Eye color is a fascinating aspect of human appearance that has long interested both scientists and laypeople alike. The hue of one’s irises ranges across the color spectrum, from deepest brown to lightest blue. Among the rarest and most striking eye colors is bluish gray. So what causes eyes to be this unusual shade? And what percentage of the population has bluish gray eyes? Let’s explore the genetics and statistics behind this eye color.
What Causes Grayish Blue Eyes?
Human eye color is determined by the amount and type of pigment in the iris. This pigmented cell layer regulates how much light enters the eye. The two main pigments involved are:
– Melanin – A brown/black pigment that also colors hair and skin. Higher levels of melanin result in brown/black eyes.
– Lipochrome – A yellow/amber pigment that produces green, hazel, and amber eyes.
Bluish gray eyes have a desaturated, muted quality that sets them apart from true bright blue. This effect occurs because they contain low levels of melanin and lipochrome pigmentation. Having little of either pigment causes the eye to take on a pale, bluish gray appearance.
The Genetics Behind Grayish Blue Eyes
There are two key genes involved in determining eye color:
– OCA2 – Controls melanin production. Variants of this gene reduce melanin levels, diluting brown eyes to lighter shades.
– HERC2 – Regulates OCA2 activity. Specific variants suppress melanin production, allowing for blue, green, and hazel eyes.
Bluish gray eyes arise when an individual inherits variants of both OCA2 and HERC2 that significantly reduce melanin levels in the iris. This minimum pigment condition creates their pale, cool-toned coloration.
In terms of inheritance, bluish gray is a polygenic recessive trait. To have bluish gray eyes, a person must inherit two copies of recessive alleles from each parent. The chances of this allele combination occurring is quite low, making the eye color genetically rare.
How Rare Are Grayish Blue Eyes?
Global estimates indicate that only about 1% of the population worldwide has bluish gray eyes. Here are some statistics on their prevalence:
| Region | Percentage with Bluish Gray Eyes |
| United States | 0.8% |
| Europe | 1-2% |
| Iceland | 8-10% |
In the United States, bluish gray is significantly rarer than blue eyes overall, which occur in about 8-10% of the population. European countries exhibit slightly higher rates at 1-2%, while Iceland has the world’s highest percentage of bluish gray eyes, at 8-10%.
This distribution is likely related to the prevalence of genetic variants that reduce melanin production. The OCA2 allele associated with bluish gray eyes reaches its highest frequency in Icelandic populations.
Celebrities with Notable Grayish Blue Eyes
Though rare, bluish gray eyes do occasionally appear in celebrities and public figures. Here are a few famous people with striking grayish blue eye coloration:
– Kate Bosworth – American actress known for roles in Superman Returns and Blue Crush. Her light eyes match her blond hair.
– Cillian Murphy – Irish actor famous for films like Peaky Blinders and Batman Begins. His cool-toned eyes contribute to his unique appearance.
– Alexander Skarsgård – Swedish actor and model who starred in True Blood and Big Little Lies. His light eyes stand out against darker hair.
– Chad Michael Murray – American actor and model who appeared on One Tree Hill, Agent Carter, and Riverdale. His eyes are an iconic bluish-gray hue.
Conclusion
In review, bluish gray eyes arise from low levels of melanin and lipochrome pigment in the iris. They require a rare combination of genetic variants to reduce melanin production. Worldwide, only 1% of people have eyes of this distinctive cool gray-blue color. While uncommon, their muted and mysterious appearance make them memorable when they do occur. So next time you encounter someone with rare bluish eyes, you’ll understand the special genetics behind their unique ocular hue.
