Eye color is complicated. But until a few years ago, few scientists described it that way. As recently as the aughts, it was believed that eye color was determined by a single gene — brown, dominant; blue, recessive. It’s a rule many may remember from high school biology class when studying Gregor Mendel, considered the father of modern genetics. But recent research has helped makes things much clearer. In fact, eye color is determined by multiple genes. And, further, eye color is as specific to an individual as a thumbprint.
In one of the most recent studies, published in Science Advances in March 2021, a team of researchers out of King’s College in London who looked at the eye color of 195,000 people and determined there are dozens of genes for eye color. “[Our eye color is] one of the most striking features of the human face,” says Pirro Hysi, an ophthalmologist at King's College and one of the study's authors. The findings not only give us a better glimpse into understanding eye color but the research is expected to help scientists find cures for eye diseases such as pigmentary glaucoma and ocular albinism.
The eyes have “mystified generations throughout our history,” says Hysi. In fact, it wasn’t until a breakthrough study published in 2007 that our perceptions about the complexity of the eye and its colors really paved the way for greater research. Researchers at The University of Queensland's Institute for Molecular Bioscience (IMB) and the Queensland Institute of Medical Research dispelled the notion that eye color was based on one gene.
Now, this most recent study has determined that there are at least 61-genes for eye color. Beyond that, the study authors say eye color is completely individualized. That is, no one else has your specific eye color. But what is your eye color, really — and where did all these seemingly-infinite shades come from in the first place?
Eye Color101
The amount of melanin, or pigment, a person has in their iris determines their eye color. So, the more melanin you have, the darker your eyes appear. Globally, brown is the most common eye color. In the US, 45% of people have brown eyes, while the rarest eye color is green — only 9% of people in the US have green eyes.
But green-eyed people don’t have green-colored pigment in their irises. The color that we see is based on light reflection. Because lighter eyed people have less melanin, their eyes absorb less light. Further, the eye color we see comes from the top of two layers of the iris. No matter a person's eye color, the back layer of everyone’s iris — called the stroma — is made up of brown pigment.
While today we see a rainbow of eye colors throughout the world, that wasn’t always the case. According to the American Academy of Ophthalmology, around 10,000 years ago, humans had only brown eyes.
Where Did All the Other Colors Come From?
Scientists say it was a single genetic mutation that led to the endless variations in eye color you see today. Since eye color is determined by the amount of melanin in a person's body (as it is, too, for hair and skin color), researchers believe the addition of a new slew of colors, such as grays, blues, greens and hazels, was caused by a change in the gene that produces melanin; that mutation, scientists have surmised, reduced the production of melanin in theiris. And further, the mutation can be linked to a single, common ancestor.
Scientists speculate that the evolution of eye color paralleled the physical movement of our ancestors from warmer to colder climates. That’s because it's believed that melanin in the eyes also acts a protective barrier from the sun. Brown eyes are seen more frequently in hotter climates — such as Africa and Asia — while in Iceland, for example, brown eyed people are in the minority.
The protective barrier, or lack thereof, can also leave people open to different types of diseases. Research suggests that people with lighter colored eyes — and therefore, with less internal protection from outside sources — are more likely to developmacular degeneration, cancer of the eye ordiabetic retinopathy. But brown-eyed people are not free from eye issues, either. Those with darker colored eyes have a higher risk of gettingcataracts, a clouding of the lens caused by a breaking down of ocular proteins over time.
Blue-Eyed Babies and Other Myths
Doesn't it seem like babies are just naturally born with crystal-clear, blue eyes? Not so, say researchers at Stanford University who studied the prevalence of blue eyes in newborns. According to the 2016 study,two-thirds of new borns are born with brown eyes and only about 20 percent are blue eyed. What's more, many of those babies lose the blues within months of birth. And, the researchers also note, the majority of babies born with blue eyes are white; most Asian and Hispanic newborns are brown-eyed.
That said, if you’re a brown-eyed couple with a blue-eyed child, it wasn’t necessarily the work of the proverbial mailman. While Mendel’s rules may have led us to believe brown-eyed parents can’t have blue-eye babies, science can show us otherwise.
FAQs
Eyes with a higher concentration of melanin absorb more light, so less light is reflected back- resulting in a dark brown iris. With lower concentrations of melanin, less light is absorbed, so more is reflected back- resulting in a green, blue or hazel color.
What is the colour of your eyes question and answer? ›
The correct answer is Iris. The pattern of brown and red pigment, collagen fibres, and the topography of the iris determines the colour of the human eye. Iris is the coloured area at the front of the eye. It is about 12 millimetres in diameter and has an opening in the middle and is called the pupil.
How do you explain eye color? ›
Eye color is directly related to the amount of melanin in the front layers of the iris. People with brown eyes have a large amount of melanin in the iris, while people with blue eyes have much less of this pigment. A particular region on chromosome 15 plays a major role in eye color.
What is the rarest eye color? ›
Of those four, green is the rarest. It shows up in about 9% of Americans but only 2% of the world's population. Hazel/amber is the next rarest color after green. Blue is the second most common and brown tops the list, found in 45% of the U.S. population and possibly almost 80% worldwide.
Can 2 brown eyed parents have a blue eyed child explain your answer? ›
If both the parents have brown eyes, then there is generally a 25% chance for their child to have blue eyes. Because both the brown-eyed parents have a recessive blue-eye gene and can pass it to the next generation. However, since eye color is polygenic, several other genes exert their effects as well.
What eye color is most common? ›
According to estimates, 70–79% of the world's population have brown eyes, making it the most common eye color worldwide. In fact, the American Academy of Ophthalmology (AAO) state that everyone on Earth had brown eyes around 10,000 years ago.
Are my eyes green or hazel? ›
Green eyes tend to have a mostly solid green color throughout the iris (the colored part of the eye). Hazel eyes, on the other hand, are multicolored. For instance, if you have green eyes with brown or gold flecks or a gradient of green, brown, and gold, then you have hazel eyes.
What is the prettiest eye color? ›
One thing these survey results have in common is that light-colored eyes — green, gray, blue, and hazel — are named as the most attractive eye colors in the world. In one large survey of more than 66,000 people, green was chosen as the most attractive eye color.
Do purple eyes exist? ›
Red and violet
Although the deep blue eyes of some people such as Elizabeth Taylor can appear purple or violet at certain times, "true" violet-colored eyes occur only due to albinism. Eyes that appear red or violet under certain conditions due to albinism are less than 1 percent of the world's population.
Are my eyes grey or blue? ›
Gray eyes may be called “blue” at first glance, but they tend to have flecks of gold and brown. And they may appear to “change color” from gray to blue to green depending on clothing, lighting, and mood (which may change the size of the pupil, compressing the colors of the iris).
People with albinism have little or no melanin in their eyes. When they have very little melanin in their irises, they can have very pale blue or gray eyes. When there's no melanin in either layer of their irises, the blood vessels in their retinas are a lot more visible, making their eyes look pink or red.
Do red eyes exist? ›
Of the less common eye colors, pink and red eyes are considered to be the most unique in the world, giving new meaning to the word “rare.” Only one in every 20,000 people have a form of albinism, according to the National Institutes of Health, and even fewer have red-tinted eyes.
Are grey eyes rare? ›
When it comes to global numbers, multiple internet sources estimate around 3% of people worldwide have grey eyes—a rarity indeed! But not enough large-scale studies have been done to provide more accurate numbers. So, it's impossible to say exactly how many people have grey eyes.
Can Asians have blue eyes? ›
So while many Asians do have the “blue-eyed allele”, blue eyes themselves are still quite rare.
Do blue eyes skip a generation? ›
But what happens if a child has blue eyes and his parents both have brown eyes? The child inherited two blue genes; although neither parent had blue eyes, it was still part of their DNA. Blue eyes can skip a generation. In other words, this child's grandparents' eyes were probably blue.
Do grandparents' eye colors affect babies? ›
If you notice one of the grandparents has blue eyes, the chances of having a blue-eyed baby go up a bit. If one parent has brown eyes and the other has blue eyes, odds are about even on eye color.
What is the color of my eye? ›
Irises are classified as being one of six colors: amber, blue, brown, gray, green, hazel, or red. Often confused with hazel eyes, amber eyes tend to be a solid golden or copper color without flecks of blue or green typical of hazel eyes. Blue eyes have a low level of pigment present in the iris.
What is the color of your eyes an example of? ›
The color of the eyes is an example of an inherited trait because the color of the eyes is determined by the genes that a person inherits from their parents. Each gene has different forms known as alleles that determine specific traits.
How do we see color with our ________ and eyes? ›
The human eye and brain together translate light into color. Light receptors within the eye transmit messages to the brain, which produces the familiar sensations of color.
What is the color of a person's eye a part of answer? ›
Iris is the part of the eye which colours the eyes.
