because they are more likely to develop various skin types than others. cancer.. Especially the most aggressive and dangerous of all is melanoma.

Lluís Montoliu, CSIC scientific researcher, National Center for Biotechnology (CNB – CSIC)

This article was originally published on The Conversation. Read the original.