Brown eyes account for the vast majority of people, while blue eyes are found in roughly eight to ten percent of the population.
But researchers say green-eyed people have something else in common besides their unusual appearance.
Although there isn’t a single ‘green eye gene,’ scientists have discovered that almost everyone with green eyes shares a fascinating genetic history that stretches back thousands of years, and it all begins with a handful of ancient mutations that spread across Eurasia.
Green eyes are much rarer than most people realize
Eye color is determined primarily by the amount and type of melanin found in the iris.
Brown eyes contain large amounts of melanin, while blue eyes contain very little.
Green eyes sit somewhere in between.
Rather than being produced by a green pigment, the color actually results from a combination of relatively low melanin levels, a yellowish pigment called lipochrome, and the way light scatters through the layers of the iris.
Researchers have found that this combination creates the green appearance people recognize.
Because so many genetic factors have to align for this to happen, green eyes remain exceptionally uncommon worldwide.
According to multiple population studies, only around two percent of people naturally have green eyes, with the highest concentrations found in Northern, Central and Western Europe.
Ireland and Scotland are widely regarded as having some of the highest proportions of green-eyed people anywhere in the world, while the trait is also relatively common in Iceland and the Netherlands.
That rarity has helped fuel centuries of myths about green-eyed people possessing everything from magical powers to mysterious personalities.
Modern science, however, tells a far more interesting story.
It’s far more complicated than one single gene
For years, many people believed eye color was inherited through a simple dominant-versus-recessive system, with brown eyes dominating over blue and green.
Scientists now know the reality is much more complex.
Rather than one gene deciding eye color, researchers have identified several genes that all contribute to the final result.
Among the most important are OCA2 and HERC2, both located on chromosome 15.
The OCA2 gene helps regulate melanin production, while HERC2 acts almost like a control switch, determining how strongly OCA2 is expressed.
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Different combinations of variants in these genes influence whether someone develops brown, hazel, green or blue eyes, although other genes—including SLC24A4, TYR, IRF4 and SLC45A2—also play important supporting roles.
Recent research published in Scientific Reports in 2026 further reinforced that eye color is a polygenic trait, meaning numerous genetic variants work together rather than one single mutation determining the final outcome.
Researchers found that even people carrying the same HERC2 variant can still end up with different eye colors because additional genes influence pigmentation.
That explains why siblings can sometimes have completely different eye colors despite sharing the same parents.
Scientists believe all green-eyed people have one thing in common
While blue-eyed people are often linked to a single ancient founder mutation near the Black Sea, green eyes appear to have emerged slightly differently.
Instead of one identifiable ancestor, scientists believe green eyes developed through a combination of genetic variants that became established in ancient Eurasian populations thousands of years ago.
Ancient DNA studies suggest some of the earliest known evidence for light-colored eyes, including green eye-associated genetic markers, has been found in human remains dating to the Bronze Age in southern Siberia.
Researchers believe those variants later spread westward through population migrations across Eurasia before becoming concentrated in areas around the Caucasus Mountains, the region stretching between modern-day Russia, Georgia, Armenia and Azerbaijan.
The European Journal of Human Genetics has previously reported that certain genetic combinations associated with green eyes are significantly more likely to occur in people with ancestry from the Caucasus than in individuals from Central Asia.
Researchers suggested this is likely due to population-specific genetic variations interacting with the OCA2 and HERC2 genes over thousands of years.
In other words, while not every green-eyed person descends from one single ancestor in the way blue-eyed people may, scientists believe they all inherited combinations of genetic variants that originated within the same broad region of Eurasia before spreading across Europe through migration.
Evolution may have helped keep the rare eye color alive
Exactly why green eyes survived, and remained so rare, continues to fascinate researchers.
Unlike skin pigmentation, where natural selection provided clear survival advantages depending on sunlight exposure, eye color appears to have been shaped by several different evolutionary pressures.
Researchers have suggested that everything from environmental adaptation to sexual selection may have contributed.
One theory proposes that unusual eye colors became attractive simply because they were uncommon.
The European Journal of Human Genetics noted that eye color may have evolved under multiple ‘sexual, cultural, and environmental’ selection pressures rather than one single biological advantage.
That could explain why lighter eye colors became increasingly common across parts of Europe despite offering no obvious survival benefit.
Unlike brown eyes, which dominate globally because they contain more protective melanin, green eyes appear to have persisted largely because the underlying genetic combinations continued being passed down through generations.