Eye color probability chart & facts: Which is the rarest eye color?

Eye color probability

/ 34 min

Our statistical experts bring you the facts about eye color genetics and eye color probability. Here is how eye color is inherited and which is the rarest eye color.

Eye color odds Infographic

Eye color probability chart & facts infographic

Key points on eye color probability

Critical points on eye color probability

  • Most frequently occurring baby eye colors result from the alleles of the parents.
  • The visible eye color depends on the parent genes’ dominant and recessive nature. Using their qualities, you can compute the eye color probability.
  • Eye color probability is not deterministic, with 16 genes contributing to it. The two most important ones are OCA2 and HERC2.
  • Brown eyes are the most frequently encountered, with a 1 in 1.82 to 1 in 1.27 chance of the average person having them.
  • Blue eyes are not as rare as you may think, despite being recessive, with 8% to 10% of all people exhibiting them.
  • Grey eyes are similar to blue ones but showcase more collagen in the stroma. Less than 1% of the population has grey eyes.
  • Hazel eyes are obtained difficultly, as they depend on the distribution of one or more pigments in the iris. Still, there is a 1 in 20 eye color probability of a person having them.
  • Hazel eyes are referred to as central heterochromia (color difference between the center and the edges of the iris).
  • Lateral heterochromia is rarer (1 in 166.667 odds) and can be inherited, as well as caused by congenital or acquired syndromes.
  • “Black eyes” do not really exist, but some conditions like aniridia, where the pupil is dilated and the iris is lacking, make eyes appear black.
  • There are between 1 in 50,000 and 1 in 100,000 chances of having aniridia.
  • Pink, red, or purple eyes are a result of albinism. There is no reddish pigmentation, and their iris color comes from the retina.
  • Babies with naturally low melanin can be born with blue eyes. Their iris color changes as melanin is secreted during the first year of life.

Eye colour odds

Eye type Chances of having it Likeliest parents’ eye colours Least likely parents’ eye colours
Blue eyes 1 in 12.5 – 1 in 10 Blue + blue Green + brown
Hazel eyes 1 in 20 Green + brown, blue + brown Brown + brown/green + green, blue + blue
Brown eyes 1 in 1.82 – 1 in 1.27 Brown + brown Blue + blue/blue + green
Green eyes 1 in 50 Green + green Blue + green
Grey eyes <1 in 100 Blue + blue Green + brown
Amber eyes 1 in 20 Brown + brown Blue + blue/blue + green
Lateral heterochromia 1 in 166.67
“Black eyes” (aniridia) 1 in 50,000 – 1 in 100,000
Red/pink/purple eyes (albinism) <1 in 100

What gives the chances for eye colour

Eye color probability generally results from a series of genetic traits of a person and one’s parents.

The main genetic factors for the color of baby eyes are homozygous and heterozygous genes, the parents’ dominant and recessive eye colors, melanin concentrations, genotype, and phenotype.

Eye color genetics terminology

Eye color genetics terminology

  • Chromosome – the nucleic acids and proteins structure at eh nucleus of most cells. It contains genetic information in the form of genes.
  • Gene – the basic physical and functional unit of heredity.
  • Allele – each of the two or more alternative forms of a gene resulting from a mutation found at the same locus in the chromosome. The iris color is resultant of such an allele.
  • Homozygous – an organism with two identical copies of the same allele at a specific gene locus.
  • Heterozygous – an organism with differing alleles at a particular gene locus.
  • Dominant allele – an allele that manifests its associated traits even if an individual has one copy. So dominant alleles manifest when they are homozygous and heterozygous. Green and brown eyes are dominant.
  • Recessive allele – alleles that manifest only when the individual has identical copies. In other words, recessive alleles manifest when they are homozygous. Blue is recessive.
  • Melanin – the chemical substance in our body that produces hair, eye, and skin pigmentation.
  • Genotype – the complete set of the genetic material of an organism. It can also refer to the specific alleles an individual carries at a locus. Melanin regulating genes and iris color alleles are part of the genotype.
  • Phenotype – the resultant manifestations, characteristics, and traits of an organism’s genotype. All eye colors are part of the phenotype.

How a baby’s eye colour emerges

How a baby’s eye colour emerges

Each parent contributes with two alleles, arriving at four possible combinations with 25% odds each. Eye color genetics follow the same pattern of inheritance.

Each option denotes another possibility for the baby and the baby’s eye colour. Most biologists use a similar graphical representation for the process, called the Punnett square calculator.

The Punnett square calculator for baby eyes

We will share the simplest form of the Punnett square calculator for a baby’s eye colour and follow up with examples for eye color genetics.

The basic model

The basic model

The rows and columns of a Punnett square calculator represent the alleles for the baby’s eye color. The cells combine two alleles resulting in eye color genetics variation.

Each outcome has an equal 1 in 4 chance of occurrence. There are no other potential outcomes. The baby eyes must “resemble” one of the alleles coming from a parent. It cannot normally variate outside of the genotype.

Eye color genetics and the baby’s eye color

Eye color genetics and the baby’s eye color

However, the baby’s eye color may not directly reflect any of the ones their parent has. In other words, the phenotype is more complicated.

Framework for our example

We will take A as a dominant gene for baby eyes while a being recessive. For the sake of argument, A can signify either brown or green eyes, and a can only signify blue eyes.

Eye color probability based on alleles

While the inheritance outcomes have an equal 1 in 4 chance, the eye color probability changes based on gene dominance.

In the example, we have a case of two parents with two identical alleles, one dominant (A) and one recessive (a). They combine to form four possibilities: (AA), (Aa) twice, and (aa).

While three of them differ, they will manifest in the phenotype in two distinct ways.

Eye color probability and “visible” outcomes

Eye color probability and “visible” outcomes

  • The dominant A allele manifests with 75% odds.
  • The recessive gene manifests with 25% odds.

In other words, the baby eye color will most probably manifest visibly according to the dominant allele. However, 2 in 3 variations will be dominant and heterozygotic in this case.

The heterozygotic distinction is essential since it will influence the iris color probability of future offspring.

Heterozygotic vs Homozygotic

  • Two homozygous recessive alleles

Two homozygous recessive alleles

Two parents with homozygous recessive alleles (i.e., blue eyes) can only give birth to a child with homozygous recessive alleles (identical blue eyes).

More than the 100% chance of eye color being blue, the child will bear the same genetic structure, two recessive alleles.

  • Two parents with heterozygous alleles (both dominant and recessive)

Two parents with heterozygous alleles (both dominant and recessive)

We have seen this eye color genetics chart before. The Punnett square calculator for two heterozygous parents gives three different options.

The first is a homozygous dominant allele child (that would have green eyes or brown eyes), two heterozygous variants (that will also manifest as green eyes or brown eyes), and one homozygous recessive allele child (who would have blue eyes).

  • One dominant homozygous and one heterozygous

One dominant homozygous and one heterozygous

In this case, the baby eyes can only manifest as a dominant color variation (brown or green eyes). The child will be homozygous with a 50% rate and heterozygous with a 50% rate.

  • One recessive homozygous and one heterozygous

One recessive homozygous and one heterozygous

If one father is recessive homozygous (has blue eyes), and the other is heterozygous (which manifests like brown or green eyes), their child has a 50/50 chance of taking after either.

Aside from the phenotype (the way the eyes are colored), it

  • Two homozygous dominant alleles

Two homozygous dominant alleles

In general homozygous parents can only give birth to homozygous children that only share their iris color.

For dominant colors, the baby eyes will be green if the parents have green eyes and brown if both parents have brown eyes.

  • Two homozygous alleles (one dominant, one recessive)

Two homozygous alleles (one dominant, one recessive)

Here, all possible outcomes are heterozygous combinations of the dominant and recessive alleles. Thus, there’s a 100% chance that the child will have this combination.

The phenotype or visual physical trait will resemble the one related to the dominant allele, but the child will bear the recessive one too.

Variation in dominant alleles

The simplified Prunett square calculator chart does not tell the whole story of eye color genetics.

While it is descriptive of the prevalent genotype, the phenotype or the visible manifestation of baby eye color also depends on the dominant allele variation.

Humans have two dominant alleles for iris color, brown and green. This leads to additional variations.

Inheritance-based eye color probability chart

Iris color inheritance depends on the alleles one’s parents carry, resulting in differing chances of eye color traits manifesting for the same visible parent traits.

We will consider all possible combinations of parent alleles, compute the genotypic results, and then derive the eye color probability or the phenotype.

Eye color genetics rules

Eye color genetics rules

  • Brown and green are dominant. However, when they meet, green acts as recessive in relation to brown.
  • Blue is always recessive. Blue eyes only manifest when both alleles correspond to the recessive gene.
  • We exclude the case of hazel eyes from computing eye color probability.
  • We will provide exact chances of eye color exhibiting. However, the particular phenotype for eyes depends on no less than 16 genes. The actual iris color probability may slightly variate.

  • Both parents are homozygous

Both parents have Genotypic results and odds Phenotype & eye color probability
Homozygous brown eyes 100% homozygous brown 100% brown eyes
Homozygous green eyes 100% homozygous green 100% green eyes
Homozygous blue eyes 100% homozygous blue 100% blue eyes

The main takeaway for eye color genetics

If both parents have the same homozygous genetic makeup, there is a 100% eye color probability that the child will exhibit the same trait as them.

This fact goes regardless of the dominant or recessive iris color.

  • One homozygous parent and one homozygous parent

Homozygous parent Heterozygous parent Genotypic results and odds Phenotype & eye color probability
Brown eyes Green-brown variation 75% homozygous brown, 25% heterozygous green-brown 100% brown eyes
Brown eyes Blue-brown variation 75% homozygous brown, 25% heterozygous blue-brown 100% brown eyes
Brown eyes Blue-green variation 75% homozygous brown, 25% heterozygous blue-green 75% brown eyes, 25% green eyes
Green eyes Brown-green variation 75% homozygous green, 25% heterozygous green-brown 75% green eyes, 25% brown eyes
Green eyes Blue-brown variation 75% homozygous green, 25% heterozygous blue-brown 75% green eyes, 25% brown eyes
Green eyes Blue-green variation 75% homozygous green, 25% heterozygous blue-green 100% green eyes
Blue eyes Brown-green variation 50% heterozygous blue-green, 50% heterozygous blue-brown, 50% green eyes, 50% brown eyes
Blue eyes Blue-brown variation 50% heterozygous blue-brown, 50% homozygous blue 50% brown eyes, 50% blue eyes
Blue eyes Blue-green variation 50% heterozygous blue-green, 50% homozygous blue 50% green eyes, 50% blue eyes

Main takeaways for eye color genetics

  • Blue eyes only occur with 50% odds if one parent has both blue alleles and the other has at least one such allele.
  • The child will likely have brown eyes if one parent is homozygous dominant with brown eyes.
  • Green eyes are inheritable with 100% odds if one parent is homozygous with green eyes and the other is heterozygous with the blue-green variation (which would also manifest as green).

  • Homozygous parents with eyes of differing colors

Homozygous parent 1 Homozygous parent 2 Genotypic results and odds Phenotype & eye color probability
Brown eyes Green eyes 100% heterozygous brown-green 100% brown eyes
Brown eyes Blue eyes 100% heterozygous brown-blue 100% brown eyes
Green eyes Blue eyes 100% heterozygous green-blue 100% green eyes

A homozygous parent with dominant alleles (i.e., brown and green eyes) will entirely dictate the baby eye color.

The main takeaway for baby eye color odds

If one of the parents is homozygous dominant, there is no chance that the child will develop blue eyes.

Both parents are heterozygous

Heterozygous parent 1 Heterozygous parent 2 Genotypic results and odds Phenotype & eye color probability
Brown-green variation Brown-green variation 50% heterozygous brown-green, 25% homozygous brown, 25% homozygous green 75% brown eyes, 25% green eyes,
Brown-green variation Brown-blue variation 25% homozygous brown, 25% heterozygous brown-green, 25% heterozygous brown-blue, 25% heterozygous green-blue

75% brown eyes,

25% green eyes,

Brown-blue variation Brown-blue variation 25% homozygous brown, 50% heterozygous brown-blue, 25% homozygous blue 75% brown eyes, 25% blue eyes
Green-blue variation Green-blue variation 25% homozygous green, 50% heterozygous green-blue, 25% homozygous blue 75% green eyes, 25% blue eyes
Brown-green variation Green-blue variation 25% homozygous green, 25% heterozygous brown-green, 25% heterozygous green-blue, 25% heterozygous brown-blue

50% green eyes,

50% brown eyes,

Brown-blue variation Green-blue variation 25% heterozygous brown-green, 25% heterozygous green-blue, 25% heterozygous brown-blue, 25% homozygous blue 50% brown eyes, 25% green eyes, 25% blue eyes

The main takeaway for baby eye color odds

  • The rarest phenotypic result for the baby eyes color for heterozygous parents is blue. Getting blue eyes means that the child’s parents both had one blue allele. Still, it only happens 25% of the time in these cases.
  • Green comes up with a lower variation. If the green allele appears in both parents, it occurs with 75% odds, except if they have the blue allele both.
  • If they both have the brown dominant allele, green eyes occur with 25% odds (regardless if one or both parents have the green allele).
  • Green eyes occur with 50% odds if both parents have a green allele, and one has the blue allele while the other has the brown allele.

Eye color probability chart

Parents’ iris color combinations Brown eyes Green eyes Blue eyes
Brown eyes

87.5% brown,

8.3334% green,

4.1667% blue

50% brown,

46.429% green,

3.571% blue

75% brown,

25% blue,

0% green

Green eyes

50% brown,

46.429% green,

3.571% blue

91.6666% green,

8.3334% blue,

0% brown

75% green,

25% blue,

0% brown

Blue eyes

75% brown,

25% blue,

0% green

75% green,

25% blue,

0% brown

100% blue eyes,

0% green,

0% brown

Simplified data

The eye color probability chart above presents the cumulative odds for all combinations of observable iris pigmentation. The actual results are directly correlated to the allele variations of the parents. We advise you to consult the full tables.

Chances for brown eyes

Chances for brown eyes

Colors combined with green Brown eye color probability Green eye color probability Blue eye color probability
Brown eyes 87.5% 8.334% 4.167%
Green eyes 50% 46.429% 3.571%
Blue eyes 75% 0% 25%

Critical insights for brown eye color probability

The allele for brown eyes is the most dominant among possible versions, reducing the chances of emerging green or blue eyes when present in one parent.

If one of the parents has brown eyes, there is a rough minimal 50% chance that the baby eyes will also be brown.

The only case where the brown eye color probability falls to 25% even when one parent exhibits the trait is when it is heterozygous with a blue allele, and the other parent has homozygous green eyes.

Chances for amber eyes

Chances for amber eyes
Source: reddit.com

Amber eyes are a golden or coppery yellow. Around 5% of the population exhibits it, so you have 1 in 20 chances of having it, similar to green eyes.

While they are often associated with brown eyes, given their similar palette, amber eyes actually result from a pigment called lipochrome and less eumelanin and more pheomelanin.

Comparatively, brown eyes only appear when there is a higher melanin concentration in the eye.

Why is brown the most common in baby eyes?

Brown eyes indicate the presence of the dominant “brown” gene. Concerning inheritance and resulting phenotypical eye color probability, it manifests in the presence of any other allele and hides others.

In other words, the only real way of not having brown eyes is by not exhibiting any associated allele.

Chances for blue eyes

Colors combined with blue Brown eye color probability Green eye color probability Blue eye color probability
Brown eyes 75% 0% 25%
Green eyes 0% 75% 25%
Blue eyes 0% 0% 100%

The critical insight for blue eye color probability

Unlike brown eyes, the allele associated with blue ones is the most recessive. Thus, it does not manifest when in a heterozygous combination. You must have two alleles for blue eyes to have them.

Chances for dark blue eyes

Chances for dark blue eyes

Dark blue eyes are not as rare as you may think. Between 8% and 10% of the population exhibits the feature, with 1 in 12.5 to 1 in 10 odds of having them.

Dark blue eyes are nothing but a variation on the spectrum of eye colors. You can explain it by a low concentration of melanin and pigments in the front layer but high enough to scatter light less than grey eyes, for instance.

Chances of grey eyes

Chances of grey eyes
Source: twitter.com

Less than 1% of the population have grey eyes, meaning a person has a chance lower than 1 in 100 to have it.

Grey eyes appear when an individual exhibits low melanin levels (just like for blue eyes) and high collagen concentrations in the stroma.

Facts about blue eyes

  • Blue eyes really are more sensitive to light than others. Whether in the skin or in the eye, melanin protects your body from skin damage. Less pigment results in blue eyes, but they also mean more sensitivity and possible injury.
  • Blue-eyed people have one common ancestor. The individual lived in Europe around 6,000 to 10,000 years ago.
  • Blue eyes often occur at birth for Caucasian babies, as they are born with less melanin than they will exhibit later on. As the body produces more melanin, babies’ iris color eventually changes.
  • A study on European Americans concluded that people with blue eyes are 83% likelier to develop alcoholism. Researchers opine that the correlation comes from a genetic component that causes alcoholism, which is also linked to iris color genes.

Why did blue eyes persist?

There is no clear answer since blue eyes do not provide clear advantages, but sexual selection may be most likely. In other words, early humans preferred blue-eyed mates.

Percentage of blue eyes in the world

Percentage of blue eyes in the world

Blue-eyed people make up around 8% of the world’s population, making it among the rarer eye colors.

The reason for their infrequent occurrence is attributable to the genetic elements that lead to their appearance. The blue eyes gene is recessive, which makes it so that only two parents bearing the blue eye allele can give birth to a blue-eyed child.

Are blue eyes recessive?

The allele associated with blue eyes is recessive, meaning that it only manifests if both blue eye alleles are present.

While the green eyes gene acts as recessive in the presence of the brown-eye one, the gene related to blue eyes is recessive in the presence of both.

That means that, even if a child carries it in a heterozygous combination (i.e., the individual has two different alleles), it will not manifest, leaving the dominant gene to give the iris color.

Where did blue eyes come from?

Where did blue eyes come from
Source: nationalgeographic.com

Historically, blue eyes came from a gene mutation exhibited by a single individual living in Europe some time during or at the end of the Neolithic.

Most iris color variation relates to the OCA2 gene, which is involved in melanin production and pigmentation of hair, skin, and eyes. Most, but not the occurrence of blue eyes.

In recent worldwide genetic studies, scientists have related the appearance of the pigmentation that results in blue eyes to HERC2. This gene acts as a regulator or switch for the OCA2 gene.

Under certain conditions, HERC2 can switch off OCA2 and subsequently limit melanin production.

This dynamic explains why many baby eyes are blue, too, but only a certain percentage of individuals keep their baby blues. While many babies are born with a lack of melanin that manifests in blue eyes, in most cases, OCA2 activates and produces brown pigmentation.

In fewer instances, OCA2 never becomes active, courtesy of HERC2, and those individuals keep their blue eyes for life.

Chances for green eyes

Colors combined with green Brown eye color probability Green eye color probability Blue eye color probability
Brown eyes 50% 46.429% 3.571%
Green eyes 0% 91.667% 8.334%
Blue eyes 0% 75% 25%

Critical insights for green eye probability

Green eyes are dominant towards blue eyes and recessive with brown eyes. This results in a less frequent occurrence than brown eyes but more chances than blue eyes.

All things said, green eyes are arguably one of the rarest colors that is normally occurring, with around 2% of the population exhibiting the trait. This gives the average person a 1 in 50 chance of having green eyes.

Chances for dark green eyes

Chances for dark green eyes
Source: crstodayeurope.com

Dark green eyes are a subset of the more encompassing green tint spectrum. They naturally occur at a rate lower than 1 in 50, somewhere at 1 in 100 lower.

Dark green eyes appear when the front layer of the iris has an average-to-high melanin presence, and the eye exhibits the pheomelanin pigment type.

Where do green eyes come from?

Most studies point to the Caucasus Mountains as the place of origin for the green eyes mutation.

Not only are they the rarest eye color, but green eyes show the most differences from other tints.

Blue eyes are not so different from brown eyes, melanin and pigment concentrations being the only differentiating factors. However, people with green eyes have an entirely different pigment type, referred to as pheomelanin, which is reddish-yellow and contains sulfur.

Odds for heterochromia and hazel eyes

Odds for heterochromia and hazel
Source: shoplt.can-global.com

With 5% of people exhibiting hazel eyes, also referred to as central heterochromia, the average person has a 1 in 20 chance of showing the trait.

Central heterochromia can appear naturally. It is mainly generated by average melanin levels in the front layer (similar to green eyes) and a mix o eumelanin and pheomelanin.

How hazel eyes occur

Heterochromia is a case where we cannot reduce its occurrence to eye color genetics and eye color probability of inheritance.

Hazel eyes depend on the concentration and distribution of pigments and melanin across the iris layers.

The most frequent types of hazel eyes are green on the outside, brown on the inside, or blue on the outside and brown on the inside. The green-on-the-inside-blue-on-the-outside combination is rarer but does not differ radically.

Green brown hazel eyes

The most common type of hazel eyes occurs when an individual presents both eumelanin and pheomelanin. These are distributed differently, generating different colors when light hits the eye.

Melanin concentration also plays a part. Most people with hazel eyes have melanin concentrations similar to those with green eyes in the front layer.

Blue green eyes

This rarer case is no different from the previous, more frequent one. However, the color difference appears from lower melanin levels in the front layer.

Blue-with-brown heterochromia

Here, there is only one pigment type, eumelanin. The variation in eye color then emerges from different distributions of melanin in the front layer.

If the center is brown, the inner part of the layer has more melanin and retains more light. The outer layers with low melanin concentrations scatter light more and produce the blue color.

Hazel baby eye color chart

Types of heterochromia Pigments Front layer melanin levels
Green and brown hazel eyes Eumelanin, pheomelanin Average
Blue and green eyes Eumelanin, pheomelanin Low
Brown and blue heterochromia Eumelanin Low and high unevenly distributed

Lateral heterochromia

There is also the case where the baby eyes develop a different color each. Its eye color probability is hard to compute since its causes are not solely inheritable.

Lateral heterochromia can be congenital or later acquired in life.

Heterochromia affects less than 1% of the world population, making it one of the rarest color variations.

Congenital heterochromia

Congenital heterochromia
Source: lasikmd.com

Babies can be born with differently-colored eyes as a result of various benign or malign causes.

Causes for congenital heterochromia
  • Benign heterochromia (inherited)
  • Horner’s syndrome (congenital)
  • Sturge-Weber syndrome
  • Waardenburg syndrome
  • Piebaldism (absence of melanocytes and pigmentation in areas)
  • Hirschprung disease
  • Bloch-Sulzberger syndrome
  • Von Recklinghausen disease
  • Bourneville disease
  • Parry-Romberg syndrome

Acquired heterochromia

Eyes can start differing in color later in life due to various causes, mostly eye traumatism, these cases being called acquired heterochromia.

Causes for acquired heterochromia
  • Injury to the eye
  • Bleeding in the eye
  • Swelling from iritis or uveitis
  • Eye surgery
  • Fuchs’ heterochromia cyclitis
  • Horner’s syndrome (acquired)
  • Glaucoma, its treatment, and medication
  • Pigment dispersion syndrome
  • Ocular melanosis
  • Posner-Schlossman syndrome
  • Iris ectropion syndrome
  • Benign and malignant tumors of the iris
  • Diabetes mellitus
  • Central retinal vein occlusion
  • Chediak-Higashi syndrome

Chances for red, pink, or purple eyes

Chances of red, pink, or purple eyes

There are less than 1% of the population that present red eyes or purple eyes. Thus, the average person has less than a 1 in 100 chance of having them.

They are not naturally occurring but result from melanin deficiencies due to albinism.

Albinism and eye color genetics
Source: theyenews.com

Albinism

Genetic conditions that result in little to no melanin production in the skin, hair, and/or eyes. The conditions resemble piebaldism or vitiligo but are not local.

There is no essential difference between pink, violet, and red eyes. In all three cases, you are still seeing the color of the retina, unmasked by any pigmentation, under various light conditions.

Albinism and eye color genetics

  • People with albinism can also exhibit bright blue eyes instead of reddish ones. This depends on the affected pigment production.
  • Hazel eyes are also possible in people suffering from albinism, depending, again, on the presence of pigments and their concentration.
  • Violet or red eyes result in vision issues since light is not filtered and hits the retina in a greater amount.

Other low eye color probability cases

  • Anisocoria is the condition where one pupil is larger than the other. This case also results in the appearance of one eye as darker than the other. 1 in 5 healthy babies will showcase anisocoria.
  • Aniridia is the absence of the iris in one or both eyes. This results in “black eyes.” However, you only see the dilated pupils (mydriasis). 1 in 50,000 to 1 in 100,000 newborns will have aniridia.

More on eye color genetics

More on eye color genetics
Source: wdmws.com

We have mainly considered eye color probability in babies by way of inheritance and dominant and recessive genes.

However, the color an individual ends up having depends on no less than 16 genes, as well as the environment and further events in life.

OCA2 – The first important gene

The principal gene that acts on melanin production in the eyes is OCA2.

The gene is central in generating the P protein, which is localizable in melanocytes. As their name would indicate, melanocytes, in turn, are tasked with producing melanin, which gives our natural pigmentation.

Melanocytes are present all over our body, from the skin to hair, to the eyes, but also in the retina (the photosensitive region of our eyes).

Melanin from the front and back layers of the iris will capture and reflect light by a certain amount. Since melanin has a dark color, the more melanin in the iris, the less light scattered back. The result is a perceived dark color of the eye. This is how you get black or brown eyes.

HERC2 – The regulating gene

The HERC2 gene is a more recent discovery. Its effect is not direct, such as in the case of OCA2, but it has a significant impact on the iris color probability.

HERC2 can regulate OCA2 and, in some cases, reduce its production of P protein in the iris. The effect is a lower concentration of melanin in the outer layer of the iris and, consequently, less captured light, i.e., more scattered light and a lighter color.

Both the OCA2 and HERC2 genes are located in chromosome 15 of the human genome.

Role of pigments in iris color

Role of pigments in iris color

Beyond the yellow-brown melanin concentration in the eye (which we all have), pigments play a role in the visible eye color probability and outcomes.

Eumelanin & Melanin

Brown and blue eyes exhibit the same pigment – eumelanin. The color of the pigment itself is dark brown or black. The spectrum of variation between blue and brown eyes (including extremes like black or light grey eyes) results from melanin concentrations.

Pheomelanin

Green eyes (and hazel eyes that include the green color) have a different pigment called pheomelanin. This is a reddish-yellow pigment with a high concentration of sulfur. When light is reflected through an iris with high pheomelanin, you get a green color.

Effects on eye color genetics

More critical for heritability, pheomelanin is effectively masked by the darker eumelanin. However, when eumelanin is in low concentrations, pheomelanin will have a dominant effect.

Hence, you get the relationship between dominant and recessive “iris color genes.”

Lipochrome and collagen

There are other pigments that affect the eye color probability and phenotype. For instance, amber eyes appear due to lipochrome. Different variations like grey eyes occur when there is more collagen in the stroma.

Emergent eye color genetics and inheritance

  • Brown is dominant in relation to HERC2-related blue eyes and will also mask the pheomelanin of green eyes.
  • Green will manifest as dominant in reaction to blue eyes with lower melanin and eumelanin concentrations due to HERC2 effects on OCA2.
  • Blue is recessive. It only manifests if both parents exhibit it and contribute with the genetic material that conditions the HERC2 effect on OCA2 and no other pigmentation.

The interesting case of hazel eyes

The interesting case of hazel eyes
Source: twitter.com

Hazel eyes are proof that simple eye color genetics and inheritance do not always reflect the reality of the phenotypic manifestation of baby eyes.

The fact that 16 genes regulate ocular pigmentation rings true in the case of hazel eyes. In these cases, the pigments that often mask each other are simultaneously present and visible in the eye.

Hazel vs green eyes

Both people with green eyes (heterozygous with brown and green alleles) and hazel eyes have both eumelanin and pheomelanin in their eyes.

Why then do they manifest differently? Simply put, pigments are not homogenously distributed across the iris.

This is the case for hazel eyes, which only manifest in a very frail balance of heterogeneous distribution of pigments, light scattering depending on pigment molecules, and visibility conditions.

Remember

You do not have the pigment of your eye’s color in the iris. The resulting color only results from light reflection and refraction.

More special cases for eye color

More special cases for iris pigmentation
Source: pinterest.com

Variation in ocular pigmentation can go further under the effects of both genetic and acquired traits.

Lateral heterochromia is one example that does not occur frequently but is both inheritable and acquirable. Beyond malignant causes, lateral heterochromia can result from conditions that affect melanin production.

Red or purple eyes

Similarly, we have the emergence of naturally occurring “red eyes” or “purple eyes.” Their color is not a result of an exotic pigment but the total lack thereof. What seems to be purple eyes occurs when an individual has no pigments in the iris. The color you see is actually the retina. Lateral heterochromia can be a failure in the production of eumelanin in one eye.

There are many syndromes and diseases that create these two limit examples. However, the most frequent are syndromes that affect melanin production, such as albinism, piebaldism, and vitiligo.

The final result of eye colors

The final result of eye colors

Sixteen genes contribute to eye color genetics, with OCA2 and HERC2 being the primary ones.

These regulate the production of melanin (which is yellow-brown and present in all eyes), eumelanin (present in brown, hazel, and blue eyes), and pheomelanin (present in hazel and green eyes). These pigments can obscure one another. This fact, together with genetic heritability, results in dominant and recessive traits.

However, eye color probability goes beyond heritability, with pigments being distributed unevenly in the iris. Other causes, either congenital or acquired, also play a role.

There are no easy answers

Eye color probability is complicated and provides no easy answers. There is a limit to all facts we presented. For instance, blue-eyed parents can have a brown-eyed child. However, the facts on eye color probability and heritability we shared are the starting point for a better understanding of baby eyes.

What determines a baby’s eye color?

What determines a baby’s eye color

You now know that for a baby, eyes will be influenced by its parents’ genes and various congenital and acquired traits.

Are all babies born with blue eyes?

This is a common misconception. Many babies are indeed born with blue eyes. However, this is true for babies of Caucasian descent.

A baby’s blue eyes reflect either its genes or a temporary lack of melanin. The latter case occurs in populations with naturally occurring lower melanin levels, such as Europeans.

If the child does not have the correct HERC2 modification, the eyes will change in color later on.

This is not the case for children of people with higher melanin levels, such as those of African, Asian, and Native American descent.

When does a baby’s eye color change?

Once melanin production increases, non-genetic blue eyes will slowly change to the final color. This occurs from six months to one year.

This is the case for normal development. However, melanin production changes across an individual’s life. In a small percentage of adults, eyes can darken later on.

But, generally, after one year, a baby should exhibit the color they will have for the rest of one’s life.

What color eyes are babies born with?

Babies with low melanin will be born with blue eyes. In the case of those with high melanin levels or pheomelanin, they will have brown or green eyes.

No matter the initial color, baby eyes will darken naturally within one year. Some children can also develop hazel eyes during this period.

What will my baby look like?

The Punnett square shows the eye color probability for your child for your genetic makeup. It is not only your visible traits that will determine it but also those of your forerunners.

In slim cases, your baby can have a trait that is not immediately deducible from simple heritability.

What is the rarest eye color?

What is the rarest eye color

The rarest naturally occurring eye colors are grey eyes (<1 in 100). Lateral heterochromia is also rare, with 1 in 166.667 people exhibiting it.

Non-normally occurring baby eye color probability

We have “black eyes” due to aniridia, with 1 in 50,000 to 100,000 odds, and red or purple eyes with less than 1 in 100 chances.

How many people have blue eyes?

8 to 10% of people worldwide have blue eyes of different variations. This points to a 1 in 12.5 to 1 in 10 chance of having blue eyes.

What percentage of people have hazel eyes?

Around 5% of people have hazel eyes, corresponding to a 1 in 20 eye color probability.

What percentage of people have green eyes?

Green is the rarest of all frequently occurring colors, with 2% of the population having them. This corresponds to a 1 in 50 eye color probability.

Methodology and sources for eye color probability

Our statistical experts constantly analyze and compute the probabilities for various real-life concerns and issues.

Our aim in publishing their content is to educate our readers and provide informative and verifiable data.

Previously analyzed issues

Our approach

While the subjects may vary, some bordering on the sensitive and contentious, our principal approach is to provide an accurate statistical breakdown of each issue.

Our observations are based on intensive computations of official and trusted data.

Source selection process

We base our statistical analysis solely on data from official sources, peer-reviewed studies, or expert curation.

All the information we provide comes with specifications on the source and process employed to arrive at the published final result.

Limits on published data

Each piece of information is accompanied by specifications on its limit and reliability.

Our content is informative and fact-based, but we always invite our readers to cross-check our findings and follow the advice of official sources.

Finally, most subjects we approach are dynamic and subject to change. We update our published data as soon as new information is available. Make sure to return for updates on data.

References

F.A.Q

What will my baby look like?

Babies will resemble their parents and close relatives. This is true for eye colors, too.

Are all babies born with blue eyes?

No. Many newborns with low melanin levels can exhibit blue eyes during the first year of their life, but this is not universal.

When do baby eyes change color?

Babies will change their iris color after six months to one year, generally getting a darker tint.

What is the rarest eye color?

The rarest naturally occurring iris color is grey, with less than 1 in 100 odds of having grey eyes.

How many people have blue eyes?

Between 8% and 10% of the population has blue eyes. Since the associated gene is recessive, there may be more blue eyes gene carriers.

What percentage of people have green eyes?

Green eyes are the second rarest variation, with only 2% of the population having them.

Where do green eyes come from?

Green eyes most probably originated in the Caucasus region, hence being encountered in areas ranging from northwestern Europe to central Asia.

Are blue eyes recessive?

Yes. The HERC2 mutation related to blue eyes is recessive.

Where did blue eyes come from?

Scientists agree that the original mutation that led to blue eyes can be tracked to one individual that lived in the northwestern part of the Black Sea region 6,000 to 10,000 ago. The gene then moved to northern Europe following agricultural migrations during the Neolithic.

Are green eyes recessive?

Green eyes "act" recessive in relation to brown eyes. This is caused by the masking effect eumelanin (a dark pigment related to brown eyes) has over pheomelanin (a reddish pigment that creates green and hazel eyes).

What color will my baby's eyes be?

You can use the Punnett square calculator to determine the eye color probability for your child based on your iris color, your partner's, and your broader family.

What color eyes are babies born with?

Most babies will exhibit a lighter tint of the iris color they will have for the rest of their adult lives. In some cases, brown or green eyes may appear blue for the first year. Hazel eyes may be masked as green during the same time.

Can two brown eyes make a blue?

There is a 25% chance that two brown-eyed parents will have a blue-eyed child under the right conditions. Each parent must have the blue eyes recessive gene.

What is the rarest hair color and eye color combination?

It may come as a surprise, but the combination of red hair and blue eyes is the rarest. This is because both red hair and blue eyes are recessive. We can further intuit that grey eyes and red hair are even less common.

What are the odds of my baby having blue eyes?

The average person has a 1 in 12.5 to 1 in 10 chance of having blue eyes. If neither you, your partner, your parents, nor your family have blue eyes, the odds go down to less than 1%.

Can 2 blue eyes make a brown eyed baby?

According to simple heritability, this is impossible since both parents must have both blue alleles to manifest blue eyes. This would entail that their offspring would also have blue eyes. However, recent studies have indicated that this is possible, albeit unlikely.

Is eye color determined by mother or father?

Both the mother and father determine iris color. More so, the final pigmentation will depend on traits that are not necessarily visible.

Do purple eyes exist?

People with albinism have eyes that can appear to be purple or red. This is because you can see the retina due to the lack of pigmentation in the iris.

Does eye color affect vision?

There is a slight variation in naturally occurring colors, with blue eyes being more sensitive to light. People with albinism, aniridia, or other rare situations can encounter more issues.

Why are hazel eyes so rare?

Hazel eyes generally require two pigment types, the right amount of melanin and the correct distribution of eumelanin and pheomelanin in the iris. Additionally, hazel eyes may act as recessive in relation to brown eyes.

How do hazel eyes start out?

During early infancy, hazel eyes may appear bright green or blue. They change to hazel after one year.

Is there a benefit to blue eyes?

Benefits are scarce, with no iris color providing the bearer with more than aesthetic difference. However, some researchers found that blue-eyed people cope better with seasonal affective disorder.
Francisc Csiki
Author Francisc Csiki Author & Editor at CasinoAlpha
Adina Minculescu
Author Adina Minculescu Senior Author & Editor at CasinoAlpha

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