Dark grey or blue eyes are extremely striking eye colors that stand out in a crowd. While most people have brown eyes, eyes in shades of grey, blue, and green are considered rare and unique. But just how uncommon are dark grey blue eyes?
What Causes Eye Color?
Eye color is determined by genetics. The amount of melanin pigment in the iris of the eye is what gives eyes their color. People with a lot of melanin have brown or black eyes. Those with less melanin have blue, green, or hazel eyes.
There are two factors that determine eye color:
- The amount of melanin present
- The way light scatters through the iris
Darker eyes like brown and black contain a high amount of melanin. Lighter eyes like blue and green have much less melanin in the iris. The light scattering effect causes grey, blue, and green eyes to appear the color that they are.
Genetics of Eye Color
Eye color is inherited through genetics. The gene variants responsible for eye color are the OCA2 and HERC2 genes. These genes are located on chromosome 15.
The OCA2 gene contains the genetic instructions for producing the melanin pigment. The HER2 gene controls the activation of the OCA2 gene. So these two genes work together to determine eye color.
Most of the world’s population has brown eyes. This is because brown eye color is dominant over other colors. Blue and green eye colors are recessive traits. This means you need two copies of the recessive allele for blue or green eyes to have those colors show up.
Since grey, blue and green eye colors require very specific combinations of genes, this makes these colors quite rare compared to brown eyes which only need one brown allele.
What Determines Grey, Blue, and Green Eyes?
Here is a breakdown of how the different versions of the OCA2 and HERC2 genes result in rare eye colors:
- Green eyes – You need one copy of the dominant brown/black allele and one copy of the recessive blue allele of the OCA2 gene
- Blue eyes – You need two copies of the recessive blue allele of the OCA2 gene
- Hazel eyes – You need one copy of the dominant brown/black allele and one copy of the recessive blue allele of the OCA2 gene. The ray scattering effect causes the flecks of color in hazel eyes.
- Grey eyes – You need two copies of the recessive blue allele of the OCA2 gene plus a variant of the HERC2 gene that reduces melanin production
As you can see, grey eyes require very specific genetic combinations. Having two recessive blue alleles of OCA2 is already quite rare. Pairing that with the unique HERC2 variant makes grey eyes exceptionally uncommon.
Global Eye Color Statistics
Here are some statistics on the distribution of eye colors worldwide:
| Eye Color | Global Population |
|---|---|
| Brown | 79% |
| Blue | 8-10% |
| Hazel | 5% |
| Green | 2% |
| Grey | Less than 1% |
As you can see, brown eyes make up the vast majority of eye colors globally. Blue eyes are relatively rare at only 8-10% of the population. Green, hazel, and grey eyes are incredibly uncommon.
Which Ethnic Groups Have the Most Grey Eyes?
Grey eyes are more common in certain ethnic groups, particularly those from Northern and Eastern European descent. Here are the ethnic groups that are more likely to have grey eyes:
- Eastern European – Those with Slavic heritage like Russians, Poles, and Ukrainians have a higher rate of grey eyes.
- Northern European – People with Scandinavian or Nordic ancestry have increased grey eye pigmentation.
- Germanic – Germans have a moderate percentage of grey eyed individuals.
- Celtic – The Irish and Scottish have a higher likelihood of possessing grey eyes compared to the rest of Europe.
Interestingly, research has found that people with Celtic heritage have the highest percentage of grey eyes in the world. Over 30% of Irish and Scottish people are thought to have blue or grey eyes.
Grey Eyes in the United States
In the multicultural society of the United States, grey eyes remain quite unusual. Estimates of grey eye prevalence in the US population vary:
- Around 3-10% of Americans are thought to have blue eyes
- Just 1% of the US population is estimated to have grey eyes
So conservatively, only around 1 in 100 Americans are likely to have rare grey eye coloration. The highest concentrations are found in states with large Irish, German, Polish, and Eastern European immigrant populations.
Conclusion
Grey eyes are exceptionally rare globally, occurring in less than 1% of the world’s population. They require very specific combinations of genetic variants. Ethnic groups with significant Northern European or Celtic ancestry exhibit higher rates of grey eyes.
In the United States, grey eyes are thought to occur in only 1% of citizens. They are truly a distinctive eye color that stands out due to their rarity. So if you have been blessed with alluring dark grey or blue eyes, know that you have a genuinely uncommon eye color!