determines their eye color. So, the more melanin you have, the darker your eyes appear. Globally, brown is the most common eye color. In the US, 45% of people have brown eyes, while the rarest eye color is green — only 9% of people in the US have green eyes.
But green-eyed people don’t have green-colored pigment in their irises. The color that we see is based on light reflection. Because lighter eyed people have less melanin, their eyes absorb less light. Further, the eye color we see comes from the top of two layers of the iris. No matter a person's eye color, the back layer of everyone’s iris — called the stroma — is made up of brown pigment.
While today we see a rainbow of eye colors throughout the world, that wasn’t always the case. According to the American Academy of Ophthalmology, around 10,000 years ago, humans hadScientists say it was a single genetic mutation that led to the endless variations in eye color you see today.
Scientists speculate that the evolution of eye color paralleled the physical movement of our ancestors from warmer to colder climates. That’s because it's believed that melanin in the eyes also acts a protective barrier from the sun. Brown eyes are seen more frequently in hotter climates — such as Africa and Asia — while in Iceland, for example, brown eyed people are in the minority.
The protective barrier, or lack thereof, can also leave people open to different types of diseases. Research suggests that people with lighter colored eyes — and therefore, with less internal protection from outside sources — are more likely to develop
Interesting article.
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