It’s said that the eyes are the window to the soul. When viewed up close it is easy, however, to note that eyes are far from transparent. If you’ve ever looked at up-close images of the iris, you may have noticed incredible patterns. These patterns resemble stormy skies, thriving trees, or crystal blue waters.
What you see is dependent upon the color of the iris. If you’ve ever wondered why some people have brown eyes and others have green or blue eyes people have different colored eyes, you’re not alone. In fact, it’s a wonder so common scientists have conducted a number of studies revolving around the origin of blue eyes. Their discoveries led to the conclusion that people with blue eyes all have a common ancestor.
Blue Eye Discovery
As it turns out, all people with blue eyes have more than just blue eyes in common. Scientists have learned that people with blue eyes are all descended from the same person, meaning all share an ancestor. This ancestor lived anywhere from 6,000 to 10,000 years ago. Prior to that, there were no blue eyes, only brown, according to Hans Eiberg from the department of cellular and molecular medicine.
His research is done at the University of Copenhagen.  Eiberg and his team examined DNA and found a genetic mutation thus creating blue eyes. “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,” Eiberg said. The study looked at individuals from many countries including several from the Middle East.
Scientists looked at patterns found within DNA, specifically the OAC2 gene to find out how to “turn down” melanin production.  The mutation discovered by scientists was discovered to be on an entirely different gene called HERC2. This gene is what “turns off” OCA2. This inhibits brown pigments, revealing various shades of blue. 
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More than one study has been done over the years. John Hawks of the University of Wisconsin-Madison was not a researcher for the first study conducted. However, he has taken part in the research conducted since 2008, when the original study was done. He said of the discovery, “What they were able to show is that the people who have blue eyes in Denmark, as far as Jordan, these people all have this same haplotype, they all have exactly the same gene changes that are all linked to this one mutation that makes eyes blue.”
Essentially these findings show that every person with blue eyes has the same ancestor. Only one person experienced this genetic mutation and then passed the genes onto their offspring, for generations to come.
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A Brief Look at the Science of DNA
The DNA observed for this study came from the mitochondria, which are energy-producing structures within cells. This mutation impacts a gene called OCA2. OCA2 is the gene responsible for the production of melanin. Melanin gives color to our skin, eyes, and hair, so the coloration and differences of each person are dependent upon how much or how little melanin is produced. This amount varies from person to person and is deeply rooted in our ancestral pasts.
Throughout generations, DNA gets shuffled and its structure changes causing a variety of results. These DNA chains, scientifically known as Polynucleotides, sometimes do not shuffle their order. There is a multitude of reasons this might happen and the result is known as “haplotypes”. In this case, the DNA sequence didn’t have enough time between generations to become mixed up.
Participants in the research all lived in different countries, regions, and climates. Because they had very little in common with one another scientists were able to determine that all people with blue eyes share the same haplotype. It is not known what exactly caused this mutation or how DNA changes will impact future generations. While scientists also don’t know the exact time frame for when this change occurred one thing is clear.
Research has shown that eye color began to change before recorded human history began. Peering into the eyes of someone you love is mesmerizing. It can help bring people closer together by reinforcing the connection they feel toward one another. Eyes can provide some “metaphorical” insight into who people are but the science behind their make and function is fascinating and complex.
This study was initially done years ago, in 2008 and has since been revisited. Science is always changing and learning new things so it’s not unlikely scientists will further research this in the future.
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- “One common ancestor behind Blue Eyes.” Live Science. Jeanna Bryner. January 31, 2008.
- “Every blue eyed person on Earth is a descendant of one single person, scientists find.” LAD Bible. Shola Lee. October 4, 2022. YouTube. November 16, 2017.
- “What is a chain of nucleotides called?” Sage- Advices. August 18, 2019.
- “All blue-eyed people have a single ancestor in common.” Business Insider. Zach Williams. September 21, 2017.