How Did Blue Eyes Evolve?

How Did Blue Eyes Evolve
Blog 1. Only 8 Percent of the World’s Population Has Blue Eyes If you have got blue eyes, you might just belong to one of the world’s most exclusive groups without realising it! Since blue eyes are genetically recessive, only 8 percent of the world’s population has blue eyes.

While blue eyes are significantly less common than brown eyes worldwide, they are frequently found from nationalities located near the Baltic Sea in northern Europe.2. There is No Blue Pigment in Blue Irises The colour of our eyes depends on how much melanin is present in the iris. Blue eyes get their colour the same way water and the sky get their blue colour — they scatter light so that more blue light reflects back out.

The iris is made up of two layers. For almost everyone — even people with blue eyes — the back layer (called the pigment epithelium) has brown pigment in it. The front layer of the iris (called the stroma) is made up of overlapping fibers and cells. For people with brown eyes, some of the cells also have brown pigment in them.

If there is no pigment at all in this front layer, the fibers scatter and absorb some of the longer wavelengths of light that come in. More blue light gets back out and the eyes appear to be blue.3. Blue Eyes are More Sensitive to Light Melanin in the iris of the eye appears to help protect the back of the eye from damage caused by UV radiation and high-energy visible “blue” light from sunlight and artificial sources of these rays.

Since blue eyes contain less melanin than green, hazel or brown eyes, photophobia is more prevalent in blue eyes compared to darker coloured eyes. For these reasons, having less melanin in your irises means that you need to protect your eyes more from the sun’s UV rays.

Therefore, it is recommended to those with blue eyes to stay out of the sun for long periods of time and try to wear protective eyewear when you are outdoors.4.
All Blue-Eyed People May Have A Common Ancestor Originally we all had brown eyes, however, according to researchers at the University of Copenhagen, it appears that a genetic mutation in a single individual in Europe 6,000 to 10,000 years ago led to the development of blue eyes.

Therefore, we can conclude that this genetic mutation is the cause of eye colour of all blue-eyed humans alive on the planet today. What is the genetic mutation? A genetic mutation affecting the OCA2 gene in our chromosomes resulted in the creation of a “switch”, which “turned off” the ability to produce brown eyes.

The OCA2 gene codes for the ‘P protein’, which is involved in the production of melanin (the pigment that determines the colour of our eyes, skin and hair).
The “switch”, 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.

According to Hans Eiberg, associate professor in the Department of Cellular and Molecular Medicine from the University of Copenhagen, “From this, we can conclude that all blue-eyed individuals are linked to the same ancestor. They have all inherited the same switch at exactly the same spot in their DNA.” 5.

Blue Eyes at Birth Doesn’t Mean Blue Eyes For Life While blue eyes may be rare, they’re among the most common eye colours at birth. Since the human eye does not have its full adult amount of pigment at birth, most Caucasian babies are born with blue eyes. However, since human melanin tends to develop over time — this causes the child’s eye colour to change as more melanin is produced in the iris during early childhood.6.

People With Blue Eyes May Have a Higher Risk of Alcoholism A new study suggests that individuals with blue eyes are at a higher risk for alcohol dependency compared to those with darker eyes. Therefore, this finding adds further evidence to the idea that alcoholism has a genetic component.

A study published in American Journal of Medical Genetics, Part B: Neuropsychiatric Genetics found that European Americans with blue eyes had up to 83 percent higher odds of becoming dependent on alcohol, compared with matched controls who had darker eye colours. This research suggests that alcoholism has a genetic component linked to genetic sequences that determine eye colour, which may help explain the association.

However, at this stage, the reason for the correlation is still unknown and further research is required to fully understand this correlation in the findings.7. You Can’t Predict the Colour of Your Child’s Eyes Since it was once believed that eye colour — including blue eyes — was a simple genetic trait, many people used to believe that blue-eyed people could only have blue-eyed children.

Before geneticists fully understood how human eye colour inheritance works, a child’s eye colour to used be used as a paternity test — based on the assumption that you could predict a child’s eye colour if you knew the colour of the parents’ eyes and perhaps the colour of the grandparents’ eyes.
But geneticists now know that this concept is far more complicated, as eye colour is influenced by an interaction of as many as 16 different genes — not just one or two genes as once thought.

Additionally, the anatomic structure of the iris can also influence eye colour to some degree. In summary, it’s impossible to know for sure if your children will have blue eyes. Even if you and your partner both have blue eyes, that’s no guarantee your child’s eyes will also be blue.

Why did we evolve to have blue eyes?

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.

Who were the first humans to have blue eyes?

Behind Blue Eyes: A Look at the Genetic and Cultural Components that Propelled the Spread of Blue-Eyed Humans

This thoroughly-researched piece is by Sarah Henry, an instructor at Delaware County Community College and tour guide at the Mütter Museum.-KI

I have blue eyes and I have always been interested in exploring my own genetic origins, but I’m not the only one interested in this genetic trait. Countless songs and poems reference people with blue eyes, whether considered a mark of beauty, a representation of sadness, or, in certain cultures, a sign of the oppressor.

But blue eyes, so popular in art, are relatively new in human evolution, as new as the invention of writing itself. My interest in this subject was sparked, in part, by a unique archaeological discovery; in 2006, researchers uncovered the world’s oldest confirmed blue-eyed person, dating to approximately 7,000 years ago.

This discovery helped to confirm theories regarding the familial relationship of nearly all blue-eyed individuals. This article will exam the genetic origins of blue eyes in humans, the spread of the blue-eyed gene, and the future of this genetic trait.

Genetics: How Do They Work? The basic explanation of eye-color works like this: a person needs only one dominant brown-eyed gene (from one parent) to be brown-eyed but needs to have two recessive blue-eyed genes (one from each parent) to be blue-eyed. You have probably seen this explanation accompanied by a simple Punnet square (Image 1) in your science textbooks.

However, new studies illustrate that the genetics behind eye color are not so straightforward. There are actually two separate genes that control eye color in humans. In his article, “Blue Eye Color in Humans,” Hans Eiberg writes, “Blue/Brown eye-color are known to the public as a school example of inheritance of monogenetic inheritance, however, the variation in pigment concentration and the iris suggest the eye color genetics to be far more complex as supported by recent data.” In other words, eye color is controlled not by one gene passed from parent to offspring, but by two genes working in tandem; a more complex chart would take both of these genes into consideration (Image 2).

These genes are called OCA2 and HERC2 (represented as O, o, H and h in Image 2). The simplified explanation is that the OCA2 gene controls pigment in the stroma (the tissue and blood vessels) of the iris (the colored part of the eye around the pupil) and the HERC2 gene is needed to help turn on the OCA2 gene to cause it to produce this pigment, resulting in brown eyes.

If a person has a non-functioning OCA2 gene, they will always have blue eyes, because the HERC2 gene can’t make the broken OCA2 gene work. Likewise, if a person has a HERC2 gene which doesn’t work, the OCA2 gene will “underachieve,” failing to produce enough pigment to make brown eyes, resulting in blue eyes.

These two genes aren’t directly related to each other, yet they affect each other. In this dependent relationship, both of these genes must work to give an individual brown eyes, a genetic relationship known as “epistasis.” Because of this process, it is actually possible (although rare) for two blue-eyed parents to have a brown-eyed child.

How Do We Know All Blue-eyed People Are Related?

Homo sapiens (modern humans) emerged around 200,000 years ago in Africa, but the mutation that causes blue eyes did not appear until sometime around 10,000 years ago. In a study conducted by Professor Hans Eiberg and a team from the University of Copenhagen, researchers examined mitochondrial DNA from 155 blue-eyed subjects from Denmark, two from Jordan, five from Turkey, and 45 brown-eyed candidates, looking at the locus (specific location or position of a gene) responsible for brown or blue eyes.

The result was the discovery that more than 97% of blue-eyed people share the single H-1 haplotype (a group of genes within an organism that was inherited together from a single parent). Eiberg and his team write, “A shared haplotype among blue-eyed individuals is almost perfect and suggests the blue color phenotype is caused by a founder mutation.” This means that the vast majority of people with blue eyes share a single inherited genetic mutation, rather than each person with blue eyes possessing a unique mutation.

The study also tested seven blue-eyed Mediterranean individuals unrelated to the Danish participants as a control group. They, too, carried the H-1 haplotype. These individuals with the H-1 haplotype all inherited the same switch at the same location in their genetic coding, whereas, brown-eyed individuals have a number of variations in melanin production and DNA, with brown-eyed phenotypes being spread out between haplotypes H-5 and H-10.

In short, almost all blue-eyed people came from a single ancestor, which is proven by the possession of the exact mutation at the same location in their genetic coding. That leads us back to the blue-eyed man from the article that sparked this entire investigation. Why is This Stone Age Body in Spain so Important? In 2006, researchers discovered a 7,000 year old body from the Stone Age in the La Brana cave system in Leon in Northern Spain (Image 4).

Genetic testing determined that this man had blue eyes. It was not in itself unusual, but what is remarkable is that he is the earliest known person with blue eyes. Far from being a fair-haired, far-skinned man that we may have expected, his genetics reveal he’s a mixture of other traits. In order to answer this question, we need to delve into Stone Age migratory patterns. According to Pickrell and Reich, there are two theories of cultural migration: Demographic Stasis vs. Demographic Change. In Demographic Stasis, inhabitants living in a particular region are the descendants of the first people to arrive in that region, meaning the people in a certain area were never integrated into or replaced by people from a second migration. Specifically, we can see this during the Neolithic (New Stone Age) Revolution, a period of time where humans began to cultivate crops, domesticate animals, and use polished stone tools. Prior to the Neolithic Revolution, almost all the world’s inhabitants subsisted primarily by hunting and gathering, but after the Neolithic Revolution, small pockets of farming emerged, first in the Fertile Crescent, China, and India and then spreading across Eurasia.

The Neolithic Revolution occurred between 6,000-10,000 years ago, and because people were better able to procure a steady source of food, the population increased significantly. The technologies which emerged during this time allow archaeologists and researchers to track cultural migration from the northwestern part of the Black Sea region (where the first humans with blue eyes lived) into the rest of Europe.

A study of Armenian haplotypes determined, “.hospitable climatic conditions and the key geographic position of the Armenian Highland suggest that it may have served as a conduit for several waves of expansion of the first agriculturalists from the Near East to Europe and the North Caucasus.” People migrated out of the Caucuses (modern-day Georgia, Azerbaijan, and Armenia) and into other parts of Europe (Image 6). Another study, focusing specifically on the genetics of residents of the Iberian Peninsula (excluding the Basques), indicates a mixture of genetic traits from the Caucuses, Central Asia and North Africa, probably related to migration during the Neolithic Era.

A study of eight Bronze Age individuals dated to between 5,500 and 3,500 years ago shows an admixture between existing hunter-gatherer groups and people from later migrations, meaning people who migrated to this area began to blend into the peoples that already lived there by blending both their culture and genetics.

Why Did this Recessive Genetic Trait Survive for Thousands of Years? How did the blue-eyed gene persist if there’s no overt evolutionary advantage to possessing it? One argument would be that those original groups of people who possessed blue eyes produced offspring with other blue-eyed people in their own group, leading to a population where blue eyes were the norm.

However, there are both objective and subjective benefits to possessing blue eyes. Subjectively, possessing blue eyes may just make one individual more sexually attractive to another. Objectively, blue eyes filter light differently than dark eyes (dark eyes, like dark skin, possess more pigment which can protect those organs from sun damage), which make them especially advantageous in the low light of Northern European winters.

Because people with light eyes are more sensitive to light, they can see better in areas that lack sufficient sunlight for large portions of the year. Conversely, while light sensitivity (photophobia) proved useful in a world prior to electricity, it actually opens blue-eyed people up to a host of medical problems including an increased risk of macular degeneration, which can ultimately lead to blindness because light eyes are worse at filtering out harmful UV light.

What is the future of blue eyes? At the turn of the 20 th century, 50 percent of people living in the United States had blue eyes. Now, however, people are more likely than ever to marry outside of their ethnic group, leading to more genetically diverse offspring and a decline in blue eyes due to the dominance of the brown-eyed genes.

Currently, in the U.S., only 17 percent of the population (1 in 6) has blue eyes and only between 5-8% of people worldwide possess the trait. (Green eyes are even more rare, but they are a topic for another article.) Even though they are new in human history, blue eyes are already on the decline.

Whether used to convey beauty, as one writer notes about the poetry of Longfellow and Romanticism, “It delighted in sentimental musings amid the ruins, in pathetic legend, in dreamy pictures of monks and harpers and knights and radiant maidens with soft blue eyes” or to convey sadness like in the Who song “Behind Blue Eyes,” where Roger Daltry sings, “No one knows what it’s like/ To be the bad man/ To be the sad man/ Behind blue eyes,” or as Kristina Richardson writes in her article regarding the perception of blue eyes in the Islamic Middle Ages, “My preliminary archival work suggests the Medieval Muslim male writers overwhelmingly accepted the characterization of blue and green eyes as unattractive and deviant,” a line of thinking fueled by the brutality of European crusaders who raped, pillaged and murdered in an attempt to reclaim the Holy Land.

Blue eyes have been a notable trait in literature across cultures for centuries. Though the future of blue eyes is unclear, nearly all living and dead blue-eyed individuals share a familial relationship through a single genetic mutation. If you have blue eyes or know someone with blue eyes, they are more than likely related to that 7,000 year old man whose remains that researchers found in a remote cave in Spain.

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Hoyhannisyan, Z.
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Hrechdakian, et all.
Different waves and directions of Neolithic migrations in the Armenian Highland.
Investigative Genetics 5 (2014).B. Starr.
Eye Color.” TheTech.
TheTech, 14 October 2004.B. Starr.
How Blue Eyed Parents Can Have Brown Eyed Children: Two Different Ways to Get Blue Eyes.” TheTech.F.L.

Patty. Sidelights on American Literature. “The Shadow of Longfellow.” Century Company, 1922: p.237.H. Eiberg, J. Troelsen, M. Nielsen, A. Mikkelsen, J. Mengel-From, K.W. Kjaer, L. Hansen. Blue eye color in humans may be caused by a perfectly associated founder mutation in a regulatory element located within the HERC2 gene inhibiting OCA2 expression.

Human Genetics 123 (2008): 177-187.I.
Lazaridis, et all.
Ancient human genomes suggest three ancestral populations for present-day European.
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Blue eyes in Islamic Middle Ages.” Medievalists.
Medievalists, 16 February 2014.J. Bryner.
One Common Ancestor Behind Blue Eyes.” LiveScience.

LiveScience, 31 January 2008.J.K. Pickrell and D. Reich. Toward a new history and geography of human genes informed by ancient DNA. Trends in Genetics Vol.30, No.9 (Sept 2014): 377-389.J. Mengel-From, C. Borsting, J.J. Sanchez, Hans Eiberg, Neils Morling. Human eye colours and HERC2, OCA2 and MATP.

Forensic Science International: Genetics 4 (2010): 323-328.S. Connor. “Revealed: First Ol’ Blue Eyes is 7,000 years old and was a caveman living in Spain.” IndependentUK. IndependentUK, 26 January 2014.T. Günther, C. Valdiosera, H. Malmström, I Urena, et all. Ancient genomes link early farmers from Atapuerca in Spain to modern-day Basques.

PNAS 112 (2015): 11917-11922 University of Copenhagen. “Blue-eyed humans have a single, common ancestor.” ScienceDaily. ScienceDaily, 31 January 2008. : Behind Blue Eyes: A Look at the Genetic and Cultural Components that Propelled the Spread of Blue-Eyed Humans

What Colour was the first human?

Evolution of skin color – Loss of body hair in Hominini species is assumed to be related to the emergence of bipedalism some 5 to 7 million years ago. Bipedal hominin body hair may have disappeared gradually to allow better heat dissipation through sweating.

The emergence of skin pigmentation dates to about 1.2 million years ago, under conditions of a megadrought that drove early humans into arid, open landscapes.
Such conditions likely caused excess UV-B radiation.
This favored the emergence of skin pigmentation in order to protect from folate depletion due to the increased exposure to sunlight.

A theory that the pigmentation helped counter xeric stress by increasing the epidermal permeability barrier has been disproved. With the evolution of hairless skin, abundant sweat glands, and skin rich in melanin, early humans could walk, run, and forage for food for long periods of time under the hot sun without brain damage due to overheating, giving them an evolutionary advantage over other species.

By 1.2 million years ago, around the time of Homo ergaster, archaic humans (including the ancestors of Homo sapiens ) had exactly the same receptor protein as modern sub-Saharan Africans,
This was the genotype inherited by anatomically modern humans, but retained only by part of the extant populations, thus forming an aspect of human genetic variation,

About 100,000–70,000 years ago, some anatomically modern humans ( Homo sapiens ) began to migrate away from the tropics to the north where they were exposed to less intense sunlight. This was possibly in part due to the need for greater use of clothing to protect against the colder climate.

Under these conditions there was less photodestruction of folate and so the evolutionary pressure working against the survival of lighter-skinned gene variants was reduced.
In addition, lighter skin is able to generate more vitamin D (cholecalciferol) than darker skin, so it would have represented a health benefit in reduced sunlight if there were limited sources of vitamin D.

Hence the leading hypothesis for the evolution of human skin color proposes that:

From about 1.2 million years ago to less than 100,000 years ago, archaic humans, including archaic Homo sapiens, were dark-skinned.
As Homo sapiens populations began to migrate, the evolutionary constraint keeping skin dark decreased proportionally to the distance north a population migrated, resulting in a range of skin tones within northern populations.
At some point, some northern populations experienced positive selection for lighter skin due to the increased production of vitamin D from sunlight and the genes for darker skin disappeared from these populations.
Subsequent migrations into different UV environments and admixture between populations have resulted in the varied range of skin pigmentations we see today.

The genetic mutations leading to light skin, though partially different among East Asians and Western Europeans, suggest the two groups experienced a similar selective pressure after settlement in northern latitudes. The theory is partially supported by a study into the SLC24A5 gene which found that the allele associated with light skin in Europe “determined that 18,000 years had passed since the light-skin allele was fixed in Europeans” but may have originated as recently as 12,000–6,000 years ago “given the imprecision of method”, which is in line with the earliest evidence of farming.

Research by Nina Jablonski suggests that an estimated time of about 10,000 to 20,000 years is enough for human populations to achieve optimal skin pigmentation in a particular geographic area but that development of ideal skin coloration may happen faster if the evolutionary pressure is stronger, even in as little as 100 generations.

The length of time is also affected by cultural practices such as food intake, clothing, body coverings, and shelter usage which can alter the ways in which the environment affects populations. One of the most recently proposed drivers of the evolution of skin pigmentation in humans is based on research that shows a superior barrier function in darkly pigmented skin.

Most protective functions of the skin, including the permeability barrier and the antimicrobial barrier, reside in the stratum corneum (SC) and the researchers surmise that the SC has undergone the most genetic change since the loss of human body hair.
Natural selection would have favored mutations that protect this essential barrier; one such protective adaptation is the pigmentation of interfollicular epidermis, because it improves barrier function as compared to non-pigmented skin.

In lush rainforests, however, where UV-B radiation and xeric stress were not in excess, light pigmentation would not have been nearly as detrimental. This explains the side-by-side residence of lightly pigmented and darkly pigmented peoples. Population and admixture studies suggest a three-way model for the evolution of human skin color, with dark skin evolving in early hominids in Africa and light skin evolving partly separately at least two times after modern humans had expanded out of Africa,

Where in Europe did blue eyes come from?

Okay, let me preview this article: I posted this scientific finding about the MUTATION of Brown eyes to being Blue due to a recent post on the subjects in a couple of threads. My parents tell me, out of my siblings that I was born with blue eyes and red hair and red skin.

By the time of my 4th month baby picture, I can see that my eyes were light brown, and my hair and skin was very red. Not anymore. My siblings came out brown. One of my younger siblings was born very chocolate and she was clean bald but later, she grew beautiful and very black hair that does not ‘fro’, but it has a combination texture.

A couple of years ago, scientist determined that BLUE EYES was a MUTATION that occurred around 6,000 years ago and it stems from A BLACK MALE AFRICAN ORIGIN. They report several archeological proofs puts this event around the BLACK SEA AREA. Based on my research, I absolutely agree.

Blonde hair and Blue eyes is NOT a White European trait in origin for significant reasons and although the scholars today give partial break down on this subject, it still is scientifically based. Blue eyes stem from ‘PIGMENTATION’ and without this, eyes will not have any coloring such as in a pure ALBINO.

So this has been obvious to the scientific community for a long time, but for some reason they just are reporting this now. Like Blue eyes, ‘Blonde hair’ also has pigmentation! –But not, White hair. There is a difference between Blonde hair, White hair and Graying hair.

BTW—This would be the same account given in my reference source, scientific reference source, about the Biblical Cain.
His descendants migrated NODEAST and that would have been, Northeast of ‘Eden’ where the four rivers began, and thus, around the Black Sea Area were the first ancient city-civilization set up in CATAL HUYUK.

======================================================= How one ancestor helped turn our brown eyes blue Thursday 31 January 2008 01:00 Steve Connor “The mutations responsible for blue eye colour most likely originate from the north-west part of the Black Sea region, where the great agricultural migration of the northern part of Europe took place in the Neolithic periods about 6,000 to 10,000 years ago,” the researchers report in the journal Human Genetics.

https://www.independent.co.uk/news/science/how-one-ancestor-helped-turn-our-brown-eyes-blue-776170.html 84,112 views Jan 27, 2014, 12:23 pm Blue-Eyed African Caveman Found In Europe Paul Rogers, Contributor A stone-age hunter’s wisdom tooth has revealed that he had an unusual mix of racial traits – dark, African skin, curly brown hair and blue eyes,

Preliminary DNA analysis of the exceedingly well-preserved 7,000-year-old skeleton, dubbed Brana-1, has overturned ideas about the descent of modern Europeans. Although the hunter’s closest modern-day relatives live in Sweden and Finland, the genes for his skin colour are African.

Https://www.forbes.com/sites/paulrodgers/2014/01/27/stone-age-hunter-had-blue-eyes-and-dark-african-skin/ JOHN BRYSON/SYGMA/CORBIS Don’t It Make Your Brown Eyes Blue? Feb.1, 2008, 12:00 AM 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 http://www.sciencemag.org/news/2008/02/dont-it-make-your-brown-eyes-blue How Did Blue Eyes Evolve The skeleton of La Braña 1, as it was discovered in 2006. Credit: J.M. Vidal Encina Ethiopian boy has a form of albinism that only affects his eyes, turning them bright blue. April 29, 2016 admin Human Ethiopian boy with Ble eyes Babies with both Blonde Hair & Blue Eyes

How did Europeans get blue eyes?

Blog How Did Blue Eyes Evolve 1. Only 8 Percent of the World’s Population Has Blue Eyes If you have got blue eyes, you might just belong to one of the world’s most exclusive groups without realising it! Since blue eyes are genetically recessive, only 8 percent of the world’s population has blue eyes.

While blue eyes are significantly less common than brown eyes worldwide, they are frequently found from nationalities located near the Baltic Sea in northern Europe.2. There is No Blue Pigment in Blue Irises The colour of our eyes depends on how much melanin is present in the iris. Blue eyes get their colour the same way water and the sky get their blue colour — they scatter light so that more blue light reflects back out.

If there is no pigment at all in this front layer, the fibers scatter and absorb some of the longer wavelengths of light that come in.
More blue light gets back out and the eyes appear to be blue.3.
Blue Eyes are More Sensitive to Light Melanin in the iris of the eye appears to help protect the back of the eye from damage caused by UV radiation and high-energy visible “blue” light from sunlight and artificial sources of these rays.

Therefore, it is recommended to those with blue eyes to stay out of the sun for long periods of time and try to wear protective eyewear when you are outdoors.4. All Blue-Eyed People May Have A Common Ancestor Originally we all had brown eyes, however, according to researchers at the University of Copenhagen, it appears that a genetic mutation in a single individual in Europe 6,000 to 10,000 years ago led to the development of blue eyes.

The OCA2 gene codes for the ‘P protein’, which is involved in the production of melanin (the pigment that determines the colour of our eyes, skin and hair).
The “switch”, 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.

Blue Eyes at Birth Doesn’t Mean Blue Eyes For Life While blue eyes may be rare, they’re among the most common eye colours at birth.
Since the human eye does not have its full adult amount of pigment at birth, most Caucasian babies are born with blue eyes.
However, since human melanin tends to develop over time — this causes the child’s eye colour to change as more melanin is produced in the iris during early childhood.6.

A study published in American Journal of Medical Genetics, Part B: Neuropsychiatric Genetics found that European Americans with blue eyes had up to 83 percent higher odds of becoming dependent on alcohol, compared with matched controls who had darker eye colours.
This research suggests that alcoholism has a genetic component linked to genetic sequences that determine eye colour, which may help explain the association.

Before geneticists fully understood how human eye colour inheritance works, a child’s eye colour to used be used as a paternity test — based on the assumption that you could predict a child’s eye colour if you knew the colour of the parents’ eyes and perhaps the colour of the grandparents’ eyes. But geneticists now know that this concept is far more complicated, as eye colour is influenced by an interaction of as many as 16 different genes — not just one or two genes as once thought.

Are all humans related to each other?

Basic math tells us that all humans share ancestors, but it’s amazing how recently those shared ancestors lived. Thanks to genetic data in the 21st century, scientists are discovering that we really are all descended from one mother.

Did all humans come from Africa?

Experts question study claiming to pinpoint birthplace of all humans A new genetic study suggests all modern humans trace our ancestry to a single spot in southern Africa 200,000 years ago. But experts say the study, which analyzes the DNA of living people, is not nearly comprehensive enough to pinpoint where our species arose.

“I’m persuaded that southern Africa was an important area for human evolution,” says population geneticist Aylwyn Scally of the University of Cambridge in the United Kingdom who was not involved with the work. But, he says, studies of living people’s DNA can’t reveal the precise location of our ancestors.

“It would be astonishing if all our genetic ancestry at this time arose in one small homeland.” Modern humans arose in Africa at least 250,000 to 300,000 years ago, and DNA reveal. But scientists have been unable to pinpoint a more specific homeland because the earliest Homo sapiens fossils are found across Africa, and ancient DNA from African fossils is scarce and not old enough.

In the new study, researchers gathered blood samples from 200 living people in groups whose DNA is poorly known, including foragers and hunter-gatherers in Namibia and South Africa who speak Khoisan languages with click consonants. The authors analyzed the mitochondrial DNA (mtDNA), a type of DNA inherited only from mothers, and compared it to mtDNA in databases from more than 1000 other Africans, mostly from southern Africa.

Then the researchers sorted how all the samples were related to each other on a family tree. Confirming earlier studies, the data reveal that one mtDNA lineage in the Khoisan speakers—L0—is the oldest known mtDNA lineage in living people. The work also tightens the date of origin of L0 to about 200,000 years ago (with a range of error of 165,000 to 240,000; previous studies had a range of error from 150,000 to 250,000), the team reports today in Nature, Vanessa Hayes has long studied the Juǀ’hoansi of the Kalahari Desert of Namibia who speak a Khoisan click language. © Chris Bennett/Evolving Picture Specifically, Hayes and her colleagues argue that the homeland was in what is now the Kalahari region of northern Botswana.

Although the Kalahari is mostly desert and salt flats today, it was a lush wetland from 200,000 to 130,000 years ago near what would have been the largest lake in Africa, according to climate data and simulations in the study.
The team proposes that people with the L0 mtDNA thrived in their Kalahari homeland until about 130,000 to 110,000 years ago, when climate change opened green corridors to the northeast and southwest.

Some individuals left their homeland and evolved new mtDNA lineages that the team identifies. But mtDNA alone in living people is a poor tool for tracking ancient population history in Africa, says evolutionary geneticist Sarah Tishkoff of the University of Pennsylvania.

MtDNA traces only one genetic lineage passed from mothers to their children over time.
If the researchers had traced the evolution of Y chromosomes inherited from fathers or of any nuclear genes inherited from both parents, they might have gotten many different answers, Scally adds.
Hayes responds that the team chose mtDNA because it doesn’t get shuffled in early fetal development like other types of DNA do.

As a result, it can be used to trace living people’s evolution in a direct line to a small number of female ancestors who only lived in southern Africa, she says. “It acts like a time capsule for our ancestral mothers.” Most of the data on Khoisan speakers’ Y chromosomes has disappeared as men mixed with other groups, she says.

Critics also warn that the female ancestors of the Khoisan speakers may not have lived in the same place 200,000 years ago.
The ancestral women with the L0 lineage could have migrated to southern Africa from elsewhere or been part of a larger population whose descendants outside of southern Africa went extinct, Tishkoff says.

The bottom line, says population geneticist Pontus Skoglund of the Francis Crick Institute in London, is that populations move and mix so much over the millennia that studying DNA from living humans is “very limited when it comes to reconstructing what happened to populations 70,000 to 200,000 years ago.” For that, he says, you need ancient DNA.

Why did blonde hair and blue eyes evolve?

Caveman blondes also had more fun Researchers say the tradition of blondes having more fun goes back to the end of the Ice Age.A report from the University of St. Andrews, published this week in Evolution and Human Behavior, says north European women evolved blond hair and blue eyes to make them stand out from their rivals at a time of fierce competition for scarce males, the Sunday Times of London reported.

An analysis of north European genes carried out at three Japanese universities has isolated the date of the genetic mutation that resulted in blond hair to about 11,000 years ago.A study by the World Health Organization found that natural blondes are likely to be extinct within 200 years because there are too few people carrying the blond gene, the newspaper said. Copyright 2006 by United Press International

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Why did human eyes evolve visible light?

Humans evolved the ability to detect the wavelengths of light that are the most informative for helping us survive and reproduce in our particular environment. Similarly, other animals are able to see the wavelengths of light that are most useful to them in their environments.

Did blue eyes come from one ancestor?

Scientists reveal that a genetic mutation, happening around 10,000 years ago, led to the repression of melanin for humans with blue eyes – This theory finds that every human with blue eyes today can be traces back to one ancestor with one genetic mutation.