<P> The eyes of some pigeons contain yellow fluorescing pigments known as pteridines . 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 . In humans, yellowish specks or patches are thought to be due to the pigment lipofuscin, also known as lipochrome . 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 . </P> <P> There is no blue pigmentation either in the iris or in the ocular fluid . Dissection reveals that the iris pigment epithelium is brownish black due to the presence of melanin . Unlike brown eyes, blue eyes have low concentrations of melanin in the stroma of the iris, which lies in front of the dark epithelium . 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 . This is the same frequency - dependence of scattering that accounts for the blue appearance of the sky . The result is a "Tyndall blue" structural color that varies with external lighting conditions . </P> <P> 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). In 2008, new research tracked down a single genetic mutation that leads to blue eyes . "Originally, we all had brown eyes," said Eiberg . 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 . 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 ." </P> <Table> <Tr> <Th_colspan="5"> Blue - eyed populations </Th> </Tr> <Tr> <Td> Country </Td> <Td> </Td> <Td> </Td> <Td> Percent of population </Td> <Td> </Td> </Tr> <Tr> <Td_colspan="2"> Finland </Td> <Td> </Td> <Td_colspan="2"> 89% </Td> </Tr> <Tr> <Td_colspan="2"> Estonia </Td> <Td> </Td> <Td_colspan="2"> 89% </Td> </Tr> <Tr> <Td_colspan="2"> Ireland </Td> <Td> </Td> <Td_colspan="2"> 57% </Td> </Tr> <Tr> <Td_colspan="2"> Scotland </Td> <Td> </Td> <Td_colspan="2"> 50% </Td> </Tr> <Tr> <Td_colspan="2"> England </Td> <Td> </Td> <Td_colspan="2"> 48% </Td> </Tr> <Tr> <Td_colspan="2"> Wales </Td> <Td> </Td> <Td_colspan="2"> 45% </Td> </Tr> <Tr> <Td_colspan="2"> Belgium (adult population) </Td> <Td> </Td> <Td_colspan="2"> 28.9% </Td> </Tr> <Tr> <Td_colspan="2"> France (adult pop .) </Td> <Td> </Td> <Td_colspan="2"> 20.2% </Td> </Tr> <Tr> <Td_colspan="2"> United States </Td> <Td> </Td> <Td_colspan="2"> 16.6% </Td> </Tr> <Tr> <Td_colspan="2"> Spain </Td> <Td> </Td> <Td_colspan="2"> 16.3% </Td> </Tr> <Tr> <Td_colspan="2"> Algeria (adult pop .) </Td> <Td> </Td> <Td_colspan="2"> 2.6% </Td> </Tr> <Tr> <Td_colspan="2"> Morocco (adult pop .) </Td> <Td> </Td> <Td_colspan="2"> 2.1% </Td> </Tr> <Tr> <Td_colspan="2"> Tunisia (adult pop .) </Td> <Td> </Td> <Td_colspan="2"> 1.2% </Td> </Tr> <Tr> <Td_colspan="5"> sources: </Td> </Tr> </Table>

Where does the blue eye gene come from