Where Does Eye Colour Come From?

Have you ever caught someone’s gaze and wondered why their eyes look so different to yours? Some shimmer like the sea, others glow warm and dark like polished wood. Eye colour is one of those traits that feels deeply personal — yet it’s also a shared chapter in the story of human evolution.

Believe it or not, all of us trace back to ancestors who once had brown eyes. So where did blues, greens and greys come from? The answer lies in pigment, light, and the remarkable adaptability of the human species.

Eye Colour = Melanin 👁️

At the heart of eye colour is melanin, the natural pigment that gives colour to our hair, skin, and eyes. The more melanin your iris contains, the darker your eyes appear. Brown eyes are rich in melanin. Blue and green eyes, on the other hand, have much less — so little, in fact, that their colour comes from how light scatters within the iris rather than from pigment itself.

That scattering effect is called Rayleigh scattering — the same reason the sky looks blue. In a sense, blue eyes are an optical illusion, created by light bouncing around inside the iris rather than by any blue pigment. Fascinating, isn’t it?

The exact shade of your eyes — whether deep brown, amber, hazel, grey or turquoise — depends on a complex mix of genes. Scientists have identified several key genes, like OCA2 and HERC2, that influence how much melanin is produced and where it’s stored in the iris.

Brown = Most Melanin, More Protection 🌞

Brown eyes are the oldest and most common eye colour on Earth. Around 70–80% of the global population has them. That’s because dark eyes evolved first, offering an evolutionary advantage in sunny climates.

Melanin acts like a natural sunblock. It absorbs light and shields the delicate tissues of the eye from harmful ultraviolet rays. For our ancestors living in Africa, Asia, and the Middle East — regions with intense sunlight — darker eyes helped protect vision and reduce glare.

Even today, brown-eyed people tend to have better natural protection against bright light and certain eye conditions related to UV exposure. In short: brown eyes weren’t just beautiful — they were practical.

Blue = Less Melanin, More Light Sensitivity 💡

Blue eyes, by contrast, are a more recent development. Genetic research suggests that every blue-eyed person alive today shares a common ancestor who lived roughly 6,000 to 10,000 years ago — likely near the Black Sea region.

A small mutation in the HERC2 gene essentially “switched off” the melanin production in the iris. The result was blue eyes — and that trait spread as humans migrated north into Europe, where sunlight was weaker and there was less need for heavy UV protection.

While blue eyes can appear striking and luminous, they also come with trade-offs. People with lighter eyes often experience more glare and are slightly more sensitive to bright light. However, in dimmer environments, such as the long winters of northern Europe, those same eyes may have offered better contrast vision and light perception.

Evolution, as always, balanced beauty with function.

Green, Grey and Hazel – Nature’s Middle Ground 🌿

Not everyone fits neatly into the brown-or-blue divide. Green, grey, and hazel eyes sit beautifully in between — the result of moderate melanin levels and subtle structural differences in the iris.

Green eyes, for example, are rare, found in only about 2% of people worldwide. They’re most common in Northern and Central Europe, especially in Celtic regions like Ireland and Scotland. The green hue occurs when a small amount of melanin combines with the way light scatters through the iris, producing a luminous jade tone.

Hazel eyes shift in colour depending on the light — sometimes brown, sometimes golden green. That variation reflects a layered mix of melanin concentrations across the iris, like a painter’s brush blending tones.

Your Eyes = Part of Human Evolution ✨

Our eyes are so much more than windows to the soul — they’re maps of human history. Every shade tells a story of adaptation: of sunlight and shadow, migration and mutation.

When you look in the mirror, the colour of your eyes connects you to countless generations before you — from the first humans walking under the African sun to the early settlers exploring the icy north.

Even today, eye colour continues to evolve. New gene combinations emerge, and scientists continue to learn about the subtle interactions that create every unique hue. It’s a reminder that evolution never really stops — it’s still at work in every one of us.

So next time someone compliments your eyes, remember: they’re looking at thousands of years of history.