Both green and grey eyes are considered to be relatively rare eye colors. Determining which one is more uncommon has been the subject of much debate and research. In this article, we will examine the latest scientific data on green and grey eye color prevalence to see if we can settle the question of which iris shade is less common globally.
The Genetics Behind Eye Color
The color of our eyes is determined by the amount and type of melanin pigment in the iris. Melanin comes in two forms: eumelanin which produces brown/black pigment, and pheomelanin which produces red/yellow pigment. Most people have a combination of both melanins in their iris, resulting in the common eye colors of blue, green, and brown.
What makes green and grey eyes so unusual is that they have low amounts of melanin overall. Green eyes only have small amounts of brown eumelanin. Grey eyes meanwhile have an even lower melanin concentration with barely any pigment at all. This lack of melanin causes grey eyes to appear blue in some lighting.
Genetically, green and grey eyes are linked to mutations in the OCA2 and HERC2 genes which regulate melanin production. These mutations dial back the activity of these genes, leading to low melanin levels. Grey eyes, for example, are associated with a mutation that completely deactivates OCA2.
Global Prevalence of Eye Colors
When looking at worldwide averages, brown eyes are by far the most common at around 79% of the global population. Next most prevalent are blue eyes at 8-10%, followed by green at 2-3%. Grey eyes are estimated to occur in around 1-2% of people globally according to scientific surveys and DNA databases.
| Eye Color | Global Prevalence |
|---|---|
| Brown | 79% |
| Blue | 8-10% |
| Green | 2-3% |
| Grey | 1-2% |
Based on these worldwide averages, grey eyes edge out green eyes as the rarest color by a small margin. However, as we’ll see next, these global numbers do not tell the full story.
Geographic Distribution of Green & Grey Eyes
When looking regionally, the prevalence of grey and green eyes can vary substantially. This is because the genetic mutations linked to these colors originated in specific ancestral populations.
Green eye color is most frequently seen in people of Celtic and Germanic ancestry. Countries like Ireland, Scotland, and Finland have some of the highest rates of green eyes globally. It has been estimated that nearly 88% of Irish people have either blue or green colored eyes.
Grey eyes on the other hand are most common in people of Eastern European heritage. Countries like Russia, Lithuania, Latvia, and Belarus tend to have higher than average numbers of grey-eyed individuals.
So while grey eyes are rarest on a worldwide scale, in certain regions and ethnic groups, green eyes can be less common than greys. Ultimately there is no universally agreed upon answer as to which eye shade is more rare.
Difficulties in Determining Exact Rates
Part of the challenge in pinpointing exactly how common green and grey eyes are comes from limitations in research methodology. Most data we have relies on self-reported eye color, which can be unreliable.
For example, many people falsely report having green eyes due to confusion differentiating between hazel, green and grey. True green eyes with no brown pigment are very rare. Similarly, grey eyes are often misclassified as blue by study participants and even eye doctors.
Environmental lighting conditions also play a role. Grey eyes can appear blue, green or even dark brown depending on the illumination. Getting accurate eye color statistics requires controlling for lighting and manually classifying eye color rather than relying on self-reporting.
Are Grey Eyes Getting Rarer?
While the jury is out on whether green or grey eyes are rarer, some research suggests that grey eyes are becoming less common. A study of Icelandic patients found that gray eyes declined significantly in prevalence over time from around 90% in 1800 down to 10% in 1980.
Possible reasons for this include lower rates of endogamous marriage which could concentrate the gene mutations. Increased travel and migration may also be diversifying the Icelandic gene pool. It remains to be seen if similar declines are occurring elsewhere in the world.
| Year | Grey Eye Prevalence in Iceland |
|---|---|
| 1800 | ~90% |
| 1920 | ~50% |
| 1980 | ~10% |
Conclusion
The current scientific evidence shows grey eyes edging out green eyes for the title of rarest eye color on a global scale. However, in specific ethnic groups and nationalities, green eyes can be more unusual and less prevalent than greys. Many factors make it challenging to determine precise frequencies for these rare colors. Both remain quite uncommon compared to brown, blue and hazel eyes.
While more research is still needed, some studies suggest grey eyes are declining in certain populations like Iceland. But on the whole, there is no clear consensus on whether green or grey irises are rarer worldwide. The many nuances in how these eye colors manifest and are classified means the jury is still out on which shade is least common globally.
