Hair color
The hair color of a person depends on the amount of pigment eumelanin and pheomelanin from that in the fibrous layer of the hair are included. If the pigments are completely absent, the hair is pale. This is the case with people with albinism .
Hair colors
White
Gray
brown
black
| White | blond | darkblond | red | red brown, henna | light brown | brown | dark brown | black |
Development of the natural hair color of a person
The melanins are produced by melanocytes . These are cells that are located in the hair follicles. They convert the body's own amino acids into different types of the color pigment melanin, which provide the color palette in human hair.
- Eumelanin is a black-brown pigment. It primarily determines how dark the color of the hair is. It occurs in recognizable grains (granules) in brown and black hair.
- The pheomelanin is a red-gold pigment. It is found in larger quantities in light blonde, blonde, and red hair. This pigment is much smaller than eumelanin. The structure is also finer and more diffuse.
The color variations known to humans arise depending on the mixing ratio of these two types of pigments. All shades of hair in between, such as brunette (brownish), reddish brown or reddish blonde, arise from different mixing ratios of the two types of melanin. A person's natural hair color can be changed through bleaching or hair coloring . Whether the hair color has a strong glow or appears matt does not depend on the color pigments, but on the colorless scale cells (cuticula) on the hair surface. If the scales of this layer stand out, the color of the hair appears dull and dull. If the scales are on, the color glows brightly. The color of the hair, whether it is straight or curly, thick or thin and when the first gray hairs start to grow is largely genetic.
Distribution in human populations
More than half of all people have black hair, around three quarters in total are dark-haired. Black hair is genetically dominant and can therefore be found in almost all human populations . Black is not always black: The hair of Eurasians - with the exception of the Far East - is often a very deep brown, while Black Africans, East Asians and Indians mostly have deep black hair. In the areas of Europe with lightened hair colors, black occurs mainly among the descendants of the Celts in Ireland, England and Brittany.
The most common hair colors of Europeans are in the range of brown tones, which from deep brown in the Mediterranean area become lighter and lighter towards the north, where they are replaced by more blonde tones. Brown is also common among the indigenous people of Australia, New Guinea, and Melanesia.
Naturally blonde hair only retains around 2% of the world's population into adulthood. They were originally most common in Northern and Eastern Europe (and, after European expansion , their descendants around the world). In Southwest and Central Asia as well as Northwest Africa, blonde hair occurs locally. This is presumably due to the contacts with Northern Europeans since the Great Migration . In addition, blonde hair is common among the Aborigines of Central and Western Australia , but mainly among children and women . Local occurrences of blonde hair can also be found in New Guinea and Melanesia. Numerous legends tell of blond or red-haired Indians who lived in America before Columbus. In fact, clearly lightened hair occurs among the Mandan people on the Missouri and among the descendants of the Chachapoya in Peru. The cause can either be based on a mutation like the Melanesians or on European influences before the colonial era. The latter is more likely to be rejected by science.
Red hairs have a similar distribution. With 1–2% of the world's population, it is the rarest hair color. It is most common in Scotland, Wales and Ireland, with 13% of Scots having red hair. As you can see on the map, local occurrences of red hair are often found where there is also occasional blonde hair.
Graying of human hair
Strictly speaking, there is no such thing as gray hair. The optical impression of gray hair comes from the mixture of pigmented and pigmentless hair. It's either white or colorless. Hair doesn't turn gray suddenly, but step by step. One reason for graying out (canities) is that the body does not produce sufficient amounts of the amino acid tyrosine , which is essential for melanin production, in old age or due to certain diseases . Decreasing catalase activity, via the accumulation of hydrogen peroxide in the hair shaft, can lead to only limited repair of oxidative damage in the active center of the enzyme tyrosinase . The lack of melanin leads to hypopigmentation and is replaced by the accumulation of air bubbles in the hair shaft . Such hairs appear white to the viewer.
Another reason for the graying is seen in the loss of stem cells in the hair follicle. Melanocyte stem cells are therefore induced, among other things by the age-related accumulation of DNA damage, either to differentiate into mature melanocytes or to initiate programmed cell death ( apoptosis ). Hair lives on average for three to seven years, then it falls out and new hair grows at this point. Gradually the proportion of white hair predominates. Hair on the temples has a shorter lifespan, just like beard hair. That's why most of the people here turn gray first.
Cultural role of hair coloring
Hair coloring can be traced back to ancient Egyptian times. The practice of artificially changing hair color was often accompanied by moral criticism. This changed with the marketing of hair dyes. After the discovery of advanced hair coloring methods around 1860, the cosmetics industry succeeded on the one hand in making colored hair look more natural and on the other hand in setting the scene in the context of blonde Hollywood stars. The outstanding media presentations of hair coloring include Alfred Hitchcock's Vertigo (1958) and Jean Echenoz 's novel Les grandes blondes (1995).
Related topics
- In addition to albinism and piebaldism, there is also melanism in animals , which leads to a black color of the fur , skin or scales.
- Melanocyte (pigment cell of the skin)
- " Grandma gray " as artificial hair coloring
See also
literature
- H. Zahn: The hair from the chemist's point of view. In: Chemistry in Our Time. 23rd year No. 5, 1989, ISSN 0009-2851 , p. 141.
- Ralf Junkerjürgen : Hair colors: a cultural history in Europe since ancient times. Böhlau, Cologne et al. 2009, ISBN 978-3-412-20392-4 .
Individual evidence
- ↑ brunett is the Germanized form of the French. brunette , the feminine form of the adjective brunet ("with brownish hair", "brown-haired"), which in turn is derived from brun (brown).
- ↑ see extensive literature on the map .
- ↑ Gray Hair: Myths and Facts. on: frisuren.t-online.de
- ↑ JM Wood et al .: Senile hair graying: H2O2-mediated oxidative stress affects human hair color by blunting methionine sulfoxide repair. In: FASEB Journal. 23 (7), 2009, pp. 2065-2075. doi: 10.1096 / fj.08-12543 . PMID 19237503
- ↑ Petra Giegerich: Gray hair in old age: hydrogen peroxide inhibits the formation of melanin. In: Information Service Science. March 3, 2009.
- ^ EK Nishimura et al.: Mechanisms of hair graying: incomplete melanocyte stem cell maintenance in the niche . In: Science. 307 (5710), 2004, pp. 720-724. doi: 10.1126 / science.1099593 . PMID 15618488
- ↑ K. Inomata et al.: Genotoxic stress abrogates renewal of melanocyte stem cells by triggering their differentiation . In: Cell. 137 (6), 2009, pp. 1088-1099. doi: 10.1016 / j.cell.2009.03.037 . PMID 19524511
- ↑ Ralf Junkerjürgen : Dizziness, fall, blond curls: On the mythology of the wrong blonde. In: Crossing borders. Contributions to a modern Romance studies. (33), 2010, pp. 68-84. (Abstract)
