A baby’s eye color is determined by the eye colors of both parents. While it is impossible to predict with 100% accuracy what color eyes a baby will have, genetics can give us a good indication of the possibilities. Below we’ll explore what factors influence a baby’s eye color and the genetic mechanisms behind inheritance.
What Determines a Baby’s Eye Color?
There are two key factors that influence a baby’s eye color:
- The pigmentation in the parent’s eyes
- The genes a baby inherits from their parents
Human eye color is controlled by melanin, a pigment that gives color to skin, hair, and eyes. Eyes with darker coloration have more melanin deposits in a layer of the iris called the stroma. Eyes with lighter coloration have fewer deposits of melanin.
The amount and type of melanin present are controlled by genes. There are several genes that influence eye color, but two of the most important ones are:
- HERC2 – regulates the production of melanin
- OCA2 – produces a specific kind of melanin
The versions of these genes a parent passes down to their child will help determine the child’s eye color. But genetics isn’t the whole picture.
How Genetics Determine Eye Color
Our eyes can have shades of brown, green, blue, gray, hazel or a blend of colors. This range comes down to one simple genetic fact:
- The presence of melanin leads to darker eyes.
- Less melanin results in lighter colored eyes.
If a baby inherits genes for lots of melanin production, their eyes will be darker. If a baby inherits genes for less melanin, their eyes will be lighter.
When a baby inherits a version of the HERC2 or OCA2 gene that limits melanin production, that can reduce pigmentation in the iris leading to green, blue or gray eyes. Theversions inherited from mom and dad are what ultimately determine the baby’s eye shade.
The Role of Melanin
The melanin in our irises comes in two forms that also influence eye color:
- Eumelanin – A brown/black melanin that leads to brown or darker eyes.
- Pheomelanin – A red/yellow melanin that leads to lighter coloration in green and hazel eyes.
The combination and concentration of these two types of melanin present are what creates the range of human eye colors we see.
Amount of Pigmentation Determines Shade
The actual shade of a baby’s eyes will be determined by the amount of melanin they end up having. Here’s an overview:
- More melanin = darker brown/black
- Moderate melanin = medium brown
- Low concentrations of melanin = hazel, green, blue, gray
- Very little melanin = light blue/gray
Babies are almost always born with blue or gray eyes that darken over the first year of life as melanin accumulates. The final shade is often set by age 3.
What Eye Colors Can Parents Pass On?
The range of possible colors a parent can pass on depends on their genetics. But in general:
- Brown-eyed parents tend to have brown-eyed kids because brown eye color is dominant.
- Parents with lighter eye colors can have children with lighter or darker eyes.
- Kids can end up with a blend of mom and dad’s eye colors.
Some examples:
- If one parent has blue eyes and the other brown eyes, the child may end up with hazel eyes.
- If both parents have green eyes, the child is more likely to also have green eyes.
- Even two blue-eyed parents can have a brown-eyed child due to recessive genes.
The possibilities are endless when it comes to eye color genetics, but in general darker traits tend to be dominant.
Brown Eyes Are Dominant
If one parent has brown eyes and the other has blue eyes, the child most often ends up with brown eyes. That’s because the genes that code for brown/black melanin are dominant over genes for little to no melanin production.
For a child to have blue eyes, both parents need to pass down copies of the recessive blue eye genes. But there’s still a possibility of the brown eye gene sneaking in there too.
Lighter Eyes Have More Variability
Parents with green, blue or hazel eyes have more variability in what they can pass down. Light eye colors do not “overwrite” brown eyes when it comes to genetics.
Lighter-eyed parents can pass down copies of either:
- Genes limiting melanin = lighter eyes
- Genes allowing melanin = darker eyes
Their genetics allow for a broader range of possibilities in their children.
Does Eye Color Come from Mom or Dad?
A child’s eye color comes from both parents. Each parent passes down one copy of the various eye color genes that make up their genetic code. The combo of what mom and dad contribute is what leads to the child’s eye shade.
Sometimes genetics makes it seem like eye color “comes from” one parent more than the other. Here are some examples:
- If dad has brown eyes and mom has blue, baby often ends up with dad’s brown eyes.
- If mom has green eyes and dad has brown eyes, baby may end up with a hazel/green blend like mom.
- If both parents have blue eyes, the baby usually has blue eyes too.
But in the end, both parents make an equal genetic contribution. The dominance patterns in eye color inheritance just make certain colors prevail more in kids.
Can Eye Color Come Only from Mom?
There is no scenario where eye color comes only from mom. Since each parent passes down one copy of their genes, both mom and dad’s DNA get passed on – even if we can’t always tell in the end result.
Sometimes people think eye or hair color comes just from mom because lighter features tend to get overshadowed by darker ones when it comes to dominance. But the father’s genes are still there.
Does the Mother’s Genetics Dominate?
It is not true that the mother’s eye color always dominates genetically. Each parent contributes one set of genes. In some cases, the mother’s lighter eye color genes may be overshadowed by the father’s darker eye color genes in determining the child’s eye color. But the father’s genes do not always dominate either.
Can Parents with Brown Eyes Have a Blue-Eyed Child?
Two brown-eyed parents can indeed have a blue-eyed child. Brown eye color is dominant, but parents with brown eyes may both be “hiding” the recessive blue eye gene in their genetic code.
If both parents carry a recessive blue eye gene, their baby has a 25% chance of inheriting two copies of the blue eye gene – which allows for blue eyes to show through despite the parents’ brown coloration.
Blue Eyes Are a Recessive Trait
Blue eyes are recessive, meaning you need two copies of the blue eye gene to have blue eyes. If someone only has one copy, brown eyes will prevail.
So two brown-eyed parents may each have a brown eye gene (dominant) and carry one hidden blue eye gene. Their baby would then have a 1 in 4 chance of inheriting both recessive blue genes (one from each parent) and ending up with blue eyes.
Unlocking Recessive Genes
Two brown-eyed mates allows the recessive blue eye genetic code to pair up in their child and express itself. This “hiding” of recessive traits over generations is called genetic carryover and can lead to some surprising outcomes!
Are Babies Born with Blue Eyes?
Babies of all races are often born with blue or gray eyes that darken later. This is because it takes time for melanin to accumulate in the iris after birth. More melanin builds up gradually as the infant ages.
Some fun facts about newborn eye color:
- Around 60% of Caucasian babies are born with blue eyes.
- Around 80% of babies born with blue eyes transition to green, hazel or brown eyes over the first 3 years.
- All babies are usually born with “some” melanin present except for those with albinism.
- Eye color is often set by age 3, but can continue darkening into early childhood.
So while most babies are born with blue/gray eyes, only a small percent retain that eye color. But it is a very common temporary shade in newborns.
Why Are Babies’ Eyes Blue at Birth?
Babies of all ethnicities are often born with blue eyes because they have not yet built up enough melanin in their irises to show their true color. Melanin continues accumulating as the baby grows to eventually darken their eyes to their natural shade.
When Do Babies’ Eyes Change Color?
For Caucasian babies born with blue eyes, the eye color change begins around 6-9 months of age as more melanin develops in the iris. Most eye colors are set by age 3, but changes can continue into early childhood.
Babies with brown eyes usually show their natural color sooner, within a few months after birth. Darker eyes have faster melanin production.
How to Predict Your Baby’s Eye Color
While genetics makes it tricky to say with 100% certainty what eye color a baby will end up with, there are some guidelines that can help predict the possibilities based on the parents’ eyes:
Predicting Baby’s Eye Color If Parents Have Brown Eyes
- If both parents have brown eyes, the baby will most likely have brown eyes as well since brown is the dominant trait.
- There is a small chance for a green/hazel outcome if hidden green/hazel genes get paired up.
- The odds of a blue eyed baby are only about 1 in 16 (6%) since blue is recessive.
Predicting Baby’s Eye Color If One Parent Has Brown Eyes
- If one parent has brown eyes and one parent has blue eyes, the baby will most likely have brown eyes.
- Hazel/green eyes are possible if the blue eyed parent carries those recessive traits.
- There is only about a 12.5% chance of the baby having blue eyes in this scenario.
Predicting Baby’s Eye Color If Parents Have Blue Eyes
- This scenario offers the most possibilities, but blue eyes have the highest chance.
- If both parents have blue eyes, over 3/4 of their children should have blue eyes as well.
- But there are recessive genes at play, so green and brown are still possibilities.
What Affects the Odds of Your Baby’s Eye Color?
While genetics are responsible for eye color, there are some other factors that can slightly alter the odds, including:
- Ethnic background – Certain ethnicities have higher frequencies of lighter or darker eyes.
- Number of eye colors in family history – More variety indicates more recessive traits.
- Melanin levels – The precise amount of melanin made impacts the shade.
- Eye conditions/diseases – Some disorders like Horner’s syndrome can change melanin deposition.
In addition to genetics, the odds may shift a bit based on environmental and disease causes of variation in melanin production.
Ethnicity Influences Melanin Levels
Certain ethnic backgrounds have higher occurrences of lighter or darker eyes:
- Lighter eyes are more common in Caucasians
- Darker eyes are more common in Africans, Asians, Hispanics
A baby’s natural melanin levels are often somewhat influenced by their ethnicity’s overall pigmentation.
Look for Recessive Traits in the Family
Examining family history for recessive traits can give clues about rare colors. If grandparents/distant relatives have green eyes, chances increase for that recessive gene combination in the baby.
Diseases/Disorders Change Melanin
Certain conditions like Horner’s syndrome disrupt melanin deposition. Albinism prevents melanin production completely. The less melanin made, the lighter baby’s eyes will be.
Conclusion
While genetics make it hard to predict with certainty, a baby’s eye color results from a combination of the eye colors and key genes inherited from both parents. Darker eyes tend to be dominant, but many genetic factors ultimately affect the amount and type of melanin produced.
Examining each parent’s eye color and family histories provides clues about a child’s probable eye shade. And remember that babies of any ethnicity can be born with blue eyes initially as their irises continue to develop pigmentation.
In the end there is an exciting element of surprise with each new baby when it comes to their eye color! Parents will simply have to wait and see what genetics and melanin have in store for their child.