Have you ever noticed how many different eye colours there are? All these different eye colours are formed by the same pigment: melanin.

Whether you have dark or light eyes depends almost entirely on genetics. Curious about the link between your eye colour and your DNA? An AncestryDNA^® + Traits test can tell you more about the role your genes play in your eye colour.

How Many Eye Colours Are There?

Humans have a wide range of eye colours, although some are more common than others. These colours include blue, grey, green, and all the shades of brown—some so dark they almost look black. Hazel eyes typically include a blend of brown and green colours.

The more melanin that you have in your eyes—specifically in the stroma, one of the layers in the coloured part of your eye known as the iris—the darker your eyes are.

Melanin comes in two varieties: eumelanin and pheomelanin. Eumelanin controls black and brown colours. Pheomelanin controls red and yellow hues. It's the mix of these two types of melanin that determines whether your eye colour is coffee black, honey brown, hazel, or even green, for example.

Eye Colour Genetics: Myths and Facts

Eye colour used to be thought of as a pretty simple trait. Brown-eyed parents, it was thought, could have kids with any eye colour—although they usually had brown-eyed kids. And blue-eyed parents, it was believed, could only have children with blue eyes. In this overly simple scenario, the brown eye colour was "dominant" over the blue eye colour.

It turns out that in real life, the determination of eye colour—which is a physical characteristic known as a phenotype—is a bit more complicated. More often than this simple model in which brown eyes are dominant might predict, blue-eyed parents can have brown-eyed kids. This is because more than one gene is involved in the eye colour trait.

How Many Genes Determine Your Eye Colour?

There are dozens of eye colour-related genes that scientists know of. And there are plenty more they don't know about yet.

AncestryDNA looks at over 7,000 DNA markers found in multiple genes linked to eye colour. Your pattern at these genetic markers is what determines your eye colour result.

Some people have markers linked only to light eye colour. Some have markers tied only to dark colour. And others have a combination of both light eye colour markers and dark eye colour markers.

Eye Colour Fun Facts

Green eyes are the rarest eye colour in the world’s population. The most common eye colour in humans is brown.

It's likely that originally all humans had brown eyes. Around 6,000 to 10,000 years ago a genetic mutation popped up in the Black Sea region that likely led to blue eyes.

Brown eyes get their colour from melanin, but blue eyes don't have any blue pigment. Instead, if you have blue eyes, the front part of your eye has hardly any pigment.

Why does the lack of pigment look blue? For the same reason the sky looks blue. Particles in the rest of your eye scatter blue more than the other colours of the rainbow, making your eyes appear blue.

 

References

Gudgel, Dan T. "Your Blue Eyes Aren’t Really Blue." American Academy of Ophthalmology. June 16, 2023. https://www.aao.org/eye-health/tips-prevention/your-blue-eyes-arent-really-blue.

Khan, Razib. "What Does Eye Colour What does eye colour have to do with skin colour?" Discover Magazine. February 5, 2009. https://www.discovermagazine.com/the-sciences/what-does-eye-colour-have-to-do-with-skin-colour.

Liu, Fan, et al. "Eye Colour and the Prediction of Complex Phenotypes from Genotypes." Current Biology. March 10, 2009. https://pubmed.ncbi.nlm.nih.gov/19278628/.

Manco, Jean. Ancestral Journeys: The Peopling of Europe from the First Venturers to the Vikings. 2nd ed. Thames & Hudson. 2015.

Pośpiech, Ewelina et al. "Gene–gene Interactions Contribute to Eye Colour Variation in Humans." Journal of Human Genetics. April 7, 2011. https://www.nature.com/articles/jhg201138.

Southworth, Lucy. "Eye Colour." The Tech Museum of Innovation. Stanford University. September 21, 2007. http://genetics.thetech.org/ask/ask232.

"The World’s Population By Eye Colour." World Atlas. Accessed July 3, 2023. https://www.worldatlas.com/articles/which-eye-colour-is-the-most-common-in-the-world.html.