Only 8 to 10% of the global population has blue eyes, and recent research has shown that they share a common ancestor.
Genetics is a fascinating field as it determines our physical traits and appearance. However, scientists have identified that people with blue eyes may have only one unique ancestor, meaning that all blue-eyed individuals could be related to each other.
If you pay close attention, you will notice that blue eyes are a recessive gene, meaning you need to have at least two of the genes associated with blue eye color for it to be expressed. Scientists have traced a gene mutation that occurred between 6,000 to 10,000 years ago, which is responsible for the eye color of all blue-eyed individuals living on the planet today.
Blue eyes are a recessive gene, which is why only 8 to 10% of the world’s population has blue eyes.
Blue eyes are a recessive gene, and thus only 8 to 10% of the global population has blue eyes. Although blue eyes are significantly less common than brown eyes worldwide, blue-eyed individuals are often found in countries near the Baltic Sea in Northern Europe. Because blue eyes contain less pigment than green, hazel, or brown eyes, light sensitivity is often more common among blue-eyed people compared to those with darker eye colors. Initially, we all had brown eyes; however, according to researchers at the University of Copenhagen, it appears that a gene mutation in an individual in Europe 6,000 to 10,000 years ago led to the development of blue eyes. Therefore, we can conclude that this gene mutation is the reason for the eye color of all blue-eyed individuals living on the planet today.
Professor Hans Eiberg from the Department of Cell and Molecular Medicine at the University of Copenhagen discovered this in 2008. Based on this research and many others conducted earlier focusing on the human genome, Professor Eiberg made an intriguing conclusion: “It simply shows that nature is continuously reshuffling the human genome, creating a genetic mix of human chromosomes.”
Initially, all our ancestors had brown eyes, but a mutation affecting the OCA2 gene in our chromosomes caused humans to be born with different eye colors, and currently, 8% to 10% of the global population has blue eyes. However, the question that perhaps everyone is asking is: who is this special ancestor?
Blue-eyed individuals inherit the same switch at the same position in their DNA.
A genetic mutation affecting the OCA2 gene in our chromosomes leads to the creation of a “switch,” which “turns off” the ability to produce brown eyes. The OCA2 gene encodes ‘protein P,’ which is involved in the production of melanin (the pigment that determines our eye, skin, and hair color). However, the “switch” does not completely turn off the gene but limits its activity in reducing pigment production in the iris—effectively “diluting” brown eyes into blue. According to Hans Eiberg, an associate professor at the Department of Cell and Molecular Medicine at the University of Copenhagen, “From this, we can conclude that all blue-eyed individuals are related to the same ancestor. They all inherited the same switch at the same position in their DNA.”
In 2013, Peter Ralph from USC Dornsife—a university in Southern California—used mathematics, statistics, and gene data analysis to explore human demographics and evolution.
“The fact that everyone has parents means that the number of ancestors for each individual doubles every generation. By using basic math, we can calculate that ten generations ago, each individual had a thousand ancestors, and 20 generations ago, they had a million, and so on. However, when we reach 40 generations back, around the time of Charlemagne, we would have up to a trillion ancestors, which is a problem because we currently have more ancestors than there are people alive.” Peter Ralph stated.
Therefore, with the current level of science, we cannot infer who that specific ancestor is because we do not have the necessary data to direct research towards a single individual, but most studies conducted indicate that blue-eyed individuals have only one unique ancestor.
Alcoholism has a genetic component linked to the gene sequences determining eye color.
Recent research shows that blue-eyed individuals have a higher risk of alcohol dependence compared to those with darker eyes. Thus, this finding adds evidence to the argument that alcoholism has a genetic component. A study published in the American Journal of Medical Genetics, Part B: Neurogenetics found that blue-eyed individuals of European descent have up to an 83% higher rate of alcohol dependence compared to control subjects with darker eye colors. This study indicates that alcoholism has a genetic component linked to the gene sequences determining eye color, which may help explain the correlation. However, at this stage, the reason for the correlation remains unknown and requires further research to fully understand this association in the findings.
