No two people’s eyes are exactly the same color
Not unlike snowflakes and fingerprints, human eyes are never exactly alike from person to person — in terms of color, that is. While brown may be the most common eye color, there are so many shades of it — not to mention blue, green, and other hues — that no two irises are identical, even among identical twins.
Eyes get their color from the two-layered iris, with the back layer (officially known as the pigment epithelium) almost always containing brown pigment. The amount of pigment in the front layer (stroma) usually determines a person’s eye color — a lot of brown pigment results in brown eyes, whereas people with blue eyes have no pigment at all in their stroma. Those with just a bit of pigment end up with green or hazel eyes. And there’s always just the tiniest amount of variation in the results: If you’ve ever tinkered with a color slider, you’ll have a better understanding of how rare it is for any two colors to actually be the same, even if the difference between them is so minute as to barely be detectable by, well, the naked eye.
Then there’s heterochromia — when one person has eyes of two different colors. Complete heterochromia is when both eyes are different (one brown and one blue, for example), while sectoral heterochromia is when one section of the iris is different from the rest. Central heterochromia is when the iris has a ring around it that’s different. Though it can sometimes be a sign of an injury or other condition, heterochromia is most often a harmless — and cool-looking — genetic anomaly.
Numbers Don’t Lie
Light-sensitive cells in the human eye
107 million
Times a person blinks per minute
14-17
Main eye colors (brown, amber, green, hazel, blue, gray)
6
Estimated number of colors most people can see
1 million
THINK TWICE
More than 50% of the worldwide population has brown eyes.
Brown is the most common eye color, and by a lot — more than 50% of all people worldwide have brown eyes, including 45% in America. In the U.S., blue eyes are in second place at 27%, followed by hazel at 18%, and green at 9%. All other eye colors account for just 1% of the domestic population. The numbers are quite different elsewhere, with blue being the most common eye color in countries such as Iceland (75%) and the Netherlands (61%), whereas brown eyes are even more dominant in Uzbekistan (91%) and Armenia (80%).
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