The perception of color depends upon various factors. These are the same eyes; however, depending on the light and surrounding hues, the eye color can appear quite different.
Blue
Blue eyes contain low amounts of melanin within the iris stroma; longer wavelengths of light tend to be absorbed by the underlying iris pigment epithelium, and shorter wavelengths are reflected and undergo Rayleigh scattering.[5] The type of melanin present is eumelanin.[21] The inheritance pattern followed by blue eyes is considered similar to that of a recessive trait, however it is a polygenic trait (meaning that it is controlled by the interactions of several genes, not just one).[7] Eiberg and colleagues showed in a study published in Human Genetics that a mutation in the 86th intron of the HERC2 gene, which is hypothesized to interact with the OCA2 gene promoter, reduced expression of OCA2 with subsequent reduction in melanin production.[22]
The authors concluded that the mutation may have arisen in a single individual around the Black Sea region 6,000-10,000 years ago, perhaps suggesting that all people with true blue eyes are more closely related. However, blue eyes with brown spots around the pupil are not related to this mutation.[22]
Blue eyes are most common in Poland[23], Ireland[24] [25] , Netherlands[26], Iceland[27] , Austria[28], Sweden[29], Norway[30], Denmark[31], Russia[23], Finland[32], Germany[33], France[34], Estonia[35], and the United Kingdom[36][37] They are also present in Southern Europe, Spain[38], Portugal[39],Italy[40] and the Balkans [41], the Middle East [42] (especially in Israel and Lebanon), India and are also found in Afghanistan. A 2002 study found the prevalence of blue eye color among Whites in the United States to be 33.8% for those born from 1936 through 1951 compared with 57.4% for those born from 1899 through 1905.
Green eyes are the product of moderate amounts of melanin. According to some researchers, green eyes are the result of mutations that change the melanin structure
[48] Green eyes are most common in
Europe and to a lesser extent in the
Middle East, Northern parts of
India,
Pakistan, and
Afghanistan. 88% of the
Icelandic population have either green or blue eye color
Gray
Gray eyes have less melanin than blue eyes, even though they are considered a darker shade of blue (like blue-green). They are most common in European Russia, Finland and the Baltic States. Under magnification, gray eyes exhibit small amounts of yellow and brown color in the iris.
A gray iris may indicate the presence of a uveitis. However, other visual signs make a uveitis obvious.
Visually, gray eyes often tend to appear to change between the shades of blue, green and gray. This is said to be influenced by the lighting and the surroundings (such as clothes, makeup, etc.).
The Greek goddess Athena was renowned for having "owl-gray" (in Greek, γλαυκῶπις – glaukōpis) or "sea-gray" eyes
Brown
Brown eyes are predominant in humans[43] and, in many populations, it is (with few exceptions) the only iris color present.[44] It is less common in countries around the Baltic Sea, such as Finland and Estonia. Germany has also shown signs that many people have dark brown eyes.
In humans, brown eyes contain large amounts of melanin (eumelanin) within the iris stroma, which serves to absorb light, particularly at the shorter wavelengths.[5][21] Very dark brown irises may appear at a glance to be black
Human amber eyes displaying the yellow pigments.
This eye shows a mixture of brown, green and amber colors.
Red
The eyes of a person with albinism may appear red under certain lighting conditions due the very low quantities of melanin. "True" red eyes also exist in albinistic populations, but are very rare. [62]
The red-eye effect in flash photographs makes the pupils (rather than the irises) appear red. It is not related to eye color.
Violet
The appearance of "violet" eyes is thought to occur from the mixing of red and blue reflections.[63] Some albinos have eyes that appear violet. Violet eyes are a form of blue eyes.
Aniridia: Eyes wherein the irises are not present; the eyes appear to be two large pupils.
An example of
heterochromia. The subject has one brown and one hazel eye.
An example of
sectoral heterochromia. The subject has a blue iris with a brown section.
Often, lighter skinned newborns have blue eyes, which change to green, hazel, light brown or dark brown
Height
n the eighteenth and nineteenth centuries, Europeans in
North America were far taller than those in
Europe and were the tallest in the world.
[84] The original indigenous population of Plains Native Americans was also among the tallest populations of the world at the time.
[85] Several nations, including many nations in Europe, have now surpassed the US, particularly the
Netherlands, and the
Scandinavian nations.
A "head-measurer" tool designed for anthropological research in the early 1910s.
No comments:
Post a Comment