Brown Eyes: The World’s Most Common and Dominant Eye Color

Brown eyes are the most common eye color in the world, worn by an estimated 70–80% of the global population. Far from being ordinary, this deep, rich color is genetically dominant and comes with several unique advantages, including protection against harsh sunlight and a lowerrisk for certain eye diseases.

Yes, brown eyes are dominant, in the sense that varying shades of brown eyes are the most common eye color. Genetics also make them the most common eye color.

When comparing the genes that determine eye color, the gene for brown eye color is always the dominant trait over the gene for blue or green eyes.

To put it simply, brown eyes are caused by genes that are passed from biological parents. Genes make up a part of your DNA that work as instructions to determine your makeup as a human. DNA and all the genes within it are housed within chromosomes.

Every eye color results from a melanin combination produced in the iris (the colored part of the eye). Melanin is a substance in the body that gives it pigmentation. It’s produced by cells called melanocytes.

While all humans have the same number of melanocytes, the amount of melanin they produce varies. For example, a person who produces more melanin will have darker skin, eye, and hair color, whereas someone who produces less melanin will have lighter features.

The level of melanin reflected in the iris — that ultimately determines eye color — is controlled by two main genes:

• EYCL1has one gene variation (called an allele) for green eyes and one allele for blue eyes. In other words, this is the “light eye color” gene. In mapping for eye color, EYCL1 is represented asb.

• EYCL3has one allele for brown eyes and one allele for blue eyes. Because brown is dominant, EYCL3 is known as the “brown eye color” gene and is represented asB.

Every person receives one chromosome from each parent. So, if both parents have eyes that are brown ( B ), they would likely produce a brown-eyed child. It’s possible their kids could inherit BB : one B from each parent.

But genes are tricky, especially if one or both parents have different alleles ( BB with bb or Bb ). For example, it’s also possible for two brown-eyed parents to have a child with blue eyes. The chart below illustrates the different combinations that can happen when determining eye color.

Here’s a fact that surprises most people: almost every person in the world has brown pigment in their eyes.

The iris is made up of two layers. The back layer, called the pigment epithelium, always contains brown pigment (melanin) in nearly everyone, regardless of their outward eye color.

Brown eyes appear brown because the front layer of the iris (the stroma) is also rich with this brown-colored pigment. Lighter eyes, like blue and green, have less or no pigment in this front layer, which allows light to scatter and reflect the lighter colors.

When looking at the world population, it’s predicted that 70-80% of people have eyes that are brown. This is a pretty significant number when you consider the second most common eye color, blue, only makes up 8-10% of the global population.

Researchers have suggested that at one time — around 10,000 years ago — all human eye color was brown. Lighter eye color only emerged after a common ancestor had a genetic mutation that affected their eye color. This mutation is thought to have reduced melanin production in the iris, leading to lighter eyes.

“Brown eyes” is a general term to describe any eye color on the brown color spectrum. It encompasses many different shades of brown.

While some eye color names are open to interpretation — what some call “honey,” others may call “gold” — the following are some of the most common (and agreed-upon) shades:

Light brown eyes

• Honey– A light, almost golden shade of brown. May sometimes be mistaken for hazel eyes.

• Cognac– A little darker than honey with more red tones. May also be called amber eyes.

Medium brown eyes

• Chestnut– A warm-toned brown that is light enough for the pupil to be clearly visible.

• Russet– A cooler-toned brown that is slightly darker than chestnut, but the pupil is still visible.

Dark brown eyes

• Chocolate– A cool- or warm-toned dark brown in which the pupil can be difficult to see.

• Black-brown eyes– Pigment is deep enough that eyes may appear black, and the pupil is not easily visible.

All shades — from honey to deep brown and everything in between — are beautiful.Soembrace your brown eyes in whatever shade they are. They have otherperksbesides a stunning appearance!

Brown eyes arefrequentlyconfused with similar-looking shades, particularly hazel and amber. However, their physical makeup is what sets them apart:

• Hazel Eyes:Unlike brown eyes, which are a uniform color,hazel eyesare a multi-tonal mix of colors, typically containing flecks of brown, green, and gold. This multi-color appearance is due to the melanin being unevenly distributed across the iris.

• Amber Eyes:Amber eyesare a rare, solid golden hue caused by a concentration of the light reddish-yellow pigment, pheomelanin, which gives them a distinct yellowish-gold tint. Brown eyes are darker because they contain more eumelanin (the dark pigment).

• The Defining Feature:Brown eyes have a high concentration of melanin in the stroma (the front layer of the iris) and are defined by a single, uniform color. Hazel and amber eyes have far less melanin in this layer, allowing for the multi-colored or lighter appearance.

Research on traits linked to eye color has found that having darker eyes brings its fair share of advantages. Below are a few interesting facts about life with brown eyes.

People Whose Eyes Are Brown Are Viewed as More Trustworthy

In one study, researchers presented 80 photographs of different faces (40 males and 40 females) to participants. The participants were then asked to rate the person in each photo for how trustworthy they looked.

Of the different variations of sex and eye color, men with brown eyes were rated the most trustworthy. While the reasoning behind it is still being investigated, being perceived as trustworthy is certainly an advantage.

Brown-Eyed People Are Less Sensitive to Sunlight

Brown eyes are darker than other eye colors because their cells develop more pigment (melanin). Melanin can act as a shield by absorbing or blocking harsh light, which makes eyes with more melanin less sensitive to the sun. This is why brown eyes are even more prevalent in parts of the world with sunny climates, such as Africa and Asia, where the extra melanin provides a critical shield against harsh light.

However, some studies suggest people with darker eyes are almost twice as likely to develop cataracts. One of the biggest contributors to cataract development is unprotected UV exposure. So, whether bright light from the sun bothers you or not, it’s important to protect your eyes by wearing quality sunglasses outdoors.

Brown-Eyed People Are Less Susceptible to Certain Diseases

Experts in the eye care industry have found that people with dark eyes are less likely to get certain eye conditions such as diabetic retinopathy, eye cancer, and macular degeneration. It’s still unclear as to why this is, but it’s believed that the extra melanin acts as a protective barrier for the eye.

Regardless of how your eye color might affect your risk of developing eye disease, it’s important to have annual eye exams . By seeing your eye doctor for regular check-ups, you can help ensure your future eye health.

SOURCES

1. Genetics of eye color. News Medical. September 2019.
2. Genetics. National Institute of General Medical Sciences. May 2022.
3. Melanin: What it is, types & benefits. Cleveland Clinic. March 2022.
4. The world’s population by eye color. World Atlas. January 2023.
5. Myth or fact: Blue eyes are more sensitive to light. Duke Health. July 2021.
6. 8 things you might not know about cataracts. American Academy of Ophthalmology. May 2020.