New research shows that people with blue eyes have a single, common ancestor. A team at the University of Copenhagen have tracked down a genetic mutation which took place 6-10,000 years ago and is the cause of the eye colour of all blue-eyed humans alive on the planet today. “Originally, we all had brown eyes.”New research shows that people with blue eyes have a single, common ancestor. A team at the University of Copenhagen have tracked down a genetic mutation which took place 6-10,000 years ago and is the cause of the eye colour of all blue-eyed humans alive on the planet today.
“Originally, we all had brown eyes”, said Professor Eiberg from the Department of Cellular and Molecular Medicine. “But a genetic mutation affecting the OCA2 gene in our chromosomes resulted in the creation of a “switch”, which literally “turned off” the ability to produce brown eyes”. The OCA2 gene codes for the so-called P protein, which is involved in the production of melanin, the pigment that gives colour to our hair, eyes and skin. The “switch”, which is located in the gene adjacent to OCA2 does not, however, turn off the gene entirely, but rather limits its action to reducing the production of melanin in the iris – effectively “diluting” brown eyes to blue. The switch’s effect on OCA2 is very specific therefore. If the OCA2 gene had been completely destroyed or turned off, human beings would be without melanin in their hair, eyes or skin colour – a condition known as albinism.
Variation in the colour of the eyes from brown to green can all be explained by the amount of melanin in the iris, but blue-eyed individuals only have a small degree of variation in the amount of melanin in their eyes. “From this we can conclude that all blue-eyed individuals are linked to the same ancestor,” says Professor Eiberg. “They have all inherited the same switch at exactly the same spot in their DNA.” Brown-eyed individuals, by contrast, have considerable individual variation in the area of their DNA that controls melanin production.
Professor Eiberg and his team examined mitochondrial DNA and compared the eye colour of blue-eyed individuals in countries as diverse as Jordan, Denmark and Turkey. His findings are the latest in a decade of genetic research, which began in 1996, when Professor Eiberg first implicated the OCA2 gene as being responsible for eye colour.
Nature shuffles our genes
The mutation of brown eyes to blue represents neither a positive nor a negative mutation. It is one of several mutations such as hair colour, baldness, freckles and beauty spots, which neither increases nor reduces a human’s chance of survival. As Professor Eiberg says, “it simply shows that nature is constantly shuffling the human genome, creating a genetic cocktail of human chromosomes and trying out different changes as it does so.”
My father has blue eyes. My mother has brown eyes. My sister (child 1) has blue eyes (dark brown hair/dark skin). My brother (child 2) has blue eyes (blonde hair/fair skin/beard grows in red). I (child 3) have brown eyes (that are becoming more green than brown as I age) (reddish brown hair/fair skin). Father is Irish/Dutch decent. Mother is English/English descent.
My husband has hazel eyes/dark skin/dark curly hair. Son #1 has brown eyes/fair skin/dark curly hair. Daughter (child 2) has violet blue eyes/dark skin/honey curly hair. Son #2 (child 3) has brown eyes/fair skin/dark curly hair.
It is the luck of the draw with genetics. Why do my sons have my eyes and my skin, but their father’s hair? (except they also have red that grows in their beards, like my father and brother have, but not my husband). Where did my daughter’s funky cameleon eyes come from? If she wears blue, they are blue. If she wears purple, they are purple. If she wears green, they are green (and no, if she wears yellow they aren’t yellow, they are blue).
Why did my sister get blue eyes and tan skin, while my only hope of a tan was if all my freckles ran together?
Luck of the draw.
Genetics are fairly easy on eye and hair color. (for blue and brown eyes/blond and brown hair that is.)
Every gen has it’s copy. One from you mother, and one from you father.
A blue eye person has 2 times the same gen: bb
a Brown eye person can have mulitple genetic codes: bB/BB/Bb
brown is domiant above blue.
so:
Brown: B
blue: b
If you follow this rule, it is impossible to have a brown eye-ed kid from blue eye parents.
However, there are a few execpations: A rare gen of blue, that is dominant above brown. This can result in eyes that have 3 colors: brown on the outside, green in the middle, blue on the inside.
But it can also result in completly bleu eyes, making it possible for 2 blue eye parents to have a brown eye kid.
For hair color: brown is domiant over blond
Brown: B
blond: b
So if you are blond, you have 2 times the same gen: bb
brown people can have a ‘hidden’ gen of blond: Bb.
So if 2 brown haired people have a hidden gen, they can have a blond haired kid.
I hope this makes sence to you!
People, please stop with the ignorant comments (example – OMG – i have different eyes than my father thus my mother must have cheated…) and go read a scientific journal or book to get your facts straight.
My husband and I both have blue eyes and our son has brown eyes. Is that possible? My mom has brown eyes and my dad has blue. My husbands parents both have blue eyes.
Something is amiss, Melissa. Two people with blue eyes have a 0% chance of having brown eyed children.
There have been paternity dispute cases that have used this fact as resonable doubt for DNA testing.
Either your son doesn’t truly have “brown” eyes, or he isn’t the biological son of your husband if he is your biological child.
melissa, don’t take notice of what sunny is saying! yes its perfectly possible that your son has brown eyes! remember that nature is constantly shuffling our genes
Genetics are fairly easy on eye and hair color. (for blue and brown eyes/blond and brown hair that is.)
Every gen has it’s copy. One from you mother, and one from you father.
A blue eye person has 2 times the same gen: bb
a Brown eye person can have mulitple genetic codes: bB/BB/Bb
brown is domiant above blue.
so:
Brown: B
blue: b
If you follow this rule, it is impossible to have a brown eye-ed kid from blue eye parents.
However, there are a few execpations: A rare gen of blue, that is dominant above brown. This can result in eyes that have 3 colors: brown on the outside, green in the middle, blue on the inside.
But it can also result in completly bleu eyes, making it possible for 2 blue eye parents to have a brown eye kid.
It could also be an other rare gen: a brown that is not domiant.
It’s more likly the gen above, I know several people (2 people in my personaly life, and some other cases in literature) With the dominant blue gen.
ok, now how can you be so sure about people having blue eyes? like the above comment asked “if he and his wife has hazel eyes, would they also have kids with the same eye color?? if its this way the what about the hair, if me and my wife have brown kind of hair will we have kids with natural blonde hairs??
easy.
brown hairs are domiant above blond hair. Meaning: you and you wife have one gen for brown hair, making you hair brown. But the other gen is most likly one for blond hair.
(every gen has one copy, one form you mother and one from you father)
Because of this, it is fairly easy for a ‘blond gen’ to be passed serval generations before it has the chance to show itself again.
You know this why??
You can’t say someones cheating just because of their eye color. Actually, the genetics a person can get can go back MANY MANY years. He might have the eyes of his great-great grandpa? Or maybe another ansestor way way back. The child dosen’t HAVE TO look like either parent either. Get the facts straight first before you accuse someone of cheating.
My son and his wife both have hazel eyes and their son has blue. She did not cheat because he is the spitting image of his father and really doesn’t look like her at all. Wait…maybe he cheated and she’s not the mother!!
yea he is definitly cheating if u have blue eyes n he does to its impossible for ur kind to have brown eyes use ur brain
he is cheating on you duh
Eye color can be due to genetics, but it can also come about as a result of teratogens (foreign agents that enter the prenatal environment and disrupt gestation). This is what creates the well-known one blue / one brown combination in people like David Bowie and Gracie Burns. They actually have two dominant genes (i.e., brown/brown), but one eye becomes “infected” with some teratogen and its ability to produce melanin is inhibited. People like to find “exceptions” to rules, but in this case it’s not really much of an exception.
The other explanation is quite obvious, but I won’t make any accusations for fear I’ll cause a divorce.