But believe it or not, that wasn't always the case. Thanks to the scientists at Copenhagen University, we now know that somewhere between 6, to 10, years ago, everyone had brown eyes, according to Science Daily. But at some point during that time, a mutation occurred on the OCA2 gene, which controls how much melanin we produce. Specifically, this mutation essentially acted like a "switch" and "turned off" people's ability to produce brown eyes. Thus blue eyes were born! Not only did the team at the university identify the mutation that created blue eyes, but they also discovered that everyone with blue eyes has something in common.
If you are the lucky owner of a set of cobalt peepers, chances are you've noticed that your eyes appear to change color, sometimes looking bluer or grayer — or even lighter or darker. That was certainly the case with the famous movie actress Elizabeth Taylor , whose bright blue eyes could look violet when the light hit them just right. There's a reason blue eyes appear to change color, which is related to why they look blue in the first place.
You guessed it: It all depends on how much light is both coming into and reflecting out of the eye, according to the American Academy of Ophthalmology. Additionally, the color of the eye can look different depending on the color of clothing that a person wears, as well as the color and style of makeup that's applied around the eye. To be fair, people with green and hazel eyes are also prone to seemingly color-changing irises as well, so this isn't unique to blue-eyed folks.
But it's notable nonetheless. If you're a parent, or are close to someone who's had a baby , you might have had the experience of watching the eyes of an infant change color from bright blue to green or brown.
That's why you can't know what someone's eye color will be when they grow up until about the six-month mark, according to an article published by McGill University. The reason that many babies are born with blue eyes that can later change to brown is, once again, due to the way melanin functions in the human body.
When a baby is born, melanin hasn't yet been fully deposited into the iris of the child's eye, which results in the iris being blue. But after a certain period, the genetics kick in and melanin production either ramps up, changing the color of the baby's eye, or doesn't, rendering the color of the iris blue for life.
It's just one more way that the human body is truly a mystery. So if you happen to be the bearer of big blue eyes, shouldn't your wee one also inherit them? Conversely, if both you and your partner are of the brown-eyed persuasion, wouldn't it logically follow that your children will be too? Of course, given the complexity of genetics, it's not that simple. Surprisingly, two brown-eyed parents can have a child with blue eyes, according to an article published by the University of Delaware.
Additionally, two blue-eyed parents can give birth to a brown-eyed baby. So what's the reasoning? In a nutshell, eye color is not determined by one single allele or recessive gene. Rather, it's determined by several different genes, as well as the interplay between them. So don't be surprised if your child has eyes that don't resemble either parent — it's just how genetics work. Everyone needs vitamin D in their bodies, according to a journal article in Environmental Health Perspectives , so it's important to get a little sunlight on a regular basis.
But depending on the color of your skin, you have to be varying degrees of careful when you step outside, lest you wind up with a sunburn, according to the American Cancer Society. So if you're light-skinned, you're more at risk, though everyone should take precautions when they go out, regardless of skin color.
Just as you have to be careful with your skin when you're outside, you also have to protect your eyes accordingly, especially if they're light-colored.
Although having blue eyes or light-colored eyes is considered quite beautiful , there is one disadvantage that comes along with this phenotype. Unfortunately, those pretty eyes mean you're more susceptible to cancer, according to an article in Everyday Health.
Specifically, fair-eyed folks are more at risk of developing melanoma of the uvea that's the middle layer of your eye than their brown-eyed counterparts. Fortunately, there's a pretty simple way to protect your precious peepers from harmful UV rays, according to ophthalmologist Dr. This could have been an advantage to hunter gatherer women who needed to identify and collect plant foods — indeed blue eyes may even have evolved in women first. But Sturm has another idea.
He says blue eyes have been linked to people coping better with seasonal affective disorder, a major depressive illness that occurs when there are long periods of low light. Notably, he says, the eye has special neurones in the retina that can detect blue light and use this to help regulate circadian rhythms.
Contrary to what we might have once learned in school, it is possible for two blue-eyed parents to have a brown-eyed child, says Sturm. First there are genes that control the amount of melanin pigment in our irises — that's the part of our anatomy that acts like an aperture on a camera to control the amount of light that gets into the eye. Around 74 per cent of our eye colour can be put down to a gene called OCA2 on chromosome This gene also contributes to hair and skin colour, but to a much lesser extent.
A variation in the HERC2 gene, which sits right next to the OCA2 gene controls whether melanin is produced in the outer layer of the iris.
If you turn the switch on the eyes will be brown. If you turn it off they become blue," he says. Then there are genes that control the structure of the iris, such as it thickness and how much collagen it contains. Tags: eyes , evolution , anatomy. Email ABC Science. Use this form to email 'Why did humans evolve blue eyes? This genetic switch limits how much melanin is produced in the iris — effectively "diluting" brown eyes to a shade of blue.
In addition to having significantly less melanin in their iris than people with brown eyes, hazel eyes or green eyes , blue-eyed individuals don't have very much variation in the part of their DNA responsible for melanin production. The color of our eyes depends on how much melanin is present in the iris. Brown eyes have the highest amount of melanin in the iris, and blue eyes have the least.
Brown melanin is the only pigment that exists in the eye; there is no pigment for hazel or green — or blue. Eyes only appear to be these colors because of the way light strikes the layers of the iris and reflects back toward the viewer. At one time, it was believed that eye color, blue eyes included, was a simple genetic trait. Common knowledge said that you could predict a child's eye color if you knew the color of their parents' eyes, and possibly the color of their grandparents' eyes.
Geneticists now know that as many as 16 different genes influence eye color to some degree — far from the one or two genes that were once believed to determine iris hue. In addition to genetics, the anatomic structure of the iris can also affect eye color to some degree.
In other words, it's impossible to know for sure if your children will have blue eyes — or any other color. Both parents may have icy blue eyes, but that's no guarantee their child's eyes will even be blue at all. Human eyes don't have their full amount of melanin pigment at birth.
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