Why Do We Have Different Skin, Hair and Eye Color?

We have a wonderfully diverse and beautiful
world filled with millions of species of both animals and plants. At the top of the food chain sits us human
beings – the most dominant of predators. Us homo sapiens all share similar characteristics
with one another, but in the details we can vary dramatically. We don’t all look and sound the same. We don’t think the same. But why is this? Why do we differ in eye color, skin tone and
hair? That’s what we will find out in today’s
Infographics Show – Why do humans have different skin, hair and eye color? First let’s look at the science of skin. The color of our skin is determined by a pigment
known as melanin. All humans have melanin but it comes in different
forms and ratios. The two main forms produced by a specialized
group of cells called melanocytes are known as eumelanin (brown and black hues) and pheomelanin
(red and yellow hues.) First up, we should understand that there
is no such thing as black, white, red, or yellow skin. You have a mixture of colors, like an artist’s
palette, depending on your genetic predisposition. So should you have very dark skin you’re
mainly producing eumelanin, while if you are pasty white you lack melanin, and if you have
red hair you would be pumping out pheomelanin. Most important is the size and number of melanin
particles when determining skin color. Some people produce a low melanin count which
results in less pigment and ultimately lighter skin. Some folks can temporarily change their skin
color by laying on the beach or hitting a tanning salon. Sun stimulates the production of melanin and
inflames the skin surface to form protection against UV exposure. But this still doesn’t answer why people
have different color skin. Well if we go back in time, say, a million
years or so, anthropologists and archeologists have told us that man lost his furry coat
and began walking erect. Since that time the species has been subject
to an endless process of natural selection in which favorable genes have been naturally
selected in a Darwinian fight for survival. One of the most important human adaptations
is the ability to withstand intense sunlight. Early humans who lived in sub-Saharan Africa,
near the Equator, developed a way to tackle the pounding sunlight and radiation. Over thousands of generations, our early ancestors
developed skin with higher levels of melanin, and in particular eumelanin, to protect and
block them against the sun. Scientists reckon that it wasn’t until about
100,000 years back that people’s skin color actually began changing. Before that, apparently all humans were dark-skinned. As humans migrated to Europe, northern Asia
and the Americas, they discovered less sunny areas and as a result developed vitamin D
deficiencies. Vitamin D is essential for human health, assisting
in breaking down calcium and other essential minerals for growth. The primary source for vitamin D is, yes you
guessed it, sunshine. Sunlight radiation helps synthesize the vitamin
in the skin. In countries such as Norway or Finland where
there is little sunlight for parts of the year people have very pale skin to make sure
they are exposed to UV rays when the sun is out to process vitamin D. This lack of melanin means they can soak up
all the rays possible when the sun is out. It is interesting to note that in countries
where sunlight is the most prevalent, such as Africa, India and South East Asia people
desire to have pale skin. In countries where there is little sunlight
people desire darker skin. Both skin-lightening, and skin darkening are
huge industries. The beauty and pharmaceutical industries makes
billions from telling us we need to look the opposite of our biologically chosen appearance. Well, beauty is in the eye of the beholder
and without further ado let’s move on to eyes. What determines eye color? Well, it seems there are two large factors
at play here. The volume that dark brown pigment called
melanin is in the iris, and the way that the eye spreads light that passes through it. The pigment part of the equation is determined
by your genes and passed down by your parents. Again, as with skin, melanin is there to protect
us from those potentially harmful UV rays. And again around 10,000 years ago, all humans
had lots of melanin and pretty much everybody had brown eyes. Over the years genetic mutations began to
affect certain genes reducing the volume of pigments, resulting in bluish light reflection. Colors such as green, and grey are halfway
between brown and blue. Some rare eye colors have evolved. Amber eyes have a unique pigment called pheomelanin
dominant. People with this mutation are rather rare
to find. People and animals who have albinism exhibit
a congenital disorder related to pigment production. Albinos have a partial or total loss of pigment
meaning that you can see straight through to the reddish retina. It goes without saying that albinos are subject
to light sensitivity and often require the aid of protective glasses. And then there are those people who are born
with different color eyes. They may have one brown and one grey. This condition is known as heterochromia and
can be caused by genetics, injury, or another form of mutation. So we’ve looked at eyes and skin, now let’s
take a look at hair. What determines the color of your hair? Well, I’m sure you are keeping up and noticing
a trend here and yes, hair colour is down to melanin and those eumelanins and pheomelanins
once again. Pheomelanin produces red pigments and eumelanins
produce black and brown pigments. A person who has very little eumelanin will
usually have blond hair. Low eumelanin results in gray hair. A person well stocked in eumelanin will have
dark brown or black hair. Each and every person has some pheomelanins
but a person with red hair will have a particularly high concentration of pheomelanin pigments. The variation of hair, eye, and skin color
may be a result of what geneticist Luigi L. Cavalli-Sforza calls sexual selection. Like natural selection this phenomena is a
force that pushes one genetic variation ahead of the other. But unlike natural selection sexual selection
focuses on traits that relate to attracting mates. Hair color diversity, along with eye, and
skin color may be driven to an extent by what we find desirable in the opposite sex. Luckily we don’t find the same colors and
variations attractive so diversity looks set to remain. So what do you think is the most desirable
hair, eye, skin color? Let us know in the comments! Also, be sure to check out our other video
Weird Things Americans Do. Thanks for watching, and as always, please
don’t forget to like, share and subscribe. See you next time!


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