Human hair. Also, some of the biology

Human variation is showed in many
different ways. The way people walk, the sound of their voice, their stature,
limbs, body size, and hair color are some examples. At a simple glance, these
variations might seem quite simple to explain. It is just genetics. However,
that is not the case. There are many other aspects that can affect these
variations such as, climate, geography, environment, and diet.  The world is becoming more and more diverse
as time passes. Furthermore, it is vital to raise awareness of the causes of
variation that go beyond race and genetics. In the articles “Reversible Cutaneous Hyperpigmentation and Nails with White Hair
due to Vitamin B12 Deficiency” and “Variation of Human Hairiness: A Possible Adaptation to Solar
Radiation and Melanin”. It is explained how environment and certain diets can
affect the color of someone’s hair. Also, some of the biology behind how the
body allows these things to change hair pigmentation.  However, in the articles “Multivariate Heredity of Melanin-Based Coloration,
Body Mass and Immunity”, “Model-Based Prediction of Human Hair Color using DNA Variants”
and “Color, Hair, and Bone: Race in the
Twenty-First Century” it is explained how genetics and race can contribute to
the variation in hair pigmentation too.

Hair is a very complicated part of humans. Hair follicles
develop in the fetus around its twentieth second week. And, as people grow
older they have less and less of these follicles. hair follicles are a part of
the hair made of living cells and tissue from which hair is made. All the
hormones and vitamins that can affect hair in some way get to the hair through
hair follicles. The hair shaft is the part of the hair that is dead. It
consists of three layers made of keratin, medulla, cortex, and cuticle.   For hair to be able to grow it needs to go
through three stages, Anagen phase, Catagen phase and Telogen phase. Anagen is
the phase where is in constant growth, it is where most of the scalp hair is.
Once the hair stops growing, it is no longer on Anagen stage and passes to
Catagen phase where about 5% of the hair in the scalp is. The Telogen stage is
the resting form of hair and about 8% of hair in the scalp is at this

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Hair is very complex and so is the way it gets its color. There are many types of hair color.
All hair color is decided by the amount of melanin each one of us produces. The
gene MC1R in charge of producing the receptor Melanocortin 1. These receptors
are located in the melanocytes. melanocytes form melanin by a process called
melanogenesis and the pigmentation that give hair its color originates from the
oxidation of existing melanin. Furthermore, The Gene KITLG is in charge of
regulating the pigmentation of hair. There are 2 types of melanin that give
color to our hair. There is eumelanin which is responsible for the colors going
from black to brown and there is pheomelanin that is responsible for the color
going from red to orange.  Blond hair
color is the absence of melanin which can range from blonde to white. It has
also been found that there is an existing variation in the gene KITLG of a
single-nucleotide polymorphisms, SNP. Through studies, This variation has shown
to be correlated with lighter hair. 
Furthermore, a person with no melanin production will have white hair.
The combination of these 2 types of melanin in different amounts and
distribution can create the variation of hair color we see today.

A lot of the color of our hair has
much to do with our ancestors.  Studies
show that It is more likely for people with European ancestry to have a lighter
hair color. And those with non-European ancestry have a higher likelihood to
have darker hair color. The European are known for having the gene SLC24A4.
This gene allows blonde to be more predominant. 
The region containing the Gene OCA2 will also be associated with a hair
color, which this gene allows to happen more often. Also, the gene TYR and
6p25.3 are involved.  These genes are
capable of controlling the number of melanocytes each individual can produce. Moreover,
controlling the likelihood of having lighter or darker hair color.

Geography also affects hair
pigmentation. Is highly suggested that in the past our ancestors were located
in Africa and had mostly dark hair and as migration started to happen lighter
hair became more of an advantage in certain areas. As they moved farther from
the equator, less UV light from the sun was occurring and humans need certain
absorption of light to be healthy. The absorption of light is vital for calcium
absorption and maintaining healthy bones because it gives people vitamin D. having
a lighter hair will allow the light to be absorbed better in those places where
UV light is scarce. Those migrating closer to the equator had darker hair to
protect their skin from the absorption of so many UV lights that was received
from the sun and prevent radiation. Moreover, increasing survival rate.
Receiving too much UV light can make people become sick and develop skin cancer
and radiation. It is important to main a balance. Light absorption is needed
but just in a specific amount, which varies from person to person.

However, there are many
environmental factors affecting the pigmentation of our hair. for example, is
chronic sun exposer. Because hair is made of dead cells when UV light forms the
sun hits the hair, it oxidizes melanin into a colorless compound, making hair
become lighter. Having our hair subjected to hard chemicals like salt and
minerals also can make our hair become lighter and less healthy. This can
happen with tap water or beauty products. 
Air pollution also brings chemicals to our hair that oxidizes melanin
and makes our hair become lighter.

There are many genetic mutations
that can become very serious and dangerous and can cause loss of pigmentation.
One of them is albinism, people with this condition have no production of
melanin and because of this, their hair is white.  There are many other syndromes that it grows
peoples’ hair starts turning white, also due to low melanin production. Another
genetic mutation of the Gene MC1R is the one producing red hair in some people.
Stress hormones, such as cortisol, can affect hair pigmentation. When a person
is under a high amount of stress the number of melanocytes decreases as so the
production of melanin. This causes our hair to have less melanin. Having less
melanin to distribute makes our hair more sustainable for getting lighter.

we also see many kids being born
blond and as they get older their hair starts becoming darker. This has to do
with the kid’s genes. Genes responsible for hair color are not constant
throughout their life. As they continue to grow older there is a shift in gene
expression causing it to become darker. This change in their gene expression is
changing the amount of eumelanin produced in their hair to increased and as
they matured making is making their hair become darker. Puberty is another
factor why hair can become darker. This is more likely in girls than boys’ due
to the production of hormones such as estrogen. 

Some people can also show signs of
grey hair at an early age and this can be due to a deficiency of vitamin B12.
This vitamin is not produced by our body and is obtained from our diet. It
helps maintain a healthy skin and hair. vitamin B12 helps melanin in the
re-pigmentation of the hair and helps it keep its color. Not having enough
vitamin B12 can also lead to chronic anemia, osteoporosis, and thyroid problems
and one of the symptoms, in some cases, can be sudden greying of hair.

Because melanin is also what gives
skin its color studies have shown some correlation between hair color and skin
color. People with dark skin tend to have darker hair due to the more
production of melanin and people with lighter skin color tend to have lighter
hair color.  This also correlates with
the thickness of hair. People with blond hair tend to have thinner hair and
people with darker hair tend to have thicker hair.

There are many ideas about hair
color that are created within each culture and society. Today there are many
stereotypes exists for blondes, brunettes, and redheads. Usually, in some
societies, blonds are seen as naïve, or less intelligent, and less serious.
Brunettes’ are seen as elegant, reliable, intelligent and stable. Redhead is
seen as exotic, temperamental and impulsive. 
This is mostly seen in women and can affect their social and
professional life.  hair color is more
than just genetics or biology. It also reflects someone’s personality and can
affect their way of living.

Hair is one of the most predominant
characteristics of people. There is an uncountable number of type of hair and
hair color in the world. Each part of hair has a specific function to allow it
growth and health.  Hair pigmentation is
mainly obtained from melanin and different genes take part it making hair be
lighter or darker or red. These genes are hereditary and come from peoples’
ancestors but this does not guarantee people of the same family having same
hair color, due to the immense number of ways that genes can fold.  Even though biology and genes affect the hair
color someone has there are many other factors too. Geography sue to UV light
absorption can affect hair color to increase the level of survival. The type of
hair products or the amount of pollution that a person is exposed too can also
affect their hair. There are many medical conditions which affect the
production of melanin that can affect hair and make it become lighter. There
are many syndromes and diseases that turn hair white. Genes are also very
complex and as people grow older and they change environment different level of
hormones may affect hair. Vitamin B12 deficiency is a very common one causing
sudden graying of hair in chronic situations. Hair color is a great
representation of someone’s health and of someone personality due to existing stereotypes.
Each culture has their own, but it affects individual everywhere.