The distribution of eye color around the world: what human genetics reveals

Eye color is one of the most visible physical traits in humans. Blue, brown, green, hazel, or gray: this diversity fascinates and often raises the same question: why are some eye colors more common than others depending on the region of the world? 

The answer lies at the intersection of genetics, population history, and evolution.

Eye color: a matter of melanin

Eye color mainly depends on the amount and distribution of melanin in the iris.

High levels of melanin → dark eyes (brown, black)
Low levels of melanin → light-colored eyes (blue, green, grey)

Contrary to popular belief, there is no single “blue-eye gene” or “brown-eye gene.” Several genes interact, which explains the wide range of shades and the genetic surprises that can occur within the same family.

Brown Eyes: The Dominant Color Worldwide

Brown eyes are by far the most common eye color on the planet. It is estimated that about 70 to 80% of the world's population has dark eyes.

They are in the majority in:

Africa
Asia
Middle-East
South America
southern Europe

From an evolutionary standpoint, higher melanin levels provide better protection against ultraviolet (UV) radiation, an advantage in regions with strong sunlight.

Blue eyes: a relative rarity

blue eyes are found in approximately 8 to 10% of the world's populationThey are particularly common in:

Northern Europe (Scandinavia, Baltic countries)
Eastern Europe
Certain regions of the British Isles

Scientists believe that all current blue eyes descend from a single genetic mutation that appeared about 6 to 000 years ago, probably in the Black Sea region.

Green eyes: the rarest eye color

Green eyes accounting for about 2% of the world's populationThey are mainly found:

In Europe (Ireland, Scotland, Central Europe)
Among certain populations in the Middle East

This color results from a very specific balance between low melanin levels and light scattering, which explains its rarity.

Other colors and variations

Hazel eyes : a mix of brown, green, and sometimes golden tones; common in Europe and the Middle East
Grey eyes : similar to blue eyes but with a different iris structure
Amber eyes : a golden or copper hue; quite rare but present in various regions

There are also special cases such asheterochromiawhere a person has two eyes of different colors or several colors in the same eye.

An Evolving Diversity

With migration, intermixing, and globalization, the distribution of eye colors is constantly changing. Genetic boundaries are becoming increasingly blurred, and diversity is growing, especially in large urban areas.

Conclusion

The global distribution of eye color reflects our evolutionary and cultural history. While brown eyes remain largely dominant, rarer colors continue to fascinate and remind us of the richness of human diversity, right down to our gaze.