Why
is hair colored
Why do we have differences in hair color? In other mammals hair
color is quite important for camouflage. Leopards' spotted coats
or tigers' stripes blend into the background and thus helps with
stalking prey. However, as a rule humans do not use their hair for
camouflage.
To some extent hair color may help with protecting the skin from
ultraviolet light damage. Dark skin protects from the damaging effects
of UV light better than light skin. Not surprisingly, people with
dark skin usually have dark hair too. The pigment in hair may protect
the hair from weathering due to the effects of sunlight. However,
hair of any color has an equal ability to protect the scalp from
UV rays. It is the density of the hair that is important in skin
protection rather than the hair color. Thus hair color in itself
has little effect in skin protection.
Thus overall, hair color in humans is mostly due to the nature
of the genetics that underlie skin color and the environmental factors
that impacted on our ancestors. Pale skinned and thus blonde haired
people live predominantly in the extreme north (e.g. Scandinavia)
where limited sunlight exposure means not a lot of melanin is required.
In contrast, dark skinned and thus dark haired people live close
to the equator where pigment helps protect against UV damage to
the skin. In the modern world where people can travel vast distances
easily, these geographic distinctions in hair color break down,
but in ancestral terms the principle is clear.
In humans today hair color plays a mostly psychological role -
it is an indicator reproductive health and possibly a power display.
In the same way that birds with brightly colored plumage attract
a mate with displays of their eye catching colored feathers, so
humans may attract mates based on their physical image. Hair and
hair health is a particularly important feature in sexual attraction.
As part of that, hair color may have a role. Apparently gentlemen
prefer blondes.
Color may be an indicator of general health. Albinos mammals and
birds are usually shunned by their peers and parents. In the wild
they rarely survive for long. In human populations albinism is also
a barrier to marriage and reproduction. In past times infanticide
of albino babies was common.
A prime example of hair color used as a power display, the senior
males in groups of mountain gorillas develop gray hair. The so called
"silver backs". This provides a very clear indicator of
their power and leadership within the group. To some extent the
same may be true for humans. Gray hair can be regarded as an indicator
of wisdom. However, more commonly gray hair is taken as an indicator
of age and reduced reproductive potential. The result being that
many people dye their gray hair in an attempt to conceal their biological
age.
Use of hair dye is primarily associated with sexual attraction,
exhibitionism or in contrast, trying to blend in with their peers.
Currently in Germany, red dyed hair for women is incredibly popular
despite the fact that natural red hair in the German population
is very rare - affecting less than 1% of the population. So on the
one hand, German women want to stand out from the crowd with their
red hair and on the other hand they are trying to conform to the
image of their peers.
Why
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