“The eyes are the window to the soul,” notes a timeless quote.
And while your eyes also bring the world your way, the origins of eye color are fascinating and even mysterious.
To help lay out the details of this genetic marvel, Fox News Digital spoke to a genetics expert about the topic.
What is eye color?
Eye color refers to the color of your iris, which is the colored part of your eye that surrounds the pupil.
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Your pupil is the small black opening in the center, per the Cleveland Clinic.
“Your eye color is like your fingerprint. Nobody else in the world has the exact same eye color as you do.” (iStock)
“Your eye color is like your fingerprint. Nobody else in the world has the exact same eye color as you do,” the Cleveland Clinic noted.
How is eye color determined?
Eye color depends on the amount, type and distribution of melanin, or pigment, in the iris of the eye, said Blair Stevens, a clinical genetic counselor and the director of prenatal genetic counseling services and an associate professor at McGovern Medical School at The University of Texas Health Science Center at Houston, to Fox News Digital.
“Melanin production is determined by someone’s genetic information, which we inherit from our parents,” Stevens said.
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Eye color is considered a “polygenic” trait, meaning several genes are involved.
Some genetic variants produce more melanin, which leads to a darker color, while other genetic variants produce less melanin, which leads to lighter colored eyes. (iStock)
To that end, some genetic variants produce more melanin, which leads to a darker color, while other genetic variants produce less melanin, which leads to lighter colored eyes, Stevens said.
Melanin production continues to develop after birth.
“People often wonder why newborns’ eye color changes and that is because melanin production continues to develop after birth,” she added.
What are recessive and dominant genes?
“Recessive” traits are typically only expressed if someone inherits the recessive gene from both parents, Stevens said, whereas a “dominant” trait inherited from only one parent can mask a recessive trait from the other parent.
“Brown eye color is thought to be dominant to blue eye color, similar to the mixing of paint.” (iStock)
“Brown eye color is thought to be dominant to blue eye color, similar to the mixing of paint,” she said.
For example, if you have blue paint and mix in brown — the resulting color will appear more brown than blue.
If one parent has brown eyes and the other has green, how can a child have blue eyes?
Although brown eye color is thought to be dominant to blue, Stevens emphasized that we have two copies of each gene — one from each parent — and multiple genes are involved in determining eye color.
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“This means there are many combinations of genes that children can inherit from their parents,” she explained.
“Imagine a water color palette that has some blue, green and brown paint options.”
Does one parent usually have dominant genes for eye color and other traits like hair color or skin coloring?
Eye color, hair color and skin color are all affected by melanin, or pigment, that our bodies produce, Stevens told Fox News Digital.
“Our genes dictate the type, structure and amount of melanin,” she said.
Yes, siblings within families can have different eye colors, said one expert. (iStock)
“So, if a person has various melanin genes that produce high amounts of melanin, they are more likely to have darker eye color, hair color and skin color than someone who has genes that produce lower amounts of melanin,” she said.
There are some genes, however, that impact hair color that may not impact eye color and vice versa, she said.
Can siblings have different eye colors? If so, why?
Yes, they absolutely can have different eye colors, said Stevens.
“It will depend on the shuffle of genes that are inherited by each sibling,” she said.
What is the most common eye color of all?
Eye colors can be many different shades, the Cleveland Clinic notes.
Here are a few.
Amber. This shade is described as copper, gold or very light brown.
Blue or gray. Around 1 in 4 people in the U.S. have blue eyes, per the Cleveland Clinic.
Only about 1 in 4 people in the U.S. have blue eyes, per the Cleveland Clinic. (iStock)
Brown. This is the most common eye color in the world. Today, about half of the people in the U.S. have brown eyes.
Green. This is the least common eye color. Only 9% of people in the United States have green eyes.
Hazel. This color is a combination of brown and green.
In the United States, about 18% of people have hazel eyes.
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The inheritance pattern to determine eye color is very complex.
Stevens said there still is much to be learned about the genetics of eye color.
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She also said eye color can’t be reliably predicted using genetic testing.
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