A study conducted by the Professor Hans Rudolf Litchoff Eibergfrom the University of Copenhagen, revealed that all people with blue eyes They descend from the same ancestor who lived between 6,000 and 10,000 years ago, in the region northern Black Sea. According to Eiberg, a genetic change in a single individual affected the OCA2 gene, which regulates the production of melanin, responsible for the color of our eyes. This mutation reduced melanin production, leading to the appearance of blue eyes. What is surprising about this discovery is that this trait, which originated in a single person, has been passed down to more than 150 million people all over the world.
This phenomenon began when the first humans migrated from Africa to Europewhich would explain why the mutation is more common in Caucasian populations. Additionally, genetic combination over the centuries, through interbreeding, has allowed blue eyes to spread to other human groups. Today, we see that Estonia has the highest proportion of people with blue eyes, with almost 90% of its population carrying this trait. Others Nordic countries Countries like Finland, Sweden, and Iceland also have high frequencies of blue eyes, while in southern regions of Europe, dark eyes continue to predominate. This study highlights how a genetic mutation, although small, had a significant impact throughout the human history.
The genetic mutation causing blue eyes
The appearance of blue eyes In humans, it comes from a genetic mutation that occurred a long time ago. between 6,000 and 10,000 years agoin a single common ancestor. This discovery was made by Professor Hans Eiberg of the University of Copenhagen in 2008, after more than a decade of research. The study found that all blue-eyed individuals are descended from a single person, who lived northern Black Sea.
The genetic mutation originates from OCA2 generesponsible for the production of melanin, the pigment that determines the color of eyes, skin and hair. In its normal form, OCA2 produces enough melanin to generate brown tones in the iris. However, an alteration in a gene close to OCA2 partially prevents its functioning, leading to the creation of blue eyes by reducing the amount of pigment in the iris. This mutation does not significantly affect melanin production in other parts of the body, which explains why people with blue eyes have a reduced amount of pigment only in the iris, without leading to albinism.
The mutation confers no particular evolutionary advantage or obvious disadvantage. However, it has been observed that blue eye color has become more popular in regions like Northern Europee, where the prevalence of blue eyes is particularly high, with countries like Estonia, Finland and Sweden showing a high proportion of people with this trait. The spread of this characteristic in various populations is largely due to migration and interbreeding.
Scientists used genetic files of Danish families to trace the mutation and verify its origin. They focused on lines of individuals with blue and brown eyes, excluding those whose eyes showed mixed shades of blue and green. From this analysis, they discovered that the blue-eyed trait is linked to a change in the OCA2 gene, which is inherited recessively. This means that for an individual to be born with blue eyes, both parents must carry the mutation, even if only one of them visibly displayed this trait.
This change in the human genome demonstrates genetic variability that occurs consistently over time, without the mutation being directly linked to improvement or deterioration in an individual’s survival capabilities. This discovery also highlights how environmental conditions and migratory changes can influence the spread of genetic traits.
As humans moved to colder, less sun-exposed regions, they lost the need for melanin in their skin and eyes, which could have facilitated prevalence of lighter eyeslike blue eyes. Additionally, the mutation causing blue eyes may have been favored in certain cultures due to its rarity, which can sometimes increase its attractiveness.
In evolutionary terms, this type of mutation is just one of many that occur naturally and constantly within human populations. In summary, the mutation causing blue eyes is neither positive nor negative in terms of survival, but represents an example of the genetic diversity which characterizes the human species.
