Where do green eyes come from?

Originally posted by skeptic1
I was born with white-blonde hair and blue eyes. When I hit puberty, my hair slowly turned red and my eyes turned pure green. I think I am part lizard.

I'll do a little research post anything if I find it.

In all of this discussion, we’ve ignored green eyes. And all the colors in between. Do these results tell us anything about green eyes? A bit.

There are lots of possible theories we can come up with to explain green eyes. One idea is that OCA2 explains all eye color. The data in this paper (and all of the inheritance studies that have been done) do not support this model.

Why would people even consider this model? How could you get green eyes with just OCA2? By having it only partially on.

Remember, lots of melanin in the stroma of the iris gives brown eyes and little or no melanin here gives blue ones. Green eyes are thought to happen when there is an intermediate amount of melanin.

And genes aren’t only on or off. They are more like a dimmer switch on a light.

So green eyes might happen when OCA2 isn’t going at full strength. The findings from some early, smaller studies suggested that this might be the case. But this bigger study doesn’t really support this idea. So green eyes (and presumably all the other colors) probably come from other genes.

Originally posted by LostNemesis
I like threads like this. Very amusing thing to read about others familes and stuff like eye/hair colour.

My daughter was born with dark brown/black hair(probly cause premie), bright blue eyes.
Then it turned blonde, and now kinda strawberry blondish... Still, bright blue eyes.
Her dad is blonde, green eyes. Maybe hers will be green, but just haven't "turned" yet...

Is it true that if one parent has dark hair or eyes, the kids will have that, regardless of the other parent?

Originally posted by skeptic1
reply to post by asmeone2

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Pure green eyes are rather rare; I rarely see anyone with pure green eyes. Even mine....I have pure bottle green irises, but they are rimmed in a smoky blue. No yellow, no brown, but pure green with that smoky blue rim.

OK, all. Eye color can change over time because of age or, unfortunately, disease.


Aging, however, is the usual cause of color change over time. Color can change as we age. It does so for 10 to 15% of the normal Caucasian population. These people's eyes change slowly over many years after they reach adolescence.


Investigators considered Caucasians (non-East Asian, non-Native American, non-African) because only Caucasians commonly have lighter eyes.


"Some eyes become darker, but most become lighter with increasing age," says Richard A. Sturm, a Principal Research Fellow at the Institute for Molecular Bioscience at the University of Queensland in Brisbane, Australia.


The basis of human eye color. Pigment cells (yellow in the figure) contain brown pigment granules (shown in various intensities from neutral to light brown to very dark brown). The lighter the pigment and the fewer the granules — the lighter the iris color and the lighter the eye. The circles on the left depict irises and the colors that result from the corresponding pigment cell. Blue irises result from minimal pigment and few pigment granules. Green-hazel irises have moderate pigment levels and number of granules. Brown irises have high pigment levels and many granules. Information from Richard A. Sturm, Institute for Molecular Bioscience at the University of Queensland.

How and why eye color changes.


Pigment in the front layer of the iris (called the stroma) colors the iris. Eye color lightens when pigment granules drop in number, or when the granules make a lighter color. See figure. The iris can also lose color if the pigment degrades. Eyes, unlike skin and hair, do not synthesize color pigment continuously. Instead, eyes keep pigment granules made earlier. So, if the pigment degrades, the eye color lightens.


Likewise, eyes can darken if the number of pigment granules increase or if the granules make darker pigment.


That's how the color changes. Why does it change? Genetics is the key, as experimenters learned by studying twins. They observed the eyes and skin of identical twins and non-identical twins of American Caucasians between the ages of 3 months to 6 years.


Both sets of twins showed a "darkening with age of both the hair and eye colour," says Sturm. The identical twins changed color together, at essentially the same rate. The non-identical twins changed color but at different rates, which indicates a "strong genetic influence in the timing of these colour changes."


Eye color probably changes for the same reason we have one head instead of two: genes. Genes determine all body characteristics — including changing eye color as we age.