Many new parents wonder if all babies are born with blue eyes. This is a common misconception. While some babies may have blue or grayish eyes at birth, many infants arrive with other eye colors.
The Truth About Initial Eye Color
It is a myth that all babies are born with blue or gray eyes. While many babies of Caucasian descent may initially have lighter eye colors, this is not the case for all newborns. Babies of African, Asian, and Hispanic descent are more often born with brown or dark brown eyes. A 2016 study of 192 newborns found that nearly two-thirds were born with brown eyes, while only about one in five had blue eyes.
A baby’s initial eye color is influenced by the amount of melanin in the iris at birth. Melanin is a natural pigment produced by melanocytes, which also determine skin and hair color. At birth, melanocytes in the iris may not have fully developed or begun producing melanin, leading to lighter eye colors like blue or gray. This initial lack of melanin production means that the true, stable eye color has not yet manifested.
The Science Behind Eye Color Development
Eye color is a complex trait influenced by genetic and biological factors, primarily the amount and type of melanin within the iris. The production of melanin increases and stabilizes in the months following birth, which can lead to noticeable changes in eye color. This process is why a baby’s eyes might appear blue at first, then darken to green, hazel, or brown as more melanin accumulates.
Genetics play a significant role in determining eye color. While it was once thought that eye color followed a simple dominant/recessive inheritance pattern, multiple genes contribute to this trait. Over 16 genes have been associated with eye color inheritance, with the OCA2 and HERC2 genes on chromosome 15 being key players. The OCA2 gene influences the production of the P protein, which is involved in melanin formation, while the HERC2 gene acts as a regulator, controlling the expression of OCA2.
Eye color change varies among infants. Most significant changes typically occur between 3 and 9 months of age, but the process can continue up to 1 to 3 years, or even longer in some cases. Once melanin production stabilizes, the eye color is largely set. Eye color usually changes from lighter to darker shades, not the reverse.
The final hue of an eye is determined by the amount and type of melanin. Eumelanin produces brown and black hues, while pheomelanin contributes to red and yellow shades. Blue eyes, for instance, have very low concentrations of melanin in the iris. The appearance of blue and green eyes is also influenced by the scattering of light within the iris, a phenomenon similar to the Tyndall effect. This light scattering effect, combined with specific melanin levels, creates the wide spectrum of human eye colors.