Why did we evolve to have eyes

From blue-eyed to brown Why do we have different eye colors?


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The color of the eyes is also included in our passport as a "special feature". There are brown, blue or green - and very rarely there are even people with two different eye colors. How does the color get in our eyes?

By: Susanne Vellmer and Veronika Baum

Status: April 8th, 2020

Most fair-skinned babies born with us are born with blue eyes. Whether a baby inherited his mother's blue eyes or his father's brown eyes does not become apparent until the first few months. Even if both parents have brown eyes.

The color of our eyes is determined by color cells. your name isMelanocytes. These melanocytes are like tubes of paint. You sit in the coloredIris around the black pupil. These tubes of paint press a dye, melanin, into the iris. The least color is needed for blue eyes. If the paint tubes add a tiny bit more color to the iris, the eye turns green. A little more color and the eye will turn brown. With the melanin, which determines the color of the eyes, the eyes protect themselves from harmful sun rays. We also have this color protection for skin and hair.

Blue-eyed? Warning - not quite finished yet!

The paint tubes only start working when the sun protection is also needed: they only start shortly before the birth. So a newborn's eye is not yet fully developed. It just hasn't made a lot of melanin yet. The dye in the eye is also not necessary for vision. In the course of the first year of life, the production of the dye in the dye tubes, the melanocytes, then really starts. Now it becomes clear which eye color the baby has inherited. In some children, the eyes remain blue. The tubes of paint in their eyes produce little dye. But if a blue-eyed baby suddenly gets brown spots in its eyes, it's a pretty sure sign that their eyes will soon turn all brown.

By the way: dark-skinned babies usually have brown eyes when they are born. They produce a large amount of dye during pregnancy. However, even with dark-skinned children, the color of the eyes and the skin change in the course of the first few months: They become darker because more dye is now being formed.

Two-tone? A freak of nature

One eye is blue, one eye is brown? It does exist. But it happens very rarely: it happens in four people in a million. Nor is it a disease, but a freak of nature. Animals, too, such as huskies, sometimes have two different eye colors. The explanation: It is a disturbance in melanin production. Not as much dye was produced in one eye as in the other.