Biochemistry
The pigment eumelanin gives brown hair its distinctive color. Brown hair has more eumelanin than blond hair but also has much less than black. There are two different types of eumelanin, which are distinguished from each other by their pattern of polymer bonds. The two types are black eumelanin and brown eumelanin. Black eumelanin is the darkest; brown eumelanin is much lighter than black. Black eumelanin is mostly present in non-Europeans, while brown eumelanin is mostly present in Europeans, and very rarely, people of other ethnicities. A small amount of black eumelanin in the absence of other pigments causes grey hair. A small amount of brown eumelanin in the absence of other pigments causes yellow (blond) color hair. Often, natural blond or red hair will darken to a brown color over time. Brown-haired people have medium-thick strands of hair.
Brown-haired people are thought to produce more skin-protecting eumelanin and are associated with having a more even skin tone. The range of skin colors associated with brown hair is vast, ranging from the palest of skin tones to an olive complexion. Brunettes can have dark or light eyes.
Read more about this topic: Brown Hair