Did you know that only eight percent of the world’s population has blue eyes? Brown eyes are far more common worldwide, while those with blue eyes are far rarer. Here are five eye-opening facts about blue eyes that you may not have known!
1. Everyone with blue eyes has a common ancestor
According to researchers at the University of Copenhagen, roughly 6,000 to 10,000 years ago a harmless genetic mutation in a baby born in Europe led to the development of blue eyes.
According to researchers, this was the first person with blue eyes, therefore they believe everyone who has blue eyes today is a very distant relative of this person.
"Originally, we all had brown eyes," said Hans Eiberg, associate professor in the Department of Cellular and Molecular Medicine at the University of Copenhagen. "But a genetic mutation affecting the OCA2 gene in our chromosomes resulted in the creation of a 'switch,' which literally turned off the ability to produce brown eyes."
A person’s eye colour depends on the amount of a pigment called melanin, that lives in the iris of the eye. This genetic switch limits how much melanin is produced in the iris — effectively "diluting" brown eyes to a shade of blue.
2. Blue eyes at birth doesn’t mean you’ll have blue eyes for life
At birth, babies may be born with blue eyes but this does not mean that they will have blue eyes for life! How can this be? Human eyes don’t have their full amount of melanin pigment at birth. Melanin is the pigment that determines the colour of our eyes, skin and hair and develops over time.
A child's eye colour can change as more melanin is produced in the iris during early childhood. This colour transition can take anywhere from a few months to three years to fully develop.
3. You can't predict if a child will have blue eyes
If both parents have blue eyes it is assumed that their child would also have blue eyes, or so we thought. Previously, it was believed that eye colour, blue eyes included, was a simple genetic trait. Many believed that you could predict a child’s eye colour based on the parents and even the grandparent’s eye colour.
Geneticists have now discovered that as many as 16 different genes and even the anatomic structure of the iris can influence eye colour to some degree.
4. Blue eyes aren't actually blue
The colour of our eyes depends on the amount of melanin pigment that is present in the iris, and melanin is actually brown by nature.
Brown eyes have the most amount of melanin pigment in the iris, while blue eyes have the least. Brown melanin is actually the only pigment that exists in the eye! For those who have hazel, green or blue eyes there is no pigment. Eyes only appear to be these colours because of the way light strikes the layers of the iris and reflects back toward the viewer.
5. Blue eyes are more sensitive to light
Do you have blue eyes? If you do, you may have experienced sensitivity to light.
Melanin in the iris of the eye helps to protect the back of the eye from damage caused by UV rays and blue light from the sun and artificial sources like screened electronics.
Since blue eyes contain less melanin, they may be at a higher risk of sensitivity to light.
It is especially important for blue-eyed people to protect their eyes from the sun’s UV rays. It is recommended to stay out of the sun for long periods of time and to wear protective eyewear when you are outdoors. Be sure to wear sunglasses that block 100% UV.