Our iris colour is part of what makes us who we are. It identifies the family that we come from, and our greater heritage from a global perspective.
Amazing what they can find out in our genes these days. One study found that everyone with blue eyes can have their ancestry traced back to a single person who lived about 10,000 years ago in the Black Sea region. They have found that more than 99.5% of blue-eyed people who volunteered to have their DNA analysed have the same tiny mutation of a gene that determines the colour of their iris.
Brown is the default colour of our iris and is inherited via a dominant genetic marker. Approximately 50% of the world’s population have brown eyes. Our eyes are brown due to the build-up of the dark skin pigment, called melanin. Eyes with very little melanin in the iris are blue. Eyes with a bit more melanin are green, hazel or light brown. And those with a high concentration of melanin are medium or dark brown.
One out of every 6 people are blue-eyed people or those who only have a small amount of melanin in their iris. It is not known why blue eyes has become so common among European and Russian populations. But it is thought that the blue eye colour offered some advantage in the long hours of daylight in the summer. Or, that the trait was deemed attractive and therefore advantageous in terms of sexual selection.
Darker eyes or those with more melanin are less likely to have macular degeneration. A dark iris blocks more UV light – protecting the retina from damage from the UV light. Macular degeneration is a disease where the sensitive cells of the retina, in a special part of our eye called the macula, slowly dies off due to oxidative damage and stress. This process is exacerbated in those with a poor diet, a genetic tendency and also with UV light.
Darker eyes are considered more trustworthy in personality surveys. But the news isn’t all stacked in favour of the darker eyed people among us! Darker irises are more likely to get cataracts earlier. The research suggests that they are less likely to wear sunglasses, and UV damage to the eye can cause cataracts to develop earlier.
Green eye colour is the rarest colour found around the world, and it is estimated that only around 2% of the world's population has green coloured eyes. Green eye colour is a result of a mild amount of pigmentation in the eye with a golden tint. It is thought to be inherited from people who lived in south Siberia during the Bronze Age. Because there is only a small amount of the population with green eyes, there really isn’t accurate studies which identify whether green eyes have any link with eye diseases.
From my perspective, the point that comes across time and time again is the importance of UV protection. I say there are three things you can do to look after your eye health, number 1 is sunglasses. Number 2 is a good diet and Number 3 is not smoking. Whether your iris colour is light or dark, or some colour you really can’t name – it doesn’t matter, but my message to you is to wear sunglasses more in 2020.