Blue-Eyed Humans Have A Single, Common Ancestor

• Published by Editorial Staff
• Posted on April 17, 2013
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According to an epidemiologist, Mark Grant from Loyola University, Chicago, one out of every 6 people in the US have blue eyes, which makes 16.6% of the entire U.S. population. His research was published under the title, “Cohort effects in a genetically determined trait: eye color among US whites.”

Blue is the second rarest eye color in the world after green, especially in the Asian and African countries. This must be the reason why blue eyes always get lucky in grabbing people’s attention. Hollywood stars like Cameron Diaz, Nicole Kidman, and Marilyn Monroe are all blue-eyed beauties who rule the heart of millions. In fact, in some cultures blue eyes and blond hair are associated with fertility in women. Companies selling colored contact lenses claim that the most popular color for the contact lenses being sold is blue.

Now the question is how did this eye color originate? You can consider blue eyed people as mutants. Yes! It is true. The blue colored eyes originated because of the genetic mutation that took place way back in time, almost 6 to 10 thousand years ago. According to a study published in, “Human Genetics”, this miracle happened in the region near Black Sea during Neolithic revolution.

According to the explanation by Wikipedia, blue eyes consists of “low amounts of melanin within the iris stroma; longer wavelengths of light tend to be absorbed by the underlying iris pigment epithelium, and shorter wavelengths are reflected and undergo Ryleigh scattering.”

The origin of blue eyes was traced for the first time in 2008, by a group of researchers from Copenhagen University who claimed that just one person is responsible for the blue colored eyes of million people living on the planet. This means all blue-eyed people have single common ancestor.

Dr. Eiberg explains that, “Originally, we all had brown eyes.” Melanin is the main component responsible for the brown-black pigmentation in the iris. As discussed earlier in case of blue eyes the melanin concentration is low in the iris stroma.

What caused this low concentration of melanin? Professor Eiberg the team leader and professor at the Department of Cellular and Molecular Medicine explained, “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 is responsible for producing melanin, which gives color to our skin, eyes and hair. There is a “switch” located adjacent to the OCA2 gene, in the case of blue eyes the switch is not entirely turned off but limits the action of the OCA2 gene. This reduces the production of melanin as a result brown color of the eye is diluted to blue.

Another interesting fact is that if in any case this switch gets destroyed or if it is completely turned off your skin, hair and eyes would be without melanin. This condition is also known as, “Albinism”.

The amount of melanin is responsible for the variation of the eye color ranging from brown to green, but in case of blue eyes there is only a small degree of variation in the melanin of the eye. Professor Eiberg states, “From this we can conclude that all blue-eyed individuals are linked to the same ancestor,” he adds, “They have all inherited the same switch at exactly the same spot in their DNA.”

Professor Eiberg also compared the blue color of the eyes of individuals living in different countries living in Denmark, Turkey and Jordan and also examined their mitochondrial DNA. His findings enabled him to conclude that all blue-eyed individuals were related to a common blue-eyed ancestor.

Professor Eiberg suggests that the genetic mutation turning the brown eyes to blue does not have any negative effect on the human body, he also states that, “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.”

The percentage of people with blue eyes is decreasing in the US with the passage of time. Factors could be an increase in immigrants from Asian countries with brown eyes and also because of interracial relationships. The countries where you will find blue eyes commonly are Germany, Netherlands, Scandinavia and the Baltic States. You will rarely find blue eyes in North Africa, Southwest Asia and Southern Europe.

Blue eye color is also common among Israeli Jews. In Estonia 99% of the population have blue eyes. In Denmark only 11% of the population has brown eyes and in Germany almost 75% population have blue eyes.

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