The Mystery of Eye Color

A child's eye color is an individual process that depends on the traits the child inherits from their parents. These traits are located in chromosomes. In every pair of chromosomes, one chromosome comes from the father and the other from the mother. If a child receives traits for blue eye color from both their father and mother, the child will have blue eyes. If the child receives traits for brown eye color from both parents, the child will have brown eyes.

If the child receives a trait for blue and one for brown eye color, the child will usually have brown eyes. Brown color produces more pigment and is therefore dominant. But it is not certain that the child will have brown eyes just because one parent has brown eye color. This is because the parent may carry genes for blue eye color despite having brown eyes themselves. If the child has brown eyes, the trait of blue eye color still exists and can be passed on to the next generation.

Melanin pigment

A child's eye color can also change over time. Some children are born with very dark eyes, blue or gray eyes, which can later change color to brown or green. The color depends on the pigment melanin, which is produced in the so-called stromal cells in the colored part of the eye, the iris. The maturation of melanocytes in combination with stimulation from the sun provides the melanin that then gives color to the iris. If the cells contain a large amount of pigment, the eyes will become brown or black. If they contain little pigment, they primarily reflect blue light. This can be likened to small molecules in the air making the sky look blue.

The newborn baby has immature melanin cells, but production develops continuously. As the child grows, the cells mature, which causes color change. This is often seen around 6 months of age. After 8 months, the child has a more defined eye color, this is known as the iris' true pigmentation.

The final eye color of your child is determined by the individual "recipe" for melanin in the cells' DNA. In newborn babies, the cells have not started "reading the recipe" yet. The process starts when the child first opens their eyes outside the womb. The length of time the process lasts is individual. In some newborn babies, the eyes change color quickly, in others, it takes longer. Generally, the process starts when the pigmentation of the iris changes to its final eye color around 6 to 12 months of age.