Why Did Blue Eyes Evolve?
- Pieter Maas
One Common Ancestor – According to recent studies, people with blue eyes have a common ancestor, The new research has tracked down a genetic shift that leads to blue eyes. This significant research shows that the gene mutations affected the OCA2 gene.
- This gene is involved in producing the pigment (melanin) that creates the color of eyes, hair, and skin.
- The genetic shift turned down the ability to produce brown eyes, resulting in the creation of eyes with less pigment (blue eyes).
- Over time, some of the elements of the genes change while others remain unchanged.
The unchanged segments are called haplotypes, When individuals share these haplotypes, scientists believe that it shows common ancestry. In recent studies, scientists are showing that people with blue eyes in Denmark share the genetic traits of people as far as Jordan.
What caused blue eyes to evolve?
Vitamin D Theory – One theory is the Vitamin D hypothesis, which is the idea that light colored skin, hair, and eyes co-evolved as humans moved into latitudes with shorter days, shorter summers, and therefore, less sunlight. However, molecular geneticist and Associate Professor Rick Sturm of the University of Queensland had a problem with this hypothesis.
- He said that there is no evidence that light-colored irides let in more light or help you see better in low lighting than dark colored irises.
- Additionally, there is evidence that blue eyes evolved before light skin.
- Sturm and his team did a study looking at the genetic information extracted from a 7000-year-old tooth belonging to a hunter-gatherer dubbed La Brana 1, unearthed from the northwestern Spain.
When studying the hunter-gatherer’s genetic information, the team discovered that the man had dark hair, dark skin, and blue eyes. This archeological finding contradicts the theory that hair, skin, and eyes co-evolved in reaction to the limited sunlight.
Why do people get blue eyes?
Don’t It Make Your Brown Eyes Blue? Blue-eyed? Thank a genetic switch that turns off your body’s ability to make brown pigment in your peepers. Researchers have finally located the mutation that causes blue eyes, and the findings suggest that all blue-eyed humans share a single common ancestor born 6000 to 10,000 years ago.
- Researchers have implicated the OCA2 gene in several eye colors.
- The gene is involved in the production of melanin, a pigment that gives hair and skin their hues.
- It also codes for brown eyes and can lead to green or hazel eyes when mutated.
- Despite years of searching, however, scientists have not found a mutation for blue eyes on the gene.
It turns out they were looking in the wrong place. Trying to narrow the site of the mutation, gene mapper Hans Eiberg of the University of Copenhagen and colleagues examined members of a large Danish family, an approach that allowed them to follow DNA as it passed from one generation to another.
Then, by comparing people with brown or blue eyes, including people from Jordan and Turkey, the researchers were able to pinpoint the exact mutation. It wasn’t on the OCA gene but rather on a nearby gene called HERC2, The mutation works like a switch that regulates the OCA gene, the team reports in the January issue of Human Genetics, turning off the production of brown eye color and allowing blue eyes to shine through.
Because blue eye color is found almost exclusively in people of European descent, Eiberg’s team speculates that the mutation traces back to the Neolithic expansion, when people in the Black Sea region migrated to northern Europe 6000 to 10,000 years ago.
- Two other studies, both appearing in this month’s issue of The American Journal of Human Genetics, examined blue eyes in different populations and found the same mutation.
- The researchers also suggested a common ancestor for all blue-eyed individuals.
- These teams, however, did not estimate an age for the mutation.
Geneticist Richard Sturm of the University of Queensland in Brisbane, Australia, an author of one of the papers says that someday scientists may find additional mutations that cause blue eyes but for now, the signs point to a single change. Sturm says that it’s not uncommon for one gene to regulate another, but it is difficult to locate the mutation in the controlling gene.
One of the most cited examples is the mutation involved in lactose tolerance, which is also caused by regulation from outside the gene. Sturm says that such regulating genes may contribute more to genetic diversity than previously thought. The findings also have applications in forensics. Geneticist Manfred Kayser of the Erasmus University Medical Center in Rotterdam, the Netherlands, an author of the other paper that appears in The American Journal of Human Genetics, says if police fully understood mutations behind eye color, for example, then they could use them to determine the eye color of a suspect based solely on DNA evidence.
Geneticist Tony Frudakis of DNAPrint Genomics Inc., a Sarasota, Florida, company that develops genetic-testing products, is shocked that the mutation happened just once. Although there are about 10 ways to get someone with red hair, the scientists found only one way to get someone with blue eyes.
- I would have thought blue eyes arose several times independently,” Frudakis says.
- There are still large questions, though.
- Why did blue eyes persist? Scientists say it is difficult to see how eye color would have an environmental advantage, as skin color does.
- Some theories suggest that women may have played a role in driving the selection.
Perhaps, Kayser says, “the females thought it more exciting to have a male with blue eyes.” Related site : Don’t It Make Your Brown Eyes Blue?
Can two brown eyed parents have a blue-eyed child?
Myth: Two blue-eyed parents can’t produce a child with brown eyes. Fact: Two blue-eyed parents can have a child with brown eyes, although it’s very rare. Likewise, two brown-eyed parents can have a child with blue eyes, although this is also uncommon.
When did blue eyes originate?
New research shows that people with blue eyes have a single, common ancestor. A team at the University of Copenhagen have tracked down a genetic mutation which took place 6-10,000 years ago and is the cause of the eye colour of all blue-eyed humans alive on the planet today.
What is the genetic mutation “Originally, we all had brown eyes,” said Professor Hans Eiberg from the Department of Cellular and Molecular Medicine. “But a genetic mutation affecting the OCA2 gene in our chromosomes resulted in the creation of a “switch,” which literally “turned off” the ability to produce brown eyes.” The OCA2 gene codes for the so-called P protein, which is involved in the production of melanin, the pigment that gives colour to our hair, eyes and skin.
The “switch,” which is located in the gene adjacent to OCA2 does not, however, turn off the gene entirely, but rather limits its action to reducing the production of melanin in the iris – effectively “diluting” brown eyes to blue. The switch’s effect on OCA2 is very specific therefore.
- If the OCA2 gene had been completely destroyed or turned off, human beings would be without melanin in their hair, eyes or skin colour – a condition known as albinism.
- Limited genetic variation Variation in the colour of the eyes from brown to green can all be explained by the amount of melanin in the iris, but blue-eyed individuals only have a small degree of variation in the amount of melanin in their eyes.
“From this we can conclude that all blue-eyed individuals are linked to the same ancestor,” says Professor Eiberg. “They have all inherited the same switch at exactly the same spot in their DNA.” Brown-eyed individuals, by contrast, have considerable individual variation in the area of their DNA that controls melanin production.
- Professor Eiberg and his team examined mitochondrial DNA and compared the eye colour of blue-eyed individuals in countries as diverse as Jordan, Denmark and Turkey.
- His findings are the latest in a decade of genetic research, which began in 1996, when Professor Eiberg first implicated the OCA2 gene as being responsible for eye colour.
Nature shuffles our genes The mutation of brown eyes to blue represents neither a positive nor a negative mutation. It is one of several mutations such as hair colour, baldness, freckles and beauty spots, which neither increases nor reduces a human’s chance of survival.
Why do black people’s eyes turn blue as they age?
The more melanin we have, the darker the color is. However, as we get older, there is not only less melanin in the skin, there is also less melanin in the eye. So, what you will see in older people is skin turning lighter and eye color also lightening.