Why Are My Eyes Blue?

If you have ever been curious about why your eyes are a light blue while your husband’s are brown and your son has green, this is the article for you. While scientists can predict blue or brown eyes with 80% accuracy by evaluating only six genomes, very little is actually known about the genetics behind why different people have different coloured eyes.
Until recently, many opticians, physicians and scientists thought that blue eyes were a recessive trait and could only occur when two people with the same recessive trait had offspring. This myth was dispersed by studies from the Human Genome Project with conclusive evidence that the genetics behind eye colour is so complex that almost any colour is possible from any set of parents. What the scientific community can say is that brown eyes are the most common in the world while green eyes are the least common. Contrary to this statement, however, is the fact that Wales is the only place in the British Isles where the population has less than 50% light coloured eyes.
If you have a child you may have noticed their eye colour change dramatically from the time they were born. That is because it is determined by two main biological parts: pigment and cellular density in the eyes. Pigment determines what colour the eyes will actually be whereas cellular density relates to how much light is reflected and absorbed, which means that two people with the exact same pigment could have starkly different eye colours based on how much light the eye reflects towards the person looking at them. Most people of European decent begin life with little-to-no pigment, causing the eyes to be very light, and while the cellular density is pretty much set from birth, around the age of one year babies start to develop melanocyte cells, which produce pigment and change the eye colour.
After this period the eye colour can be pretty much set until a person reaches puberty, where fluctuations in hormone levels can change chemical balances that shift the colour again. Hazel eyes in Caucasians are the most prone to change during this time.
Surprisingly it has been discovered that eyes with mixed colours, like hazel, are created by an entirely different gene than solid eye colours, rather than a mix of blue and brown genes.
Lastly, there is much to be said about your future based on the colour of your eyes. It has been researched recently that people with brown eyes are more prone to developing cataracts, necessitating glasses or surgery later in life while people with lighter colours are more susceptible to other medical problems, such as age-related mascular degeneration.
So now you know more about eye colour than you ever thought was necessary. You’re welcome.