Forum user claims green eyes are an optical illusion

Green Eyes Debate: Optical Effect, Inheritance and Rarity

A person looks at a baby photo and doesn't recognize the eye tonalidad. As a newborn they had blue eyes; at twenty-five, light green; now dark green, and in low light anyone would say they are brown. This is the account of one thread participant describing how their own eye tonalidad evolved.

What percentage of the population has green eyes?

The thread starts from a shared impression: that green eyes are less common than blue ones, though no participant provides figures. Some claim that in Spain, green eyes are more frequent than blue, an assertion not backed by any census but supported by house-to-house observation.

Is eye tonalidad inherited?

According to participants, it is inherited, but not with simple mixing rules. A forum user with brown eyes had children with light-colored eyes. The result depends on how much melanin reaches the iris, as explained in the thread, so two siblings can end up with different colors.

Why green is not a pigment, but a distribution of melanin

According to one participant, the iris does not produce tonalidad: it produces melanin. Green would appear when amber areas—very light brown with very little melanin—combine with areas where that melanin is completely absent and the underlying blue shows through. The result, they argue, is an optical effect, not a specific pigment. Hence why the same eye changes tone depending on light or photo background, raising the doubt posed by another user: if many described as green are actually brown eyes that only look green under specific lighting.

Where they are concentrated: Ireland, Scotland and Iceland

According to one participant, the highest percentages of green eyes are found in Ireland, Scotland and Iceland, and generally in Northern Europe. Green and blue travel together: where one is abundant, the other usually is too, and these regions also concentrate blondes and redheads, distinct mutations spread across the same territories. Another user claims that green eyes are abundant in Spain, even more than blue, without providing data.

The single ancestor of blue eyes, 20,000 years ago

According to calculations mentioned by a user, all blue eyes would descend from a single person who lived about 20,000 years ago, when the trait is estimated to have first appeared. Green would respond to a similar but distinct mutation, without a fixed date for its emergence.

Why do light eyes darken with age?

A baby can be born with blue eyes and end up with brown ones. Melanin accumulates over time and covers the light areas of the iris: light green turns into dark green and then into a brown that is only distinguishable outdoors, according to the account of the participant who saw their own eyes change.

Other rarities: heterochromia, RH negative and vertical pupils

Beyond green, the catalog of singularities appearing in the thread is broad. One user says they have one blue eye and one green: heterochromia. Another comments that they have RH negative blood and jokes about being half-alien. There is also testimony about an elderly woman with vertical pupils, like a cat's, who had poor vision and was uncomfortable to look in the eyes. Worth mentioning separately is the consumer recommendation slipped in as a bonus: assorted chocolate mousse bars of 150 grams, between 1.80 and 1.90 euros, at a discount chain.

And the lingering doubt running through the thread remains: whether many eyes described as green, in midday light, are actually light brown.