You may have noticed that your best friend’s newborn baby’s eyes are now brown. But you could have sworn that just months ago at the baby’s first coming home party, they had those beautiful blue eyes. Well, you can stop with the brain wracking because no tricks are being played here. In fact, it’s a pretty common occurrence.
Recent studies have discovered that a baby’s eye color isn’t necessarily determined by whether or not their parents have blue eyes. In fact, studies have shown that there may be up to 15 genetic traits that determine a baby’s eye color! We’ll get to explain this in just a bit.
But first, some frequently asked questions:
Are all babies born with blue eyes?
The simple answer is no. Not all babies are born with blue eyes, although most Caucasian babies are. Babies with more skin and hair pigmentation, such as those of African American and Hispanic ethnicities, are less likely to be born with blue eyes.
Because Caucasian babies have less pigmentation in both the skin and hair, most are born with blue eyes, but most of them don’t stay that way. Only one in four adults have blue eyes and the reason for this is that babies’ eyes change to either brown or green.
When do babies’ eyes start to change?
A baby’s eye color normally changes within the first six months of being born, but can keep changing until the age of three! There is also no guarantee that your baby’s eyes will change. They may get lucky and get to keep those piercing baby blues!
How can I know if my baby’s eyes will change?
There is an easy trick to know if your newborn baby’s irises will change color in the next few months. Now this trick isn’t foolproof, but if you’re not a fan of surprises this is a good way to guess what color your baby’s eyes will be.
Take a look at you baby’s eye from the side. This will eliminate any light reflecting off the iris. If there are flecks of gold in the blueness of the eye, then this probably means that your baby’s eyes will change to either green or brown as they grow. If there are minimal or no flecks of gold, then chances are those blue eyes are here to stay!
Why do babies’ eye colors change?
Remember that stuff mentioned about pigmentation? The pigmentation of our skin and hair colors is determined by the amount of melanin we’ve inherited from our parent’s genes. Melanin is a type of pigment that is also present in the eyes. It’s a simple concept to understand, the more melanin present in a baby’s eye, the darker their eyes are likely to be.
That’s to say that babies with a high amount of melanin will often have brown or hazel eyes; babies with a “medium amount” (that’s about as specific as it gets) will likely have green eyes; and finally babies with very little melanin will have blue eyes. This lack of pigmentation is also the reason why we find a majority of blond babies to have blue eye.
The reason this pigment change in babies’ eyes is because babies are not born with their full amount of melanin. As they grow older, the melanin levels increase to the amount your baby should have, thus giving your baby their permanent eye color.
If you’re interested in a visual explanation, here’s a video by Mental Floss that will help:
How is eye color determined?
A baby’s eye color, like any other physical trait is inherited through their parents’ genetics. But then why do some babies have blue eyes when both parents have brown eyes? The answer is simple: eye color determination is a lot more complex than we had assumed it to be.
The pigment of a baby’s eyes is a polygenic trait, or rather a trait determined by multiple genes. As of now, experts have estimated that there are 15 genes that play a role in determining eye color. Parents may have babies with different eye colors than themselves because eye color depends on so many factors.
Though we put a lot of emphasis on melanin being the decider of eye color, the truth is it plays but one out of potentially 15 genes that have the final word. Researchers are working on finding what genes are in fact the deciding ones. As of now, we only know the basics.
When a baby is conceived, they inherit one chromosome from each parent. A chromosome is a strand made up of pieces of DNA called genes, which eventually determine what a baby will look like. The two genes, experts agree are the most important in determining eye color are the OCA2 and the HERC2 genes.
HERC2 genes have been the agreed upon gene that causes babies to have blue eyes and eventually keep their blue eyes. But then we have the OCA2 gene, which gives babies green or brown eyes. So how do blue eyes happen? Researchers believe that in order to have a blue iris, the OCA2 genes must be inactive for the HERC2 gene to take precedent.
Let’s break these genes down a little more, just for fun. Genes are made up of alleles, which carry the code for specific genes. Theses alleles are inherited through the parents. For every trait, including eye color, a baby would inherit two, one from each parent.
If two alleles of the same nature are inherited they are called homozygous. Chances are if a baby inherits two alleles for brown eyes from their parents, they will have brown eyes. However there is an exception. Though brown may be the dominant pigment in both parent’s eyes, it’s possible that one carry a blue or green gene as well. In cases such as this, a baby of brown eyed parents may have blue or green eyes.
On the other hand, if a baby inherits two different alleles, this is called heterozygous. In this case, the dominant allele will be the determining factor of eye color. Brown is generally the dominant over green and blue; and green the dominant over blue.
Whatever the eye color, you love your baby. Take care of their eyes and your own. Visit our eye vitamins page for more information!