The gene involved in the production of melanin was literally 'turned off' which affected the ability to produce brown eyes
"I could swim in those eyes of yours," is a smooth line often told to people with blue eyes. There is something so hypnotizing about light color of the eyes that makes it just as fascinating. Over the years, blue eyes have come to signify a quality of attractiveness in a person. But what is perhaps mind-boggling to think about is that there was a time when blue eyes were non-existent. Research has shown that a genetic mutation that occurred in a single person, thousands of years ago is why anyone who has blue eyes today even exists. So yes, all people with blue eyes are descendants of that person.
The research was published in Science Daily as scientists managed to track down the genetic mutation which took place 6,000-10,000 years ago. This mutation caused the eye color of all blue-eyed humans alive on the planet today. "Originally, we all had brown eyes," Professor Hans Eiberg from the Department of Cellular and Molecular Medicine stated. "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." This gene is involved in the production of melanin, the pigment that gives color to our hair, eyes, and skin.
All people with blue eyes share a common ancestor who lived between 6,000 to 10,000 years ago.— UberFacts (@UberFacts) September 21, 2020
Until then, every human had brown eyes.
"From this we can conclude that all blue-eyed individuals are linked to the same ancestor," Eiberg said. "They have all inherited the same switch at exactly the same spot in their DNA." The research team examined the mitochondrial DNA and compared the eye color of blue-eyed individuals from diverse locations such as Jordan, Denmark and Turkey. Their findings are the latest addition to the genetic research, Eiberg has been working on since 1996. The professor had first implicated that the OCA2 gene was responsible for the varying eye color.
All people with blue eyes have a common ancestor pic.twitter.com/LfkjWfjAx1— Business Insider (@businessinsider) May 30, 2019
When it comes to deliberating why the mutation took place at all, it is hypothesized that it happened when humans migrated from Africa to Europe. This would also explain why only people of European descent have blue eyes. It would also mean that all blue-eyed people share a single European ancestor. But one thing is for sure, as per Business Insider, eye color began to change long before recorded history even began. This genetic mutation has now spread across the world. "It's exactly what I sort of expected to see from what we know about selection around this area," John Hawks of the University of Wisconsin-Madison said referring to the study.
The blue color of a person's eyes is therefore not because of a pigment in their eyes but rather the lack of it. The variety of eye colors from brown to green can all be explained by the amount of melanin in the iris. In the case of blue-eyed individuals, there is only a small degree of variation in the amount of melanin in their eyes. The OCA2 gene limits the action of the gene to reduce the production of melanin in the iris. So the blue color of the eyes is just a "diluted" version of brown eyes. On the other hand, if the OCA2 gene was completely destroyed or turned off, human beings would be without melanin in their hair, eyes or skin color. This is a condition commonly known as albinism. This genetic mutation has no bearing on the ability of an individual to survive. "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," Eiberg said.