![]() In addition to having significantly less melanin in their irises than people with brown eyes, hazel eyes or green eyes, blue-eyed individuals don’t have very much variation in the part of their DNA responsible for melanin production.īrown-eyed individuals, on the other hand, have a lot more variation. This genetic switch limits how much melanin is produced in the iris - effectively “diluting” dark brown eyes to a shade of light eyes, like blue. Melanin is also responsible for the color of our skin, eyes and hair. “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.”Įye color depends on how much of a pigment called melanin lives in the iris of the eye. “Originally, we all had brown eyes,” said Hans Eiberg, associate professor in the Department of Cellular and Molecular Medicine at the university. That little DNA blip was blue eye color, according to researchers at the University of Copenhagen.Īs far as researchers can tell, this was the first blue-eyed person, and everyone who has blue eyes today is a (very) distant relative of this ancient human. Everyone with blue eyes is relatedīetween 6,000 and 10,000 years ago, a baby was born in Europe with a harmless genetic mutation. Rather than including a blue pigment, they actually just lack the pigment that makes eyes brown. Worldwide, fewer than 9% of people have blue eyes. Just as many genetic factors affect eye color, there may have been a combination of several factors that lead to the evolution of blue eyes.About half as many Americans have blue eyes as brown eyes. Eye color is affected by several genes, including the genes that control the amount of melanin pigment in our irides, a gene that controls whether melanin is produced in the outer layer of the iris, and the genes that control the structure of the iris and how much collagen it contains. There are a lot of factors that contribute to eye color. Some of you may remember making Punnett Squares in school and learning that two blue eyed individuals would always have blue eyed offspring. Perhaps those individuals were more motivated to go out hunting and take care of themselves. Sturm suggests that blue eyed individuals may have been better able to withstand the dark days of the Neolithic European winters. Seasonal affective disorder occurs in some people during extended periods of low light. He says blue eyes have been linked to people coping better with seasonal affective disorder, also known as seasonal depression. This theory is possible, though difficult to prove. Perhaps people were attracted to the novelty of blue eyes and therefore people with blue eyes were more likely to find mates. Sexual Attractiveness TheoryĪnother theory is that people considered blue eyes to be more sexually attractive. This archeological finding contradicts the theory that hair, skin, and eyes co-evolved in reaction to the limited sunlight. When studying the hunter-gatherer’s genetic information, the team discovered that the man had dark hair, dark skin, and blue eyes. 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. Additionally, there is evidence that blue eyes evolved before light skin. 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. However, molecular geneticist and Associate Professor Rick Sturm of the University of Queensland had a problem with this hypothesis. 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, they have several interesting theories. Blue eyes have been around for at least 7,000 years, but scientists still cannot agree on why they evolved. The short answer is that scientists are not exactly sure. ![]() The question is why humans evolved to have blue eyes in the first place? Ultimately it must have started out as a genetic mutation, but what led this mutation to be passed on to offspring and to spread? However, in Northern European countries, such as Iceland, blue-eyed individuals find themselves in the majority. Blue eyed people make up an estimated 8% of the population.
0 Comments
Leave a Reply. |