What Makes Blue Eyes?

What Makes Blue Eyes
Your eyes aren’t blue (or green) because they contain pigmented cells. As Paul Van Slembrouck writes for Medium, their colour is actually structural – and it involves some pretty interesting physics. The coloured part of your eye is called the iris, and it’s made up of two layers – the epithelium at the back and the stroma at the front.

  1. The epithelium is only two cells thick and contains black-brown pigments – the dark specks that some people have in their eye is, in fact, the epithelium peeking through.
  2. The stroma, in contrast, is made up of colourless collagen fibres.
  3. Sometimes the stroma contains a dark pigment called melanin, and sometimes it contains excess collagen deposits.

And, fascinatingly, it’s these two factors that control your eye colour. Brown eyes, for example, contain a high concentration of melanin in their stroma, which absorbs most of the light entering the eye regardless of collagen deposits, giving them their dark colour.

  • Green eyes don’t have much melanin in them, but they also have no collagen deposits.
  • This means that while some of the light entering them is absorbed by the pigment, the particles in the stroma also scatter light as a result of something called the Tyndall effect, which creates a blue hue (it’s similar to Rayleigh scattering which makes the sky look blue ).

Combined with the brown melanin, this results in the eyes appearing green. Blue eyes are potentially the most fascinating, as their colour is entirely structural. People with blue eyes have a completely colourless stroma with no pigment at all, and it also contains no excess collagen deposits.

  • This means that all the light that enters it is scattered back into the atmosphere and as a result of the Tyndall effect, creates a blue hue.
  • Interestingly, this means that blue eyes don’t actually have a set colour – it all depends on the amount of light available when you look at them.
  • Structural colouration also gives colour to butterflies, beef and berries,

It’s pretty mind-blowing stuff. Van Slembrouck writes for Medium : “Imagine that you could shrink yourself to a microscopic size and then climb through the mesh of fibres in the stroma. That’s where structural colouration is coming from and in the mesh are also strands of smooth muscle tissue that contract to dilate (expand) the pupil, pulling the inner edge of the iris toward the outer edge.

  • When this happens, the stroma fibres slacken and may become wiggly as tension is released.
  • This makes me wonder, does that slightly alter the colour of your eye as well?” Check out Van Slembrouck’s great story to find out how hazel and grey eyes get their colour, and also to check out his beautiful diagrams that explain structural colouring.

Source: Medium

What is the cause of blue eyes?

Don’t It Make Your Brown Eyes Blue? Blue-eyed? Thank a genetic switch that turns off your body’s ability to make brown pigment in your peepers. Researchers have finally located the mutation that causes blue eyes, and the findings suggest that all blue-eyed humans share a single common ancestor born 6000 to 10,000 years ago.

Researchers have implicated the OCA2 gene in several eye colors. The gene is involved in the production of melanin, a pigment that gives hair and skin their hues. It also codes for brown eyes and can lead to green or hazel eyes when mutated. Despite years of searching, however, scientists have not found a mutation for blue eyes on the gene.

It turns out they were looking in the wrong place. Trying to narrow the site of the mutation, gene mapper Hans Eiberg of the University of Copenhagen and colleagues examined members of a large Danish family, an approach that allowed them to follow DNA as it passed from one generation to another.

Then, by comparing people with brown or blue eyes, including people from Jordan and Turkey, the researchers were able to pinpoint the exact mutation. It wasn’t on the OCA gene but rather on a nearby gene called HERC2, The mutation works like a switch that regulates the OCA gene, the team reports in the January issue of Human Genetics, turning off the production of brown eye color and allowing blue eyes to shine through.

Because blue eye color is found almost exclusively in people of European descent, Eiberg’s team speculates that the mutation traces back to the Neolithic expansion, when people in the Black Sea region migrated to northern Europe 6000 to 10,000 years ago.

  1. Two other studies, both appearing in this month’s issue of The American Journal of Human Genetics, examined blue eyes in different populations and found the same mutation.
  2. The researchers also suggested a common ancestor for all blue-eyed individuals.
  3. These teams, however, did not estimate an age for the mutation.

Geneticist Richard Sturm of the University of Queensland in Brisbane, Australia, an author of one of the papers says that someday scientists may find additional mutations that cause blue eyes but for now, the signs point to a single change. Sturm says that it’s not uncommon for one gene to regulate another, but it is difficult to locate the mutation in the controlling gene.

One of the most cited examples is the mutation involved in lactose tolerance, which is also caused by regulation from outside the gene. Sturm says that such regulating genes may contribute more to genetic diversity than previously thought. The findings also have applications in forensics. Geneticist Manfred Kayser of the Erasmus University Medical Center in Rotterdam, the Netherlands, an author of the other paper that appears in The American Journal of Human Genetics, says if police fully understood mutations behind eye color, for example, then they could use them to determine the eye color of a suspect based solely on DNA evidence.

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Geneticist Tony Frudakis of DNAPrint Genomics Inc., a Sarasota, Florida, company that develops genetic-testing products, is shocked that the mutation happened just once. Although there are about 10 ways to get someone with red hair, the scientists found only one way to get someone with blue eyes.

  • I would have thought blue eyes arose several times independently,” Frudakis says.
  • There are still large questions, though.
  • Why did blue eyes persist? Scientists say it is difficult to see how eye color would have an environmental advantage, as skin color does.
  • Some theories suggest that women may have played a role in driving the selection.

Perhaps, Kayser says, “the females thought it more exciting to have a male with blue eyes.” Related site : Don’t It Make Your Brown Eyes Blue?

Can two brown-eyed parents have a blue-eyed child?

Myth: Two blue-eyed parents can’t produce a child with brown eyes. Fact: Two blue-eyed parents can have a child with brown eyes, although it’s very rare. Likewise, two brown-eyed parents can have a child with blue eyes, although this is also uncommon.

Can blue eyes go extinct?

Nerdfighteria Wiki – Are Blue Eyes Endangered? Despite the apparent prevalence of the trait among swanky crooners and British spies and creepy old creatures who just hung onto the ring for too long, only about 8% of the world’s human population has blue eyes. Here in the U.S. it’s about twice that, but that’s still a lot less than it was at the turn of the twentieth century when nearly half of all Americans had the trait.

So what happened? Are blue-eyed humans going the way of the dodo?Well, no. We cleared up that rumor about redheads going extinct; the same goes for blue eyes. While the trait is becoming more rare, it’s unlikely it will disappear all together. Which is crazy when you consider that 10,000 years ago blue eyes didn’t even exist.

In fact, there’s a good chance that blue-eyed people may all share one common ancestor. Studies over the past decade have actually traced the trait to a mutation that most likely arose among brown-eyed people in a single human in the Black Sea region of southeastern Europe between 6,000 and 10,000 years ago.The mutation affected what’s known as the OCA2 gene, which helps our bodies produce melanin, the brownish pigment that gives color to our hair and eyes and skin.

  1. The mutation created kind of a dimmer switch for the pigmentation, but it didn’t affect the entire gene.
  2. Instead, it only affected the production of melanin in the iris, the ring structure around the eye that regulates how much light gets in.The bulk of the iris is a thick layer of melanin-producing cells called the stroma.

And the OCA2 mutation turns the production of melanin in the stroma way down, but the pigmentation still shows up elsewhere, like in the hair and skin and other parts of the iris. Basically, the mutation keeps the stroma from being brown.So why blue then? Well, strictly speaking, blue eyes aren’t actually blue.

  1. Instead, in people with this mutation, the stroma is full of nearly colorless cells.
  2. And when the light strikes them, they scatter the wavelengths back out, in a process similar to what makes smoke or fog look blue when light passes through them.If there is some yellowish pigment in the stroma, then the blue light will combine with that to make green.

Throw in a little bit of brown, and you have hazel.So how did we go from having no blue-eyed people, to hundreds of millions of them in less than 10 millennia? No one’s entirely sure why the trait spread so quickly through Europe. Some scientists think the mutation could have helped prevent certain eye disorders related to long, dark northern winters.But another factors appears to be that, for whatever reason, lots of blue-eyed people simply mated with other blue-eyed people in the past, which kept the trait in circulation.

Because for each of your genes, you have two different versions, called alleles, one from your father and one from your mother. If you have at least one dominant allele for a gene, that’s the trait you have.The blue eyes come from a recessive allele, which means if you inherit one allele for blue eyes and another for brown, you’re going to have brown eyes.

But you still carry the recessive blue allele, which can be passed on. Which means that that first person that had that blue-eyed mutation didn’t have blue eyes. They had to pass that onto their children, and their children had to pass it onto their children, until eventually they came back together to make someone with two blue-eyed alleles.When both parents have blue eyes, they both have two recessive blue-eyed genes, which means their children will also have blue eyes since there’s no dominant gene to mask the recessive one.

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This is how you end up with Scandinavian countries that are 95% blue-eyed, and it also explains why the percentage of blue eye-ers is dropping in much of the western world.Human populations are a lot more evenly spread throughout the world than they were 10,000 years ago, so more blue eyes are pairing up with brown eyes and producing brown-eyed offspring.I wouldn’t go so far as to call them endangered, but safe to say those blue-eyed singers and spies and Gollums will always be in the minority.

Thanks for watching this SciShow Dose. If you’d like to help us keep exploring the world, just go to to find out how you can become a supporter. And if you want to keep getting smarter with us, don’t forget to go to and subscribe. : Nerdfighteria Wiki – Are Blue Eyes Endangered?

How to have a blue eyed baby?

Making Eye Color Predictions with Basic Genetics – If you want to try and predict your baby’s eye color, pull out your high school biology textbook to help narrow down just how likely it is that your baby will have blue eyes. If you didn’t keep it, don’t worry, I’ll give you a quick review.

  1. As FamilyEducation’s Genetics Expert, I have developed my knowledge on these topics through a combination of college classes, teaching, and self-study.
  2. We all inherit two copies of each gene (allele), eye color included.
  3. One copy comes from our mother, and one from our father.
  4. Both alleles are stored in our chromosomes (our genetic code) and can be passed on to our children, but only one presents in how we look.

Dominant genes present while recessive genes “hide out” in the DNA code for a chance to pass on to future generations. Generally, darker colors are the dominant traits, while lighter colors are recessive, so a person with one brown-eyed gene and one blue-eyed gene will have brown eyes.

Blue eyes + blue eyes = 100% chance of blue eyes Brown eyes + blue eyes = 50% chance of blue eyes, but only if the brown-eyed parent carries a blue-eyed gene. If not, the chance is 0% Brown eyes + brown eyes = 25%, but only if both parents carry the blue-eyed gene. If not, the chance is 0%

It is important to remember that this theory is a simplified version of what really happens at the genetic level. Human eye coloring is actually controlled by a complex genetic process and there are many different eye colors other than just blue eyes and brown eyes.

Do blue eyes come from mom or dad?

Blue eyes – A clue to paternity Before you request a paternity test, spend a few minutes looking at your child’s eye color. It may just give you the answer you’re looking for. According to Bruno Laeng and colleagues, from the University of Tromso, Norway, the human eye color reflects a simple, predictable and reliable genetic pattern of inheritance.

  1. Their studies1, published this week in the Springer journal Behavioral Ecology and Sociobiology, show that blue-eyed men find blue-eyed women more attractive than brown-eyed women.
  2. According to the researchers, it is because there could be an unconscious male adaptation for the detection of paternity, based on eye color.

The laws of genetics state that eye color is inherited as follows:

If both parents have blue eyes, the children will have blue eyes. If both parents have brown eyes, a quarter of the children will have blue eyes, and three quarters will have brown eyes. The brown eye form of the eye color gene (or allele) is dominant, whereas the blue eye allele is recessive.

It then follows that if a child born to two blue-eyed parents does not have blue eyes, then the blue-eyed father is not the biological father. It is therefore reasonable to expect that a man would be more attracted towards a woman displaying a trait that increases his paternal confidence, and the likelihood that he could uncover his partner’s sexual infidelity.

Eighty-eight male and female students were asked to rate facial attractiveness of models on a computer. The pictures were close-ups of young adult faces, unfamiliar to the participants. The eye color of each model was manipulated, so that for each model’s face two versions were shown, one with the natural eye color (blue/brown) and another with the other color (brown/blue).

The participants’ own eye color was noted. Both blue-eyed and brown-eyed women showed no difference in their preferences for male models of either eye color. Similarly, brown-eyed men showed no preference for either blue-eyed or brown-eyed female models.

However, blue-eyed men rated blue-eyed female models as more attractive than brown-eyed models. In a second study, a group of 443 young adults of both sexes and different eye colors were asked to report the eye color of their romantic partners. Blue-eyed men were the group with the largest proportion of partners of the same eye color.

9 Amazing Facts About Blue Eyes

According to Bruno Laeng and colleagues, “It is remarkable that blue-eyed men showed such a clear preference for women with the same eye color, given that the present experiment did not request participants to choose prospective sexual mates, but only to provide their aesthetic or attractiveness responsesbased on face close-up photographs.” Blue-eyed men may have unconsciously learned to value a physical trait that can facilitate recognition of own kin.1.

  1. Laeng B et al (2006).
  2. Why do blue-eyed men prefer women with the same eye color? (Behavioral Ecology and Sociobiology, DOI 10.1007/s00265-006-0266-1) Article is available to journalists as a pdf.
  3. Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.
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: Blue eyes – A clue to paternity

Can kids get blue eyes from grandparents?

What color eyes will my child have? – There’s no guarantee when it comes to your offspring’s eye color. While a baby inherits half of their eye color genetics from one parent and half from the other parent, the way that the genes interact also plays a role in determining eye color.

  1. Differences in eye color are also influenced by differing amounts of melanin, the pigment responsible for eye color (plus hair color and skin tone).
  2. For instance, many white non-Hispanic babies are born with blue eyes because they don’t have the full amount of melanin present in their irises at birth.

As the child grows older, if they’ve developed slightly more melanin in their irises, the eyes will be green or hazel, When the iris stores a lot of melanin, the eyes will be amber (a golden brown), light brown or dark brown. Even though you don’t know the amount of melanin your baby will have, you can still get a pretty good sense of eye color from the parents’ eye colors.

Two blue-eyed parents are likely to have a blue-eyed child, but it’s not guaranteed. Two brown-eyed parents are likely to have a brown-eyed child. Again, it’s not guaranteed. Two green-eyed parents are likely to have a green-eyed child, although there are exceptions. Two hazel-eyed parents are likely to have a hazel-eyed child, although a different eye color could emerge. If one of the grandparents has blue eyes, the odds of having a baby with blue eyes increases slightly. If one parent has brown eyes and the other has blue eyes, the chances of having a brown-eyed or blue-eyed baby are roughly even.

The Fertility Institutes, which offers fertility services in California, New York, Utah and Mexico, offers the following odds of a baby’s eye color based on the parents’ eye colors. (Due to rounding, percentages don’t always add up to 100%.)

Both parents with brown eyes: 75% chance of baby with brown eyes, 18.8% chance of baby with green eyes, 6.3% chance of baby with blue eyes. Both parents with blue eyes: 99% chance of baby with blue eyes, 1% chance of baby with green eyes, 0% chance of baby with brown eyes. Both parents with green eyes: 75% chance of baby with green eyes, 25% of baby with blue eyes, 0% chance of baby with brown eyes. One parent with brown eyes and one parent with blue eyes: 50% chance of baby with brown eyes, 50% chance of baby with blue eyes, 0% chance of baby with green eyes. One parent with brown eyes and one parent with green eyes: 50% chance of baby with brown eyes, 37.5% chance of baby with green eyes, 12.5% chance of baby with blue eyes. One parent with blue eyes and one parent with green eyes: 50% of chance of baby with blue eyes, 50% chance of baby with green eyes, 0% chance of baby with brown eyes.

Keep in mind that it may take six to 12 months for a baby’s true eye color to emerge, so the color you see at birth can certainly change. SEE RELATED: Is it true all babies are born with blue eyes?

Which parent does a child get their eye color from?

BLUE – 6.25% What Makes Blue Eyes Baby Eye Color Calculator for Grandparents Congratulations on becoming a grandparent! Watching your child have their own baby is one of the most magical feelings in the world. It’s time to get excited about the baby’s personality and features! Are you excited to see what they’ll inherit from you? Do you hope they’ll have the same eye color as you? With our easy-to-use baby eye color calculator for grandparents, you can help your kids get ready for their newborn by better predicting what the baby’s eye color might be.

  1. What Determines a Baby’s Eye Color? Your grandchildren inherit their eye colors from your child and their partner.
  2. It’s a combination of mom and dad’s eye colors.
  3. Generally, the color is determined by this mix and whether the genes are dominant or recessive.
  4. Since the inheritance of eye color is polygenic, eye color traits are influenced not only by one gene but by various genes.

Simply put, what determines a baby’s eye color includes: -Parents’ eye colors -If parents are homozygous or heterozygous dominant for a specific color -If parents’ eye colors are dominant or recessive However, since you played a part in the color of your own child’s eyes, it technically has an impact on what eye color the newborn baby may have.

Is it rare to have blue eyes?

What Causes Blue Eyes? – Blue eyes have fascinated people for centuries. In cultures around the world, they are seen as beautiful yet also cold. Blue eyes are rare, making up just 8-10% of the world’s population. Blue eyes are caused by a relative lack of melanin in the iris.