Wednesday, April 17, 2024
World News

Every blue-eyed person’s ancestor comes from a single human in this pretty European region | World | News

Between eight percent and 10 percent of the world’s population has blue eyes.

The relatively low figure makes it one of the rarest colours, much rarer than brown eyes, which are found in between 70 to 80 percent of people on Earth.

Eye colour is directly related to the amount of melanin in the front layers of the iris, and the more you have of it, the more likely you are to have brown eyes.

The history and genetic process behind eye colour is something that has long fascinated scientists.

One team was so intrigued that it set out to find the origins of the eye colour blue, tracing it back to a single person who once called a stretch of the Black Sea coast home.

The team, consisting of a group from the University of Copenhagen, managed to find a genetic mutation which took place 6,000 to 10,000 years ago.

This single event was the trigger point for all humans with blue eyes that came afterwards, a monumental event that has seldom been repeated since.

“Originally, we all had brown eyes,” Professor Hans Eiberg, from the Department of Cellular and Molecular Medicine, wrote in a 2008 paper in the journal Science Daily.

“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 hair, eyes, and skin.

It doesn’t create the blue colour so much as it turns off the mechanism which produces brown melanin pigment, effectively “diluting” brown eyes to blue.

We know the OCA2 gene isn’t destroyed or turned off in those with blue eyes because without it, their hair, eyes, or skin colour would be completely without melanin, a condition otherwise known as albinism.

Variation in the colour of brown to green eyes is explained by the amount of melanin in the iris, but blue-eyed people only have a minuscule amount of variation in their eyes’ melanin.

“From this, we can conclude that all blue-eyed individuals are linked to the same ancestor,” explained Prof Eiberg. “They have all inherited the same switch at exactly the same spot in their DNA.”

But who exactly is this ancestor? And where did they live? The answer may be surprising, but the team narrowed the location down to somewhere along the present-day Black Sea coast.

It means people with blue eyes have ancestors in one of six potential countries, present-day Ukraine, Russia, Georgia, Turkey, Romania and Bulgaria.

Though Prof Eiberg and his team were uncertain as to when the mutation occurred exactly, evidence suggests it likely happened around 10,000 years ago when the population of humans boomed after the introduction of agricultural techniques from the Middle East.

From this, the experts placed the blue-eyed ancestor as coming from the northwest part of the Black Sea, a stretch of land that makes up modern-day Romania, Bulgaria, or Ukraine.

The mutation of brown eyes into blue eyes does not, the team said, mark any sort of positive or negative gain. Rather, it is simply one of several mutations observed in humans, things like hair colour, baldness, the emergence of freckles and beauty spots.

Prof Eiberg said: “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.”

Around 800 people were included in the study. They varied from people with fair skin and blonde hair living in Northern Europe to those with dark skin and blue eyes living in Asia and the Middle East.

Prof Eiberg noted: “All of them, apart from possibly one exception, had the same DNA sequence in the region of the OCA2 gene. This to me indicates very strongly that there must have been a single, common ancestor of all these people.”

Leave a Reply

Your email address will not be published. Required fields are marked *