Hair color map. Dark hair color in the map: black hair. Light hair colors: brown red fair and blonde hair variants
Human beings have three distinct types of hair:
* Lanugo is fine hair that covers nearly the entire body of a fetus. Unless born prematurely, the fetus loses this layer of hair before birth. Lanugo also sometimes returns in cases of malnutrition or extreme anorexia nervosa, as the starved body attempts to insulate itself.
* Vellus hair is extremely short, fine, scarcely noticeable hair that covers most the human body in both sexes.
* Terminal hair is fully developed hair, which is generally longer, coarser, thicker, and darker than vellus hair.
The tendency of older people to develop grey hair is due to "a massive build up of hydrogen peroxide due to wear and tear of our hair follicles ...[which] winds up blocking the normal synthesis of melanin, our hair's natural pigment." Grey hair is considered to be a characteristic of normal aging. The age at which this occurs varies from person to person, but in general nearly everyone 75 years or older has grey hair, and in general men tend to become grey at younger ages than women. It should be noted however, that grey hair in itself is not actually grey; the grey head of hair is a result of a combination of the dark and white/colourless hair forming an overall 'grey' appearance to the observer. As such, people starting out with very pale blond hair usually develop white hair instead of grey hair when aging. Red hair usually doesn't turn grey with age; rather it becomes a sandy colour and afterward turns white. Some degree of scalp hair loss or thinning generally accompanies aging in both males and females, and it's estimated that half of all men are affected by male pattern baldness by the time they are 50[3]. The tendency toward baldness is a trait shared by a number of other primate species, and is thought to have evolutionary roots.
Human beings have three distinct types of hair:
* Lanugo is fine hair that covers nearly the entire body of a fetus. Unless born prematurely, the fetus loses this layer of hair before birth. Lanugo also sometimes returns in cases of malnutrition or extreme anorexia nervosa, as the starved body attempts to insulate itself.
* Vellus hair is extremely short, fine, scarcely noticeable hair that covers most the human body in both sexes.
* Terminal hair is fully developed hair, which is generally longer, coarser, thicker, and darker than vellus hair.
The tendency of older people to develop grey hair is due to "a massive build up of hydrogen peroxide due to wear and tear of our hair follicles ...[which] winds up blocking the normal synthesis of melanin, our hair's natural pigment." Grey hair is considered to be a characteristic of normal aging. The age at which this occurs varies from person to person, but in general nearly everyone 75 years or older has grey hair, and in general men tend to become grey at younger ages than women. It should be noted however, that grey hair in itself is not actually grey; the grey head of hair is a result of a combination of the dark and white/colourless hair forming an overall 'grey' appearance to the observer. As such, people starting out with very pale blond hair usually develop white hair instead of grey hair when aging. Red hair usually doesn't turn grey with age; rather it becomes a sandy colour and afterward turns white. Some degree of scalp hair loss or thinning generally accompanies aging in both males and females, and it's estimated that half of all men are affected by male pattern baldness by the time they are 50[3]. The tendency toward baldness is a trait shared by a number of other primate species, and is thought to have evolutionary roots.
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