Humans may appear to have a range of eye colors such as blue and green. But a recent CNN article reveals that, contrary to this perception, all human eyes are brown.
The rationale behind this statement is that eye color is determined by a pigment called melanin, which itself is brown but can appear to be different shades depending on how much of it is present.
As the National Institutes of Health (NIH) explains on its website, “People with brown eyes have a large amount of melanin in the iris, while people with blue eyes have much less of this pigment.”
The difference in color is the result of how much light is absorbed versus reflected out. Eyes with the least amount of melanin reflect the most light which can appear blue, whereas eyes with more of the pigment tend to appear green, hazel or brown.
The NIH also points out that, “While a child’s eye color can often be predicted by the eye colors of his or her parents and other relatives, genetic variations sometimes produce unexpected results.”