However, there are phenotypically identical, but genotypically different, blue-eyed white cats (where the coat color is caused by the gene for white spotting) where the coat color is not strongly associated with deafness. The mutation found in blue-eyed solid white cats (where the coat color is caused by the gene for 'epistatic white') is linked with deafness.

The mutation found in the Siamese cats is associated with strabismus (crossed eyes). But in cats alone, there are four identified gene mutations that produce blue eyes, some of which are associated with congenital neurological disorders. While some cats and dogs have blue eyes, this is usually due to another mutation that is associated with deafness. The trait is hitherto known only from a single primate other than humans – Sclater's lemur ( Eulemur flavifrons) of Madagascar. Blue eyes are continuing to become less common among American children.īlue eyes are rare in mammals one example is the recently discovered marsupial, the blue-eyed spotted cuscus ( Spilocuscus wilsoni). As of 2006, one out of every six people, or 16.6% of the total population, and 22.3% of whites, has blue eyes. As of 2016, the earliest light-pigmented and blue-eyed remains of Homo Sapiens were found in 7,700 years old Mesolithic hunter-gatherers from Motala, Sweden.Ī 2002 study found that the prevalence of blue eye color among the white population in the United States to be 33.8% for those born from 1936 through 1951 compared with 57.4 percent for those born from 1899 through 1905. The same DNA sequence in the region of the OCA2 gene among blue-eyed people suggests they may have a single common ancestor.ĭNA studies on ancient human remains confirm that light skin, hair and eyes were present at least tens of thousands of years ago on Neanderthals, who lived in Eurasia for 500,000 years. The first blue-eyed koala known to be born in captivity in the world. The authors suggest that the mutation may have arisen in the northwestern part of the Black Sea region, but add that it is 'difficult to calculate the age of the mutation.' Blue-eyed populations Eiberg and colleagues suggested 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. 'Originally, we all had brown eyes,' said Eiberg. In 2008, new research tracked down a single genetic mutation that leads to blue eyes. In humans, the inheritance pattern followed by blue eyes is considered similar to that of a recessive trait (in general, eye color inheritance is considered a polygenic trait, meaning that it is controlled by the interactions of several genes, not just one). The result is a ' Tyndall blue' structural color that varies with external lighting conditions. This is the same frequency-dependence of scattering that accounts for the blue appearance of the sky. Longer wavelengths of light tend to be absorbed by the dark underlying epithelium, while shorter wavelengths are reflected and undergo Rayleigh scattering in the turbid medium of the stroma. Unlike brown eyes, blue eyes have low concentrations of melanin in the stroma of the iris, which lies in front of the dark epithelium. Dissection reveals that the iris pigment epithelium is brownish black due to the presence of melanin. There is no blue pigmentation either in the iris or in the ocular fluid. Many animals such as canines, domestic cats, owls, eagles, pigeons and fish have amber eyes as a common color, whereas in humans this color occurs less frequently. In humans, yellowish specks or patches are thought to be due to the pigment lipofuscin, also known as lipochrome. The bright yellow eyes of the great horned owl are thought to be due to the presence of the pteridine pigment xanthopterin within certain chromatophores (called xanthophores) located in the iris stroma.

The eyes of some pigeons contain yellow fluorescing pigments known as pteridines. Amber eyes may also contain amounts of very light gold-ish gray. Even though amber is considered to be like gold, some people have russet or copper colored amber eyes that many people mistake for hazel, though hazel tends to be duller and contains green with red/gold flecks, as mentioned above. Also, hazel eyes may appear to shift in color and consist of flecks and ripples, while amber eyes are of a solid gold hue. Amber eyes should not be confused with hazel eyes although hazel eyes may contain specks of amber or gold, they usually tend to comprise many other colors, including green, brown and orange. This may be due to the deposition of the yellow pigment called lipochrome in the iris (which is also found in green eyes). Amber eyes in sunlight – displaying an orange color rather than brownĪmber eyes are of a solid color and have a strong yellowish/golden and russet/coppery tint.

Yellow ring around pupil called