According to the findings of recent research, those who have blue eyes all share a single ancestor. The genetic mutation that causes blue eyes has been located and characterized by a group of researchers. This change in genetic makeup took place between 6,000 and 10,000 years ago. Before that time, there was no such thing as blue eyes.
According to Hans Eiberg, a researcher working in the Department of Cellular and Molecular Medicine at the University of Copenhagen, “Originally, we all had brown eyes.” [Citation needed]
The mutation damaged a gene known as OCA2, which plays a role in the creation of the pigment melanin. Melanin is responsible for giving our hair, eyes, and skin their distinctive colors.
“A genetic mutation that affected the OCA2 gene in our chromosomes led in the construction of a’switch,’ which essentially ‘shut off’ the ability to generate brown eyes,” said Eiberg. “The ability to produce brown eyes was lost as a result of this.”
The genetic switch is found in the gene that is close to OCA2. Rather than totally turning off the gene, the switch just limits the action of the gene, which in turn reduces the amount of melanin that is produced in the iris. The impact of turning the switch down was to make brown eyes appear more blue. The disorder known as albinism would manifest itself in our hair, eyes, and skin if the OCA2 gene had been rendered incapable of producing melanin.
In reference to the findings of the study about the OCA2 gene, John Hawks of the University of Wisconsin–Madison stated, “It’s exactly what I sort of anticipated to see given what we know about selection around this area.” In this particular study, Hawks did not contribute in any way.
Eiberg and his team analyzed the DNA extracted from the mitochondria, the structures within a cell that are responsible for producing energy, of blue-eyed people from a variety of nations, including Jordan, Denmark, and Turkey. As a result of the fact that this genetic material is derived from females, it is possible to trace maternal lineages.
They focused their attention primarily on the sequences of DNA found on the OCA2 gene as well as the genetic mutation linked to a reduced level of melanin production.
Different people have different sequences of genes because, over the course of several generations, different bits of their ancestors’ DNA get mixed up and shifted around. On the other hand, some of these segments have not been reshuffled, and those are referred to as haplotypes.
When a group of people have the same lengthy haplotype, it indicates that the sequence of DNA in question first appeared in our human ancestors only recently. There just wasn’t enough time for the DNA sequence to become jumbled up.
In a telephone interview, Hawks stated that “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,” which means that “they all have exactly the same gene changes that are all linked to this one mutation that makes eyes blue.”
Switch for melanin
The mutation is what controls the OCA2 switch, which is necessary for the creation of melanin. And the amount of melanin that is present in the iris of a person determines the final color of their eyes, which can range anywhere from brown to green.
There is a large amount of individual diversity in the region of brown-eyed people’s DNA that is responsible for controlling the creation of melanin. However, they discovered that the quantity of melanin contained in the eyes of people with blue eyes only varies by a modest amount from person to person.
In reference to the discovery that individuals with blue eyes all shared the same sequence of DNA connected with melanin synthesis, Eiberg told LiveScience, “Out of 800 persons we have only identified one person which didn’t fit.” The individual in question had blue eyes with a single brown patch.
According to Eiberg, the conclusion that can be drawn from this is that all people with blue eyes are descended from the same progenitor. They have all inherited the identical switch, which is located in their DNA in precisely the same location. The findings of the study that Eiberg and his colleagues conducted were published in the online version of the journal Human Genetics.
This genetic shift has now made its way to other regions of the world after initially appearing only in Europe.
“The fundamental question is, ‘Why did there used to be nobody on Earth with blue eyes 10,000 years ago, and now there are 20 or 40 percent of Europeans who have blue eyes?” Hawks said. “This gene contributes something beneficial to the human population. It encourages them to have more children.
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