Many people wonder if all babies are born with blue eyes. While it is a common observation that many newborns have blue or grayish-blue eyes, this is not a universal truth. For a significant number of infants, this initial eye color is not permanent and will change as they develop.
Initial Eye Color at Birth
The common appearance of blue or grey-blue eyes in newborns, particularly those of Caucasian descent, is due to the limited presence of melanin in the iris at birth. Melanin is the pigment that gives color to our eyes. The iris contains specialized cells called melanocytes that produce and store melanin.
At birth, these melanocytes have not yet fully produced and distributed their melanin. When light enters an iris with very little melanin, it scatters off the clear fibers within the iris, creating a blue appearance. Babies born with darker skin tones often have more melanin present in their irises from birth and may be born with darker eyes like brown.
How Eye Color Develops and Changes
Eye color often changes during a baby’s first few months and years. Most noticeable shifts occur between 6 and 12 months, but the process can continue up to three years. As a baby is exposed to more light after birth, the melanocytes in the iris begin to produce and store more melanin.
The amount and type of melanin produced directly influence the resulting eye color. Increased melanin production leads to darker eye colors. Moderate melanin results in green or hazel eyes, while a high concentration results in brown eyes. Once a baby’s eye color has changed and deepened, it does not revert to a lighter shade.
The Role of Genetics in Eye Color
A baby’s eventual eye color is largely determined by genetic factors. Eye color is considered a polygenic trait, meaning multiple genes work together to influence the final outcome, rather than being controlled by a single gene. This complex inheritance pattern explains why a child’s eye color can differ from that of their parents.
Key genes involved include OCA2 and HERC2, located on chromosome 15. The OCA2 gene plays a significant role in melanin production, while the HERC2 gene influences OCA2’s expression and activity. The specific combinations of these genes affect the amount and distribution of melanin in the iris, which dictates the baby’s adult eye color.