Fascinating and Unusual Facts About Green Eye Color
Among all of my friends, only one has green eyes. Her eyes are the first things you notice when you first meet her. Green is the rarest eye color in the world. However, in some countries, they are common. Lots of people in Iceland have green eyes. In fact, over 80% of Icelanders have either green or blue eyes.
Scientists used to think that eye color is a simple genetic trait. They now believe it is a complex one. This means that the genetic trait for eye color is determined not by a single pair, but by multiple pairs of genes interacting with each other.
Questions This Article Will Answer
- What are the eye pigments?
- What is melanin and why do green eyes appear green?
- Are green eyes genetically determined?
- Are there any personality traits associated with green-eyed people?
1. What Are the Eye Pigments?
Before we dive into why some eyes appear green, let’s get one thing straight. There are no green pigments in the eye!
Let’s define a couple of things:
- Eye Pigmentation: The coloring of a person's eyes, especially when abnormal or distinctive.
- Iris: This is the part that surrounds the pupil and contains the color. The iris controls the dilation and constriction of the pupils. If you shine a light into someone’s eye, his or her iris will contract. This reduces the size of the pupil. This function of the iris is important in terms of regulating the amount of light that enters the eye.
- Lipochrome: Lipochrome is a yellowish pigment responsible for the golden tone in amber eyes.
Eye color depends very much on the amount of pigment on the surface of the iris. It also depends on the way light is scattered inside the eye. Two pigments involved in eye color, which we'll explore further, are Melanin and Lipochrome.
2. What Is Melanin and Why Do Green Eyes Appear Green?
Melanin is a brown pigment that is also responsible for the color of your skin and hair. Before melanin takes effect, the iris usually has a bluish tint to it. This is the reason most babies are born with blue/bluish eyes. Melanin starts creeping into the eye as the baby grows up (around the sixth month after birth).
What Does Melanin Have to Do With Having Blue-Eyes?
Blue-eyed individuals have little melanin and lipochrome on their irises. The blue eye color is caused by a low melanin concentration and the way light is scattered in the iris. This phenomenon of light scattering in the iris is known as Rayleigh scattering.
How Does Rayleigh Scattering Affect the Eye?
Rayleigh scattering happens in the presence of very little melanin. Longer wavelengths of light pass straight through the eye, then they are absorbed at the back of the eye. Shorter wavelengths (blue wavelengths) are reflected and randomly scattered by the opaque layer of the iris. The blue wavelengths are responsible for the blue of the iris. This doesn’t work for brown eyes because they have much more melanin. This absorbs the light.
What Does Melanin Have to Do With Green and Brown Eyes?
People with green eyes have a bit more melanin than people with blue eyes. The green color is from a combination of a blue hue from Rayleigh scattering and “yellow” from the yellow pigment called lipochrome.
The higher the melanin concentration in the iris, the darker the eye color will be. People with brown eyes have high concentrations of melanin on their irises than people with blue or green eyes. That means that everyone with dark eyes have blue ones underneath all their pigments.
3. Are Green Eyes Genetically Determined?
We used to believe that eye color is a simple genetic trait. For example, it was thought that two parents with blue eyes can never have an offspring with brown eyes. This has been repeatedly shown to be wrong. Why?
What Is a Polygenic Trait?
Scientists now believe that eye color is a polygenic trait. That is, a complex trait determined by multiple genes. There are several genes thought to play a role in human pigmentation.
When it comes to genes for melanin production, one that stands out is OCA2. Scientists believe this gene is probably one of the most important genes in determining the amount of melanin to be produced in the iris.
What Is the OCA2 Gene?
The OCA2 gene contains instructions for melanin production. You may look at it like a recipe for melanin production. As we all know, sometimes there is an unexpected change in part of a gene. This is called Mutation. It results in an altered or damaged gene. Some mutations are severe, such as "growing an extra leg" Other mutations are unnoticeable, such as those for green or blue eyes.
Mutation in the OCA2 gene can cause melanin production to shutdown completely, such as in albinism. Or it could be less severe, only reducing the production down to a minimum, such as for green or blue eyes.
4. Are There Any Personality Traits Associated With Green-Eyed People?
Here is an interesting theory you may have already heard about. It is completely based on observation:
People often associated certain eye colors with specific personality traits. Some say that people with blue eyes tend to be kind and sweet. If it is true that people often associated certain eye colors with specific personality traits, then you could wear contacts to alter the way people perceive you. Maybe you should try some blue contacts. It might make you look a little "sweeter." Nevertheless, the connection between eye-color and behavior is not seen as legitimate by the scientific community. Just think about the billions upon billions of people who have brown or blue eyes. How could any of these
Supposed Personality Traits Associated with Eye Color
Egocentric, competitive, skeptical, curious, cautious.
Intelligent, great leaders, Passionate, Mysterious, Creative, Devious, Jealous.
Risk takers, sensitive, outgoing, impulsive, witting, mischievous.
Trustworthy, Outgoing, vivacious, and affable.
Frequently Asked Questions About green Eyes
Are All Green-Eyed People Also Fair-Skinned?
Africa, Asia, Europe, the middle east and the America's have been home to those with green eyes for thousands of years. Iran, Pakistan, Afghanistan, Central Asia, Russia, Spain, and Brazil all have had small populations with green eyes. All races, including Caucasian, African, Asian, Pacific Islander, Arabic, Hispanic, and the Indigenous Peoples of the Americas can have green eyes (though it is rare).
Which Country Has the Most Green-Eyed People?
Light eyes are standard in many northern countries. Sweden, Norway and Denmark have high percentages of light-eyed people. In Finland and Iceland around 90% of people have light eyes (green, grey, and blue).
How Many People in the World Have Green Eyes?
Green Eyes. Green eye color is often confused with hazel eye color, yet is entirely separate and distinct. Green eye color is the rarest color found around the world, and it is estimated that only around 2% of the world's population has green colored eyes.