Babies with red hair and blue eyes

If you have the rarest hair and eye color combination, you're one in a million—or more!

If you have dark brown hair and brown eyes, you have something in common with most people around the globe. According to the World Atlas, between 75% and 85% of the world’s population has dark brown or black hair, and 70% to 79% of people have brown eyes. So what are the rarest hair and eye color combinations? To understand that, we need to understand a bit of genetics.

There’s a lot more to it than the simple dominant and recessive traits we learned about in high school biology. Those lessons taught us that different versions of a gene can be dominant (what you see) or recessive (what you don’t see), and they helped explain fun facts like why some people are born with blue eyes versus brown or green.

But that’s a simplistic view of eye color, and determining hair color is even more complex. According to Julie Kaplan, MD, a physician at the Cleveland Clinic’s Center for Personalized Genetic Healthcare, your hair color in particular is tied to variations in a specific gene. Knowing which genes play a role in hair and eye color variation can help us understand why some hues are more common than others. Keep reading to learn what the rarest hair and eye color combinations are, plus other tidbits of information, including facts about redheads.

The rarest hair color

Your father has brown hair. Your mother’s a blonde. And you somehow ended up with flaming red hair. It’s all thanks to a single gene.

The MC1R (or melanocortin 1 receptor) gene helps decide your hair, skin and eye coloring. It sends signals to the melanocytes—cells that create melanin in your body—and depending on your genes, it creates eumelanin (usually associated with darker hair and skin) or pheomelanin (associated with light-colored hair, like red or blond, and fairer skin). In redheads in particular, the MC1R gene doesn’t function the correct way and causes these cells to make mostly pheomelanin, which is barely present in any of the other hair colors. (The lack of melanin also puts redheads at a higher risk for skin cancer.)

“Hair color is a bit more complex than dominant and recessive and is related to variants in the MC1R gene,” says Dr. Kaplan. “There are nine variants described in this gene.”

Red is the rarest hair color, according to Dr. Kaplan, and that’s because so few MC1R variants are associated with the shade. “Only three variants are associated with red hair,” she says. “If a person has two of these three variants, they almost certainly have red hair. If they only have one of the three variants, there is still a greater chance of red hair, though they may be more likely to have strawberry blond. The other six variants can lead to a range of blond to brown hair color.”

So while blondes may have more fun, redheads are halfway to having the rarest hair and eye color combination.

And it’s not just because of MC1R. According to a 2018 study published in Nature, the OCA2 gene, which is important for eye color, also interacts with the MC1R gene and can reduce your likelihood of having red hair.

Another fun fact about redheads? They have a fascinatingly high pain tolerance. “MC1R—the same gene that plays a large role in hair color—also modulates pain sensitivity,” Dr. Kaplan says. “Studies have shown that nonfunctional MC1R, as seen in redheads, yields a higher tolerance to electrical stimulation and increased sensitivity to cold and heat.”

The rarest eye color

Just as the MC1R gene determines your hair color, a single gene, OCA2, is 75% responsible for your eye color, Dr. Kaplan says.

For eye color, the OCA2 gene determines how much melanin is in the iris (the colorful ring around your pupil) by controlling how much P protein is produced. For people with blue eyes (considered a recessive trait), there’s very little P protein. “Two nonfunctional copies of OCA2 yield blue eyes,” says Dr. Kaplan. “If a person has two functional copies of OCA2, they are more likely to be on the spectrum of blue-green-hazel brown.”

But OCA2 isn’t the only gene that has a say in what color eyes you’re born with. There’s HERC2, a gene that controls how the OCA2 gene works, essentially turning P protein production on and off. And there are eight additional genes that play at least a small role in eye color, which makes determining what eye color any particular baby might have extremely hard—even if you try to base it on their parents or grandparents. A pair of blue-eyed parents can still have a brown-eyed child, depending on how all the genes interact.

So what’s the rarest eye color? According to an American Academy of Ophthalmology survey, green eyes are the rarest. Only 9% of Americans have green eyes, compared with 45% who have brown eyes and 27% who have blue eyes.

But it’s not quite that simple.

See, we like to think there’s a rainbow of eye color options out there—violet, blue, gray, hazel, green, brown, near-black—but scientists believe that they’re all slightly different manifestations of blue eyes or brown eyes. “It may seem like green is rare,” says Dr. Kaplan, “but there are many people who have green-brown eyes.”

The rarest hair and eye color combination

What are the rarest hair and eye color combinations? That’d be red hair with blue eyes.

There’s a little genetic tweak that makes the combination of red hair and blue eyes the rarest of them all. The same Nature study mentioned above found that another gene variant, HERC2, interacts with both the MC1R gene and the OCA2 gene—and it can shut off the redhead gene while expressing blue eyes and blonde hair. That makes the blue eye and red hair combination even more unlikely to happen.

In addition, with both red hair and blue eyes being something akin to recessive traits, having parents that are able to pass on two sets of recessive genes is very unlikely. In most cases, you’d have blue eyes and hair somewhere on the spectrum of blond to brown, or red hair with brown, hazel or green eyes.

According to an article by evolutionary biology professor Mark Elgar, PhD, of the University of Melbourne, blue-eyed redheads are the absolute rarest, with 0.17% of the population having that combination of hair and eye color. So if that describes you, you’re most likely one in a million (or more!).

Sources:

• Julie Kaplan, MD, physician at the Cleveland Clinic’s Center for Personalized Genetic Healthcare
• World Atlas: “The World’s Population by Eye Color”
• World Atlas: “What Percentage of the World’s Population Has Brown Hair?”
• Nature: “Genome-wide study of hair colour in UK Biobank explains most of the SNP heritability”
• American Academy of Ophthalmology: “Your Blue Eyes Aren’t Really Blue”
• University of Melbourne: “Are Redheads with Blue Eyes Really Going Extinct?”

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