The color blue is considered a genetic alteration, which may have occurred about 6,000 to 10,000 years ago. Before that point, it was believed that most people had brown eyes.
In the United States, blue eyes are becoming less common. In the 1950s, more than half the population had blue eyes. Now, it is estimated that one in six babies has blue eyes.
What Causes Blue Eyes?
The color of the eye is created by the different layers in the iris. Even in blue-eyed individuals, the back layer has brown pigment, but the front layer in blue eyes has no pigment.
Because of this lack of pigment in the front layer of the iris, the fibers interact with light and absorb some of the longer light rays. The outcome? The eye appears a blue color.
According to the American Academy of Ophthalmology, the blue color is not due to a blue pigment but to a lack of pigment to stop the light rays. As there is no blue pigment in the irises, the eyes appear blue due to physics.
How Common Are Blue Eyes?
The American Academy of Ophthalmology cites a 2014 Harris Poll confirming that in the United States, 27 percent of the population has blue eyes. It is estimated that about 8 to 10 percent of the world population has blue eyes.
Blue Eyes & Eye Health: Advantages & Disadvantages
Certain health conditions and traits are more common in people with blue eyes versus people with other eye colors.
Advantages of Blue Eyes
A big advantage to blue eyes is that research shows they might be linked to a lower risk of developing cataracts. Cataracts are clouding of the eye’s lens.
According to some studies, blue eyes may have evolved because these individuals were able to cope better with seasonal affective disorders. The theory is that people with blue eyes may be better equipped to tolerate long periods of low light.
Disadvantages of Blue Eyes
Typically, people with blue eyes are likely to be more sensitive to light. With less pigment in the layers of the iris, they may be unable to block out the effects of bright fluorescent lights or sunlight.
This condition of light sensitivity is called photophobia. It does not indicate vision loss, but it can create some difficulty focusing or seeing clearly in bright lights. It may also cause pain around the eyes.
According to the American Cancer Society, several risk factors can increase the chances of getting eye cancer. Eye color is only one of the factors, so it doesn’t mean you will develop eye cancer simply because you have blue eyes.
One Common Ancestor
According to recent studies, people with blue eyes have a common ancestor. The new research has tracked down a genetic shift that leads to blue eyes.
This significant research shows that the gene mutations affected the OCA2 gene. This gene is involved in producing the pigment (melanin) that creates the color of eyes, hair, and skin.
The genetic shift turned down the ability to produce brown eyes, resulting in the creation of eyes with less pigment (blue eyes).
Over time, some of the elements of the genes change while others remain unchanged. The unchanged segments are called haplotypes. When individuals share these haplotypes, scientists believe that it shows common ancestry.
In recent studies, scientists are showing that people with blue eyes in Denmark share the genetic traits of people as far as Jordan.
Interestingly, the same studies also show that people with blue eyes have very little variation in the amount of melanin pigment. This confirms the theory of one common ancestor with a shared DNA sequence.
5 Interesting Facts About Blue Eyes
Studies are continually identifying interesting new facts about blue eyes. Here are five of them:
1. Risk of Alcohol Dependence
Research shows that individuals with blue eyes may be at a higher risk of becoming alcohol dependent.
This recent study suggests that European Americans with lighter eyes had higher odds of becoming dependent on alcohol compared to people with darker eye colors. While the mechanisms are still being studied, further research is needed to fully understand why this may be the case.
2. Blue Eyes Can Change
Babies may be born with blue eyes, but the color can change over time. The color of a baby’s eyes can change due to increased melanin production, causing the color of the eye to become hazel, green, or brown.
This is perfectly normal and the color transition can occur in the first few months or years of life. The biggest changes in eye color occur between 3 and 6 months of age.
3. Blue Eyes Are Rare
According to the World Atlas, only 8 to 10 percent of the world’s population has blue eyes. Blue-colored eyes are most commonly found in northern Europe.
4. Blue Eyes Are Not Predictable
While the old model of genetics believed that blue eyes could only be inherited from two blue-eyed parents, genetic models have evolved. The new understanding is that eye color is influenced by as many as 16 genes.
Studies show that brown-eyed parents can carry a recessive gene for blue eyes. If both parents have blue eyes, it doesn’t necessarily mean their child will. Likewise, two brown-eyed parents can have a baby with blue eyes.
5. Blue Eyes Are More Light-Sensitive
Blue eyes contain less melanin, making the eyes more sensitive to bright lights. Wear sunglasses to protect your eyes from UV light, and wear them more frequently if your eyes feel particularly sensitive.
If you have blue eyes, you may want to limit sun exposure overall.
The World’s Population by Eye Color. World Atlas.
Your Blue Eyes Aren’t Really Blue. (May 2021). American Academy of Ophthalmology.
9 Pros and Cons of Blue Eyes. Health Research Funding.
Physics Proves That No One Really Has Blue Eyes. (April 2011). Gizmodo.
Iris Color and Associated Pathological Ocular Complications: A Review of Epidemiologic Studies. (October 2014). International Journal of Ophthalmology.
Why Did Humans Evolve Blue Eyes? (September 2015). Ask an Expert (ABC Science)
Myth or Fact: Blue Eyes Are More Sensitive to Light. (July 2021). Duke Health.
Risk Factors for Eye Cancer. American Cancer Society.
What Is Ocular Melanoma? (January 2022). American Academy of Ophthalmology.
Eye (Ocular) Cancer. Yale Medicine.
One Common Ancestor Behind Blue Eyes. (January 2008). LiveScience.
Eye Color: A Potential Indicator of Alcohol Dependence Risk in European Americans. (April 2015). American Journal of Medical Genetics Part B: Neuropsychiatric Genetics.
Will My Baby Have Blue Eyes? A Genetic Explanation & Eye Color Chart. (April 2022). Family Education.
When Will Your Baby’s Eyes Change Color? (June 2021). What to Expect.
Last Updated July 20, 2022
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