Although you may know someone with red hair, the probability of having red hair is significantly low, estimated at 0.64% worldwide. However, this does not mean that redheads are “endangered”.
Hair color is due to the presence of two chemicals, eumelanin and pheomelanin. These two pigments are inherited from the father and the mother. There are two types of inheritance: dominant and recessive. Eumelanin (responsible for darker hair colors) is dominant over pheomelanin (responsible for lighter colors). Therefore, for a person to have red hair, two copies of pheomelanin are needed; if only one copy is present, the hair will be darker in color.
So does this mean that in the long run redheads will disappear? The answer is no, and it is thanks to the type of inheritance these genes have. Natural selection explains why some characteristics disappear or remain for generations. This selection applies to expressed traits, i.e. dominant genes. So recessive genes (in this case the red-haired MC1R gene) can remain unexpressed for many generations without being harmed by natural selection.
This explains that, in their DNA traits test, many people can be brown, brunette or black-haired, but have the red-haired recessive gene. If two people with the red-haired gene have offspring, the probability of having a red-haired child increases because he or she could inherit both copies of the red-haired MC1R gene and, therefore, would express the red color in the hair.
In addition, red hair is known to be more common in Irish, Dutch, Swedish and Icelandic populations, although it is also occasionally found in other populations around the world. Hence, the red hair gene is thought to be of Neanderthal origin.
In short, although eumelanin pigments are more common and predominate in most cases, many people possess pheomelanin, with the redhead MC1R gene remaining generation after generation, making the extinction of red hair color impossible.
And how can we know if we have this gene? With a DNA test it is possible to know whether the variants that determine red hair color are present or absent. In this way, you can inherit two copies of the recessive gene inherited by redheads and genetically preserve this peculiar characteristic of the hair.