Despite the apparent prevalence of the trait among swanky croonerse and british spies and creepy old creatures
who just hung onto the ring for too long,
only about 8% of the world,s human population has blue eyes
in U.S its about twice that,
but that is still a lot less than it was at the turn of the 20th century when nearly half of all americans had the trait
so what happened ?
are blue-eyed humans going the way of the dodo?
well, NO
we cleared up that the rumors about the redheads going extinct ;
the same goes for blue eyes.
while the trait is becoming more rare,
its unlikely it will disappear all together
which is crazy
when you consider that 10,000 blue years ago blue eyes did not even exist.
in fact there,s a good chance that blue-eyed people may all share one common ancestor .
studies over the past decade have actually traced the trait to a mutation
that most likely arose among brown eyed people in a single human in the black sea region of south eastern europe between 60,000 and 10,000 years ago.
the mutation affected
whats known as the OCA2 gene.
which helps over bodies produce Melanin.
The brownish pigment that gives the color to our hair ,eyes and skin.
the mutation created kind of a dimmer switch for the pigmentation,
but it did not affect the entire gene .
instead it only affected the production of the melanin in the iris
the ring structure around the eye that regulates how much light gets in.
the bulk of the iris is a thick layer of melanin-producing cells called storma.
and the OCA2 mutation turns the production of the melanin in the stroma way down,
but the pigmentation still shows up elsewhere.
like in the hair and skin and other parts of the iris.
basically the mutation keeps the stroma from being brown.
so whyblue then?
well strictly speaking ,
blue eyes are not actually blue.
instead, in people with this mutation,
the stroma is full of nearly colorless cells.
and when the light strikes them,
they scatter the wavelength back out,
in a process similar to what makes smoke or fog look blue when light passes through them.
if there is some yellowish pigment in the stroma,
then the blue light will combine with that to make green.
throw in a little bit of brown.
and you have hazel.
so how did we go from having no blue eyed people to hundreds of millions of them in less then 10 millennia?
no ones entirely sure why the trait spread so quickly through europe.
some scientists think the mutation could have helped prevent certain eye disorders related to long,
dark northern winters.
but another factors appears to be that for whatever reasons,
lots of blue eyed people simply mated
with other blue eyed people in the past,
which kept the trait in circulation because for each of your genes,
you have two different versions ,
called alleles, one from your father and one from your mother,
if you have at least one dominant allele for a gene,
thats the trait you have the blue eyes come from a recessive allele which means
if you inherit one allele for blue eyes and another for brown you are going to have brown eyes
but you still carry the recessive blue allele ,
which can be passed on,
which means that 1st person that had that blue eyed mutation did not have blue eyes.
they had to pass that onto their childrens and their children had to pass it onto their childrens until eventually they come back together to make someone with two blue eyed alleles
when both parents have blue eyes they both have two recessive blue eyed genes
which means their childrens will also have blue eyes since their is no dominant gene to make them recessive one.
this is now you end up with scandinovian countries that are 95% blue eyed and it also explains.
why the % of blue eye-ers is dropping in much of the westren world human population are a lot more evenly spread throughout the world than they were 10,000 years ago.
so more blue eyes are pairing up with brown eyes and producing brown eyed offspring .
i would not go so far as to call them endangered
but safe to say these blue eyed singers and spies and gollums will always be in the minority.
