They (Green eyes) are most common in Northern and Central Europe. They can also be found in Southern Europe and North Africa. In fact, Turkey, at 20%, is the country with the largest percentage of green eyes. In Iceland, 89% of women and 87% of men have either blue or green eye color. A study of Icelandic and Dutch adults found green eyes to be much more prevalent in women than in men. Among European Americans, green eyes are most common among those of recent Celtic and Germanic ancestry, about 16%. SourceSo countries that have a higher percentage of fair eye color also have more people with green eyes. I might be rare here, but in Scotland for example, I could blend in.
About Genghis & MeI should say, while history is of interest to me, Genghis and I have never gotten close. It would be a stretch to say that I know much about it at all, though I am interested in the region. Just not his exploits. This will not be a history lesson, nor are all of my facts, checked and doubled checked. So take information revolving around him with a grain of salt. Wikipedia has a lot of good primary sources for this information. The question of where a group of people came from, sadly, isn’t really a direct and certain answer, as it is unknown how the migrations of other peoples to the region exactly affected the genetic composition of the ethnicity.
Red Hair, Green EyesHaving any of those traits was at the time of Genghis Khan uncommon. He came form Temujin, and there are few surviving accounts of what he actually looked like. Some claim he had red hair and blue/green eyes, yet you should be skeptical. Why? There are Uyghur with these vary traits living there now. Yet, Ugyhurs with red hair and/or very light eyes are generally a result of the fact that they were not the original inhabitants of Xinjiang, the area in which they mostly currently reside. Tocharians held the area before the Uyghurs, and they were an Indo-European people who had a tendency towards light hair/eyes (see Tarim mummies). The closest modern relatives to the Tocharians are of course the Afghans and Pashtuns, but in China the, Uyghurs would be most closely related to Tocharians, not the Mongols. It’s not uncommon for Afghans to have light eyes and hair. There’s no real evidence to suggest Genghis Khan had green eyes and red hair. It’s not an outlandish claim since there are a good number of Mongols with lighter hair and eyes but this gives people the wrong idea.
They infer that these traits must mean there are “white” Mongols. There aren’t. They just look like Asian people with green or blue eyes, just like how white people don’t look “Asian” just because they might have dark hair and eyes. They share a similar culture, language, and history with the other Indo-Iranian peoples in the region, which is important to note considering that Tocharians traditions would have otherwise been more prevalent. Of course, there could be some modern day relationship between the two ethnicities, but the Tocharians, for the most part, did not live in that area, but more towards the Tarim Basin. This is evident in genetic testing that has shown relations between the modern Uyghur peoples and Europeans, which can easily be read about here. So, in short, the Tocharians weren’t related directly to the Afghans, as they are Iranian. For more information on the Iranian migrations, look here. Of course, I am only referring to “descendants” in terms of ancestors with the most effect on the modern population; if we want to go thousands of years back, there is evidence that the entire region of the Indian subcontinent was inhabited by peoples who shared a common, non-Indo-European genetic background. If you go back far enough, the Afghans becone Proto-Indo-Europeans, people of the Indus Valley Civilization, and the inhabitants of the BMAC, but on the other hand we all have diverse ancestral backgrounds, some untraceable, within us. I hope this has given some clarification about what I was trying to say.
I have green eyes. What you see in my eyes is not the same thing that scientists see in them. The current thought behind green eyes is that a thin layer of yellow pigmentation overlays the "blue" color of an iris, and the result is a yellow color.
The gene responsible for this yellow pigmentation is completely separate from the brown/blue gene; thus, to have green eyes, one must have a low concentration of melanin in the iris and produce the yellow pigment.
Here is a chart that demonstrates how melanin in the front and back epithelia of the iris and the structure of the stroma create eye color. You will notice that the specific combination which is required for green eyes is more complicated.
Of course, we're talking about gene networks here so in reality this isn't cut and dry as I made it sound. If it was, there were be a higher percentage of the population with green eyes.
Eye color is complicated than many may think and the combination required to be born with green eyes is rare. And it has been an area of study for scientist for decades. A lot of people tend to tell me it is because of X or Y, but they are just using layman's terms to try and explain something that they are ignorant about. In other words, anyone who says they know definitively isn't being completely insightful or in other cases honest.
Eye color is highly polygenic and not entirely understood.
A lot of genetics is not as simple as Mendel's pea experiments might lead you to think. Mendel figured the basics out mostly because he picked traits that have distinct, qualitative phenotypes that were only controlled by the expression of a single gene.
This tends to be the exception rather than the rule, but it's still taught in schools because it provides a clear simplified way of explaining the mechanism of why traits are passed on or not.
It is more likely that many different genes play a role in determining eye color (which is a spectrum of colors really, not just "green" or "blue"). While some of the Brown vs. Blue in European populations genes have been worked out (OCA2), the mixtures that make up intermediaries are not entirely clear. What would start off as a binary state becomes very messy when you start adding in 11 other SNPs with incomplete penetrance and variable dominance terms.
As for the rarity, that's just simple population genetics.
The alleles for green eyes, whatever their nature, are simply less common in European and Middle Eastern populations than brown or blue. Hence, they are less likely to be observed.
Since eye color is usually not selected for or against when people choose whom they wish to mate with, the frequency of the "green allele" remains more or less the same. Though I did have a boyfriend tell me once that he was only together with me because of my eye color. That sort of creeped me out and I dumped him a week or so later.