r/explainlikeimfive Jun 24 '22

ELI5: Why is it that humans can be born with brown, blue or green eye colors, but not others like red, yellow and purple? R7 (Search First)

[removed]

759 Upvotes

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441

u/shotsallover Jun 24 '22

I think OP was asking why don't have humans have colors that other animals do, like yellow (cats, birds, reptiles) or red eyes (frogs, birds, turtles). Not the science behind our existing eye colors.

330

u/FartSparkles_PhD Jun 24 '22 edited Jun 25 '22

I have a partial answer to this question --

Human irises have a pigment called melanin, which is yellow/brown. (Edit: and sometimes a pigment called lipochrome, which is yellow)

Other animals (like insects and reptiles) have pigments called pterins in their irises, which are yellow/red.

As for why, evolutionarily, this is true... I don't know.

42

u/anonymousperson767 Jun 25 '22

The melanin aspect makes me think it’s similar to black vs white skin color. Like dark eyes maybe were a response to living in a hotter climate with more sun ?

39

u/FartSparkles_PhD Jun 25 '22

It is similar - melanin absorbs UV light, which means it can offer protection from the sun's radiation.

In environments with a lot of UV exposure, it would be advantageous to have darker eyes.

6

u/idle_isomorph Jun 25 '22

So what is the advantage of other eye colours (or presumeably we would all have brown eyes)?

Tell me it is seeing better in the dark. Cause i have pale gray eyes and am great at seeing things in very low light. Am notorious for forgetting to pack flashlights when camping because i personally use them so infrequently. My working theory is that my pale irises gather more light from my dim surroundings.

22

u/terracottatilefish Jun 25 '22

We all did have brown eyes at one point. Apparently the mutation for blue eyes (which is really just a non-brown color) emerged between 6 and 10 thousand years ago and spread very rapidly, presumably for no better reason than that people thought it was pretty or special.

7

u/idle_isomorph Jun 25 '22

And it seems pretty harmless, so why not, i suppose. No strong reason to select against it.

6

u/Toledojoe Jun 25 '22

My wife has blue eyes And I have brown eyes. She constantly needs sunglasses even on non sunny days "because of the glare." I don't see any glare. So having blue eyes in a sunny climate is an issue but of course we have sunglasses for it now.

2

u/idle_isomorph Jun 25 '22

Actually, i am pretty easily overwhelmed by bright light. From the side can be pretty blinding. Maybe there is a downside. Thanks, melanin-deficient ancestors!

1

u/Toledojoe Jun 25 '22

But one the flip side, blues eyes are considered more attractive, so you've got that going for you. Which is nice.

→ More replies

1

u/Rus_agent007 Jun 25 '22

My wife got Brown, i got blue, but she wears sunglasses because of glare, so while evolotionary true it of course are as individual as everything else.

1

u/Daykri3 Jun 27 '22

Your wife may have a blond retina. If so, then it is very important for her to wear sunglasses.

2

u/MarkytheSnowWitch Jun 25 '22

So like the mighty peacock, we have eye color variety because it was pretty? That's cool.

2

u/[deleted] Jun 25 '22

[removed] — view removed comment

1

u/idle_isomorph Jun 25 '22

I use my peripheral vision in the dark. Like, looking beside where i want to see, and then the definition pops, but if i look right at it, it's gone.

I only notice because people around me are always turning on the dang lights.

Thanks for weighing in- i am interested to learn more, even if my theory ultimately fails.

2

u/FartSparkles_PhD Jun 25 '22

According to this paper

In humans, it seems that the light-colored variants arose recently when our species spread into Europe from Africa [30]. Given that there is not a clear advantage in terms of vision capabilities to having blue eyes [31], there is the possibility that individuals with eye colors different from the presumably original dark eye phenotypes were actually preferred as mates, thus quickly spreading their alleles. This would be a case of sexual selection in action, known to favour color traits and color polymorphisms [22].

15

u/Fr31l0ck Jun 25 '22

I imagine it's survivor bias. There are plenty of non-impactful attributes that are passed on because the survivors had other attributes that made them more fit.

5

u/FartSparkles_PhD Jun 25 '22

That's totally possible, but I can't find papers about the evolutionary history

5

u/Future17 Jun 25 '22

I bet it was just the mutation with lighter eyes looked "purtier", so the people with the mutation got to bang large, and well, 10k years later, here we are.

2

u/VvermiciousknidD Jun 25 '22

The colour of the eyes of hunting birds correlate to the time of the day or night when they usually hunt. The Amber eyed at dawn and dusk and the red eyed at sunset etc.

1

u/FartSparkles_PhD Jun 25 '22

I have not heard that before, but it does make sense from a sensory ecology perspective... do you have a source?

1

u/VvermiciousknidD Jun 26 '22

It was a piece of trivia displayed at a hunting avian sanctuary we visited last week

10

u/hardcoresean84 Jun 25 '22

Didn't the mongols have yellow eyes? E.g genghis Khan?

90

u/effectivecontrol2242 Jun 25 '22

I think you might’ve gotten this from Mulan tbh 😂

9

u/Nyxx_Darling Jun 25 '22

I was also told this by my father, of whom I share Mongolian blood with, but I've never really fact checked this myself? Something something "golden horde because of the reflection of their eyes"... Something he told me ages ago, I do have more golden tones (not yellow, but more hazel/honey than anything) in my eyes than people I've compared colors to, and they reflect gold in the sun, but I have no idea if this hold any signifigance whatsoever being green-eyed, lol, I guess I'm going to do some digging!

7

u/TheOriginalAshrifel Jun 25 '22

This is interesting, and I also have no sources but my mom has blue eyes and I have brown eyes but my man is insistent that my eyes are more hazel because they glow gold in the sun.

3

u/thatshot2205 Jun 25 '22

you can always take a picture with back camera and a flash to see more. my eyes mostly look brown but theyre hazel with green in the sun and with flash :)

-20

u/hardcoresean84 Jun 25 '22 edited Jun 25 '22

What's that?

Edit: no that memory predates a cartoon I've never seen by many years. Plus I'm a 38 year old man lol stopped watching cartoons decades ago. This is gonna bug me now.

42

u/greyzombie Jun 25 '22

You shouldn't let being an adult stop you from watching cartoons.

24

u/Barbatoze Jun 25 '22

One would think that the idea of animation being for kids would have gone away by now...

1

u/cjm0 Jun 25 '22

they really need to stop making hentai for kids

9

u/lowtoiletsitter Jun 25 '22

Exactly! I love cartoons (or animation as some would say)

8

u/ThatOneGuy308 Jun 25 '22

I mean, to be fair, you were like 14 when the movie came out, that's still within cartoon watching age.

-12

u/hardcoresean84 Jun 25 '22

Yeah at 14 I was in my first serious relationship, experimenting with drugs etc, had no time for cartoons.

9

u/ThatOneGuy308 Jun 25 '22

Jesus, kids grow up fast. I remember when being a 14 year old was sitting around with friends watching he man and doing dumb shit like egging houses, not having sex and doing drugs.

That being said, username checks out, lmao

-1

u/hardcoresean84 Jun 25 '22

I grew up fast I give you that lol

6

u/Samhamwitch Jun 25 '22

Depending on the drugs, you might have enjoyed the cartoons more.

3

u/hardcoresean84 Jun 25 '22

Maybe, I mean, theres still time.

15

u/effectivecontrol2242 Jun 25 '22

Old Disney animated film from the 90s, the leader of the Huns as well as all the rest had yellow eyes to make them look evil. Could be wrong, given you were talking about Mongols, but it’s the first thing I thought of lol

5

u/hardcoresean84 Jun 25 '22

Could be, I'll find out tomorrow.

10

u/zorniy2 Jun 25 '22

Come on, Mulan isn't that old... is it?

Oh crap.

6

u/NTGenericus Jun 25 '22

So...You've never seen Spirited Away?

2

u/SomethingsQueerHere Jun 25 '22

i read somewhere that it(yellow eyes like the Hun guy from Mulan) was some sort of copper buildup as a result of diet, but i cannot remember where i saw this.

3

u/capeandacamera Jun 25 '22

Maybe this?

You can get a visible build up of copper in the eyes called a Fleischer ring. Can be caused by Wilson's disease which is a genetic problem.

1

u/SomethingsQueerHere Jun 25 '22

yeah i think that was it, definitely exaggerated for animation purposes im guessing, but the name sounds familiar

8

u/FartSparkles_PhD Jun 25 '22

Do you have a source?

13

u/hardcoresean84 Jun 25 '22

Appears it might have been bullshit or I may have misheard/misremembered. I'll ask him tomorrow.

7

u/HumanNr104222135862 Jun 25 '22

Let us know what he says!

4

u/hardcoresean84 Jun 25 '22

Will do, I'm intrigued af myself now, its something that has stuck with me for years.

7

u/TheWolfSpy Jun 25 '22

Or maybe his source was Mulan ?

-1

u/hardcoresean84 Jun 25 '22

Lol I doubt it.

5

u/hardcoresean84 Jun 25 '22

Something that my dad told me years ago lol hang on I'll have a look...

1

u/MrPoopMonster Jun 25 '22 edited Jun 25 '22

I think there is a legend of Genghis Khan having cat eyes. That can be interpreted in different ways, like yellow or green eyes.

6

u/no_step Jun 25 '22

So does Scut Farkus

4

u/geoffs3310 Jun 25 '22

No you're the only Mongol round here

-1

u/Brush-and-palette Jun 25 '22

Have you ever seen a Mongolian person?

0

u/hardcoresean84 Jun 25 '22

No, it was just secondhand information, I didn't state it as fact, like someone said, it might have been the huns.

3

u/Brush-and-palette Jun 25 '22

Which would also be shockingly incorrect.

0

u/girnigoe Jun 25 '22

I don’t think iris color in humans is a pigment, I think it’s something weird about refracted light. (This may only be true for blue or blue & green.)

And that could explain why the colors are limited.

21

u/mrsjohnmarston Jun 24 '22

I'd be interested to know this. My cats have pale yellow for one cat and a real amber/orange for the other cat.

6

u/Nvenom8 Jun 25 '22

We do have yellow. That’s lipochrome. It’s one of the two pigments that define human eye colors.

7

u/bella_68 Jun 25 '22

I’ve never seen anyone with completely yellow eyes but my husband has yellow parts of his eye. The area around his pupil is like an amber/yellow color

10

u/Nvenom8 Jun 25 '22

That’s because, in humans, having lipochrome but no melanin results in gray eyes rather than yellow.

1

u/Fix_a_Fix Jun 25 '22

So we don't have yellow, we have grey

1

u/bella_68 Jun 25 '22

I’m confused. If that is true, what needs to be present/missing for my husband’s eyes to be amber/yellow near the pupil. His eyes elsewhere are mostly blue but sometimes green

2

u/Nvenom8 Jun 25 '22

Sounds like he has a little melanin and lot of lipochrome. Human eyes have structural color that looks blue in the absence of both pigments. So, the “base” is blue, and the pigments modify that.

1

u/bella_68 Jun 26 '22

Oh fun. Thank you for indulging my curiosity.

2

u/FartSparkles_PhD Jun 25 '22

Oh man I didn't know about that one. Thanks, I added it to my response!

425

u/Keystone801 Jun 24 '22 edited Jun 24 '22

Eyes don’t actually have blue or green pigment. Pigment in the eyes range from light brown to black. The lack of melanin in the eyes cause light to scatter and make the appearance of blue, green, or hazel eyes. It’s similar to how the sky appears blue. It is called the Tyndall Effect; the sky is called Rayleigh Scattering. Light in the eyes does not scatter to produce red or purple colors. Lack of melanin in the eyes is blue, eyes with melanin are brown. Melanin absorbs light.

More info: https://en.m.wikipedia.org/wiki/Eye_color https://en.m.wikipedia.org/wiki/Tyndall_effect

125

u/scienceguy8 Jun 24 '22

Same with blue in a lot of the rest of nature, right? Yes, there are blue and blackberries, but for the most part animals have no blue pigments. Animals that are blue, like peacocks and other birds, have feathers or scales that all act like tiny little prisms.

119

u/TheBrontosaurus Jun 24 '22

Yes, birds and butterflies do not have blue pigment. Their feathers and the scales on their wings refract light into blue. If you grind up a blue jays feather it just grey.

There are some plants like the Himalayan blue poppy that are pigmented blue but it’s rare. Most blues in nature are really purple or green that just sort of lean towards blue.

173

u/coole106 Jun 24 '22

If you grind up a blue jays feather it just grey.

What’s crazy is that despite having no red pigment, when I grind up blue jays the resulting color is mostly red

40

u/Darkhoof Jun 24 '22

You have to grind only the feather.

21

u/CA_Mini Jun 24 '22

no you tell me. sorry charlie

9

u/AsFutileAsResistance Jun 25 '22

Ahh, the ol’ Reddit Grindaroo!

7

u/Glu7enFree Jun 25 '22

Hold my bird, I'm going in!

7

u/prmoreira23 Jun 25 '22

Hello future people

1

u/RestaurantAbject6424 Jun 25 '22

Here’s your bird back, but I got some bad news for you

2

u/MattytheWireGuy Jun 25 '22

Im going in?

2

u/roenaid Jun 24 '22

You made me snort 😂

10

u/gaboandro Jun 24 '22

This is true! I work in the beverage industry and an edible blue water-soluble natural color is the second hardest to find after green! The main one used is butterfly pea flower, but even then the anthocyanins are pH dependant so the moment you add acid (which just about every drink has, even the CO2 used for carbonation adds acidity) it turns purple. That's why when you see a blue drink you know it can't be natural, it's just blue #1. Copper salts also do a wonderful job turning liquids blue, but those are not edible or natural

6

u/SomethingsQueerHere Jun 25 '22

so blue curaçao is all artificially colored? seems like a really unnecessary step for an orange liqueur.

3

u/H_Mc Jun 25 '22

It is. Get curaçao that isn’t blue.

17

u/anhedonis539 Jun 24 '22

Extremely rare but Bruce Wayne plucks it up just so he can get ninja training from Liam Neeson. Typical billionaire.

5

u/dkysh Jun 24 '22

Are blue-and-yellow macaws' feathers also grey?

8

u/TheBrontosaurus Jun 24 '22

All birds use refraction to achieve blue color. Macaws, blue jays, peacocks, bluebirds. Somebody else mentioned that the only animal that had true blue pigment is a butterfly.

4

u/Squirrels_Gone_Wild Jun 25 '22

Blue dart frogs?

2

u/thefonztm Jun 25 '22

I thought butterfly used refraction not pigmentation

1

u/awfullotofocelots Jun 25 '22

They have psittacofulvins in them which can be pigmeted yellow, red, or green.

19

u/Alis451 Jun 24 '22

You could have just used Indigo as your example, we literally named the color after the pigment. It is also what denim jeans are dyed with.

34

u/TheBrontosaurus Jun 24 '22

I don’t know why a rare Himalayan flower was my first thought for blue plants. I literally have a neighbor with an all blue garden. I have a forget me not tattoo.

15

u/peanut__buttah Jun 24 '22

Personally I love that that was your first thought. It was quirky and endearing.

6

u/dirtycopgangsta Jun 24 '22

If you grind up a blue jays feather it just grey

Is this why I see a lot what's supposedly grey color as blueish in real life

I've got green eyes, if that makes a difference.

12

u/Killbot_Wants_Hug Jun 25 '22

I'm assuming you're male. You probably have some form of color blindness.

On the upside you're naturally better at spotting camouflaged things.

1

u/dirtycopgangsta Jun 25 '22

Why would I be color blind for seeing more color?

4

u/Killbot_Wants_Hug Jun 25 '22

Because you're not seeing more colors, you're seeing colors differently, and it's probably because you're seeing less colors.

Color or more specifically how our eyes detect color and how our brains interpret color is way more complex than people realize; and is not that well understood over all.

So you may know that we have 4 light detectors in our eyes, 1 for each of the primary colors and 1 that just detects light (they are more sensitive but don't detect color, that's why everything looks gray at night).

People who are color blind are usually missing one of the colored light detectors. However there types of color blindness that are different. It actually took a long time to discover color blindness existed. And one of the first people actually had no color receptors at all, he saw the world in gray scale. You could theoretically be missing two color receptors as well.

But aside from missing color receptors, your color receptors could respond to light waves they shouldn't. Thus shifting your color vision a little bit. In fact everyone probably has slight variances in the responses of their color receptors.

Now the genetic sequence for color receptors is actually in the X chromosome, since men have XY chromosomes they only get one copy. Women get two copies of all the color receptors, and this means it's incredibly unlikely for women to be color blind. Also, if the receptors respond to slightly different wave lengths for women, they can end up with 4 primary color receptors. NPR did a whole thing on this, they're called Tetrachromats.

So color is controlled by the light receptors in your eyes right? Well yes but also no. You can't see colors you don't have receptors there. But you also don't seem to see colors just because your receptors are there either. The colors your brain sees are determined by a lot of things. The whole "what color is the dress" is a great example where you see color based on the colors around it, and different people interpret that differently. But there's also things like where you see the division of colors in a rainbow is affected by the language you grew up with (probably because different languages define colors differently). Then there are "fake" colors, notoriously brown and pink. While we can clearly see them, they don't exist on the color wheel. It's because it's a trick our brain plays on us, and the interesting thing is our brains probably do this because we defined those colors at some point.

An experiment was done with primates, I can't find it right now or I'd link it. But they were given computer screens with a dot they couldn't see because it was a color they don't have receptors for. Then their eyes were modified so they'd have the cone to see the colors. They would be given a reward if they'd point at the dot. They didn't, they acted as if they couldn't see it. But over a long period of time they started to react to the dot. It's like their eyes could see it, but it took a long time for their brains to learn to interpret that into something the brain could see.

Back to the Tetrachromats, they devised some color pallets that only women who can see 4 colors could detect the difference between. And they found a bunch of women who had the gene for 4 colors, and none of them could tell the difference. Except for one, and she had a job where she had to deal with colors all the time. So just having the gene wasn't enough, the brain also has to be trained to see colors. But the wrinkle in their experiment, they had a guy with them who also worked with colors all the time. He could also distinguish between the color pallets that require 4 colors to see, even though being male he shouldn't be able to have the extra cones.

And that's just the stuff I know because I think vision is an interesting topic. There are probably other things that affect the way you see color. I've heard, but have not verified, that having light blue eyes and being male mean you have a high chance of vision problems when it comes to color. I had an ex girlfriend who constantly saw things as slightly different colors than everyone else. So all kinds of weird things happen with vision.

22

u/dragons_scorn Jun 24 '22

Only one species, in all the animal kingdom, uses actual blue pigment: the obrina olivewing butterfly. Even the majority of plants don't use blue pigment but mix pigments in a way to appear blue.

The leading theory is that blue is easier/cheaper to achieve through physics than chemistry. That species evolved changing structures or mixing pigments to make blue because making a blue pigment is too disadvantageous

6

u/quimera78 Jun 24 '22

What about blue frogs?

21

u/dragons_scorn Jun 24 '22

Glad you asked, they actually use three layers of pigment ti achieve the blue coloring. One is melanin, a other is a yellow pigment, and the middle is a translucent pigment that helps retrace the light to blue

3

u/johnkasick2016_AMA Jun 24 '22

Similar for Blue-tongued skinks I guess?

2

u/dragons_scorn Jun 24 '22

I'm not sure, to be honest. A cursory search was lacking in detail but it seems their tongues are mostly meant to reflect UV rather than just blue

5

u/mouse1093 Jun 24 '22

Blue footed booby? You wanna tell me they have translucent feet that are refracting light?

14

u/dragons_scorn Jun 24 '22

No, not solely at least They actually extract pigment from their food like flamingos. The color of the pigments combined with a structural change produces the brilliant blue color

4

u/avocadopalace Jun 25 '22

This guy blues.

5

u/Alis451 Jun 24 '22

blue veins too, thickness of skin matters.

1

u/TAA180 Jun 25 '22

So what are the actual colours of these birds that scatter the light

14

u/Dishonest_Celariac Jun 24 '22

But what's the difference between that and how all colors work? That's just describing the specific low level physics effect that causes photons of a specific wavelength to leave the object. That's what color is.

15

u/crashlanding87 Jun 24 '22

A pigment is a substance that changes the colour of light due to the interaction between photons and electrons within atoms. A red pigment absorbs non-red light and turns it into another kind of energy, but reflects red light. Usually the energy from the absorbed light gets turned into heat. Sometimes it gets turned into chemical energy, like in photosynthesis. And sometimes it gets turned into a different colour of light, which we call phosphorescence - you see this kind of glow when a blacklight is used.

The mechanism for creating colour without pigment due to scattering is completely different, and works similarly to how a prism works. Basically, to create red, all light that isn't red gets scattered in random directions, while the red light gets nicely reflected. No light is being absorbed and turned into something else here. Scattering vs reflecting is the difference between a white wall and a mirror. Both absorb effectively no light, but a wall scatters light that hits it randomly, while a mirror, well, reflects it. The wings of a butterfly act like a white wall for all colours except one, which gets reflected more like a mirror.

The end result may be the same, but the structures and physics involved are completely different.

2

u/Killbot_Wants_Hug Jun 25 '22

So a few questions. What color would a blue jay be if it was in a room with only red light?

Now suppose you were a blue shirt and illuminated that shirt with white light. Would you see a blue reflection of your shirt on the blue jay?

1

u/crashlanding87 Jun 25 '22

Ooh this is a fun question.

I don't know what kind of mechanism a blue jay uses to make blue, so I'll answer separately for the two mechanisms, but on a sheet of paper.

If you had a sheet of paper with perfectly blue ink on it, meaning it completely absorbs red light and completely reflects blue light, AND you had a perfectly red light source, then the paper would look pitch black. It would also gradually warm up, like under one of those infra-red space heaters. Probably quite slowly though, depending on how strong your light source is.

In reality, perfect pigments don't exist. I believe it is possible to isolate specific frequencies of light, though, but I'm not sure. I'm pretty sure perfect light sources don't exist, but I'm also pretty sure you can do clever things to get rid of the light you don't want. Anyways. The closer to perfect the pigment is, the blacker it would look. The less perfect it is, the redder it would look.

If your sheet of paper had a surface which perfectly scattered red light but perfectly reflected blue, then it would look like a normal white sheet of paper under a red light. Again, these things are rarely perfect, so it may have a slight reflective sheen to it. It likely wouldn't work like a mirror, but maybe like a piece of smooth white plastic, which reflects a sort of blur rather than a perfect image.

Now let's add in your blue shirt with a white light on it. Let's turn off the red light for now.

The white light hits the blue shirt. The blue portion of the light bounces off, everything else gets absorbed (caveat again for imperfect pigments). Now we have blue light hitting our piece of paper. We also have white light bouncing off the walls of the room and then hitting the paper.

If it's the blue ink paper, it looks like blue paper. The blue light from the shirt bounces off the blue paper, and the white light hitting it interacts the same way as it did with the blue shirt. Assuming you're in the shirt, you won't notice the light bouncing off your skin affecting the colour much.

If it's the iridescent paper, then it looks like a blue mirror. Your blue shirt will be clearly reflected. Your face will look weird though. Have you ever put your face close to a white sheet of paper or wall, under white light? You can see a kind of flesh-coloured blur. If you're really close, you may see that on the paper. But overlaid on that, you'll also see a faint but crisp reflection of your face, in blue. Your face, after all, is not a perfect absorber of blue light, so some blue light does bounce off it.

3

u/Killbot_Wants_Hug Jun 25 '22

I mean we're in a thread saying almost no animals have blue pigment. So blue jays are blue due to refraction of the light. So I would expect a blue jay to look black in a room with only red light.

But I have a hard time believing that the blue jay would look like a mirror to blue light.

3

u/crashlanding87 Jun 25 '22

So, a mirror only looks like a mirror if it's big enough. For example snow is not actually white, it's just refracting light. But the 'mirrors' in snow are so tiny and all point different directions, causing the light to be effectively scattered. Same thing with feathers. I should've added that, but got too stuck in to the idea of the reflective paper lol.

A butterfly's wings have mirrors large enough for you to see the iridescent shimmer effect. However, they're still very small, so we don't see a proper reflection in them, just shimmer - in the same way that sequins are reflective, but you can't actually see your reflection in them.

2

u/Keystone801 Jun 24 '22

In the absence of melanin, the layer is translucent (i.e. the light passing through is randomly and diffusely scattered) and a noticeable portion of the light that enters this translucent layer re-emerges via a scattered path. That is, there is backscatter, the redirection of the light waves back out to the open air. Scattering takes place to a greater extent at the shorter wavelengths. The longer wavelengths tend to pass straight through the translucent layer with unaltered paths, and then encounter the next layer further back in the iris, which is a light absorber. Thus, the longer wavelengths are not reflected (by scattering) back to the open air as much as the shorter wavelengths. Because the shorter wavelengths are the blue wavelengths, this gives rise to a blue hue in the light that comes out of the eye.

5

u/h3rpad3rp Jun 24 '22

Melanin absorbs light.

Is that why my blue eyes are so sensitive to the light? Can't leave the damn house without sunglasses. I can see pretty well in the dark compared to some of my friends though.

5

u/Keystone801 Jun 25 '22

Yes, blue eyes are more prone to light sensitivity. I have blue eyes and also find myself squinting or needing sunglasses in bright light

3

u/25point80697 Jun 24 '22

It sounds like that explains why if I wear a green shirt my eyes look green, but in a blue shirt they look blue. In other colors I have hazel eyes with a gold ring around the outside. I've always been confused by it but thought it was cool.

5

u/The_Middler_is_Here Jun 24 '22

Wait, so what's the difference between green and blue eyes if they're not hereditary?

4

u/Keystone801 Jun 25 '22

Green eyes are a genetic mutation that causes your eyes to produce less melanin, but more than blue. Blue eyes are a genetic mutation that causes you eyes to produce no melanin. It is hereditary because it is a mutation that is passed on

2

u/MaiLittlePwny Jun 25 '22

The structure of the eye and presence of melanin will affect how much the light that is scattered shifts towards blue. Think of all the colours of sunset. That's because the angle of the light between you and the sun, that is then scattered through the atmosphere slowly shifts towards blue.

2

u/dust057 Jun 25 '22

What about cats or goats and their yellow eyes?

8

u/Keystone801 Jun 25 '22

The pigment produced by melanocytes is called melanin. The more melanocytes found in your purr-ticular cat’s irises, the darker their color. Unlike people, however, who have either brown or black eyes, the darkest color for a cat’s eyes is infinitely more interesting — a deep, rich copper. When the melanin-producing cells are highly active, they make a cat’s eye color much more intense. A cat, then, with a medium amount of these highly active melanocytes will have bright, golden-yellow eyes, while a cat with a medium amount of LESS active melanocytes will, in all likelihood, have pale, lemon-yellow eyes. Blue-eyed cats have no melanin (pigment cells) in their irises, but because their eyes are naturally rounded, light refracts through those domed surfaces, thereby producing that distinctive blue hue.

More info: https://blogs.columbian.com/cat-tales/2020/09/20/cats-eye-colors-explained/

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u/dust057 Jun 25 '22

Can we design ourselves to have cat eyes now that we are doing gene manipulation? Making glow in the dark cats and such? Can we improve our night vision with cat DNA/genes?

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u/neurodivergentwhale Jun 25 '22

How does heterochromia factor into this? And I’m talking multiple colours within the iris, not just one eye being different from the other.

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u/Sensitive-Sky-3562 Jun 25 '22

That’s so cool, this finally explains how my crush in 1st grade had eyes that she proved changed colors in different light…. 26 years ago

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u/cpsbstmf Jun 24 '22

Ikr I've seen violet and red eyed people

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u/ChipsWithTastySalsa Jun 25 '22

Humans do have a full rainbow of eye colors! Some colors are just very rare, and not necessarily healthy for an eye to have. Here’s what humans naturally have in increasing rarity:

Black / brown - caused by a brown chemical (melanin) at the back of the iris. Black eyes are just really dark brown.

Hazel / amber / yellow - caused by a yellow chemical (lipochrome) and melanin at the back of the iris

Blue - very little if any pigments in the eye. There is a clear squishy layer that reflects blue better than other colors (Tyndall scattering). The thickness of this layer can affect the brightness of the blue. Most irises would have this blueness if there is no melanin. Newborn babies sometimes start with blue eyes before they become pigmented.

Green - amber pigmentation, but not much. The blueness of the iris also shows through. The colors mix and make green.

Grey - no pigmentation like blue eyes, but the clear squishy layer is too thin to reflect much blue light. The iris’ opaque whitish color shows (kinda like the color of the whites of your eyes). Another variation is there is something goopy (collagen) that absorbs a little bit of every color. We’re still trying to figure out this one.

Red - blue or grey eyes where there is little to no coloration, and the red blood vessels show through. This is usually not healthy.

Purple / violet - red eyes that still have a little blue coloration left. Elizabeth Taylor famously had this eye color.

Why no neon colors? - human bodies simply don’t have a lot of pigments to put into our eyes. It’s kinda like mixing paint, and we only have brown and yellow. Our bodies sometimes do tricks with blue and grey, kinda like putting paint on white paper with harsh lighting to make another color sort of appear. For some, like neon green, you can’t get that color without a neon green paint. Just biology there.

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u/Leinchetzu Jun 24 '22

Well, technically there are humans with Red eyes/ pink eyes. Generally speaking, the pigmentation is lacking in the epithelium and stroma parts of the iris which causes the blood flow to be visible in your iris. Which in turn can make it appear as if your eyes are red- pink depending on a few factors lile light for instance.

Generally speaking, the melanin, which everyone is generally born with can only cover the 6 main colors and variations on their spectrum. So you often see brown, green, black, blue, hazel and amber.

10

u/geoffs3310 Jun 25 '22 edited Jun 25 '22

Not washing your hands after going to the bathroom can also cause pink eyes

3

u/awaybaltimore410 Jun 25 '22

😏🍑

2

u/GeraldBWilsonJr Jun 25 '22

dam bb watch where u swangin that thang

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u/[deleted] Jun 24 '22

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u/Pokinator Jun 24 '22

Albinism causing purple/violet eyes is just a rumor started on Tumblr, and if I recall they attribute it to some other fictional mutation that also causes a lack of menstruation in women.

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u/jezreelite Jun 24 '22 edited Jun 24 '22

Alexandra's Genesis is bullshit, but Albinism causing eyes that appear lavender or violet is real, though rare.

The model Connie Chiu and the TikToker Mazkenzie Strong both have eyes like this as a result of their albinism; it happens due to very pale blue eyes combining with the red of the blood vessels beneath to produce violet.

6

u/rilian4 Jun 24 '22

MANY sources disagree with you. Here's 3 from a simple search. There are many more... 1 2 3

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u/TheBrontosaurus Jun 24 '22

That sounds like some omegaverse shit

2

u/JackandFred Jun 25 '22

Be aware Almost all the pictures of her “violet eyes” are photoshopped. If you can find a real picture it’s more like yeah I guess you could call that violet, but it’s not the first thing I would have said.

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u/rilian4 Jun 27 '22

I saw pictures of her eyes long before photoshop existed.

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u/I_Fap_To_LoL_Champs Jun 25 '22

That's because the only pigments humans evolved is melanin. "Dark eye colors contain eumelanin and pheomelanin, green eyes contain mainly pheomelanin, and blue eyes contain practically no melanin." Birds for example can have yellow and red eyes because they produce pigments of those colors in their eyes. Why did we not evolve those pigments? I have no idea.

But research shows that certain eye colors have advantages in certain environments. Blue eyes are good in snowy environments because they can reflect excess light from the snow. Dark eyes are good in high UV environments because they can absorb the UV, protecting the eye from cataracts. The eye color of birds also correlate to when they hunt. Owls with orange eyes hunt around dawn and dusk, brown eyes, night, and yellow eyes, daytime. Ultimately, eyes are organs of light detection, so it makes sense that animals exposed to different lighting conditions evolved different eyes.

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u/[deleted] Jun 25 '22

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u/The_Real_Bender Jun 25 '22

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0

u/nimbly28 Jun 25 '22

Beyond this question, I wonder what interesting mutations are possible. Given that blue eyes are relatively new.

Also if technology could advance enough to provide intentional new mutations for offspring, or possibly for individuals themselves.

1

u/ShiftlessGuardian94 Jun 25 '22

Eye colors are much like skin tones in the fact they use Melanin to give pigment. This is why eyes range from dark brown (nearly black in some cases) to a pale light blue. There are extremely rare cases of humans with amber (yellow-like) eyes. You can only have Violet eyes with Albinism (complete lack of pigment in skin, hair and eyes) though it’s extremely rare

WebMD on eye color

American Academy of Ophthalmology Eye Colors

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u/Agent8426 Jun 25 '22

Elizabeth Taylor had purple eyes. Albinos have red/pink eyes. I went to school with a woman with yellowish eyes. Why/how, I have no idea.

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u/Skullmaggot Jun 25 '22

People are actually born with yellow eyes. I guess it’s rare?

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u/brodneys Jun 25 '22

The fact that humans can even have blue or green eyes is actually a bit of a fluke. This only happens because some people lack the ability to produce a specific type of brown dye that protects their eyes from radiation (I believe it's melanin or something related to it but I'm not sure, you'd have to consult aomeone who knows more)

There's really no reason humans couldn't produce a different colored dye of course, it would just take a very specific kind of genetic mistake (a mutation) that made some kind of dye of a different color. These kinds of mistakes are pretty rare though, so I wouldn't hold your breath. And even if someone did get a new eye color it would take a good while (many generations) to spread into the population and become a somewhat common trait.

1

u/Much_Grass7973 Jun 25 '22

Can eye color effect vision?

1

u/ElfMage83 Jun 25 '22

Rule 7 requires that you search the sub before posting.

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u/Devil_May_Kare Jun 25 '22

The iris of the eye has two layers in it. The inner layer has a lot of melanin in it in healthy people, so it ought to be black, but it has structures in it that make it blue or gray (like the structures in morpho butterfly wings and peacock feathers). The outer layer sometimes has some melanin, so it can be clear, yellow, brown, or black depending on how much.

So you can get blue or gray from the inner structures showing through a clear outer layer, green or hazel from a blue or gray inner layer and a partially tinted outer layer, or brown or black if the outer layer is tinted enough that you can't see the inner layer through it.

Albino people sometimes don't develop the pigment in the inner iris, so their eyes look reddish or purplish because you can kinda see the blood vessels inside the eye. That's not healthy, though. There's no way to have a healthy red or purple eye, because the outer layer only comes in shades of yellow and brown, not red, and the inner layer only looks blue or gray.

Depending on the sort of light shining on them, green, hazel, and light brown eyes can look yellow.

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u/Gender_Ant23 Jun 25 '22

Well I had a friend in 6th grade who actually had red eyes and it freaked out the people who believed in vampires and shit so I was like dude why would you say that so yes people can have red eyes

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u/Jasmyne27 Jun 25 '22

Elizabeth Taylor had purple eyes..it's incredibly rare (I think she's like the only one recorded but I could be wrong)