Green eyes are one of the least common eye colors, with only about 2% of the world's population estimated to have green eyes. People from Northern Europe and Nordic countries such as Finland or Iceland are the most likely to have green eyes. This is thought to be because their genetics are prone to reduced melanin production, the pigment produced by cells that is responsible for dark appearance in skin, hair and eyes. Some scientists believe that all humans originally had brown eyes, and a genetic mutation occurred about 6,000 to 10,000 years ago that affected melanin production and led to the introduction of blue eyes and other variations, such as green or hazel.
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