Difference between Green Eyes and Blue Eyes
Blue and green are just two of the varieties of eye color that may be seen in people. Brown eyes are far more common than either blue or green eyes. Other shades of eye color can also appear, including hazel eyes that are a mixture of brown and green and grey eyes, which are a very pale blue. Some people actually have blue-green eyes, which can appear either green or blue, depending on the light.
Genetics
The color of eyes is determined by one’s genes, although it is sometimes possible for eye color to change due to injury or illness. A number of different genes are involved in the determination of eye color. They control the production of pigments in the iris of the eye. The iris is the colored part of the eye.
It is believed that everyone who has blue eyes can trace their descent from a single common ancestor who lived in the Black Sea region between 6000 and 10,000 years ago. This ancestor had a genetic mutation in the HERC2 gene, which controls the OCA2 gene. The same mutation is found in everyone who has blue eyes. It reduces the production of the pigment melanin in the iris.
Green eyes are believed to occur due to the interaction between different variants of the OCA2 gene. Although it is often believed that two blue-eyed people cannot have a brown-eyed child, this is not true. It is very rare, but it is possible, due to the complex genetics of eye color.
Pigments
Eye color is produced by the pigments, or colored chemicals that exist in the iris. There are two layers to the iris, each of which can contain different types of pigments. The combination of the pigments in the two layers creates the color of the eye. Three different types of pigment can be found in the iris. These are blue, yellow and brown. The proportions of each pigment that are present determine the color of the eye.
Blue eyes are produced when there is blue pigment present, usually without any yellow or brown pigment. Blue eyes contain the least pigment. The outer layer of the iris is actually colorless or un-pigmented. The blue color comes from the inner layer of the iris.
Green eyes occur when there is a combination of blue and yellow pigment in the iris. Green eyes contain less pigment than brown eyes, but more than blue eyes.
Many babies, particularly when they have European ancestry, are born with blue eyes. However, their eye color can change over time as they begin to produce more pigment, becoming green or brown. The final eye color will usually appear within the first year, although it can continue to change for up to about three years.
Frequency and Distribution
Blue eyes are most commonly found in people who have Northern or Central European ancestry, although they are also found in people who have Southern European ancestry. Blue eyes are also relatively common in people who have ancestors from south Central Asia, particularly in Pakistan and Afghanistan. They can also be found in people who have ancestors from parts of Northern Africa, West Asia and South Asia, although this is less common.
Blue eyes are becoming less common, particularly in areas where people with blue eyes are less likely to have children with other blue eyes people. When a person with blue eyes has a child with a person with darker eyes, their children are less likely to be blue-eyed.
Green eyes are most commonly found in people with ancestors from Northern and Central Europe, although they may also occur in people who originated in Southern Europe or in North Africa.
Similarities and Differences
- Eye color is genetically determined by the types and proportions of pigments in the two layers of the iris.
- Blue and green eyes are rarer than brown eyes and they usually result from mutations that have reduced the amount of pigment in the iris, although blue eyes can also occur in babies who go on to develop darker eyes.
- Blue eyes contain the least pigment.
- Green eyes contain a mixture of blue and yellow pigments.
- Blue eyes and green eyes are common in people of European descent.
- Blue eyes are also found in people with Central Asian ancestry.
