The eyes are the mirror of the soul, says a timeless quote. And while your eyes can give a glimpse of what kind of person you are, the origins of eye color are fascinating and even mysterious.
Eye color refers to the color of the iris, the colored part of the eye that surrounds the pupil. Your pupil is the little black hole in the middle. "The color of your eyes is like your fingerprint. No one else in the world has exactly the same eye color as you,” the Cleveland Clinic said.
Eye color depends on the amount, type and distribution of melanin, or pigment, in the iris of the eye, said Blair Stevens, clinical genetic counselor and director of prenatal genetic counseling.
"Melanin production is determined by one's genetic information, which we inherit from our parents," Stevens said. “Eye color is considered a 'polygenic' trait, meaning that several genes are involved. "To that end, some genetic variants produce more melanin, leading to a darker eye color, while other genetic variants produce less melanin, leading to a lighter eye color," Stevens said.
"People often ask why the eye color of newborns changes, and it's because melanin production continues to develop after birth," she added. Recessive traits are usually only expressed if someone inherits the recessive gene from both parents, while a dominant trait inherited from only one parent can mask the recessive trait from the other parent.
"Brown eye color is considered dominant over blue eye color, similar to color mixing," Blair said. For example, if you have a blue color and mix it with coffee, the resulting color will look more brown than blue.
What if one parent has brown eyes and the other has green eyes, and the child has blue eyes? How does this happen?
Although brown eye color is thought to be dominant over blue, Stevens pointed out that we have two copies of each gene—one from each parent—and that multiple genes are involved in determining eye color. "This means that there are many combinations of genes that children can inherit from their parents," she explained, "Imagine a watercolor palette that has blues, greens and browns."
Does a parent usually have dominant genes for eye color and other traits such as hair or skin color? Eye color, hair and skin color are all affected by melanin, or the pigment our body produces, Stevens said: “Our genes dictate the type, structure and amount of melanin. So if a person has different melanin genes that produce large amounts of melanin, they are more likely to have darker eye, hair and skin color than someone who has genes that produce less melanin.”
However, there are some genes that affect hair color that do not necessarily affect eye color and vice versa. Can siblings have different eye colors? If so, why? "Yes, they absolutely can have different eye colors," Stevens said, "it will depend on the transfer of genes that each sibling inherits."
The inheritance pattern for determining eye color is very complex. Stevens said there is still much to learn about the genetics of eye color. She also added that eye color cannot be predicted with certainty using genetic testing, writes the New York Post.