Blue eyes have captivated us for centuries. Icons like Frank Sinatra and celebs including Megan Fox and Cillian Murphy boast the eye colour – but where did this sought-after trait come from?
Pioneering genetics research by Dr Hans Eiberg and his colleagues at the University of Copenhagen has traced blue-eyed individuals to one ancestor about 10,000 years ago near the Black Sea, unveiling the mutation that causes blue eyes and thus deepening our understanding of human history.
Eye colour hinges on melanin levels in the iris – brown being most common due to high melanin, while hues like blue and green are due to less melanin, reports the Express.
Dr Eiberg’s work identified a key alteration in the OCA2 gene – which manages melanin production – that doesn’t make blue eyes per se but limits melanin in the iris.
“Originally, we all had brown eyes,” stated Dr Eiberg in his 2008 publication. “A genetic mutation affecting the OCA2 gene in our chromosomes resulted in the creation of a ‘switch’ that literally turned off the ability to produce brown eyes.”
The recent study has unveiled a remarkable genetic link shared by people with blue eyes. Astonishingly, over 99.5 per cent of blue-eyed participants in the study have the same tiny mutation, indicating it most likely originated from a single individual.
This trait has been passed down through generations, resulting in the wide spectrum of blue-eyed individuals seen today.
Researchers pin this genetic mutation to the area around the northwest of the Black Sea, covering parts of what is now Ukraine, Russia, Georgia, Turkey, Romania, and Bulgaria. It’s believed that the mutation spread during the time agriculture was expanding from the Middle East into Europe, a period marked by rapid population growth.
The study’s scope was considerable, examining the DNA of more than 800 individuals, encompassing a varied range of skin tones from fair Scandinavians to dark-skinned, blue-eyed people in countries like Turkey and Jordan. Strikingly, nearly all subjects had identical sequences in the relevant portion of the OCA2 gene.
Dr. Eiberg commented on the findings: “This strongly indicates that all blue-eyed individuals are linked to the same ancestor. They have inherited the same switch at exactly the same spot in their DNA.”
Despite understanding where the mutation arose, scientists are still pondering why it became so widespread. Among theories is the notion that blue eyes could have been evolutionarily advantageous in areas experiencing lengthy summer daylight and brief winter days, for improved adaptation to the variations in light conditions.
Another theory suggests sexual selection, proposing that the rarity and allure of blue eyes may have made them sought-after traits in mate selection. The findings underscore the unexpected ways evolution operates.
While globally blue eyes are uncommon, over time, they became concentrated in northern and eastern Europe, where the mutation likely offered some advantage.
Today, blue eyes are admired for their beauty, but for a significant part of human history, they were an evolutionary anomaly – a random mutation that triggered a series of genetic and societal shifts.
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