Human hair color

Human hair color refers to the pigmentation of hair follicles due to two types of melanin: eumelanin and pheomelanin. Generally, if more eumelanin is present, the color of the hair is darker; if less, the hair is lighter. Levels of melanin can vary over time causing a person's hair color to change, and it is possible to have hair follicles of more than one color on the same person. Several genes influence the color of human hair, with the most well-known being the MC1R gene.

Genetics of Hair Color

The color of human hair is determined by the type and concentration of melanin produced by melanocytes in the hair follicle. The MC1R gene on chromosome 16 is a significant determinant of whether eumelanin (black or brown pigments) or pheomelanin (red or yellow pigments) is produced. Variations in the MC1R gene lead to red hair, with the presence of two mutated copies being necessary for this phenotype. Other genes that influence hair color include ASIP, TYR, and OCA2, among others.

Natural Hair Colors

1. 1. 1. Black Hair

Black hair is the darkest and most common of all human hair colors globally. It is predominant in people of Asian and African descent. Black hair has a large amount of eumelanin and is less dense than other hair colors.

1. 1. 1. Brown Hair

Brown hair is the second most common human hair color, characterized by higher levels of eumelanin and lower levels of pheomelanin. Brown hair ranges from light brown to almost black hair. It is predominant in people of Western European descent.

1. 1. 1. Blonde Hair

Blonde hair is characterized by low levels of the dark pigment eumelanin. The resultant visible hue depends on various factors but always has some sort of yellowish color. The color can be from the very pale blond (caused by a patchy, scarce distribution of pigment) to reddish "strawberry" blond or golden-brownish ("sandy") blond colors.

1. 1. 1. Red Hair

Red hair ranges from light strawberry blond shades to titian, copper, and completely red. It is caused by a variation in the MC1R gene and is most commonly found in northern and western European populations. It is the rarest hair color in humans.

1. 1. 1. Gray and White Hair

Gray or white hair is not caused by a true gray or white pigment but is due to a lack of pigmentation and melanin. The clear hairs appear as gray or white because of the way light is reflected from the hairs. Gray hair color typically occurs as people age, when melanocytes slow down or stop producing melanin.

Hair Color and Aging

The process of hair turning gray or white is called achromotrichia. It typically starts in adulthood, with the timing influenced by genetics. The change in hair color is due to the gradual decrease in melanin production in the hair follicle.

Cultural and Societal Aspects

Throughout history, hair color has often been a marker of ethnicity or social status. In some cultures, certain hair colors are associated with specific traits or stereotypes. Hair dyeing is a common practice for changing one's hair color, with a wide range of options available for temporary or permanent color change.

See Also

• Hair
• Melanin
• Genetics of hair color
• Achromotrichia

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