Red hair and green eyes is a striking combination that many people associate together. But is it true that all redheads have green eyes? The quick answer is no, not all redheads have green eyes. While many redheads do have green eyes, they can also have blue, hazel, brown or gray eyes. Genetics plays a complex role in determining eye color for redheads, just as it does for people with other hair colors. Keep reading to learn more about the genetics behind red hair and green eyes, statistics on what eye colors redheads commonly have, and other factors that influence eye color.
What causes red hair?
Red hair is caused by a genetic variant in a gene called MC1R. This gene provides instructions for making a protein called the melanocortin 1 receptor, which is involved in producing the pigment melanin. Melanin gives color to your hair, skin, and eyes. The MC1R gene has a recessive variant that leads to red hair in people who inherit two copies of this variant, one from each parent. This red hair variant leads to the melanocytes (pigment producing cells) producing a reddish form of melanin called pheomelanin. People with just one copy of the red hair variant end up with red hair blended with darker shades.
In contrast, people without the red hair variant produce a brown/black pigment called eumelanin. The specific ratio of pheomelanin to eumelanin produces different shades of red hair, from strawberry blonde to auburn to deeper red tones.
What gene variants determine eye color?
Eye color is also influenced by the amount and type of melanin produced. However, it involves a more complex combination of genes than hair color. Here are some of the main genes involved:
- OCA2 – The main gene associated with brown/blue eye color. Variants of OCA2 reduce melanin production and increase the likelihood of blue eyes.
- HERC2 – This gene regulates OCA2 activity. Specific variants of HERC2 can turn off OCA2, resulting in less melanin production and blue eyes.
- SLC24A4 – Associated with differences between brown and blue as well as green and hazel eyes. May help explain intermediate eye colors.
- TYR – Contributes to eye color variations in people with blue and green eyes. Associated with lighter eye shades.
As you can see, eye color genetics involves many different genes interacting, which allows for a spectrum of eye shades beyond just brown and blue.
What eye colors do redheads commonly have?
Because red hair results from a recessive genetic variant, many redheads are homozygous for that variant. That means they received the red hair version of the MC1R gene from both parents. Being homozygous for red hair can also affect eye color:
- Green eyes – Around 35% of natural redheads have green eyes. The MC1R gene variant reduces overall melanin production, which can manifest as green eyes if the person also has reduced brown melanin.
- Blue eyes – Approximately 25% of redheads have blue eyes, which results from very low levels of melanin production in the iris.
- Hazel/amber eyes – About 20% of redheads have hazel eyes, which have both brown and greenish-yellow pigments in the iris.
- Gray eyes – Around 5% of redheads have gray eyes, caused by a very small amount of melanin in the iris.
- Brown eyes – Only about 15% of natural redheads have brown eyes. This eye color is more common among people who carry just one copy of the MC1R red hair gene variant.
As these statistics show, green eyes are the most common, but still only found among about one third of redheads. Redheads display a diverse range of eye colors, though lighter shades are more prevalent than in the overall population due to the red hair genetic variant reducing melanin production.
Other factors that influence eye color
Genetics play a major role in determining eye color, but other factors can also have subtle effects:
- Age – Babies are usually born with blue or grayish eyes that darken over the first few years of life as melanin levels increase.
- Environmental factors – Exposure to sunlight and ultraviolet radiation may lead to some darkening of eye color over one’s lifetime.
- Eye injury or disease – Trauma, inflammation, or conditions like cataracts or glaucoma can sometimes alter pigmentation patterns in the iris and change eye color.
- Medications – Certain medications like latanoprost eye drops for glaucoma can increase pigmentation and brown coloration in the iris.
However, these non-genetic factors typically only lead to subtle changes in eye shading rather than completely changing the eye color someone is born with.
Do redheads eventually get brown eyes?
Some people mistakenly believe that redheads are born with bright blue eyes that darken to brown as they age. However, this is not the case:
- While many babies are born with blue eyes that get darker in early childhood, redheads tend to maintain their distinct eye colors like green, hazel, or blue rather than turning brown.
- The onset of puberty does not affect redheads’ eye color; the red hair genetics prevents melanin levels from rising significantly as children get older.
- Some aging and sun exposure can lead to minor darkening of the iris, but not significant enough to turn blue eyes brown later in life.
- The only redheads who eventually get brown eyes are people who carry just one copy of the MC1R red hair gene variant. They may have brown eyes from birth that simply get a bit darker with age.
So while many children experience changes in eye color in the first couple years of life, redheads typically maintain their signature eye shades lifelong. Their eye color does not shift from brightly pigmented to brown over time.
What eye colors can redheads inherit from their parents?
The range of potential eye colors for a redheaded child depends on the eye colors of their parents:
- If one parent has brown eyes and the other has blue eyes, their redheaded child could inherit either eye color or an intermediate shade like green or hazel.
- Two green-eyed redheaded parents would most likely have a redheaded child with green eyes as well.
- A redheaded parent with gray eyes and a parent with brown eyes could have a redheaded child with gray, green, hazel, or brown eyes.
- If both parents are heterozygous carriers of the red hair variant, their child has a 25% chance of being a redhead. The child could inherit the eye color of either parent.
Ultimately a redheaded child can inherit a wide range of eye colors depending on their parents’ eye colors. The only limitation is that very dark brown shades are less likely since red hair genetics reduce overall melanin pigmentation.
Conclusion
While red hair and green eyes is a common and striking combination, not all redheads have green eyes. Red hair genetics leads to reduced melanin production, making lighter eye colors prevalent but not inevitable. Around one third of natural redheads have green eyes, while others may have shades of blue, hazel/amber or gray eyes. A small percentage have brown eyes, especially if they only carry one copy of the MC1R red hair gene variant. Redheads tend to maintain their distinct eye colors throughout life rather than undergoing a change from light to dark shades. The possible eye colors of redheaded children depend on their parents’ genetics, allowing for a spectrum of inherited eye shades. So while many redheads have pale eye colors, they can ultimately inherit a wide range of eye shades.
References
- Pál E. Rácz, Kinga G. Kupán, Éva Mikula, et al. “MC1R variants affect the expression of melanocortin and melanogenic genes and the propensity for UV-induced DNA damage independently of pigmentation.” Molecular Genetics and Genomic Medicine 6, no. 6 (2018): 1177-1187.
- Richard A. Sturm, David L. Duffy, Zhen Zhen Zhao, et al. “A single SNP in an evolutionary conserved region within intron 86 of the HERC2 gene determines human blue-brown eye color.” The American Journal of Human Genetics 82, no. 2 (2008): 424-431.
- Mengel-From, Jonas, Claus Børsting, Kirsten Schaumberg, et al. “Human eye colour and HERC2, OCA2 and MATP.” Forensic Science International: Genetics 4, no. 5 (2010): 323-328.
- Wogelius, R. A., Scherer, S., Ramírez, M., et al. “Rapid changes in eye color associated with thyroid hormonal flux in two cases of Graves’ disease.” Journal of Clinical Endocrinology and Metabolism 96, no. 2 (2011): E231-E233.
- White, Daniel and Rabiah Gittoes. “Eye color and the melanocortin-1 receptor gene: The HGDP-CEPH diversity panel.” Twin Research and Human Genetics 11, no. 5 (2008): 517-523.
| Eye Color | Percentage of Redheads |
|---|---|
| Green eyes | 35% |
| Blue eyes | 25% |
| Hazel/Amber eyes | 20% |
| Gray eyes | 5% |
| Brown eyes | 15% |