Think you’ve got blue or green eyes, think again!
Eye color, like many genetic characteristics, is not always as simple as it once seemed and has several causes. Melanin pigment in our body determines the color of your eyes. More melanin means darker eyes while the smaller amount makes them brighter. The majority of the babies are born with blue eyes and they eventually slowly acquire the right shade, while melanocytes are fully formed.
“Everyone has the melanin in the iris of the eye and in fact, it is the only pigment that gives color,” explains Dr. Gary Heiting to CNN.
The level of melanin also determines the color of our skin and hair. Eye color is an inherited trait and determined by a person’s genes. Most people in the world will end up with brown eyes. The next most common colors are blue and gray, and green is the rarest color.
Besides giving our eyes color, melanin helps protect them from the sun. While all eyes have a sensitivity to the sun’s harmful rays, light eyes are much more sensitive to the sun’s ultraviolet (UV) rays than darker eyes because they have less pigment.
The higher amount of melanin in our eyes means that it absorbs more light and reflects less.
Blue eyes reflect more light at shorter wavelengths of the visible color spectrum. Have you ever noticed how some people’s eyes seem to depend upon the lighting? That sometimes the blue eyes of your loved one look golden brown in the sun? You should know that the color of the eye actually changes depending on the light conditions and the fact that iris has two layers. Sometimes there is pigment in both layers. In people with blue or green eyes, however, the front layer will have very little or no melanin. Depending upon the amount and diffraction of light, their eyes may appear to change colors.
Scientists believe that the migration of our ancestors in colder climates led to the forming of lighter eyes because their melanin was no longer much need for protection from ultraviolet solar radiation.
According to other theories, genetic mutations distinguished production of melanin and led to forming of blue eyes.
Some people have two different eye colors. This results from a condition called heterochromia. It’s very rare but usually harmless. It occurs due to differences in the early stages of iris development.
Only European populations have developed a significant lightening of the pigmentation phenotypes of skin, hair and eye color traits due to genetic selection of multiple genes.