Genetics: Why People Have Blue Eyes?

If you have ever researched your family history, you may have wondered about the physical features that you might have inherited from your ancestors, such as your hair color, nose shape, or even the size of your feet. But what about your eyes? Specifically, what about the intriguing and often coveted trait of blue eyes?

In this article, we will explore the fascinating genetics behind eye color inheritance, with a focus on the unique characteristics of blue eyes.

Have you ever looked into a mirror and wondered where your eye color came from? As someone with greenish blue eyes, I have often pondered this question and done some research to better understand the genetics behind eye color inheritance.

In this article, I will share what I have learned and explore the fascinating topic of eye color genetics, including the inheritance of blue eyes. I hope you find this article interesting, and I would love to hear your thoughts after reading it.

In reference to the article ‘Every blue eyed person on the planet is a descendant of one single person Written by Kate Plummer, On Apr 10, 2023

Eye color has long been a topic of fascination and curiosity for both scientists and the general public.

Recently, this recent article claims that every blue-eyed person on the planet is descended from a single European ancestor who lived thousands of years ago has been circulating online. While the story of the blue eye mutation is intriguing, the claims made in the article are not entirely accurate.

In this blog article, we will delve into the science behind eye color and the history of the blue eye mutation to better understand the complexity of human genetics and ancestry. By seeking out reliable sources and approaching scientific claims with a critical mindset, we can gain a deeper appreciation for the intricate tapestry of human heritage.

The Science Behind Eye Colour

Eye color is determined by the amount and type of pigment in the iris of the eye. The color of the iris ranges from dark brown to light blue, with shades of green and gray in between. The pigment that determines eye color is called melanin, which is produced by cells called melanocytes. The more melanin a person has in their iris, the darker their eye color will be. The type and amount of melanin in the iris is determined by genetics.

The genetics of eye color are complex, and many different genes are involved. One of the most important genes that determines eye color is called OCA2. This gene codes for a protein that regulates the production of melanin in the iris. The amount and type of melanin produced by the iris is also influenced by other genes, including HERC2 and SLC24A4.

Exploring the of Eye Colour Inheritance

Eye colour is a polygenic trait, meaning that it is influenced by several genes. The genetic makeup of an individual determines their eye color, and it can range from brown to blue, green, hazel, and gray.

Eye colour is a result of the amount and type of pigment present in the iris, the coloured part of the eye. One of the genes responsible for eye color is OCA2 (oculocutaneous albinism II), located on chromosome 15.

This gene controls the production of melanin, the pigment responsible for the color of the skin, hair, and eyes. OCA2 is particularly responsible for the amount of brown pigment (eumelanin) produced in the iris, which results in the color of the eyes ranging from brown to black.

Another gene that affects eye color is HERC2 (hect domain and RLD 2), located on chromosome 15. HERC2 plays a crucial role in regulating OCA2, which in turn determines the amount of melanin produced. A variation in this gene can result in reduced melanin production, leading to lighter eye colors such as green, blue, or gray.

In addition to OCA2 and HERC2, several other genes contribute to eye color, including TYR (tyrosinase), TYRP1 (tyrosinase-related protein 1), SLC24A4 (solute carrier family 24, member 4), and SLC45A2 (solute carrier family 45, member 2).

Variations in these genes can result in the production of different types and amounts of melanin, leading to different eye colors.

The inheritance of eye color is a complex process that is not fully understood. The genes responsible for eye color are inherited from both parents, and the resulting eye color depends on the combination of genes inherited. In general, brown eyes are dominant over blue, green, or gray eyes, so if one parent has brown eyes and the other has blue eyes, the child is more likely to have brown eyes.

In summing up this blog, eye color is determined by multiple genes, including OCA2 and HERC2, which control the production of melanin in the iris.

The inheritance of eye color is complex and depends on the combination of genes inherited from both parents. Understanding the genetic basis of eye color can provide valuable insights into the inheritance of other traits and genetic disorders.

The History of the Blue Eye Mutation

Blue eyes are a relatively rare trait, found in only about 8-10% of the global population. The mutation that causes blue eyes is thought to have originated in Europe, where it is more common than in other parts of the world. The exact time and place of the mutation’s origin are unclear, but it is believed to have occurred between 6,000 and 10,000 years ago. The mutation that causes blue eyes is a change in the HERC2 gene, which is located near the OCA2 gene on chromosome 15. .

The mutation alters the expression of the OCA2 gene, resulting in reduced production of melanin in the iris. People with blue eyes have the same HERC2 mutation, which is why every blue-eyed person can trace their ancestry back to a single individual who carried this mutation.


In conclusion, the story of the blue eye mutation is a fascinating example of human genetic diversity and the complex history of human migration and interbreeding.

While the claims made in the recent article about every blue-eyed person being descended from a single European ancestor are not entirely accurate, the story of the blue eye mutation remains a compelling topic of study for scientists and the general public alike.

By approaching scientific claims with a critical mindset and seeking out reliable sources, we can better understand the intricate tapestry of human heritage and the genetic factors that contribute to our physical traits. As we continue to study and appreciate the complexities of human genetics, we can gain a deeper appreciation for the rich diversity of our global community.


1. Branicki, W., Liu, F., van Duijn, K., Draus-Barini, J., Pośpiech, E., Walsh, S., Kupiec, T., Wojas-Pelc, A., Kayser, M., & Liu, F. (2013). Model-based prediction of human hair color using DNA variants. Human Genetics, 132(4), 443–454.

2. The American Society of Human Genetics. ( 2008, January 3). Blue-Eyed Humans Have A Single, Common Ancestor. ScienceDaily. Retrieved April 11, 2023, from

3. Liu, F., van der Lijn, F., Schurmann, C., Zhu, G., Chakravarty, M. M., Hysi, P. G., … & Spector, T. D. (2010). A genome-wide association study identifies five loci influencing facial morphology in Europeans. PLoS genetics, 6(9), e1000995.

4. Sturm, R. A., Duffy, D. L., Zhao, Z. Z., Leite, F. P. N., Stark, M. S., Hayward, N. K., & Martin, N. G. (2008). A single SNP in an evolutionary conserved region within intron 86 of the HERC2 gene determines human blue-brown eye color. American Journal of Human Genetics, 82(2), 424-431.

5. Walsh, S., Liu, F., Wollstein, A., Kovatsi, L., Ralf, A., Kosiniak-Kamysz, A., … & Kayser, M. (2011). The HIrisPlex system for simultaneous prediction of hair and eye colour from DNA. Forensic Science International: Genetics, 5(5), 433-445.


Published by Darrell Gibbs

A father of three children and five grandchildren who retired in 2015 and began a career as a non-fiction writer in genealogy resource ebooks for new family historians. Aspiring towards the future as a Historical Fiction Author of his premier book "Wessex Reign".

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