Human eye color has always been fascinating and mysterious. Babies are usually born with blue eyes. Those mostly change within the first three years to other colors. Some people have different colored eyes; they were celebrated back in July with “Different Colored Eyes Day.” Some emotions can cause the eyes color to change, such as when you’re angry.
Scientists still don’t know why some people’s eyes are a certain color. It is known that human eye colors originate with three genes, obviously passed down from your parents. Thing is, only two of those three genes are understood. Those two give people the common eye colors of green, blue, and brown. But scientists don’t understand why other people have gray, hazel, or eyes with multiple colors in them.
Back in the 60s the common thinking was that brown eyes were “dominant” gene traits and blue eyes were “recessive,” but that’s too simplistic. Eye colors don’t turn out to be a blend of your parents’ eyes. Really, the only predictor is if the parents both have brown eyes, then the baby will likely also have brown eyes. Dark colors dominate more, so brown wins out over green, which wins out over blue.
Baby eyes are interesting in themselves. Most babies are born with blue eyes and everyone watches to see if those eyes are going to another color. This darkening is due to melanin, just like in the skin. Babies don’t have melanin in their eyes at birth, but it develops with age and can make the eye color darken.
Some children are born with irises that don’t match in color. This can be caused by trauma in the womb or shortly after birth, a benign genetic disorder, or a developmental issue in the transport of pigment. Although, an eye doctor should check this, there is usually nothing serious about the condition. Hence, you get Kate Bosworth with her one hazel eye and one blue eye.