Hazel eyes are often described as a combination of brown and green. They are characterized by having a brownish iris with green and gold flecks or rings. Hazel eyes are considered to be rare compared to brown eyes, which are the most common eye color worldwide.
How Common Are Hazel Eyes?
It’s difficult to determine exactly how common hazel eyes are since definitions vary. However, estimates suggest hazel eyes are found in around 5-10% of the global population. In comparison, brown eyes are estimated to occur in over 75% of people worldwide. Here’s a breakdown of common eye colors and their estimated frequencies:
| Eye Color | Global Frequency |
|---|---|
| Brown | Over 75% |
| Blue | 8-10% |
| Hazel | 5-10% |
| Green | 2% |
| Gray | 1% |
As this data shows, hazel eyes are much less common globally than brown eyes. However, hazel eye color frequency varies between different geographic and ethnic populations.
Hazel Eyes are More Common in Certain Populations
While hazel eyes are relatively rare worldwide, they are more prevalent in certain ethnicities and regions. For example:
- Up to 25% of people from the Middle East and South Asia have hazel eyes
- Around 20% of North Africans have hazel eyes
- Hazel eyes are found in 15-18% of people from the Horn of Africa region
- In North America and Europe, 10-15% of Caucasians have hazel eyes
In contrast, brown eyes make up over 90% of eye colors among East Asians and Indigenous peoples of the Americas. This demonstrates that hazel eyes are much more common in Middle Eastern, North African, South Asian and European populations compared to other ethnic groups.
What Causes Hazel Eye Color?
Eye color is determined by the amount of melanin pigment in the iris. Brown eyes have a lot of melanin, while blue eyes have very little. Hazel eyes arise when moderate amounts of melanin combine with Rayleigh scattering of light through the stroma.
Hazel eyes specifically result from:
- A medium concentration of melanin that produces light brown pigmentation
- A smaller amount of collagen deposits leading to Rayleigh scattering
- The combination of these factors results in hazel eyes
The exact hue of hazel eyes depends on the ratio of melanin to Rayleigh scattering. More melanin results in darker brown/gold eyes. More Rayleigh scattering leads to greener hazel eyes.
Genetics of Hazel Eyes
The genetics behind hazel eyes are not fully understood but involve multiple genes that influence melanin and collagen production. Key genes associated with hazel eyes include:
- OCA2 – Regulates melanin production and brown/blue eye color
- HERC2 – Turns OCA2 on or off, reducing or increasing melanin
- SLC24A4 – Linked to golden ring color in hazel eyes
- TYR – Influences light coloration and Rayleigh scattering
Hazel eye color is generally inherited in a polygenic fashion, meaning multiple genes are involved. However, it is not a simple mix between parent eye colors. Children can have hazel eyes even if neither parent does. The full genetics behind hazel eyes require further research.
Are Hazel Eyes Linked to Health Issues?
There is no evidence that hazel eye color itself is associated with any health or medical issues. However, some eye diseases may show distinct symptoms in hazel eyes. For example:
- Cataracts – Can make hazel eyes appear browner
- Glaucoma – May change hazel eyes to darker brown
- Wilson’s Disease – Can produce a greenish-brown discoloration
Additionally, some genetic disorders associated with eye, skin, or hair pigmentation tend to coincide with hazel eyes, including:
- Waardenburg Syndrome
- Tietz Syndrome
- Heterochromia
However, these conditions are caused by genetic mutations rather than hazel eye color itself. Overall, hazel eyes do not pose extra health risks compared to other colors.
Interesting Facts About Hazel Eyes
- Hazel eyes can appear to shift in color from brown to green
- Two people can have hazel eyes but different shades of brown/green
- Hazel eyes are thought to have developed fairly recently in human evolution
- Babies born with hazel eyes can experience color changes during childhood
- Hazel eyes are celebrated in various art forms and poetry
Conclusion
In summary, hazel eyes are rarer globally than brown eyes but are more common in certain populations like the Middle East and Europe. Hazel eye color arises from moderate melanin with Rayleigh scattering of light. Multiple genes influence hazel eyes through complex inheritance patterns. While hazel eyes themselves don’t cause health issues, some disorders may alter hazel eye appearance. Overall, hazel eyes are a unique and relatively uncommon eye color with an intriguing genetic and geographic distribution.
