You may have heard the statement that all babies are born with blue eyes, but it’s not true. The truth is that eye color depends on genetics and a pigment called melanin, while this shade of blue appears to descend from a single ancestor who lived a few millennia ago.
Absolutely not, not all babies are born with blue eyes. In this regard, research has found that more babies are born with brown eyes than blue eyes. Out of a sample of 192 newborns from a diverse cohort, think, 63% had brown eyes while only 20% had eyes of this color.
It is also true that in some countries many babies are born with blue eyes and the color suddenly changes during growth, but this percentage is not reflected in the adult population. The reason is simple: Eye color can keep changing until about the age of two.
This is due to the amount of melanin that develops in a part of the eye called the iris. The presence of a lot of melanin will create brown eyes and, instead, the lack of it will create green, hazel or blue eyes. Blue eye color is actually caused by the Tyndall effect, a phenomenon similar to eye makeup that makes us perceive the sky as blue.
In particular, the iris consists of two layers of cells: the stroma at the top and the epithelium at the bottom. In individuals with blue eyes, the stroma is a translucent layer and contains no pigments due to a genetic mutation and for this reason, when visible light hits it, it scatters the light waves. Blue is more diffuse than other colors because it travels as shorter waves, making blue reflect more easily and making it more visible.
The Tyndall effect also occurs in green eyes, but in this case the stroma contains small amounts of melanin which causes the reflection to appear a different hue. In the meantime you must know that the eyes could reveal our biological age.