Monday, July 6, 2015

Green Eyes: Surprising Fun Facts and Research

My online time has been seriously curtailed in the last several weeks, but one quick internet surfing episode led me to an (excuse the pun) eye-opening article about green eyes. Really fascinating stuff!

I was intrigued not only because I have green eyes myself, but because this particular genetic trait will factor very heavily into one of my upcoming Science Fiction Romance works.

So what's up with green eyes? In a nutshell...

Green Eyes Aren't Really Green

In actuality, all iris colors range from light brown to black. All other eye colors are actually just a trick of the light!

Green eyes are really light brown pigmentation of the stroma of the iris as a result of low to moderate levels of melanin, that diffuse the light on the irises to make them appear green, in much the same way that the sky looks blue because of light diffusion. This is known as Raleigh Scattering which has specific properties that effect eye color.

Green Eyes are Very Rare

What makes green eyes so unique is that only 2% of the total population tend to carry the genetics that result in the appearance of green irises, though in some populations the percentage runs higher because of the regional genet pool. Green eyes are most common in individuals with recent Celtic or Germanic ancestors. (I'm descended from Scottish, German, French and Irish ancestors, so my eye coloration probably came from one or more of these branches of my family.)

Green Eyes Tend to have Chameleon Properties

Because the green coloration is actually just an effect of diffused light, things such as light conditions, the colors of eye makeup or clothing worn or colors of the surrounding environment can compliment or contrast with the green shade, making it range anywhere from a near-blue to hazel to dark gray. But these aren't the only factors can change the hue of green eyes.

So can mood. Anger can dilate blood vessel and redden the whites of the eyes, which makes the eyes appear greener in contrast. Two emotions at the opposite end of the scale--happiness and grief--can dilate the pupils, also causing the green coloration to appear darker, or even more blue.

Surprisingly, weather and temperature can also change the color of green eyes by changing the ambient light, which also affects the light diffusion and the color of the eyes.

The Genetic Origins of Green Eyes

The two genes thought to have the most influence on eye color are OCA2 and HERC2, both located in Chromosome 15, however there is evidence that up to sixteen different genes could be responsible for eye color. The genetics that affect eye color are also believed to be related to freckling, hair and skin tones. In truth, this is a pretty basic explanation. The genetics involving eye color are much more complex. (For instance, blue eyes are actually thought to be the result of a mutation in the HERC2 gene.)

Where and when green eyes emerged in the human species is not known, but research has revealed they were prevalent in southern Siberia in the Bronze age. In modern times, they are most often seen in Northern and Central Europe, and can be found in Southern Europe and Western Asia, specifically among the Ashkenazi Jews of Israel.

Green-Eyed Planet

The third novel in my SFR series (working title "Draxis" but official published title yet to be determined), brilliant green eyes are a trademark of the ancestral group that colonizes the planet. The genetics involving green eye color became dominant over time, along with a bronze skin tone and light blonde hair. This unusual pairing of lighter eye and hair color with darker skin pigmentation was the result of fixed genetics stamping the entire population with these traits.

If you're intrigued by the variants affecting green eye coloration and want to learn more, you might want to start with this article: Learn About the Origins of People with Green Eyes

Are you part of the rare genetic group who has green eyes? If so, where do you think those genetics came from? Have you read (or written) any books where the green eye color is dominant or important to your species?


14 comments:

  1. My husband has green eyes, one reason I fell for him. Unfortunately none of our monsters have inherited them. I always wanted green eyes (having green eyes and red hair meant you were either a pixie or a vampire, depending which archiac British era you lived in), so I gave my redhaired heroine the same wish. My eyes are grey (an even rarer trait than green) but I find that rather dull. >_<
    Genetics have always fascinated me. Possibly because of my own recessive genes that cause the red hair, and my fascination with it. It's also a trait used to mark a particular human civilization in my time travel series..

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    1. Gray eyes sound so mysterious, Pippa. :) I have a green-eyed redhead who is a very important character in my series. (Don't think you've read that far yet.) Genetics fascinate me too. I've learned a lot from raising Thoroughbreds, and some of that found its way into a future novel, too. (Not the Thoroughbreds, just the genetics. Ha.)

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  2. Mine are blue, but do look green sometimes.

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    1. Mine are green, Patsy, but people tell me that they turn blue when I'm in a happy mood or if I'm really interested in something. I guess that goes with the "changing color with mood" explanation. :)

      Thanks for stopping by.

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  3. I love green eyes, they're so pretty.

    Mine are bright bright bright bright, almost sapphire-like, blue. There is no doubt whatsoever what color my eyes are, and I can make them even bluer with certain eye-shadow combinations and clothing colors.

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    1. My husband and nephews have those blue, blue eyes too, Rachel. The rest of us have hazel or green. I know when I wear certain shades of green it really brings out the color.

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  4. My dad, 100% Italian, had green eyes. I don't, but one of my 3 kids do. Genetics, fun stuff!

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    1. Oh, a green-eyed Italian! I would think that's pretty rare, Sheila. Yeah, I love the genetics stuff, too. So many story ideas.

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  5. I almost always seem to want the heroes in my novels to have green eyes for some reason! Enjoyed the post...

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    1. I'm thinking through my heroes, Veronica. Two green-eyed, four brown eyed. Although, the two green-eyed heroes are related!

      Hmm, no blue-eyed heroes yet. I'll have to work on that.

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  6. My hubby has blue-green eyes, that change depending on all those things you mention--one day green, one day blue. My oldest daughter's eyes are just like his, but my youngest has very green eyes, the variability coming in the depth of the green color. Don't make that one mad! Me, I have very boring hazel eyes. **sigh**

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    1. Do your eyes ever take on a green hue depending on your surrounding, Donna?

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    2. Not that I know of. But then I'm not looking! :)

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