of melanin in the stroma of the iris, which causes light of both shorter and longer wavelengths to be absorbed and in many parts of the world, it is nearly the only iris color present. Dark pigment of brown eyes is most common in East Asia, Southeast Asia, South Asia, West Asia, Oceania, Africa, Americas, etc. as well as parts of Eastern Europe and Southern Europe. The majority of people in the world overall have dark brown eyes. Light or medium-pigmented brown eyes are common in Europe, Afghanistan, Pakistan and Northern India, as well as some parts of the Middle East. (See eye color). Brown hair Brown is the second most common color of human hair, after black. It is caused by higher levels of the natural dark pigment eumelanin, and lower levels of the pale pigment pheomelanin. Brown eumelanin is more common among Europeans, while black eumelanin is more often found in the hair on non-Europeans. A small amount of black eumelanin, in the absence of other pigments, results in grey hair. A small amount of brown eumelanin in the absence of other pigments results in blond hair. Brown skin A majority of people in the world have skin that is a shade of brown, from a very light honey brown or a golden brown, to a copper or bronze color, to a coffee color or a dark chocolate brown. Skin color and race are not the same; many people classified as "white" or "black" actually have skin that is a shade of brown. Brown skin is caused by melanin, a natural pigment which is produced within the skin in cells called melanocytes. Skin pigmentation in humans evolved to primarily regulate the amount of ultraviolet radiation penetrating the skin, controlling its biochemical effects. Natural skin color can darken as a result of tanning due to exposure to sunlight. The leading theory is that skin color adapts to intense sunlight irradiation to provide partial protection against the ultraviolet fraction that produces damage and thus mutations in the DNA of the skin cells. There is a correlation between the geographic distribution of ultraviolet radiation (UVR) and the distribution of indigenous skin pigmentation around the world. Darker-skinned populations are found in the regions with the most ultraviolet, closer to the equator, while lighter skinned populations live closer to the poles, with less UVR, though immigration has changed these patterns. While white and