Eye color

5 Fascinating Facts about Eye Colour

Many spies in movies need only their eyes to enter highly classified areas. As the spy approaches a top-secret room, a laser beam shines into the spy's eye, scanning it to verify identity.


Amazingly, eye recognition technology like this actually exists. It's one of the most reliable and hard-to-fool identification methods, and it works because our irises are unique and unchanging.


The iris is the pigmented part of the eye. Even if you don't want to gain entrance to top-secret government rooms, you probably consider your irises and their colour a big part of your identity. Get to know your irises better by discovering five fascinating facts about eye colour.

1. All blue-eyed people are related.

Blue eyes are among the least common in the world (but they are more common in people with European ancestry). A recent study gives greater insight into why blue eyes are so rare.


In 2008, researchers in Denmark completed a study that shows all blue-eyed people share a common ancestor. The common ancestor would have had brown eyes, but he or she carried the first genetic mutation for blue eyes. That gene spread to the carrier's descendants over many generations. Eventually, two carriers of the blue-eyed gene had the first baby who kept blue eyes for life.


The first blue-eyed gene carrier lived somewhere between 6,000 and 10,000 years ago. Today, he or she has approximately 300 million descendants who have the genetic code for blue eyes in their DNA.


2. Women's eye colour may indicate their pain tolerance.
If you're a woman, whether you have light or dark eyes may indicate your pain threshold. Results from a small study show that women with light eyes (blue or green) experience a less dramatic response to pain than those with darker eye colours (tan and brown).


This might seem like a strange experiment to conduct, but it's grounded in genetics. Several of the genes related to melanin (the pigment that creates eye and skin colour) also affect our pain response.


This research came out in 2014, and the study involved only 58 women. Scientists need to conduct further research to learn more about the link between eye colour and pain tolerance. But for now, these results are intriguing and encouraging.


3. Your eye colour may indicate your risk for skin problems.
A study from 2010 shows that some skin conditions occur less often in people with blue or brown eyes. Researchers looked at 3,000 people with vitiligo, a skin condition that reduces pigmentation on small patches of skin. The 3,000 people studied also have non-Hispanic European ancestry.
Researchers noticed that the eye colour distribution among those studied differs significantly from a wider population with the same ancestry. Among those with vitiligo, 43% have brown or tan eyes. On a wider scale, only 27% of people with non-Hispanic European ancestry have brown eyes.


What does this mean for your skin? If you descend from the same ancestry and have blue eyes, you stand a lower chance of having vitiligo. And if you come from that group and have brown eyes, your chances of getting melanoma diminish. A genetic predisposition for either vitiligo or melanoma usually accompanies a lower chance of having the other.


4. You can have two different eye colours.
This trait is very rare in humans, but it does happen. People with this trait, called heterochromia, either inherit it from someone in their family or get it later in life after an eye injury or disease causes it. One of your eyes could change colour due to:

  • Bleeding
  • Glaucoma
  • Inflammation
  • Eye trauma


In some people, heterochromia indicates other medical problems. These conditions might come from genetics, and they often affect nerves and vision. People with heterochromia should have their eyes examined by an optometrist to rule out other medical issues.


5. Your eyes can be a window to your personality.
Eye colour research has uncovered some interesting insights into how we act and how others perceive us:

  • Blue-eyed children tend to exhibit more inhibited behavior and are less trusting of new things.
  • Blue-eyed adults are often less open with professional counsellors.
  • People think of brown-eyed men as more dominant than blue-eyed men, but brown-eyed people are also perceived as more trustworthy.
  • Brown-eyed people demonstrate faster reaction times and enhanced hand-eye coordination.

Many factors influence our personality, so you can't necessarily say a person's drive to compete or tendency to keep secrets comes from their eye colour. However, since our eye colour comes from our genetic code, it can indicate our evolutionary background and the personality traits that combine to make us each as unique as our irises.


All these research findings show there's a lot more to iris colour than meets the eye. Show your eyes some love by making regular trips to the optometrist.

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